diff options
Diffstat (limited to 'net/ipv4/tcp_output.c')
| -rw-r--r-- | net/ipv4/tcp_output.c | 3525 |
1 files changed, 3525 insertions, 0 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c new file mode 100644 index 000000000..d80faa151 --- /dev/null +++ b/net/ipv4/tcp_output.c @@ -0,0 +1,3525 @@ +/* + * INET An implementation of the TCP/IP protocol suite for the LINUX + * operating system. INET is implemented using the BSD Socket + * interface as the means of communication with the user level. + * + * Implementation of the Transmission Control Protocol(TCP). + * + * Authors: Ross Biro + * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> + * Mark Evans, <evansmp@uhura.aston.ac.uk> + * Corey Minyard <wf-rch!minyard@relay.EU.net> + * Florian La Roche, <flla@stud.uni-sb.de> + * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> + * Linus Torvalds, <torvalds@cs.helsinki.fi> + * Alan Cox, <gw4pts@gw4pts.ampr.org> + * Matthew Dillon, <dillon@apollo.west.oic.com> + * Arnt Gulbrandsen, <agulbra@nvg.unit.no> + * Jorge Cwik, <jorge@laser.satlink.net> + */ + +/* + * Changes: Pedro Roque : Retransmit queue handled by TCP. + * : Fragmentation on mtu decrease + * : Segment collapse on retransmit + * : AF independence + * + * Linus Torvalds : send_delayed_ack + * David S. Miller : Charge memory using the right skb + * during syn/ack processing. + * David S. Miller : Output engine completely rewritten. + * Andrea Arcangeli: SYNACK carry ts_recent in tsecr. + * Cacophonix Gaul : draft-minshall-nagle-01 + * J Hadi Salim : ECN support + * + */ + +#define pr_fmt(fmt) "TCP: " fmt + +#include <net/tcp.h> + +#include <linux/compiler.h> +#include <linux/gfp.h> +#include <linux/module.h> + +/* People can turn this off for buggy TCP's found in printers etc. */ +int sysctl_tcp_retrans_collapse __read_mostly = 1; + +/* People can turn this on to work with those rare, broken TCPs that + * interpret the window field as a signed quantity. + */ +int sysctl_tcp_workaround_signed_windows __read_mostly = 0; + +/* Default TSQ limit of two TSO segments */ +int sysctl_tcp_limit_output_bytes __read_mostly = 131072; + +/* This limits the percentage of the congestion window which we + * will allow a single TSO frame to consume. Building TSO frames + * which are too large can cause TCP streams to be bursty. + */ +int sysctl_tcp_tso_win_divisor __read_mostly = 3; + +/* By default, RFC2861 behavior. */ +int sysctl_tcp_slow_start_after_idle __read_mostly = 1; + +unsigned int sysctl_tcp_notsent_lowat __read_mostly = UINT_MAX; +EXPORT_SYMBOL(sysctl_tcp_notsent_lowat); + +static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, + int push_one, gfp_t gfp); + +/* Account for new data that has been sent to the network. */ +static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + unsigned int prior_packets = tp->packets_out; + + tcp_advance_send_head(sk, skb); + tp->snd_nxt = TCP_SKB_CB(skb)->end_seq; + + tp->packets_out += tcp_skb_pcount(skb); + if (!prior_packets || icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS || + icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) { + tcp_rearm_rto(sk); + } + + NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT, + tcp_skb_pcount(skb)); +} + +/* SND.NXT, if window was not shrunk. + * If window has been shrunk, what should we make? It is not clear at all. + * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-( + * Anything in between SND.UNA...SND.UNA+SND.WND also can be already + * invalid. OK, let's make this for now: + */ +static inline __u32 tcp_acceptable_seq(const struct sock *sk) +{ + const struct tcp_sock *tp = tcp_sk(sk); + + if (!before(tcp_wnd_end(tp), tp->snd_nxt)) + return tp->snd_nxt; + else + return tcp_wnd_end(tp); +} + +/* Calculate mss to advertise in SYN segment. + * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that: + * + * 1. It is independent of path mtu. + * 2. Ideally, it is maximal possible segment size i.e. 65535-40. + * 3. For IPv4 it is reasonable to calculate it from maximal MTU of + * attached devices, because some buggy hosts are confused by + * large MSS. + * 4. We do not make 3, we advertise MSS, calculated from first + * hop device mtu, but allow to raise it to ip_rt_min_advmss. + * This may be overridden via information stored in routing table. + * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible, + * probably even Jumbo". + */ +static __u16 tcp_advertise_mss(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + const struct dst_entry *dst = __sk_dst_get(sk); + int mss = tp->advmss; + + if (dst) { + unsigned int metric = dst_metric_advmss(dst); + + if (metric < mss) { + mss = metric; + tp->advmss = mss; + } + } + + return (__u16)mss; +} + +/* RFC2861. Reset CWND after idle period longer RTO to "restart window". + * This is the first part of cwnd validation mechanism. */ +static void tcp_cwnd_restart(struct sock *sk, const struct dst_entry *dst) +{ + struct tcp_sock *tp = tcp_sk(sk); + s32 delta = tcp_time_stamp - tp->lsndtime; + u32 restart_cwnd = tcp_init_cwnd(tp, dst); + u32 cwnd = tp->snd_cwnd; + + tcp_ca_event(sk, CA_EVENT_CWND_RESTART); + + tp->snd_ssthresh = tcp_current_ssthresh(sk); + restart_cwnd = min(restart_cwnd, cwnd); + + while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd) + cwnd >>= 1; + tp->snd_cwnd = max(cwnd, restart_cwnd); + tp->snd_cwnd_stamp = tcp_time_stamp; + tp->snd_cwnd_used = 0; +} + +/* Congestion state accounting after a packet has been sent. */ +static void tcp_event_data_sent(struct tcp_sock *tp, + struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + const u32 now = tcp_time_stamp; + const struct dst_entry *dst = __sk_dst_get(sk); + + if (sysctl_tcp_slow_start_after_idle && + (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto)) + tcp_cwnd_restart(sk, __sk_dst_get(sk)); + + tp->lsndtime = now; + + /* If it is a reply for ato after last received + * packet, enter pingpong mode. + */ + if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato && + (!dst || !dst_metric(dst, RTAX_QUICKACK))) + icsk->icsk_ack.pingpong = 1; +} + +/* Account for an ACK we sent. */ +static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts) +{ + tcp_dec_quickack_mode(sk, pkts); + inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK); +} + + +u32 tcp_default_init_rwnd(u32 mss) +{ + /* Initial receive window should be twice of TCP_INIT_CWND to + * enable proper sending of new unsent data during fast recovery + * (RFC 3517, Section 4, NextSeg() rule (2)). Further place a + * limit when mss is larger than 1460. + */ + u32 init_rwnd = TCP_INIT_CWND * 2; + + if (mss > 1460) + init_rwnd = max((1460 * init_rwnd) / mss, 2U); + return init_rwnd; +} + +/* Determine a window scaling and initial window to offer. + * Based on the assumption that the given amount of space + * will be offered. Store the results in the tp structure. + * NOTE: for smooth operation initial space offering should + * be a multiple of mss if possible. We assume here that mss >= 1. + * This MUST be enforced by all callers. + */ +void tcp_select_initial_window(int __space, __u32 mss, + __u32 *rcv_wnd, __u32 *window_clamp, + int wscale_ok, __u8 *rcv_wscale, + __u32 init_rcv_wnd) +{ + unsigned int space = (__space < 0 ? 0 : __space); + + /* If no clamp set the clamp to the max possible scaled window */ + if (*window_clamp == 0) + (*window_clamp) = (65535 << 14); + space = min(*window_clamp, space); + + /* Quantize space offering to a multiple of mss if possible. */ + if (space > mss) + space = (space / mss) * mss; + + /* NOTE: offering an initial window larger than 32767 + * will break some buggy TCP stacks. If the admin tells us + * it is likely we could be speaking with such a buggy stack + * we will truncate our initial window offering to 32K-1 + * unless the remote has sent us a window scaling option, + * which we interpret as a sign the remote TCP is not + * misinterpreting the window field as a signed quantity. + */ + if (sysctl_tcp_workaround_signed_windows) + (*rcv_wnd) = min(space, MAX_TCP_WINDOW); + else + (*rcv_wnd) = space; + + (*rcv_wscale) = 0; + if (wscale_ok) { + /* Set window scaling on max possible window + * See RFC1323 for an explanation of the limit to 14 + */ + space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max); + space = min_t(u32, space, *window_clamp); + while (space > 65535 && (*rcv_wscale) < 14) { + space >>= 1; + (*rcv_wscale)++; + } + } + + if (mss > (1 << *rcv_wscale)) { + if (!init_rcv_wnd) /* Use default unless specified otherwise */ + init_rcv_wnd = tcp_default_init_rwnd(mss); + *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss); + } + + /* Set the clamp no higher than max representable value */ + (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp); +} +EXPORT_SYMBOL(tcp_select_initial_window); + +/* Chose a new window to advertise, update state in tcp_sock for the + * socket, and return result with RFC1323 scaling applied. The return + * value can be stuffed directly into th->window for an outgoing + * frame. + */ +static u16 tcp_select_window(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + u32 old_win = tp->rcv_wnd; + u32 cur_win = tcp_receive_window(tp); + u32 new_win = __tcp_select_window(sk); + + /* Never shrink the offered window */ + if (new_win < cur_win) { + /* Danger Will Robinson! + * Don't update rcv_wup/rcv_wnd here or else + * we will not be able to advertise a zero + * window in time. --DaveM + * + * Relax Will Robinson. + */ + if (new_win == 0) + NET_INC_STATS(sock_net(sk), + LINUX_MIB_TCPWANTZEROWINDOWADV); + new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale); + } + tp->rcv_wnd = new_win; + tp->rcv_wup = tp->rcv_nxt; + + /* Make sure we do not exceed the maximum possible + * scaled window. + */ + if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows) + new_win = min(new_win, MAX_TCP_WINDOW); + else + new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale)); + + /* RFC1323 scaling applied */ + new_win >>= tp->rx_opt.rcv_wscale; + + /* If we advertise zero window, disable fast path. */ + if (new_win == 0) { + tp->pred_flags = 0; + if (old_win) + NET_INC_STATS(sock_net(sk), + LINUX_MIB_TCPTOZEROWINDOWADV); + } else if (old_win == 0) { + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV); + } + + return new_win; +} + +/* Packet ECN state for a SYN-ACK */ +static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb) +{ + const struct tcp_sock *tp = tcp_sk(sk); + + TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR; + if (!(tp->ecn_flags & TCP_ECN_OK)) + TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE; + else if (tcp_ca_needs_ecn(sk)) + INET_ECN_xmit(sk); +} + +/* Packet ECN state for a SYN. */ +static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + bool use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 || + tcp_ca_needs_ecn(sk); + + if (!use_ecn) { + const struct dst_entry *dst = __sk_dst_get(sk); + + if (dst && dst_feature(dst, RTAX_FEATURE_ECN)) + use_ecn = true; + } + + tp->ecn_flags = 0; + + if (use_ecn) { + TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR; + tp->ecn_flags = TCP_ECN_OK; + if (tcp_ca_needs_ecn(sk)) + INET_ECN_xmit(sk); + } +} + +static void +tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th, + struct sock *sk) +{ + if (inet_rsk(req)->ecn_ok) { + th->ece = 1; + if (tcp_ca_needs_ecn(sk)) + INET_ECN_xmit(sk); + } +} + +/* Set up ECN state for a packet on a ESTABLISHED socket that is about to + * be sent. + */ +static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb, + int tcp_header_len) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (tp->ecn_flags & TCP_ECN_OK) { + /* Not-retransmitted data segment: set ECT and inject CWR. */ + if (skb->len != tcp_header_len && + !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) { + INET_ECN_xmit(sk); + if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) { + tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR; + tcp_hdr(skb)->cwr = 1; + skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN; + } + } else if (!tcp_ca_needs_ecn(sk)) { + /* ACK or retransmitted segment: clear ECT|CE */ + INET_ECN_dontxmit(sk); + } + if (tp->ecn_flags & TCP_ECN_DEMAND_CWR) + tcp_hdr(skb)->ece = 1; + } +} + +/* Constructs common control bits of non-data skb. If SYN/FIN is present, + * auto increment end seqno. + */ +static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags) +{ + struct skb_shared_info *shinfo = skb_shinfo(skb); + + skb->ip_summed = CHECKSUM_PARTIAL; + skb->csum = 0; + + TCP_SKB_CB(skb)->tcp_flags = flags; + TCP_SKB_CB(skb)->sacked = 0; + + tcp_skb_pcount_set(skb, 1); + shinfo->gso_size = 0; + shinfo->gso_type = 0; + + TCP_SKB_CB(skb)->seq = seq; + if (flags & (TCPHDR_SYN | TCPHDR_FIN)) + seq++; + TCP_SKB_CB(skb)->end_seq = seq; +} + +static inline bool tcp_urg_mode(const struct tcp_sock *tp) +{ + return tp->snd_una != tp->snd_up; +} + +#define OPTION_SACK_ADVERTISE (1 << 0) +#define OPTION_TS (1 << 1) +#define OPTION_MD5 (1 << 2) +#define OPTION_WSCALE (1 << 3) +#define OPTION_FAST_OPEN_COOKIE (1 << 8) + +struct tcp_out_options { + u16 options; /* bit field of OPTION_* */ + u16 mss; /* 0 to disable */ + u8 ws; /* window scale, 0 to disable */ + u8 num_sack_blocks; /* number of SACK blocks to include */ + u8 hash_size; /* bytes in hash_location */ + __u8 *hash_location; /* temporary pointer, overloaded */ + __u32 tsval, tsecr; /* need to include OPTION_TS */ + struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */ +}; + +/* Write previously computed TCP options to the packet. + * + * Beware: Something in the Internet is very sensitive to the ordering of + * TCP options, we learned this through the hard way, so be careful here. + * Luckily we can at least blame others for their non-compliance but from + * inter-operability perspective it seems that we're somewhat stuck with + * the ordering which we have been using if we want to keep working with + * those broken things (not that it currently hurts anybody as there isn't + * particular reason why the ordering would need to be changed). + * + * At least SACK_PERM as the first option is known to lead to a disaster + * (but it may well be that other scenarios fail similarly). + */ +static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, + struct tcp_out_options *opts) +{ + u16 options = opts->options; /* mungable copy */ + + if (unlikely(OPTION_MD5 & options)) { + *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) | + (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG); + /* overload cookie hash location */ + opts->hash_location = (__u8 *)ptr; + ptr += 4; + } + + if (unlikely(opts->mss)) { + *ptr++ = htonl((TCPOPT_MSS << 24) | + (TCPOLEN_MSS << 16) | + opts->mss); + } + + if (likely(OPTION_TS & options)) { + if (unlikely(OPTION_SACK_ADVERTISE & options)) { + *ptr++ = htonl((TCPOPT_SACK_PERM << 24) | + (TCPOLEN_SACK_PERM << 16) | + (TCPOPT_TIMESTAMP << 8) | + TCPOLEN_TIMESTAMP); + options &= ~OPTION_SACK_ADVERTISE; + } else { + *ptr++ = htonl((TCPOPT_NOP << 24) | + (TCPOPT_NOP << 16) | + (TCPOPT_TIMESTAMP << 8) | + TCPOLEN_TIMESTAMP); + } + *ptr++ = htonl(opts->tsval); + *ptr++ = htonl(opts->tsecr); + } + + if (unlikely(OPTION_SACK_ADVERTISE & options)) { + *ptr++ = htonl((TCPOPT_NOP << 24) | + (TCPOPT_NOP << 16) | + (TCPOPT_SACK_PERM << 8) | + TCPOLEN_SACK_PERM); + } + + if (unlikely(OPTION_WSCALE & options)) { + *ptr++ = htonl((TCPOPT_NOP << 24) | + (TCPOPT_WINDOW << 16) | + (TCPOLEN_WINDOW << 8) | + opts->ws); + } + + if (unlikely(opts->num_sack_blocks)) { + struct tcp_sack_block *sp = tp->rx_opt.dsack ? + tp->duplicate_sack : tp->selective_acks; + int this_sack; + + *ptr++ = htonl((TCPOPT_NOP << 24) | + (TCPOPT_NOP << 16) | + (TCPOPT_SACK << 8) | + (TCPOLEN_SACK_BASE + (opts->num_sack_blocks * + TCPOLEN_SACK_PERBLOCK))); + + for (this_sack = 0; this_sack < opts->num_sack_blocks; + ++this_sack) { + *ptr++ = htonl(sp[this_sack].start_seq); + *ptr++ = htonl(sp[this_sack].end_seq); + } + + tp->rx_opt.dsack = 0; + } + + if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) { + struct tcp_fastopen_cookie *foc = opts->fastopen_cookie; + u8 *p = (u8 *)ptr; + u32 len; /* Fast Open option length */ + + if (foc->exp) { + len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len; + *ptr = htonl((TCPOPT_EXP << 24) | (len << 16) | + TCPOPT_FASTOPEN_MAGIC); + p += TCPOLEN_EXP_FASTOPEN_BASE; + } else { + len = TCPOLEN_FASTOPEN_BASE + foc->len; + *p++ = TCPOPT_FASTOPEN; + *p++ = len; + } + + memcpy(p, foc->val, foc->len); + if ((len & 3) == 2) { + p[foc->len] = TCPOPT_NOP; + p[foc->len + 1] = TCPOPT_NOP; + } + ptr += (len + 3) >> 2; + } +} + +/* Compute TCP options for SYN packets. This is not the final + * network wire format yet. + */ +static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, + struct tcp_out_options *opts, + struct tcp_md5sig_key **md5) +{ + struct tcp_sock *tp = tcp_sk(sk); + unsigned int remaining = MAX_TCP_OPTION_SPACE; + struct tcp_fastopen_request *fastopen = tp->fastopen_req; + +#ifdef CONFIG_TCP_MD5SIG + *md5 = tp->af_specific->md5_lookup(sk, sk); + if (*md5) { + opts->options |= OPTION_MD5; + remaining -= TCPOLEN_MD5SIG_ALIGNED; + } +#else + *md5 = NULL; +#endif + + /* We always get an MSS option. The option bytes which will be seen in + * normal data packets should timestamps be used, must be in the MSS + * advertised. But we subtract them from tp->mss_cache so that + * calculations in tcp_sendmsg are simpler etc. So account for this + * fact here if necessary. If we don't do this correctly, as a + * receiver we won't recognize data packets as being full sized when we + * should, and thus we won't abide by the delayed ACK rules correctly. + * SACKs don't matter, we never delay an ACK when we have any of those + * going out. */ + opts->mss = tcp_advertise_mss(sk); + remaining -= TCPOLEN_MSS_ALIGNED; + + if (likely(sysctl_tcp_timestamps && !*md5)) { + opts->options |= OPTION_TS; + opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset; + opts->tsecr = tp->rx_opt.ts_recent; + remaining -= TCPOLEN_TSTAMP_ALIGNED; + } + if (likely(sysctl_tcp_window_scaling)) { + opts->ws = tp->rx_opt.rcv_wscale; + opts->options |= OPTION_WSCALE; + remaining -= TCPOLEN_WSCALE_ALIGNED; + } + if (likely(sysctl_tcp_sack)) { + opts->options |= OPTION_SACK_ADVERTISE; + if (unlikely(!(OPTION_TS & opts->options))) + remaining -= TCPOLEN_SACKPERM_ALIGNED; + } + + if (fastopen && fastopen->cookie.len >= 0) { + u32 need = fastopen->cookie.len; + + need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE : + TCPOLEN_FASTOPEN_BASE; + need = (need + 3) & ~3U; /* Align to 32 bits */ + if (remaining >= need) { + opts->options |= OPTION_FAST_OPEN_COOKIE; + opts->fastopen_cookie = &fastopen->cookie; + remaining -= need; + tp->syn_fastopen = 1; + tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0; + } + } + + return MAX_TCP_OPTION_SPACE - remaining; +} + +/* Set up TCP options for SYN-ACKs. */ +static unsigned int tcp_synack_options(struct sock *sk, + struct request_sock *req, + unsigned int mss, struct sk_buff *skb, + struct tcp_out_options *opts, + const struct tcp_md5sig_key *md5, + struct tcp_fastopen_cookie *foc) +{ + struct inet_request_sock *ireq = inet_rsk(req); + unsigned int remaining = MAX_TCP_OPTION_SPACE; + +#ifdef CONFIG_TCP_MD5SIG + if (md5) { + opts->options |= OPTION_MD5; + remaining -= TCPOLEN_MD5SIG_ALIGNED; + + /* We can't fit any SACK blocks in a packet with MD5 + TS + * options. There was discussion about disabling SACK + * rather than TS in order to fit in better with old, + * buggy kernels, but that was deemed to be unnecessary. + */ + ireq->tstamp_ok &= !ireq->sack_ok; + } +#endif + + /* We always send an MSS option. */ + opts->mss = mss; + remaining -= TCPOLEN_MSS_ALIGNED; + + if (likely(ireq->wscale_ok)) { + opts->ws = ireq->rcv_wscale; + opts->options |= OPTION_WSCALE; + remaining -= TCPOLEN_WSCALE_ALIGNED; + } + if (likely(ireq->tstamp_ok)) { + opts->options |= OPTION_TS; + opts->tsval = tcp_skb_timestamp(skb); + opts->tsecr = req->ts_recent; + remaining -= TCPOLEN_TSTAMP_ALIGNED; + } + if (likely(ireq->sack_ok)) { + opts->options |= OPTION_SACK_ADVERTISE; + if (unlikely(!ireq->tstamp_ok)) + remaining -= TCPOLEN_SACKPERM_ALIGNED; + } + if (foc != NULL && foc->len >= 0) { + u32 need = foc->len; + + need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE : + TCPOLEN_FASTOPEN_BASE; + need = (need + 3) & ~3U; /* Align to 32 bits */ + if (remaining >= need) { + opts->options |= OPTION_FAST_OPEN_COOKIE; + opts->fastopen_cookie = foc; + remaining -= need; + } + } + + return MAX_TCP_OPTION_SPACE - remaining; +} + +/* Compute TCP options for ESTABLISHED sockets. This is not the + * final wire format yet. + */ +static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb, + struct tcp_out_options *opts, + struct tcp_md5sig_key **md5) +{ + struct tcp_sock *tp = tcp_sk(sk); + unsigned int size = 0; + unsigned int eff_sacks; + + opts->options = 0; + +#ifdef CONFIG_TCP_MD5SIG + *md5 = tp->af_specific->md5_lookup(sk, sk); + if (unlikely(*md5)) { + opts->options |= OPTION_MD5; + size += TCPOLEN_MD5SIG_ALIGNED; + } +#else + *md5 = NULL; +#endif + + if (likely(tp->rx_opt.tstamp_ok)) { + opts->options |= OPTION_TS; + opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0; + opts->tsecr = tp->rx_opt.ts_recent; + size += TCPOLEN_TSTAMP_ALIGNED; + } + + eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack; + if (unlikely(eff_sacks)) { + const unsigned int remaining = MAX_TCP_OPTION_SPACE - size; + opts->num_sack_blocks = + min_t(unsigned int, eff_sacks, + (remaining - TCPOLEN_SACK_BASE_ALIGNED) / + TCPOLEN_SACK_PERBLOCK); + size += TCPOLEN_SACK_BASE_ALIGNED + + opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK; + } + + return size; +} + + +/* TCP SMALL QUEUES (TSQ) + * + * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev) + * to reduce RTT and bufferbloat. + * We do this using a special skb destructor (tcp_wfree). + * + * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb + * needs to be reallocated in a driver. + * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc + * + * Since transmit from skb destructor is forbidden, we use a tasklet + * to process all sockets that eventually need to send more skbs. + * We use one tasklet per cpu, with its own queue of sockets. + */ +struct tsq_tasklet { + struct tasklet_struct tasklet; + struct list_head head; /* queue of tcp sockets */ +}; +static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet); + +static void tcp_tsq_handler(struct sock *sk) +{ + if ((1 << sk->sk_state) & + (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING | + TCPF_CLOSE_WAIT | TCPF_LAST_ACK)) + tcp_write_xmit(sk, tcp_current_mss(sk), tcp_sk(sk)->nonagle, + 0, GFP_ATOMIC); +} +/* + * One tasklet per cpu tries to send more skbs. + * We run in tasklet context but need to disable irqs when + * transferring tsq->head because tcp_wfree() might + * interrupt us (non NAPI drivers) + */ +static void tcp_tasklet_func(unsigned long data) +{ + struct tsq_tasklet *tsq = (struct tsq_tasklet *)data; + LIST_HEAD(list); + unsigned long flags; + struct list_head *q, *n; + struct tcp_sock *tp; + struct sock *sk; + + local_irq_save(flags); + list_splice_init(&tsq->head, &list); + local_irq_restore(flags); + + list_for_each_safe(q, n, &list) { + tp = list_entry(q, struct tcp_sock, tsq_node); + list_del(&tp->tsq_node); + + sk = (struct sock *)tp; + bh_lock_sock(sk); + + if (!sock_owned_by_user(sk)) { + tcp_tsq_handler(sk); + } else { + /* defer the work to tcp_release_cb() */ + set_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags); + } + bh_unlock_sock(sk); + + clear_bit(TSQ_QUEUED, &tp->tsq_flags); + sk_free(sk); + } +} + +#define TCP_DEFERRED_ALL ((1UL << TCP_TSQ_DEFERRED) | \ + (1UL << TCP_WRITE_TIMER_DEFERRED) | \ + (1UL << TCP_DELACK_TIMER_DEFERRED) | \ + (1UL << TCP_MTU_REDUCED_DEFERRED)) +/** + * tcp_release_cb - tcp release_sock() callback + * @sk: socket + * + * called from release_sock() to perform protocol dependent + * actions before socket release. + */ +void tcp_release_cb(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + unsigned long flags, nflags; + + /* perform an atomic operation only if at least one flag is set */ + do { + flags = tp->tsq_flags; + if (!(flags & TCP_DEFERRED_ALL)) + return; + nflags = flags & ~TCP_DEFERRED_ALL; + } while (cmpxchg(&tp->tsq_flags, flags, nflags) != flags); + + if (flags & (1UL << TCP_TSQ_DEFERRED)) + tcp_tsq_handler(sk); + + /* Here begins the tricky part : + * We are called from release_sock() with : + * 1) BH disabled + * 2) sk_lock.slock spinlock held + * 3) socket owned by us (sk->sk_lock.owned == 1) + * + * But following code is meant to be called from BH handlers, + * so we should keep BH disabled, but early release socket ownership + */ + sock_release_ownership(sk); + + if (flags & (1UL << TCP_WRITE_TIMER_DEFERRED)) { + tcp_write_timer_handler(sk); + __sock_put(sk); + } + if (flags & (1UL << TCP_DELACK_TIMER_DEFERRED)) { + tcp_delack_timer_handler(sk); + __sock_put(sk); + } + if (flags & (1UL << TCP_MTU_REDUCED_DEFERRED)) { + inet_csk(sk)->icsk_af_ops->mtu_reduced(sk); + __sock_put(sk); + } +} +EXPORT_SYMBOL(tcp_release_cb); + +void __init tcp_tasklet_init(void) +{ + int i; + + for_each_possible_cpu(i) { + struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i); + + INIT_LIST_HEAD(&tsq->head); + tasklet_init(&tsq->tasklet, + tcp_tasklet_func, + (unsigned long)tsq); + } +} + +/* + * Write buffer destructor automatically called from kfree_skb. + * We can't xmit new skbs from this context, as we might already + * hold qdisc lock. + */ +void tcp_wfree(struct sk_buff *skb) +{ + struct sock *sk = skb->sk; + struct tcp_sock *tp = tcp_sk(sk); + int wmem; + + /* Keep one reference on sk_wmem_alloc. + * Will be released by sk_free() from here or tcp_tasklet_func() + */ + wmem = atomic_sub_return(skb->truesize - 1, &sk->sk_wmem_alloc); + + /* If this softirq is serviced by ksoftirqd, we are likely under stress. + * Wait until our queues (qdisc + devices) are drained. + * This gives : + * - less callbacks to tcp_write_xmit(), reducing stress (batches) + * - chance for incoming ACK (processed by another cpu maybe) + * to migrate this flow (skb->ooo_okay will be eventually set) + */ + if (wmem >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current) + goto out; + + if (test_and_clear_bit(TSQ_THROTTLED, &tp->tsq_flags) && + !test_and_set_bit(TSQ_QUEUED, &tp->tsq_flags)) { + unsigned long flags; + struct tsq_tasklet *tsq; + + /* queue this socket to tasklet queue */ + local_irq_save(flags); + tsq = this_cpu_ptr(&tsq_tasklet); + list_add(&tp->tsq_node, &tsq->head); + tasklet_schedule(&tsq->tasklet); + local_irq_restore(flags); + return; + } +out: + sk_free(sk); +} + +/* This routine actually transmits TCP packets queued in by + * tcp_do_sendmsg(). This is used by both the initial + * transmission and possible later retransmissions. + * All SKB's seen here are completely headerless. It is our + * job to build the TCP header, and pass the packet down to + * IP so it can do the same plus pass the packet off to the + * device. + * + * We are working here with either a clone of the original + * SKB, or a fresh unique copy made by the retransmit engine. + */ +static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, + gfp_t gfp_mask) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); + struct inet_sock *inet; + struct tcp_sock *tp; + struct tcp_skb_cb *tcb; + struct tcp_out_options opts; + unsigned int tcp_options_size, tcp_header_size; + struct tcp_md5sig_key *md5; + struct tcphdr *th; + int err; + + BUG_ON(!skb || !tcp_skb_pcount(skb)); + + if (clone_it) { + skb_mstamp_get(&skb->skb_mstamp); + + if (unlikely(skb_cloned(skb))) + skb = pskb_copy(skb, gfp_mask); + else + skb = skb_clone(skb, gfp_mask); + if (unlikely(!skb)) + return -ENOBUFS; + } + + inet = inet_sk(sk); + tp = tcp_sk(sk); + tcb = TCP_SKB_CB(skb); + memset(&opts, 0, sizeof(opts)); + +#ifdef TCP_STEALTH + if (unlikely(tcb->tcp_flags & TCPHDR_SYN && + tp->stealth.mode & TCP_STEALTH_MODE_AUTH)) { + skb->skb_mstamp = tp->stealth.mstamp; + } +#endif + + if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) + tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5); + else + tcp_options_size = tcp_established_options(sk, skb, &opts, + &md5); + tcp_header_size = tcp_options_size + sizeof(struct tcphdr); + + if (tcp_packets_in_flight(tp) == 0) + tcp_ca_event(sk, CA_EVENT_TX_START); + + /* if no packet is in qdisc/device queue, then allow XPS to select + * another queue. We can be called from tcp_tsq_handler() + * which holds one reference to sk_wmem_alloc. + * + * TODO: Ideally, in-flight pure ACK packets should not matter here. + * One way to get this would be to set skb->truesize = 2 on them. + */ + skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1); + + skb_push(skb, tcp_header_size); + skb_reset_transport_header(skb); + + skb_orphan(skb); + skb->sk = sk; + skb->destructor = skb_is_tcp_pure_ack(skb) ? sock_wfree : tcp_wfree; + skb_set_hash_from_sk(skb, sk); + atomic_add(skb->truesize, &sk->sk_wmem_alloc); + + /* Build TCP header and checksum it. */ + th = tcp_hdr(skb); + th->source = inet->inet_sport; + th->dest = inet->inet_dport; + th->seq = htonl(tcb->seq); + th->ack_seq = htonl(tp->rcv_nxt); + *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) | + tcb->tcp_flags); + + if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) { + /* RFC1323: The window in SYN & SYN/ACK segments + * is never scaled. + */ + th->window = htons(min(tp->rcv_wnd, 65535U)); + } else { + th->window = htons(tcp_select_window(sk)); + } + th->check = 0; + th->urg_ptr = 0; + + /* The urg_mode check is necessary during a below snd_una win probe */ + if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) { + if (before(tp->snd_up, tcb->seq + 0x10000)) { + th->urg_ptr = htons(tp->snd_up - tcb->seq); + th->urg = 1; + } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) { + th->urg_ptr = htons(0xFFFF); + th->urg = 1; + } + } + + tcp_options_write((__be32 *)(th + 1), tp, &opts); + if (likely((tcb->tcp_flags & TCPHDR_SYN) == 0)) + tcp_ecn_send(sk, skb, tcp_header_size); + +#ifdef CONFIG_TCP_MD5SIG + /* Calculate the MD5 hash, as we have all we need now */ + if (md5) { + sk_nocaps_add(sk, NETIF_F_GSO_MASK); + tp->af_specific->calc_md5_hash(opts.hash_location, + md5, sk, skb); + } +#endif + + icsk->icsk_af_ops->send_check(sk, skb); + + if (likely(tcb->tcp_flags & TCPHDR_ACK)) + tcp_event_ack_sent(sk, tcp_skb_pcount(skb)); + + if (skb->len != tcp_header_size) + tcp_event_data_sent(tp, sk); + + if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq) + TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS, + tcp_skb_pcount(skb)); + + /* OK, its time to fill skb_shinfo(skb)->gso_segs */ + skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb); + + /* Our usage of tstamp should remain private */ + skb->tstamp.tv64 = 0; + + /* Cleanup our debris for IP stacks */ + memset(skb->cb, 0, max(sizeof(struct inet_skb_parm), + sizeof(struct inet6_skb_parm))); + + err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl); + + if (likely(err <= 0)) + return err; + + tcp_enter_cwr(sk); + + return net_xmit_eval(err); +} + +/* This routine just queues the buffer for sending. + * + * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames, + * otherwise socket can stall. + */ +static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + + /* Advance write_seq and place onto the write_queue. */ + tp->write_seq = TCP_SKB_CB(skb)->end_seq; + __skb_header_release(skb); + tcp_add_write_queue_tail(sk, skb); + sk->sk_wmem_queued += skb->truesize; + sk_mem_charge(sk, skb->truesize); +} + +/* Initialize TSO segments for a packet. */ +static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb, + unsigned int mss_now) +{ + struct skb_shared_info *shinfo = skb_shinfo(skb); + + /* Make sure we own this skb before messing gso_size/gso_segs */ + WARN_ON_ONCE(skb_cloned(skb)); + + if (skb->len <= mss_now || skb->ip_summed == CHECKSUM_NONE) { + /* Avoid the costly divide in the normal + * non-TSO case. + */ + tcp_skb_pcount_set(skb, 1); + shinfo->gso_size = 0; + shinfo->gso_type = 0; + } else { + tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now)); + shinfo->gso_size = mss_now; + shinfo->gso_type = sk->sk_gso_type; + } +} + +/* When a modification to fackets out becomes necessary, we need to check + * skb is counted to fackets_out or not. + */ +static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb, + int decr) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (!tp->sacked_out || tcp_is_reno(tp)) + return; + + if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq)) + tp->fackets_out -= decr; +} + +/* Pcount in the middle of the write queue got changed, we need to do various + * tweaks to fix counters + */ +static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr) +{ + struct tcp_sock *tp = tcp_sk(sk); + + tp->packets_out -= decr; + + if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) + tp->sacked_out -= decr; + if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) + tp->retrans_out -= decr; + if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) + tp->lost_out -= decr; + + /* Reno case is special. Sigh... */ + if (tcp_is_reno(tp) && decr > 0) + tp->sacked_out -= min_t(u32, tp->sacked_out, decr); + + tcp_adjust_fackets_out(sk, skb, decr); + + if (tp->lost_skb_hint && + before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) && + (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))) + tp->lost_cnt_hint -= decr; + + tcp_verify_left_out(tp); +} + +static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2) +{ + struct skb_shared_info *shinfo = skb_shinfo(skb); + + if (unlikely(shinfo->tx_flags & SKBTX_ANY_TSTAMP) && + !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) { + struct skb_shared_info *shinfo2 = skb_shinfo(skb2); + u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP; + + shinfo->tx_flags &= ~tsflags; + shinfo2->tx_flags |= tsflags; + swap(shinfo->tskey, shinfo2->tskey); + } +} + +/* Function to create two new TCP segments. Shrinks the given segment + * to the specified size and appends a new segment with the rest of the + * packet to the list. This won't be called frequently, I hope. + * Remember, these are still headerless SKBs at this point. + */ +int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, + unsigned int mss_now, gfp_t gfp) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *buff; + int nsize, old_factor; + int nlen; + u8 flags; + + if (WARN_ON(len > skb->len)) + return -EINVAL; + + nsize = skb_headlen(skb) - len; + if (nsize < 0) + nsize = 0; + + if (skb_unclone(skb, gfp)) + return -ENOMEM; + + /* Get a new skb... force flag on. */ + buff = sk_stream_alloc_skb(sk, nsize, gfp); + if (!buff) + return -ENOMEM; /* We'll just try again later. */ + + sk->sk_wmem_queued += buff->truesize; + sk_mem_charge(sk, buff->truesize); + nlen = skb->len - len - nsize; + buff->truesize += nlen; + skb->truesize -= nlen; + + /* Correct the sequence numbers. */ + TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; + TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; + TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; + + /* PSH and FIN should only be set in the second packet. */ + flags = TCP_SKB_CB(skb)->tcp_flags; + TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH); + TCP_SKB_CB(buff)->tcp_flags = flags; + TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked; + + if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) { + /* Copy and checksum data tail into the new buffer. */ + buff->csum = csum_partial_copy_nocheck(skb->data + len, + skb_put(buff, nsize), + nsize, 0); + + skb_trim(skb, len); + + skb->csum = csum_block_sub(skb->csum, buff->csum, len); + } else { + skb->ip_summed = CHECKSUM_PARTIAL; + skb_split(skb, buff, len); + } + + buff->ip_summed = skb->ip_summed; + + buff->tstamp = skb->tstamp; + tcp_fragment_tstamp(skb, buff); + + old_factor = tcp_skb_pcount(skb); + + /* Fix up tso_factor for both original and new SKB. */ + tcp_set_skb_tso_segs(sk, skb, mss_now); + tcp_set_skb_tso_segs(sk, buff, mss_now); + + /* If this packet has been sent out already, we must + * adjust the various packet counters. + */ + if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) { + int diff = old_factor - tcp_skb_pcount(skb) - + tcp_skb_pcount(buff); + + if (diff) + tcp_adjust_pcount(sk, skb, diff); + } + + /* Link BUFF into the send queue. */ + __skb_header_release(buff); + tcp_insert_write_queue_after(skb, buff, sk); + + return 0; +} + +/* This is similar to __pskb_pull_head() (it will go to core/skbuff.c + * eventually). The difference is that pulled data not copied, but + * immediately discarded. + */ +static void __pskb_trim_head(struct sk_buff *skb, int len) +{ + struct skb_shared_info *shinfo; + int i, k, eat; + + eat = min_t(int, len, skb_headlen(skb)); + if (eat) { + __skb_pull(skb, eat); + len -= eat; + if (!len) + return; + } + eat = len; + k = 0; + shinfo = skb_shinfo(skb); + for (i = 0; i < shinfo->nr_frags; i++) { + int size = skb_frag_size(&shinfo->frags[i]); + + if (size <= eat) { + skb_frag_unref(skb, i); + eat -= size; + } else { + shinfo->frags[k] = shinfo->frags[i]; + if (eat) { + shinfo->frags[k].page_offset += eat; + skb_frag_size_sub(&shinfo->frags[k], eat); + eat = 0; + } + k++; + } + } + shinfo->nr_frags = k; + + skb_reset_tail_pointer(skb); + skb->data_len -= len; + skb->len = skb->data_len; +} + +/* Remove acked data from a packet in the transmit queue. */ +int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) +{ + if (skb_unclone(skb, GFP_ATOMIC)) + return -ENOMEM; + + __pskb_trim_head(skb, len); + + TCP_SKB_CB(skb)->seq += len; + skb->ip_summed = CHECKSUM_PARTIAL; + + skb->truesize -= len; + sk->sk_wmem_queued -= len; + sk_mem_uncharge(sk, len); + sock_set_flag(sk, SOCK_QUEUE_SHRUNK); + + /* Any change of skb->len requires recalculation of tso factor. */ + if (tcp_skb_pcount(skb) > 1) + tcp_set_skb_tso_segs(sk, skb, tcp_skb_mss(skb)); + + return 0; +} + +/* Calculate MSS not accounting any TCP options. */ +static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu) +{ + const struct tcp_sock *tp = tcp_sk(sk); + const struct inet_connection_sock *icsk = inet_csk(sk); + int mss_now; + + /* Calculate base mss without TCP options: + It is MMS_S - sizeof(tcphdr) of rfc1122 + */ + mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr); + + /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */ + if (icsk->icsk_af_ops->net_frag_header_len) { + const struct dst_entry *dst = __sk_dst_get(sk); + + if (dst && dst_allfrag(dst)) + mss_now -= icsk->icsk_af_ops->net_frag_header_len; + } + + /* Clamp it (mss_clamp does not include tcp options) */ + if (mss_now > tp->rx_opt.mss_clamp) + mss_now = tp->rx_opt.mss_clamp; + + /* Now subtract optional transport overhead */ + mss_now -= icsk->icsk_ext_hdr_len; + + /* Then reserve room for full set of TCP options and 8 bytes of data */ + if (mss_now < 48) + mss_now = 48; + return mss_now; +} + +/* Calculate MSS. Not accounting for SACKs here. */ +int tcp_mtu_to_mss(struct sock *sk, int pmtu) +{ + /* Subtract TCP options size, not including SACKs */ + return __tcp_mtu_to_mss(sk, pmtu) - + (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr)); +} + +/* Inverse of above */ +int tcp_mss_to_mtu(struct sock *sk, int mss) +{ + const struct tcp_sock *tp = tcp_sk(sk); + const struct inet_connection_sock *icsk = inet_csk(sk); + int mtu; + + mtu = mss + + tp->tcp_header_len + + icsk->icsk_ext_hdr_len + + icsk->icsk_af_ops->net_header_len; + + /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */ + if (icsk->icsk_af_ops->net_frag_header_len) { + const struct dst_entry *dst = __sk_dst_get(sk); + + if (dst && dst_allfrag(dst)) + mtu += icsk->icsk_af_ops->net_frag_header_len; + } + return mtu; +} + +/* MTU probing init per socket */ +void tcp_mtup_init(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct inet_connection_sock *icsk = inet_csk(sk); + struct net *net = sock_net(sk); + + icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1; + icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) + + icsk->icsk_af_ops->net_header_len; + icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss); + icsk->icsk_mtup.probe_size = 0; + if (icsk->icsk_mtup.enabled) + icsk->icsk_mtup.probe_timestamp = tcp_time_stamp; +} +EXPORT_SYMBOL(tcp_mtup_init); + +/* This function synchronize snd mss to current pmtu/exthdr set. + + tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts + for TCP options, but includes only bare TCP header. + + tp->rx_opt.mss_clamp is mss negotiated at connection setup. + It is minimum of user_mss and mss received with SYN. + It also does not include TCP options. + + inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function. + + tp->mss_cache is current effective sending mss, including + all tcp options except for SACKs. It is evaluated, + taking into account current pmtu, but never exceeds + tp->rx_opt.mss_clamp. + + NOTE1. rfc1122 clearly states that advertised MSS + DOES NOT include either tcp or ip options. + + NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache + are READ ONLY outside this function. --ANK (980731) + */ +unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct inet_connection_sock *icsk = inet_csk(sk); + int mss_now; + + if (icsk->icsk_mtup.search_high > pmtu) + icsk->icsk_mtup.search_high = pmtu; + + mss_now = tcp_mtu_to_mss(sk, pmtu); + mss_now = tcp_bound_to_half_wnd(tp, mss_now); + + /* And store cached results */ + icsk->icsk_pmtu_cookie = pmtu; + if (icsk->icsk_mtup.enabled) + mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low)); + tp->mss_cache = mss_now; + + return mss_now; +} +EXPORT_SYMBOL(tcp_sync_mss); + +/* Compute the current effective MSS, taking SACKs and IP options, + * and even PMTU discovery events into account. + */ +unsigned int tcp_current_mss(struct sock *sk) +{ + const struct tcp_sock *tp = tcp_sk(sk); + const struct dst_entry *dst = __sk_dst_get(sk); + u32 mss_now; + unsigned int header_len; + struct tcp_out_options opts; + struct tcp_md5sig_key *md5; + + mss_now = tp->mss_cache; + + if (dst) { + u32 mtu = dst_mtu(dst); + if (mtu != inet_csk(sk)->icsk_pmtu_cookie) + mss_now = tcp_sync_mss(sk, mtu); + } + + header_len = tcp_established_options(sk, NULL, &opts, &md5) + + sizeof(struct tcphdr); + /* The mss_cache is sized based on tp->tcp_header_len, which assumes + * some common options. If this is an odd packet (because we have SACK + * blocks etc) then our calculated header_len will be different, and + * we have to adjust mss_now correspondingly */ + if (header_len != tp->tcp_header_len) { + int delta = (int) header_len - tp->tcp_header_len; + mss_now -= delta; + } + + return mss_now; +} + +/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. + * As additional protections, we do not touch cwnd in retransmission phases, + * and if application hit its sndbuf limit recently. + */ +static void tcp_cwnd_application_limited(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open && + sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { + /* Limited by application or receiver window. */ + u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk)); + u32 win_used = max(tp->snd_cwnd_used, init_win); + if (win_used < tp->snd_cwnd) { + tp->snd_ssthresh = tcp_current_ssthresh(sk); + tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; + } + tp->snd_cwnd_used = 0; + } + tp->snd_cwnd_stamp = tcp_time_stamp; +} + +static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited) +{ + struct tcp_sock *tp = tcp_sk(sk); + + /* Track the maximum number of outstanding packets in each + * window, and remember whether we were cwnd-limited then. + */ + if (!before(tp->snd_una, tp->max_packets_seq) || + tp->packets_out > tp->max_packets_out) { + tp->max_packets_out = tp->packets_out; + tp->max_packets_seq = tp->snd_nxt; + tp->is_cwnd_limited = is_cwnd_limited; + } + + if (tcp_is_cwnd_limited(sk)) { + /* Network is feed fully. */ + tp->snd_cwnd_used = 0; + tp->snd_cwnd_stamp = tcp_time_stamp; + } else { + /* Network starves. */ + if (tp->packets_out > tp->snd_cwnd_used) + tp->snd_cwnd_used = tp->packets_out; + + if (sysctl_tcp_slow_start_after_idle && + (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto) + tcp_cwnd_application_limited(sk); + } +} + +/* Minshall's variant of the Nagle send check. */ +static bool tcp_minshall_check(const struct tcp_sock *tp) +{ + return after(tp->snd_sml, tp->snd_una) && + !after(tp->snd_sml, tp->snd_nxt); +} + +/* Update snd_sml if this skb is under mss + * Note that a TSO packet might end with a sub-mss segment + * The test is really : + * if ((skb->len % mss) != 0) + * tp->snd_sml = TCP_SKB_CB(skb)->end_seq; + * But we can avoid doing the divide again given we already have + * skb_pcount = skb->len / mss_now + */ +static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now, + const struct sk_buff *skb) +{ + if (skb->len < tcp_skb_pcount(skb) * mss_now) + tp->snd_sml = TCP_SKB_CB(skb)->end_seq; +} + +/* Return false, if packet can be sent now without violation Nagle's rules: + * 1. It is full sized. (provided by caller in %partial bool) + * 2. Or it contains FIN. (already checked by caller) + * 3. Or TCP_CORK is not set, and TCP_NODELAY is set. + * 4. Or TCP_CORK is not set, and all sent packets are ACKed. + * With Minshall's modification: all sent small packets are ACKed. + */ +static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp, + int nonagle) +{ + return partial && + ((nonagle & TCP_NAGLE_CORK) || + (!nonagle && tp->packets_out && tcp_minshall_check(tp))); +} + +/* Return how many segs we'd like on a TSO packet, + * to send one TSO packet per ms + */ +static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now) +{ + u32 bytes, segs; + + bytes = min(sk->sk_pacing_rate >> 10, + sk->sk_gso_max_size - 1 - MAX_TCP_HEADER); + + /* Goal is to send at least one packet per ms, + * not one big TSO packet every 100 ms. + * This preserves ACK clocking and is consistent + * with tcp_tso_should_defer() heuristic. + */ + segs = max_t(u32, bytes / mss_now, sysctl_tcp_min_tso_segs); + + return min_t(u32, segs, sk->sk_gso_max_segs); +} + +/* Returns the portion of skb which can be sent right away */ +static unsigned int tcp_mss_split_point(const struct sock *sk, + const struct sk_buff *skb, + unsigned int mss_now, + unsigned int max_segs, + int nonagle) +{ + const struct tcp_sock *tp = tcp_sk(sk); + u32 partial, needed, window, max_len; + + window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; + max_len = mss_now * max_segs; + + if (likely(max_len <= window && skb != tcp_write_queue_tail(sk))) + return max_len; + + needed = min(skb->len, window); + + if (max_len <= needed) + return max_len; + + partial = needed % mss_now; + /* If last segment is not a full MSS, check if Nagle rules allow us + * to include this last segment in this skb. + * Otherwise, we'll split the skb at last MSS boundary + */ + if (tcp_nagle_check(partial != 0, tp, nonagle)) + return needed - partial; + + return needed; +} + +/* Can at least one segment of SKB be sent right now, according to the + * congestion window rules? If so, return how many segments are allowed. + */ +static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp, + const struct sk_buff *skb) +{ + u32 in_flight, cwnd, halfcwnd; + + /* Don't be strict about the congestion window for the final FIN. */ + if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) && + tcp_skb_pcount(skb) == 1) + return 1; + + in_flight = tcp_packets_in_flight(tp); + cwnd = tp->snd_cwnd; + if (in_flight >= cwnd) + return 0; + + /* For better scheduling, ensure we have at least + * 2 GSO packets in flight. + */ + halfcwnd = max(cwnd >> 1, 1U); + return min(halfcwnd, cwnd - in_flight); +} + +/* Initialize TSO state of a skb. + * This must be invoked the first time we consider transmitting + * SKB onto the wire. + */ +static int tcp_init_tso_segs(const struct sock *sk, struct sk_buff *skb, + unsigned int mss_now) +{ + int tso_segs = tcp_skb_pcount(skb); + + if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) { + tcp_set_skb_tso_segs(sk, skb, mss_now); + tso_segs = tcp_skb_pcount(skb); + } + return tso_segs; +} + + +/* Return true if the Nagle test allows this packet to be + * sent now. + */ +static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb, + unsigned int cur_mss, int nonagle) +{ + /* Nagle rule does not apply to frames, which sit in the middle of the + * write_queue (they have no chances to get new data). + * + * This is implemented in the callers, where they modify the 'nonagle' + * argument based upon the location of SKB in the send queue. + */ + if (nonagle & TCP_NAGLE_PUSH) + return true; + + /* Don't use the nagle rule for urgent data (or for the final FIN). */ + if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)) + return true; + + if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle)) + return true; + + return false; +} + +/* Does at least the first segment of SKB fit into the send window? */ +static bool tcp_snd_wnd_test(const struct tcp_sock *tp, + const struct sk_buff *skb, + unsigned int cur_mss) +{ + u32 end_seq = TCP_SKB_CB(skb)->end_seq; + + if (skb->len > cur_mss) + end_seq = TCP_SKB_CB(skb)->seq + cur_mss; + + return !after(end_seq, tcp_wnd_end(tp)); +} + +/* This checks if the data bearing packet SKB (usually tcp_send_head(sk)) + * should be put on the wire right now. If so, it returns the number of + * packets allowed by the congestion window. + */ +static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb, + unsigned int cur_mss, int nonagle) +{ + const struct tcp_sock *tp = tcp_sk(sk); + unsigned int cwnd_quota; + + tcp_init_tso_segs(sk, skb, cur_mss); + + if (!tcp_nagle_test(tp, skb, cur_mss, nonagle)) + return 0; + + cwnd_quota = tcp_cwnd_test(tp, skb); + if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss)) + cwnd_quota = 0; + + return cwnd_quota; +} + +/* Test if sending is allowed right now. */ +bool tcp_may_send_now(struct sock *sk) +{ + const struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb = tcp_send_head(sk); + + return skb && + tcp_snd_test(sk, skb, tcp_current_mss(sk), + (tcp_skb_is_last(sk, skb) ? + tp->nonagle : TCP_NAGLE_PUSH)); +} + +/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet + * which is put after SKB on the list. It is very much like + * tcp_fragment() except that it may make several kinds of assumptions + * in order to speed up the splitting operation. In particular, we + * know that all the data is in scatter-gather pages, and that the + * packet has never been sent out before (and thus is not cloned). + */ +static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, + unsigned int mss_now, gfp_t gfp) +{ + struct sk_buff *buff; + int nlen = skb->len - len; + u8 flags; + + /* All of a TSO frame must be composed of paged data. */ + if (skb->len != skb->data_len) + return tcp_fragment(sk, skb, len, mss_now, gfp); + + buff = sk_stream_alloc_skb(sk, 0, gfp); + if (unlikely(!buff)) + return -ENOMEM; + + sk->sk_wmem_queued += buff->truesize; + sk_mem_charge(sk, buff->truesize); + buff->truesize += nlen; + skb->truesize -= nlen; + + /* Correct the sequence numbers. */ + TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; + TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; + TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; + + /* PSH and FIN should only be set in the second packet. */ + flags = TCP_SKB_CB(skb)->tcp_flags; + TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH); + TCP_SKB_CB(buff)->tcp_flags = flags; + + /* This packet was never sent out yet, so no SACK bits. */ + TCP_SKB_CB(buff)->sacked = 0; + + buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL; + skb_split(skb, buff, len); + tcp_fragment_tstamp(skb, buff); + + /* Fix up tso_factor for both original and new SKB. */ + tcp_set_skb_tso_segs(sk, skb, mss_now); + tcp_set_skb_tso_segs(sk, buff, mss_now); + + /* Link BUFF into the send queue. */ + __skb_header_release(buff); + tcp_insert_write_queue_after(skb, buff, sk); + + return 0; +} + +/* Try to defer sending, if possible, in order to minimize the amount + * of TSO splitting we do. View it as a kind of TSO Nagle test. + * + * This algorithm is from John Heffner. + */ +static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb, + bool *is_cwnd_limited, u32 max_segs) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); + u32 age, send_win, cong_win, limit, in_flight; + struct tcp_sock *tp = tcp_sk(sk); + struct skb_mstamp now; + struct sk_buff *head; + int win_divisor; + + if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) + goto send_now; + + if (!((1 << icsk->icsk_ca_state) & (TCPF_CA_Open | TCPF_CA_CWR))) + goto send_now; + + /* Avoid bursty behavior by allowing defer + * only if the last write was recent. + */ + if ((s32)(tcp_time_stamp - tp->lsndtime) > 0) + goto send_now; + + in_flight = tcp_packets_in_flight(tp); + + BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight)); + + send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; + + /* From in_flight test above, we know that cwnd > in_flight. */ + cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache; + + limit = min(send_win, cong_win); + + /* If a full-sized TSO skb can be sent, do it. */ + if (limit >= max_segs * tp->mss_cache) + goto send_now; + + /* Middle in queue won't get any more data, full sendable already? */ + if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len)) + goto send_now; + + win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor); + if (win_divisor) { + u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache); + + /* If at least some fraction of a window is available, + * just use it. + */ + chunk /= win_divisor; + if (limit >= chunk) + goto send_now; + } else { + /* Different approach, try not to defer past a single + * ACK. Receiver should ACK every other full sized + * frame, so if we have space for more than 3 frames + * then send now. + */ + if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache) + goto send_now; + } + + head = tcp_write_queue_head(sk); + skb_mstamp_get(&now); + age = skb_mstamp_us_delta(&now, &head->skb_mstamp); + /* If next ACK is likely to come too late (half srtt), do not defer */ + if (age < (tp->srtt_us >> 4)) + goto send_now; + + /* Ok, it looks like it is advisable to defer. */ + + if (cong_win < send_win && cong_win < skb->len) + *is_cwnd_limited = true; + + return true; + +send_now: + return false; +} + +static inline void tcp_mtu_check_reprobe(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + struct net *net = sock_net(sk); + u32 interval; + s32 delta; + + interval = net->ipv4.sysctl_tcp_probe_interval; + delta = tcp_time_stamp - icsk->icsk_mtup.probe_timestamp; + if (unlikely(delta >= interval * HZ)) { + int mss = tcp_current_mss(sk); + + /* Update current search range */ + icsk->icsk_mtup.probe_size = 0; + icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + + sizeof(struct tcphdr) + + icsk->icsk_af_ops->net_header_len; + icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); + + /* Update probe time stamp */ + icsk->icsk_mtup.probe_timestamp = tcp_time_stamp; + } +} + +/* Create a new MTU probe if we are ready. + * MTU probe is regularly attempting to increase the path MTU by + * deliberately sending larger packets. This discovers routing + * changes resulting in larger path MTUs. + * + * Returns 0 if we should wait to probe (no cwnd available), + * 1 if a probe was sent, + * -1 otherwise + */ +static int tcp_mtu_probe(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct inet_connection_sock *icsk = inet_csk(sk); + struct sk_buff *skb, *nskb, *next; + struct net *net = sock_net(sk); + int len; + int probe_size; + int size_needed; + int copy; + int mss_now; + int interval; + + /* Not currently probing/verifying, + * not in recovery, + * have enough cwnd, and + * not SACKing (the variable headers throw things off) */ + if (!icsk->icsk_mtup.enabled || + icsk->icsk_mtup.probe_size || + inet_csk(sk)->icsk_ca_state != TCP_CA_Open || + tp->snd_cwnd < 11 || + tp->rx_opt.num_sacks || tp->rx_opt.dsack) + return -1; + + /* Use binary search for probe_size between tcp_mss_base, + * and current mss_clamp. if (search_high - search_low) + * smaller than a threshold, backoff from probing. + */ + mss_now = tcp_current_mss(sk); + probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high + + icsk->icsk_mtup.search_low) >> 1); + size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache; + interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low; + /* When misfortune happens, we are reprobing actively, + * and then reprobe timer has expired. We stick with current + * probing process by not resetting search range to its orignal. + */ + if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) || + interval < net->ipv4.sysctl_tcp_probe_threshold) { + /* Check whether enough time has elaplased for + * another round of probing. + */ + tcp_mtu_check_reprobe(sk); + return -1; + } + + /* Have enough data in the send queue to probe? */ + if (tp->write_seq - tp->snd_nxt < size_needed) + return -1; + + if (tp->snd_wnd < size_needed) + return -1; + if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp))) + return 0; + + /* Do we need to wait to drain cwnd? With none in flight, don't stall */ + if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) { + if (!tcp_packets_in_flight(tp)) + return -1; + else + return 0; + } + + /* We're allowed to probe. Build it now. */ + nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC); + if (!nskb) + return -1; + sk->sk_wmem_queued += nskb->truesize; + sk_mem_charge(sk, nskb->truesize); + + skb = tcp_send_head(sk); + + TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq; + TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size; + TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK; + TCP_SKB_CB(nskb)->sacked = 0; + nskb->csum = 0; + nskb->ip_summed = skb->ip_summed; + + tcp_insert_write_queue_before(nskb, skb, sk); + + len = 0; + tcp_for_write_queue_from_safe(skb, next, sk) { + copy = min_t(int, skb->len, probe_size - len); + if (nskb->ip_summed) + skb_copy_bits(skb, 0, skb_put(nskb, copy), copy); + else + nskb->csum = skb_copy_and_csum_bits(skb, 0, + skb_put(nskb, copy), + copy, nskb->csum); + + if (skb->len <= copy) { + /* We've eaten all the data from this skb. + * Throw it away. */ + TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags; + tcp_unlink_write_queue(skb, sk); + sk_wmem_free_skb(sk, skb); + } else { + TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags & + ~(TCPHDR_FIN|TCPHDR_PSH); + if (!skb_shinfo(skb)->nr_frags) { + skb_pull(skb, copy); + if (skb->ip_summed != CHECKSUM_PARTIAL) + skb->csum = csum_partial(skb->data, + skb->len, 0); + } else { + __pskb_trim_head(skb, copy); + tcp_set_skb_tso_segs(sk, skb, mss_now); + } + TCP_SKB_CB(skb)->seq += copy; + } + + len += copy; + + if (len >= probe_size) + break; + } + tcp_init_tso_segs(sk, nskb, nskb->len); + + /* We're ready to send. If this fails, the probe will + * be resegmented into mss-sized pieces by tcp_write_xmit(). + */ + if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) { + /* Decrement cwnd here because we are sending + * effectively two packets. */ + tp->snd_cwnd--; + tcp_event_new_data_sent(sk, nskb); + + icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len); + tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq; + tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq; + + return 1; + } + + return -1; +} + +/* This routine writes packets to the network. It advances the + * send_head. This happens as incoming acks open up the remote + * window for us. + * + * LARGESEND note: !tcp_urg_mode is overkill, only frames between + * snd_up-64k-mss .. snd_up cannot be large. However, taking into + * account rare use of URG, this is not a big flaw. + * + * Send at most one packet when push_one > 0. Temporarily ignore + * cwnd limit to force at most one packet out when push_one == 2. + + * Returns true, if no segments are in flight and we have queued segments, + * but cannot send anything now because of SWS or another problem. + */ +static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, + int push_one, gfp_t gfp) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + unsigned int tso_segs, sent_pkts; + int cwnd_quota; + int result; + bool is_cwnd_limited = false; + u32 max_segs; + + sent_pkts = 0; + + if (!push_one) { + /* Do MTU probing. */ + result = tcp_mtu_probe(sk); + if (!result) { + return false; + } else if (result > 0) { + sent_pkts = 1; + } + } + + max_segs = tcp_tso_autosize(sk, mss_now); + while ((skb = tcp_send_head(sk))) { + unsigned int limit; + + tso_segs = tcp_init_tso_segs(sk, skb, mss_now); + BUG_ON(!tso_segs); + + if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) { + /* "skb_mstamp" is used as a start point for the retransmit timer */ + skb_mstamp_get(&skb->skb_mstamp); + goto repair; /* Skip network transmission */ + } + + cwnd_quota = tcp_cwnd_test(tp, skb); + if (!cwnd_quota) { + is_cwnd_limited = true; + if (push_one == 2) + /* Force out a loss probe pkt. */ + cwnd_quota = 1; + else + break; + } + + if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) + break; + + if (tso_segs == 1 || !max_segs) { + if (unlikely(!tcp_nagle_test(tp, skb, mss_now, + (tcp_skb_is_last(sk, skb) ? + nonagle : TCP_NAGLE_PUSH)))) + break; + } else { + if (!push_one && + tcp_tso_should_defer(sk, skb, &is_cwnd_limited, + max_segs)) + break; + } + + limit = mss_now; + if (tso_segs > 1 && max_segs && !tcp_urg_mode(tp)) + limit = tcp_mss_split_point(sk, skb, mss_now, + min_t(unsigned int, + cwnd_quota, + max_segs), + nonagle); + + if (skb->len > limit && + unlikely(tso_fragment(sk, skb, limit, mss_now, gfp))) + break; + + /* TCP Small Queues : + * Control number of packets in qdisc/devices to two packets / or ~1 ms. + * This allows for : + * - better RTT estimation and ACK scheduling + * - faster recovery + * - high rates + * Alas, some drivers / subsystems require a fair amount + * of queued bytes to ensure line rate. + * One example is wifi aggregation (802.11 AMPDU) + */ + limit = max(2 * skb->truesize, sk->sk_pacing_rate >> 10); + limit = min_t(u32, limit, sysctl_tcp_limit_output_bytes); + + if (atomic_read(&sk->sk_wmem_alloc) > limit) { + set_bit(TSQ_THROTTLED, &tp->tsq_flags); + /* It is possible TX completion already happened + * before we set TSQ_THROTTLED, so we must + * test again the condition. + */ + smp_mb__after_atomic(); + if (atomic_read(&sk->sk_wmem_alloc) > limit) + break; + } + + if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp))) + break; + +repair: + /* Advance the send_head. This one is sent out. + * This call will increment packets_out. + */ + tcp_event_new_data_sent(sk, skb); + + tcp_minshall_update(tp, mss_now, skb); + sent_pkts += tcp_skb_pcount(skb); + + if (push_one) + break; + } + + if (likely(sent_pkts)) { + if (tcp_in_cwnd_reduction(sk)) + tp->prr_out += sent_pkts; + + /* Send one loss probe per tail loss episode. */ + if (push_one != 2) + tcp_schedule_loss_probe(sk); + tcp_cwnd_validate(sk, is_cwnd_limited); + return false; + } + return (push_one == 2) || (!tp->packets_out && tcp_send_head(sk)); +} + +bool tcp_schedule_loss_probe(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + u32 timeout, tlp_time_stamp, rto_time_stamp; + u32 rtt = usecs_to_jiffies(tp->srtt_us >> 3); + + if (WARN_ON(icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS)) + return false; + /* No consecutive loss probes. */ + if (WARN_ON(icsk->icsk_pending == ICSK_TIME_LOSS_PROBE)) { + tcp_rearm_rto(sk); + return false; + } + /* Don't do any loss probe on a Fast Open connection before 3WHS + * finishes. + */ + if (sk->sk_state == TCP_SYN_RECV) + return false; + + /* TLP is only scheduled when next timer event is RTO. */ + if (icsk->icsk_pending != ICSK_TIME_RETRANS) + return false; + + /* Schedule a loss probe in 2*RTT for SACK capable connections + * in Open state, that are either limited by cwnd or application. + */ + if (sysctl_tcp_early_retrans < 3 || !tp->srtt_us || !tp->packets_out || + !tcp_is_sack(tp) || inet_csk(sk)->icsk_ca_state != TCP_CA_Open) + return false; + + if ((tp->snd_cwnd > tcp_packets_in_flight(tp)) && + tcp_send_head(sk)) + return false; + + /* Probe timeout is at least 1.5*rtt + TCP_DELACK_MAX to account + * for delayed ack when there's one outstanding packet. + */ + timeout = rtt << 1; + if (tp->packets_out == 1) + timeout = max_t(u32, timeout, + (rtt + (rtt >> 1) + TCP_DELACK_MAX)); + timeout = max_t(u32, timeout, msecs_to_jiffies(10)); + + /* If RTO is shorter, just schedule TLP in its place. */ + tlp_time_stamp = tcp_time_stamp + timeout; + rto_time_stamp = (u32)inet_csk(sk)->icsk_timeout; + if ((s32)(tlp_time_stamp - rto_time_stamp) > 0) { + s32 delta = rto_time_stamp - tcp_time_stamp; + if (delta > 0) + timeout = delta; + } + + inet_csk_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout, + TCP_RTO_MAX); + return true; +} + +/* Thanks to skb fast clones, we can detect if a prior transmit of + * a packet is still in a qdisc or driver queue. + * In this case, there is very little point doing a retransmit ! + * Note: This is called from BH context only. + */ +static bool skb_still_in_host_queue(const struct sock *sk, + const struct sk_buff *skb) +{ + if (unlikely(skb_fclone_busy(sk, skb))) { + NET_INC_STATS_BH(sock_net(sk), + LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES); + return true; + } + return false; +} + +/* When probe timeout (PTO) fires, send a new segment if one exists, else + * retransmit the last segment. + */ +void tcp_send_loss_probe(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + int pcount; + int mss = tcp_current_mss(sk); + int err = -1; + + if (tcp_send_head(sk)) { + err = tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC); + goto rearm_timer; + } + + /* At most one outstanding TLP retransmission. */ + if (tp->tlp_high_seq) + goto rearm_timer; + + /* Retransmit last segment. */ + skb = tcp_write_queue_tail(sk); + if (WARN_ON(!skb)) + goto rearm_timer; + + if (skb_still_in_host_queue(sk, skb)) + goto rearm_timer; + + pcount = tcp_skb_pcount(skb); + if (WARN_ON(!pcount)) + goto rearm_timer; + + if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) { + if (unlikely(tcp_fragment(sk, skb, (pcount - 1) * mss, mss, + GFP_ATOMIC))) + goto rearm_timer; + skb = tcp_write_queue_tail(sk); + } + + if (WARN_ON(!skb || !tcp_skb_pcount(skb))) + goto rearm_timer; + + err = __tcp_retransmit_skb(sk, skb); + + /* Record snd_nxt for loss detection. */ + if (likely(!err)) + tp->tlp_high_seq = tp->snd_nxt; + +rearm_timer: + inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, + inet_csk(sk)->icsk_rto, + TCP_RTO_MAX); + + if (likely(!err)) + NET_INC_STATS_BH(sock_net(sk), + LINUX_MIB_TCPLOSSPROBES); +} + +/* Push out any pending frames which were held back due to + * TCP_CORK or attempt at coalescing tiny packets. + * The socket must be locked by the caller. + */ +void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss, + int nonagle) +{ + /* If we are closed, the bytes will have to remain here. + * In time closedown will finish, we empty the write queue and + * all will be happy. + */ + if (unlikely(sk->sk_state == TCP_CLOSE)) + return; + + if (tcp_write_xmit(sk, cur_mss, nonagle, 0, + sk_gfp_atomic(sk, GFP_ATOMIC))) + tcp_check_probe_timer(sk); +} + +/* Send _single_ skb sitting at the send head. This function requires + * true push pending frames to setup probe timer etc. + */ +void tcp_push_one(struct sock *sk, unsigned int mss_now) +{ + struct sk_buff *skb = tcp_send_head(sk); + + BUG_ON(!skb || skb->len < mss_now); + + tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation); +} + +/* This function returns the amount that we can raise the + * usable window based on the following constraints + * + * 1. The window can never be shrunk once it is offered (RFC 793) + * 2. We limit memory per socket + * + * RFC 1122: + * "the suggested [SWS] avoidance algorithm for the receiver is to keep + * RECV.NEXT + RCV.WIN fixed until: + * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)" + * + * i.e. don't raise the right edge of the window until you can raise + * it at least MSS bytes. + * + * Unfortunately, the recommended algorithm breaks header prediction, + * since header prediction assumes th->window stays fixed. + * + * Strictly speaking, keeping th->window fixed violates the receiver + * side SWS prevention criteria. The problem is that under this rule + * a stream of single byte packets will cause the right side of the + * window to always advance by a single byte. + * + * Of course, if the sender implements sender side SWS prevention + * then this will not be a problem. + * + * BSD seems to make the following compromise: + * + * If the free space is less than the 1/4 of the maximum + * space available and the free space is less than 1/2 mss, + * then set the window to 0. + * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ] + * Otherwise, just prevent the window from shrinking + * and from being larger than the largest representable value. + * + * This prevents incremental opening of the window in the regime + * where TCP is limited by the speed of the reader side taking + * data out of the TCP receive queue. It does nothing about + * those cases where the window is constrained on the sender side + * because the pipeline is full. + * + * BSD also seems to "accidentally" limit itself to windows that are a + * multiple of MSS, at least until the free space gets quite small. + * This would appear to be a side effect of the mbuf implementation. + * Combining these two algorithms results in the observed behavior + * of having a fixed window size at almost all times. + * + * Below we obtain similar behavior by forcing the offered window to + * a multiple of the mss when it is feasible to do so. + * + * Note, we don't "adjust" for TIMESTAMP or SACK option bytes. + * Regular options like TIMESTAMP are taken into account. + */ +u32 __tcp_select_window(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + /* MSS for the peer's data. Previous versions used mss_clamp + * here. I don't know if the value based on our guesses + * of peer's MSS is better for the performance. It's more correct + * but may be worse for the performance because of rcv_mss + * fluctuations. --SAW 1998/11/1 + */ + int mss = icsk->icsk_ack.rcv_mss; + int free_space = tcp_space(sk); + int allowed_space = tcp_full_space(sk); + int full_space = min_t(int, tp->window_clamp, allowed_space); + int window; + + if (mss > full_space) + mss = full_space; + + if (free_space < (full_space >> 1)) { + icsk->icsk_ack.quick = 0; + + if (sk_under_memory_pressure(sk)) + tp->rcv_ssthresh = min(tp->rcv_ssthresh, + 4U * tp->advmss); + + /* free_space might become our new window, make sure we don't + * increase it due to wscale. + */ + free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale); + + /* if free space is less than mss estimate, or is below 1/16th + * of the maximum allowed, try to move to zero-window, else + * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and + * new incoming data is dropped due to memory limits. + * With large window, mss test triggers way too late in order + * to announce zero window in time before rmem limit kicks in. + */ + if (free_space < (allowed_space >> 4) || free_space < mss) + return 0; + } + + if (free_space > tp->rcv_ssthresh) + free_space = tp->rcv_ssthresh; + + /* Don't do rounding if we are using window scaling, since the + * scaled window will not line up with the MSS boundary anyway. + */ + window = tp->rcv_wnd; + if (tp->rx_opt.rcv_wscale) { + window = free_space; + + /* Advertise enough space so that it won't get scaled away. + * Import case: prevent zero window announcement if + * 1<<rcv_wscale > mss. + */ + if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window) + window = (((window >> tp->rx_opt.rcv_wscale) + 1) + << tp->rx_opt.rcv_wscale); + } else { + /* Get the largest window that is a nice multiple of mss. + * Window clamp already applied above. + * If our current window offering is within 1 mss of the + * free space we just keep it. This prevents the divide + * and multiply from happening most of the time. + * We also don't do any window rounding when the free space + * is too small. + */ + if (window <= free_space - mss || window > free_space) + window = (free_space / mss) * mss; + else if (mss == full_space && + free_space > window + (full_space >> 1)) + window = free_space; + } + + return window; +} + +/* Collapses two adjacent SKB's during retransmission. */ +static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *next_skb = tcp_write_queue_next(sk, skb); + int skb_size, next_skb_size; + + skb_size = skb->len; + next_skb_size = next_skb->len; + + BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1); + + tcp_highest_sack_combine(sk, next_skb, skb); + + tcp_unlink_write_queue(next_skb, sk); + + skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size), + next_skb_size); + + if (next_skb->ip_summed == CHECKSUM_PARTIAL) + skb->ip_summed = CHECKSUM_PARTIAL; + + if (skb->ip_summed != CHECKSUM_PARTIAL) + skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size); + + /* Update sequence range on original skb. */ + TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq; + + /* Merge over control information. This moves PSH/FIN etc. over */ + TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags; + + /* All done, get rid of second SKB and account for it so + * packet counting does not break. + */ + TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS; + + /* changed transmit queue under us so clear hints */ + tcp_clear_retrans_hints_partial(tp); + if (next_skb == tp->retransmit_skb_hint) + tp->retransmit_skb_hint = skb; + + tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb)); + + sk_wmem_free_skb(sk, next_skb); +} + +/* Check if coalescing SKBs is legal. */ +static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb) +{ + if (tcp_skb_pcount(skb) > 1) + return false; + /* TODO: SACK collapsing could be used to remove this condition */ + if (skb_shinfo(skb)->nr_frags != 0) + return false; + if (skb_cloned(skb)) + return false; + if (skb == tcp_send_head(sk)) + return false; + /* Some heurestics for collapsing over SACK'd could be invented */ + if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) + return false; + + return true; +} + +/* Collapse packets in the retransmit queue to make to create + * less packets on the wire. This is only done on retransmission. + */ +static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to, + int space) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb = to, *tmp; + bool first = true; + + if (!sysctl_tcp_retrans_collapse) + return; + if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN) + return; + + tcp_for_write_queue_from_safe(skb, tmp, sk) { + if (!tcp_can_collapse(sk, skb)) + break; + + space -= skb->len; + + if (first) { + first = false; + continue; + } + + if (space < 0) + break; + /* Punt if not enough space exists in the first SKB for + * the data in the second + */ + if (skb->len > skb_availroom(to)) + break; + + if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp))) + break; + + tcp_collapse_retrans(sk, to); + } +} + +/* This retransmits one SKB. Policy decisions and retransmit queue + * state updates are done by the caller. Returns non-zero if an + * error occurred which prevented the send. + */ +int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct inet_connection_sock *icsk = inet_csk(sk); + unsigned int cur_mss; + int err; + + /* Inconslusive MTU probe */ + if (icsk->icsk_mtup.probe_size) { + icsk->icsk_mtup.probe_size = 0; + } + + /* Do not sent more than we queued. 1/4 is reserved for possible + * copying overhead: fragmentation, tunneling, mangling etc. + */ + if (atomic_read(&sk->sk_wmem_alloc) > + min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf)) + return -EAGAIN; + + if (skb_still_in_host_queue(sk, skb)) + return -EBUSY; + + if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) { + if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) + BUG(); + if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) + return -ENOMEM; + } + + if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk)) + return -EHOSTUNREACH; /* Routing failure or similar. */ + + cur_mss = tcp_current_mss(sk); + + /* If receiver has shrunk his window, and skb is out of + * new window, do not retransmit it. The exception is the + * case, when window is shrunk to zero. In this case + * our retransmit serves as a zero window probe. + */ + if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) && + TCP_SKB_CB(skb)->seq != tp->snd_una) + return -EAGAIN; + + if (skb->len > cur_mss) { + if (tcp_fragment(sk, skb, cur_mss, cur_mss, GFP_ATOMIC)) + return -ENOMEM; /* We'll try again later. */ + } else { + int oldpcount = tcp_skb_pcount(skb); + + if (unlikely(oldpcount > 1)) { + if (skb_unclone(skb, GFP_ATOMIC)) + return -ENOMEM; + tcp_init_tso_segs(sk, skb, cur_mss); + tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb)); + } + } + + tcp_retrans_try_collapse(sk, skb, cur_mss); + + /* Make a copy, if the first transmission SKB clone we made + * is still in somebody's hands, else make a clone. + */ + + /* make sure skb->data is aligned on arches that require it + * and check if ack-trimming & collapsing extended the headroom + * beyond what csum_start can cover. + */ + if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) || + skb_headroom(skb) >= 0xFFFF)) { + struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER, + GFP_ATOMIC); + err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) : + -ENOBUFS; + } else { + err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); + } + + if (likely(!err)) { + TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS; + /* Update global TCP statistics. */ + TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS); + if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN) + NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS); + tp->total_retrans++; + } + return err; +} + +int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + int err = __tcp_retransmit_skb(sk, skb); + + if (err == 0) { +#if FASTRETRANS_DEBUG > 0 + if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { + net_dbg_ratelimited("retrans_out leaked\n"); + } +#endif + if (!tp->retrans_out) + tp->lost_retrans_low = tp->snd_nxt; + TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS; + tp->retrans_out += tcp_skb_pcount(skb); + + /* Save stamp of the first retransmit. */ + if (!tp->retrans_stamp) + tp->retrans_stamp = tcp_skb_timestamp(skb); + + /* snd_nxt is stored to detect loss of retransmitted segment, + * see tcp_input.c tcp_sacktag_write_queue(). + */ + TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt; + } else if (err != -EBUSY) { + NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL); + } + + if (tp->undo_retrans < 0) + tp->undo_retrans = 0; + tp->undo_retrans += tcp_skb_pcount(skb); + return err; +} + +/* Check if we forward retransmits are possible in the current + * window/congestion state. + */ +static bool tcp_can_forward_retransmit(struct sock *sk) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); + const struct tcp_sock *tp = tcp_sk(sk); + + /* Forward retransmissions are possible only during Recovery. */ + if (icsk->icsk_ca_state != TCP_CA_Recovery) + return false; + + /* No forward retransmissions in Reno are possible. */ + if (tcp_is_reno(tp)) + return false; + + /* Yeah, we have to make difficult choice between forward transmission + * and retransmission... Both ways have their merits... + * + * For now we do not retransmit anything, while we have some new + * segments to send. In the other cases, follow rule 3 for + * NextSeg() specified in RFC3517. + */ + + if (tcp_may_send_now(sk)) + return false; + + return true; +} + +/* This gets called after a retransmit timeout, and the initially + * retransmitted data is acknowledged. It tries to continue + * resending the rest of the retransmit queue, until either + * we've sent it all or the congestion window limit is reached. + * If doing SACK, the first ACK which comes back for a timeout + * based retransmit packet might feed us FACK information again. + * If so, we use it to avoid unnecessarily retransmissions. + */ +void tcp_xmit_retransmit_queue(struct sock *sk) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + struct sk_buff *hole = NULL; + u32 last_lost; + int mib_idx; + int fwd_rexmitting = 0; + + if (!tp->packets_out) + return; + + if (!tp->lost_out) + tp->retransmit_high = tp->snd_una; + + if (tp->retransmit_skb_hint) { + skb = tp->retransmit_skb_hint; + last_lost = TCP_SKB_CB(skb)->end_seq; + if (after(last_lost, tp->retransmit_high)) + last_lost = tp->retransmit_high; + } else { + skb = tcp_write_queue_head(sk); + last_lost = tp->snd_una; + } + + tcp_for_write_queue_from(skb, sk) { + __u8 sacked = TCP_SKB_CB(skb)->sacked; + + if (skb == tcp_send_head(sk)) + break; + /* we could do better than to assign each time */ + if (!hole) + tp->retransmit_skb_hint = skb; + + /* Assume this retransmit will generate + * only one packet for congestion window + * calculation purposes. This works because + * tcp_retransmit_skb() will chop up the + * packet to be MSS sized and all the + * packet counting works out. + */ + if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) + return; + + if (fwd_rexmitting) { +begin_fwd: + if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp))) + break; + mib_idx = LINUX_MIB_TCPFORWARDRETRANS; + + } else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) { + tp->retransmit_high = last_lost; + if (!tcp_can_forward_retransmit(sk)) + break; + /* Backtrack if necessary to non-L'ed skb */ + if (hole) { + skb = hole; + hole = NULL; + } + fwd_rexmitting = 1; + goto begin_fwd; + + } else if (!(sacked & TCPCB_LOST)) { + if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED))) + hole = skb; + continue; + + } else { + last_lost = TCP_SKB_CB(skb)->end_seq; + if (icsk->icsk_ca_state != TCP_CA_Loss) + mib_idx = LINUX_MIB_TCPFASTRETRANS; + else + mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS; + } + + if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS)) + continue; + + if (tcp_retransmit_skb(sk, skb)) + return; + + NET_INC_STATS_BH(sock_net(sk), mib_idx); + + if (tcp_in_cwnd_reduction(sk)) + tp->prr_out += tcp_skb_pcount(skb); + + if (skb == tcp_write_queue_head(sk)) + inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, + inet_csk(sk)->icsk_rto, + TCP_RTO_MAX); + } +} + +/* We allow to exceed memory limits for FIN packets to expedite + * connection tear down and (memory) recovery. + * Otherwise tcp_send_fin() could be tempted to either delay FIN + * or even be forced to close flow without any FIN. + */ +static void sk_forced_wmem_schedule(struct sock *sk, int size) +{ + int amt, status; + + if (size <= sk->sk_forward_alloc) + return; + amt = sk_mem_pages(size); + sk->sk_forward_alloc += amt * SK_MEM_QUANTUM; + sk_memory_allocated_add(sk, amt, &status); +} + +/* Send a FIN. The caller locks the socket for us. + * We should try to send a FIN packet really hard, but eventually give up. + */ +void tcp_send_fin(struct sock *sk) +{ + struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk); + struct tcp_sock *tp = tcp_sk(sk); + + /* Optimization, tack on the FIN if we have one skb in write queue and + * this skb was not yet sent, or we are under memory pressure. + * Note: in the latter case, FIN packet will be sent after a timeout, + * as TCP stack thinks it has already been transmitted. + */ + if (tskb && (tcp_send_head(sk) || sk_under_memory_pressure(sk))) { +coalesce: + TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN; + TCP_SKB_CB(tskb)->end_seq++; + tp->write_seq++; + if (!tcp_send_head(sk)) { + /* This means tskb was already sent. + * Pretend we included the FIN on previous transmit. + * We need to set tp->snd_nxt to the value it would have + * if FIN had been sent. This is because retransmit path + * does not change tp->snd_nxt. + */ + tp->snd_nxt++; + return; + } + } else { + skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation); + if (unlikely(!skb)) { + if (tskb) + goto coalesce; + return; + } + skb_reserve(skb, MAX_TCP_HEADER); + sk_forced_wmem_schedule(sk, skb->truesize); + /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */ + tcp_init_nondata_skb(skb, tp->write_seq, + TCPHDR_ACK | TCPHDR_FIN); + tcp_queue_skb(sk, skb); + } + __tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF); +} + +/* We get here when a process closes a file descriptor (either due to + * an explicit close() or as a byproduct of exit()'ing) and there + * was unread data in the receive queue. This behavior is recommended + * by RFC 2525, section 2.17. -DaveM + */ +void tcp_send_active_reset(struct sock *sk, gfp_t priority) +{ + struct sk_buff *skb; + + /* NOTE: No TCP options attached and we never retransmit this. */ + skb = alloc_skb(MAX_TCP_HEADER, priority); + if (!skb) { + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED); + return; + } + + /* Reserve space for headers and prepare control bits. */ + skb_reserve(skb, MAX_TCP_HEADER); + tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk), + TCPHDR_ACK | TCPHDR_RST); + /* Send it off. */ + if (tcp_transmit_skb(sk, skb, 0, priority)) + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED); + + TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS); +} + +/* Send a crossed SYN-ACK during socket establishment. + * WARNING: This routine must only be called when we have already sent + * a SYN packet that crossed the incoming SYN that caused this routine + * to get called. If this assumption fails then the initial rcv_wnd + * and rcv_wscale values will not be correct. + */ +int tcp_send_synack(struct sock *sk) +{ + struct sk_buff *skb; + + skb = tcp_write_queue_head(sk); + if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) { + pr_debug("%s: wrong queue state\n", __func__); + return -EFAULT; + } + if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) { + if (skb_cloned(skb)) { + struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC); + if (!nskb) + return -ENOMEM; + tcp_unlink_write_queue(skb, sk); + __skb_header_release(nskb); + __tcp_add_write_queue_head(sk, nskb); + sk_wmem_free_skb(sk, skb); + sk->sk_wmem_queued += nskb->truesize; + sk_mem_charge(sk, nskb->truesize); + skb = nskb; + } + + TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK; + tcp_ecn_send_synack(sk, skb); + } + return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); +} + +/** + * tcp_make_synack - Prepare a SYN-ACK. + * sk: listener socket + * dst: dst entry attached to the SYNACK + * req: request_sock pointer + * + * Allocate one skb and build a SYNACK packet. + * @dst is consumed : Caller should not use it again. + */ +struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, + struct request_sock *req, + struct tcp_fastopen_cookie *foc) +{ + struct tcp_out_options opts; + struct inet_request_sock *ireq = inet_rsk(req); + struct tcp_sock *tp = tcp_sk(sk); + struct tcphdr *th; + struct sk_buff *skb; + struct tcp_md5sig_key *md5 = NULL; + int tcp_header_size; + int mss; + + skb = sock_wmalloc(sk, MAX_TCP_HEADER, 1, GFP_ATOMIC); + if (unlikely(!skb)) { + dst_release(dst); + return NULL; + } + /* Reserve space for headers. */ + skb_reserve(skb, MAX_TCP_HEADER); + + skb_dst_set(skb, dst); + + mss = dst_metric_advmss(dst); + if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss) + mss = tp->rx_opt.user_mss; + + memset(&opts, 0, sizeof(opts)); +#ifdef CONFIG_SYN_COOKIES + if (unlikely(req->cookie_ts)) + skb->skb_mstamp.stamp_jiffies = cookie_init_timestamp(req); + else +#endif + skb_mstamp_get(&skb->skb_mstamp); + +#ifdef CONFIG_TCP_MD5SIG + rcu_read_lock(); + md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req)); +#endif + tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5, + foc) + sizeof(*th); + + skb_push(skb, tcp_header_size); + skb_reset_transport_header(skb); + + th = tcp_hdr(skb); + memset(th, 0, sizeof(struct tcphdr)); + th->syn = 1; + th->ack = 1; + tcp_ecn_make_synack(req, th, sk); + th->source = htons(ireq->ir_num); + th->dest = ireq->ir_rmt_port; + /* Setting of flags are superfluous here for callers (and ECE is + * not even correctly set) + */ + tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn, + TCPHDR_SYN | TCPHDR_ACK); + + th->seq = htonl(TCP_SKB_CB(skb)->seq); + /* XXX data is queued and acked as is. No buffer/window check */ + th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt); + + /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */ + th->window = htons(min(req->rcv_wnd, 65535U)); + tcp_options_write((__be32 *)(th + 1), tp, &opts); + th->doff = (tcp_header_size >> 2); + TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_OUTSEGS); + +#ifdef CONFIG_TCP_MD5SIG + /* Okay, we have all we need - do the md5 hash if needed */ + if (md5) + tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location, + md5, req_to_sk(req), skb); + rcu_read_unlock(); +#endif + + /* Do not fool tcpdump (if any), clean our debris */ + skb->tstamp.tv64 = 0; + return skb; +} +EXPORT_SYMBOL(tcp_make_synack); + +static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + const struct tcp_congestion_ops *ca; + u32 ca_key = dst_metric(dst, RTAX_CC_ALGO); + + if (ca_key == TCP_CA_UNSPEC) + return; + + rcu_read_lock(); + ca = tcp_ca_find_key(ca_key); + if (likely(ca && try_module_get(ca->owner))) { + module_put(icsk->icsk_ca_ops->owner); + icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst); + icsk->icsk_ca_ops = ca; + } + rcu_read_unlock(); +} + +/* Do all connect socket setups that can be done AF independent. */ +static void tcp_connect_init(struct sock *sk) +{ + const struct dst_entry *dst = __sk_dst_get(sk); + struct tcp_sock *tp = tcp_sk(sk); + __u8 rcv_wscale; + + /* We'll fix this up when we get a response from the other end. + * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT. + */ + tp->tcp_header_len = sizeof(struct tcphdr) + + (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0); + +#ifdef CONFIG_TCP_MD5SIG + if (tp->af_specific->md5_lookup(sk, sk)) + tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED; +#endif + + /* If user gave his TCP_MAXSEG, record it to clamp */ + if (tp->rx_opt.user_mss) + tp->rx_opt.mss_clamp = tp->rx_opt.user_mss; + tp->max_window = 0; + tcp_mtup_init(sk); + tcp_sync_mss(sk, dst_mtu(dst)); + + tcp_ca_dst_init(sk, dst); + + if (!tp->window_clamp) + tp->window_clamp = dst_metric(dst, RTAX_WINDOW); + tp->advmss = dst_metric_advmss(dst); + if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss) + tp->advmss = tp->rx_opt.user_mss; + + tcp_initialize_rcv_mss(sk); + + /* limit the window selection if the user enforce a smaller rx buffer */ + if (sk->sk_userlocks & SOCK_RCVBUF_LOCK && + (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0)) + tp->window_clamp = tcp_full_space(sk); + + tcp_select_initial_window(tcp_full_space(sk), + tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0), + &tp->rcv_wnd, + &tp->window_clamp, + sysctl_tcp_window_scaling, + &rcv_wscale, + dst_metric(dst, RTAX_INITRWND)); + + tp->rx_opt.rcv_wscale = rcv_wscale; + tp->rcv_ssthresh = tp->rcv_wnd; + + sk->sk_err = 0; + sock_reset_flag(sk, SOCK_DONE); + tp->snd_wnd = 0; + tcp_init_wl(tp, 0); + tp->snd_una = tp->write_seq; + tp->snd_sml = tp->write_seq; + tp->snd_up = tp->write_seq; + tp->snd_nxt = tp->write_seq; + + if (likely(!tp->repair)) + tp->rcv_nxt = 0; + else + tp->rcv_tstamp = tcp_time_stamp; + tp->rcv_wup = tp->rcv_nxt; + tp->copied_seq = tp->rcv_nxt; + + inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT; + inet_csk(sk)->icsk_retransmits = 0; + tcp_clear_retrans(tp); +} + +static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); + + tcb->end_seq += skb->len; + __skb_header_release(skb); + __tcp_add_write_queue_tail(sk, skb); + sk->sk_wmem_queued += skb->truesize; + sk_mem_charge(sk, skb->truesize); + tp->write_seq = tcb->end_seq; + tp->packets_out += tcp_skb_pcount(skb); +} + +/* Build and send a SYN with data and (cached) Fast Open cookie. However, + * queue a data-only packet after the regular SYN, such that regular SYNs + * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges + * only the SYN sequence, the data are retransmitted in the first ACK. + * If cookie is not cached or other error occurs, falls back to send a + * regular SYN with Fast Open cookie request option. + */ +static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct tcp_fastopen_request *fo = tp->fastopen_req; + int syn_loss = 0, space, err = 0, copied; + unsigned long last_syn_loss = 0; + struct sk_buff *syn_data; + + tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */ + tcp_fastopen_cache_get(sk, &tp->rx_opt.mss_clamp, &fo->cookie, + &syn_loss, &last_syn_loss); + /* Recurring FO SYN losses: revert to regular handshake temporarily */ + if (syn_loss > 1 && + time_before(jiffies, last_syn_loss + (60*HZ << syn_loss))) { + fo->cookie.len = -1; + goto fallback; + } + + if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE) + fo->cookie.len = -1; + else if (fo->cookie.len <= 0) + goto fallback; + + /* MSS for SYN-data is based on cached MSS and bounded by PMTU and + * user-MSS. Reserve maximum option space for middleboxes that add + * private TCP options. The cost is reduced data space in SYN :( + */ + if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->rx_opt.mss_clamp) + tp->rx_opt.mss_clamp = tp->rx_opt.user_mss; + space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) - + MAX_TCP_OPTION_SPACE; + + space = min_t(size_t, space, fo->size); + + /* limit to order-0 allocations */ + space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER)); + + syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation); + if (!syn_data) + goto fallback; + syn_data->ip_summed = CHECKSUM_PARTIAL; + memcpy(syn_data->cb, syn->cb, sizeof(syn->cb)); + copied = copy_from_iter(skb_put(syn_data, space), space, + &fo->data->msg_iter); + if (unlikely(!copied)) { + kfree_skb(syn_data); + goto fallback; + } + if (copied != space) { + skb_trim(syn_data, copied); + space = copied; + } + + /* No more data pending in inet_wait_for_connect() */ + if (space == fo->size) + fo->data = NULL; + fo->copied = space; + + tcp_connect_queue_skb(sk, syn_data); + + err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation); + + syn->skb_mstamp = syn_data->skb_mstamp; + + /* Now full SYN+DATA was cloned and sent (or not), + * remove the SYN from the original skb (syn_data) + * we keep in write queue in case of a retransmit, as we + * also have the SYN packet (with no data) in the same queue. + */ + TCP_SKB_CB(syn_data)->seq++; + TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH; + if (!err) { + tp->syn_data = (fo->copied > 0); + NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT); + goto done; + } + +fallback: + /* Send a regular SYN with Fast Open cookie request option */ + if (fo->cookie.len > 0) + fo->cookie.len = 0; + err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation); + if (err) + tp->syn_fastopen = 0; +done: + fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */ + return err; +} + +/* Build a SYN and send it off. */ +int tcp_connect(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *buff; + int err; + + tcp_connect_init(sk); + + if (unlikely(tp->repair)) { + tcp_finish_connect(sk, NULL); + return 0; + } + + buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation); + if (unlikely(!buff)) + return -ENOBUFS; + + tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN); +#ifdef CONFIG_TCP_STEALTH + /* The timetamp was already made at the time the ISN was generated + * as we need to know its value in the stealth_tcp_sequence_number() + * function. + */ + tp->retrans_stamp = tp->stealth.mstamp.stamp_jiffies; +#else + tp->retrans_stamp = tcp_time_stamp; +#endif + tcp_connect_queue_skb(sk, buff); + tcp_ecn_send_syn(sk, buff); + + /* Send off SYN; include data in Fast Open. */ + err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) : + tcp_transmit_skb(sk, buff, 1, sk->sk_allocation); + if (err == -ECONNREFUSED) + return err; + + /* We change tp->snd_nxt after the tcp_transmit_skb() call + * in order to make this packet get counted in tcpOutSegs. + */ + tp->snd_nxt = tp->write_seq; + tp->pushed_seq = tp->write_seq; + TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS); + + /* Timer for repeating the SYN until an answer. */ + inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, + inet_csk(sk)->icsk_rto, TCP_RTO_MAX); + return 0; +} +EXPORT_SYMBOL(tcp_connect); + +/* Send out a delayed ack, the caller does the policy checking + * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check() + * for details. + */ +void tcp_send_delayed_ack(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + int ato = icsk->icsk_ack.ato; + unsigned long timeout; + + tcp_ca_event(sk, CA_EVENT_DELAYED_ACK); + + if (ato > TCP_DELACK_MIN) { + const struct tcp_sock *tp = tcp_sk(sk); + int max_ato = HZ / 2; + + if (icsk->icsk_ack.pingpong || + (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)) + max_ato = TCP_DELACK_MAX; + + /* Slow path, intersegment interval is "high". */ + + /* If some rtt estimate is known, use it to bound delayed ack. + * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements + * directly. + */ + if (tp->srtt_us) { + int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3), + TCP_DELACK_MIN); + + if (rtt < max_ato) + max_ato = rtt; + } + + ato = min(ato, max_ato); + } + + /* Stay within the limit we were given */ + timeout = jiffies + ato; + + /* Use new timeout only if there wasn't a older one earlier. */ + if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) { + /* If delack timer was blocked or is about to expire, + * send ACK now. + */ + if (icsk->icsk_ack.blocked || + time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) { + tcp_send_ack(sk); + return; + } + + if (!time_before(timeout, icsk->icsk_ack.timeout)) + timeout = icsk->icsk_ack.timeout; + } + icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER; + icsk->icsk_ack.timeout = timeout; + sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout); +} + +/* This routine sends an ack and also updates the window. */ +void tcp_send_ack(struct sock *sk) +{ + struct sk_buff *buff; + + /* If we have been reset, we may not send again. */ + if (sk->sk_state == TCP_CLOSE) + return; + + tcp_ca_event(sk, CA_EVENT_NON_DELAYED_ACK); + + /* We are not putting this on the write queue, so + * tcp_transmit_skb() will set the ownership to this + * sock. + */ + buff = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC)); + if (!buff) { + inet_csk_schedule_ack(sk); + inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN; + inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, + TCP_DELACK_MAX, TCP_RTO_MAX); + return; + } + + /* Reserve space for headers and prepare control bits. */ + skb_reserve(buff, MAX_TCP_HEADER); + tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK); + + /* We do not want pure acks influencing TCP Small Queues or fq/pacing + * too much. + * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784 + * We also avoid tcp_wfree() overhead (cache line miss accessing + * tp->tsq_flags) by using regular sock_wfree() + */ + skb_set_tcp_pure_ack(buff); + + /* Send it off, this clears delayed acks for us. */ + skb_mstamp_get(&buff->skb_mstamp); + tcp_transmit_skb(sk, buff, 0, sk_gfp_atomic(sk, GFP_ATOMIC)); +} +EXPORT_SYMBOL_GPL(tcp_send_ack); + +/* This routine sends a packet with an out of date sequence + * number. It assumes the other end will try to ack it. + * + * Question: what should we make while urgent mode? + * 4.4BSD forces sending single byte of data. We cannot send + * out of window data, because we have SND.NXT==SND.MAX... + * + * Current solution: to send TWO zero-length segments in urgent mode: + * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is + * out-of-date with SND.UNA-1 to probe window. + */ +static int tcp_xmit_probe_skb(struct sock *sk, int urgent) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + + /* We don't queue it, tcp_transmit_skb() sets ownership. */ + skb = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC)); + if (!skb) + return -1; + + /* Reserve space for headers and set control bits. */ + skb_reserve(skb, MAX_TCP_HEADER); + /* Use a previous sequence. This should cause the other + * end to send an ack. Don't queue or clone SKB, just + * send it. + */ + tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK); + skb_mstamp_get(&skb->skb_mstamp); + return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC); +} + +void tcp_send_window_probe(struct sock *sk) +{ + if (sk->sk_state == TCP_ESTABLISHED) { + tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1; + tcp_xmit_probe_skb(sk, 0); + } +} + +/* Initiate keepalive or window probe from timer. */ +int tcp_write_wakeup(struct sock *sk) +{ + struct tcp_sock *tp = tcp_sk(sk); + struct sk_buff *skb; + + if (sk->sk_state == TCP_CLOSE) + return -1; + + skb = tcp_send_head(sk); + if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) { + int err; + unsigned int mss = tcp_current_mss(sk); + unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; + + if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq)) + tp->pushed_seq = TCP_SKB_CB(skb)->end_seq; + + /* We are probing the opening of a window + * but the window size is != 0 + * must have been a result SWS avoidance ( sender ) + */ + if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq || + skb->len > mss) { + seg_size = min(seg_size, mss); + TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH; + if (tcp_fragment(sk, skb, seg_size, mss, GFP_ATOMIC)) + return -1; + } else if (!tcp_skb_pcount(skb)) + tcp_set_skb_tso_segs(sk, skb, mss); + + TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH; + err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); + if (!err) + tcp_event_new_data_sent(sk, skb); + return err; + } else { + if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF)) + tcp_xmit_probe_skb(sk, 1); + return tcp_xmit_probe_skb(sk, 0); + } +} + +/* A window probe timeout has occurred. If window is not closed send + * a partial packet else a zero probe. + */ +void tcp_send_probe0(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct tcp_sock *tp = tcp_sk(sk); + unsigned long probe_max; + int err; + + err = tcp_write_wakeup(sk); + + if (tp->packets_out || !tcp_send_head(sk)) { + /* Cancel probe timer, if it is not required. */ + icsk->icsk_probes_out = 0; + icsk->icsk_backoff = 0; + return; + } + + if (err <= 0) { + if (icsk->icsk_backoff < sysctl_tcp_retries2) + icsk->icsk_backoff++; + icsk->icsk_probes_out++; + probe_max = TCP_RTO_MAX; + } else { + /* If packet was not sent due to local congestion, + * do not backoff and do not remember icsk_probes_out. + * Let local senders to fight for local resources. + * + * Use accumulated backoff yet. + */ + if (!icsk->icsk_probes_out) + icsk->icsk_probes_out = 1; + probe_max = TCP_RESOURCE_PROBE_INTERVAL; + } + inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, + inet_csk_rto_backoff(icsk, probe_max), + TCP_RTO_MAX); +} + +int tcp_rtx_synack(struct sock *sk, struct request_sock *req) +{ + const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific; + struct flowi fl; + int res; + + res = af_ops->send_synack(sk, NULL, &fl, req, 0, NULL); + if (!res) { + TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_RETRANSSEGS); + NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNRETRANS); + } + return res; +} +EXPORT_SYMBOL(tcp_rtx_synack); |