diff options
Diffstat (limited to 'net/dccp/output.c')
| -rw-r--r-- | net/dccp/output.c | 698 |
1 files changed, 698 insertions, 0 deletions
diff --git a/net/dccp/output.c b/net/dccp/output.c new file mode 100644 index 000000000..0248e8a34 --- /dev/null +++ b/net/dccp/output.c @@ -0,0 +1,698 @@ +/* + * net/dccp/output.c + * + * An implementation of the DCCP protocol + * Arnaldo Carvalho de Melo <acme@conectiva.com.br> + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + +#include <linux/dccp.h> +#include <linux/kernel.h> +#include <linux/skbuff.h> +#include <linux/slab.h> + +#include <net/inet_sock.h> +#include <net/sock.h> + +#include "ackvec.h" +#include "ccid.h" +#include "dccp.h" + +static inline void dccp_event_ack_sent(struct sock *sk) +{ + inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK); +} + +/* enqueue @skb on sk_send_head for retransmission, return clone to send now */ +static struct sk_buff *dccp_skb_entail(struct sock *sk, struct sk_buff *skb) +{ + skb_set_owner_w(skb, sk); + WARN_ON(sk->sk_send_head); + sk->sk_send_head = skb; + return skb_clone(sk->sk_send_head, gfp_any()); +} + +/* + * All SKB's seen here are completely headerless. It is our + * job to build the DCCP header, and pass the packet down to + * IP so it can do the same plus pass the packet off to the + * device. + */ +static int dccp_transmit_skb(struct sock *sk, struct sk_buff *skb) +{ + if (likely(skb != NULL)) { + struct inet_sock *inet = inet_sk(sk); + const struct inet_connection_sock *icsk = inet_csk(sk); + struct dccp_sock *dp = dccp_sk(sk); + struct dccp_skb_cb *dcb = DCCP_SKB_CB(skb); + struct dccp_hdr *dh; + /* XXX For now we're using only 48 bits sequence numbers */ + const u32 dccp_header_size = sizeof(*dh) + + sizeof(struct dccp_hdr_ext) + + dccp_packet_hdr_len(dcb->dccpd_type); + int err, set_ack = 1; + u64 ackno = dp->dccps_gsr; + /* + * Increment GSS here already in case the option code needs it. + * Update GSS for real only if option processing below succeeds. + */ + dcb->dccpd_seq = ADD48(dp->dccps_gss, 1); + + switch (dcb->dccpd_type) { + case DCCP_PKT_DATA: + set_ack = 0; + /* fall through */ + case DCCP_PKT_DATAACK: + case DCCP_PKT_RESET: + break; + + case DCCP_PKT_REQUEST: + set_ack = 0; + /* Use ISS on the first (non-retransmitted) Request. */ + if (icsk->icsk_retransmits == 0) + dcb->dccpd_seq = dp->dccps_iss; + /* fall through */ + + case DCCP_PKT_SYNC: + case DCCP_PKT_SYNCACK: + ackno = dcb->dccpd_ack_seq; + /* fall through */ + default: + /* + * Set owner/destructor: some skbs are allocated via + * alloc_skb (e.g. when retransmission may happen). + * Only Data, DataAck, and Reset packets should come + * through here with skb->sk set. + */ + WARN_ON(skb->sk); + skb_set_owner_w(skb, sk); + break; + } + + if (dccp_insert_options(sk, skb)) { + kfree_skb(skb); + return -EPROTO; + } + + + /* Build DCCP header and checksum it. */ + dh = dccp_zeroed_hdr(skb, dccp_header_size); + dh->dccph_type = dcb->dccpd_type; + dh->dccph_sport = inet->inet_sport; + dh->dccph_dport = inet->inet_dport; + dh->dccph_doff = (dccp_header_size + dcb->dccpd_opt_len) / 4; + dh->dccph_ccval = dcb->dccpd_ccval; + dh->dccph_cscov = dp->dccps_pcslen; + /* XXX For now we're using only 48 bits sequence numbers */ + dh->dccph_x = 1; + + dccp_update_gss(sk, dcb->dccpd_seq); + dccp_hdr_set_seq(dh, dp->dccps_gss); + if (set_ack) + dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), ackno); + + switch (dcb->dccpd_type) { + case DCCP_PKT_REQUEST: + dccp_hdr_request(skb)->dccph_req_service = + dp->dccps_service; + /* + * Limit Ack window to ISS <= P.ackno <= GSS, so that + * only Responses to Requests we sent are considered. + */ + dp->dccps_awl = dp->dccps_iss; + break; + case DCCP_PKT_RESET: + dccp_hdr_reset(skb)->dccph_reset_code = + dcb->dccpd_reset_code; + break; + } + + icsk->icsk_af_ops->send_check(sk, skb); + + if (set_ack) + dccp_event_ack_sent(sk); + + DCCP_INC_STATS(DCCP_MIB_OUTSEGS); + + err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl); + return net_xmit_eval(err); + } + return -ENOBUFS; +} + +/** + * dccp_determine_ccmps - Find out about CCID-specific packet-size limits + * We only consider the HC-sender CCID for setting the CCMPS (RFC 4340, 14.), + * since the RX CCID is restricted to feedback packets (Acks), which are small + * in comparison with the data traffic. A value of 0 means "no current CCMPS". + */ +static u32 dccp_determine_ccmps(const struct dccp_sock *dp) +{ + const struct ccid *tx_ccid = dp->dccps_hc_tx_ccid; + + if (tx_ccid == NULL || tx_ccid->ccid_ops == NULL) + return 0; + return tx_ccid->ccid_ops->ccid_ccmps; +} + +unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + struct dccp_sock *dp = dccp_sk(sk); + u32 ccmps = dccp_determine_ccmps(dp); + u32 cur_mps = ccmps ? min(pmtu, ccmps) : pmtu; + + /* Account for header lengths and IPv4/v6 option overhead */ + cur_mps -= (icsk->icsk_af_ops->net_header_len + icsk->icsk_ext_hdr_len + + sizeof(struct dccp_hdr) + sizeof(struct dccp_hdr_ext)); + + /* + * Leave enough headroom for common DCCP header options. + * This only considers options which may appear on DCCP-Data packets, as + * per table 3 in RFC 4340, 5.8. When running out of space for other + * options (eg. Ack Vector which can take up to 255 bytes), it is better + * to schedule a separate Ack. Thus we leave headroom for the following: + * - 1 byte for Slow Receiver (11.6) + * - 6 bytes for Timestamp (13.1) + * - 10 bytes for Timestamp Echo (13.3) + * - 8 bytes for NDP count (7.7, when activated) + * - 6 bytes for Data Checksum (9.3) + * - %DCCPAV_MIN_OPTLEN bytes for Ack Vector size (11.4, when enabled) + */ + cur_mps -= roundup(1 + 6 + 10 + dp->dccps_send_ndp_count * 8 + 6 + + (dp->dccps_hc_rx_ackvec ? DCCPAV_MIN_OPTLEN : 0), 4); + + /* And store cached results */ + icsk->icsk_pmtu_cookie = pmtu; + dp->dccps_mss_cache = cur_mps; + + return cur_mps; +} + +EXPORT_SYMBOL_GPL(dccp_sync_mss); + +void dccp_write_space(struct sock *sk) +{ + struct socket_wq *wq; + + rcu_read_lock(); + wq = rcu_dereference(sk->sk_wq); + if (wq_has_sleeper(wq)) + wake_up_interruptible(&wq->wait); + /* Should agree with poll, otherwise some programs break */ + if (sock_writeable(sk)) + sk_wake_async(sk, SOCK_WAKE_SPACE, POLL_OUT); + + rcu_read_unlock(); +} + +/** + * dccp_wait_for_ccid - Await CCID send permission + * @sk: socket to wait for + * @delay: timeout in jiffies + * + * This is used by CCIDs which need to delay the send time in process context. + */ +static int dccp_wait_for_ccid(struct sock *sk, unsigned long delay) +{ + DEFINE_WAIT(wait); + long remaining; + + prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE); + sk->sk_write_pending++; + release_sock(sk); + + remaining = schedule_timeout(delay); + + lock_sock(sk); + sk->sk_write_pending--; + finish_wait(sk_sleep(sk), &wait); + + if (signal_pending(current) || sk->sk_err) + return -1; + return remaining; +} + +/** + * dccp_xmit_packet - Send data packet under control of CCID + * Transmits next-queued payload and informs CCID to account for the packet. + */ +static void dccp_xmit_packet(struct sock *sk) +{ + int err, len; + struct dccp_sock *dp = dccp_sk(sk); + struct sk_buff *skb = dccp_qpolicy_pop(sk); + + if (unlikely(skb == NULL)) + return; + len = skb->len; + + if (sk->sk_state == DCCP_PARTOPEN) { + const u32 cur_mps = dp->dccps_mss_cache - DCCP_FEATNEG_OVERHEAD; + /* + * See 8.1.5 - Handshake Completion. + * + * For robustness we resend Confirm options until the client has + * entered OPEN. During the initial feature negotiation, the MPS + * is smaller than usual, reduced by the Change/Confirm options. + */ + if (!list_empty(&dp->dccps_featneg) && len > cur_mps) { + DCCP_WARN("Payload too large (%d) for featneg.\n", len); + dccp_send_ack(sk); + dccp_feat_list_purge(&dp->dccps_featneg); + } + + inet_csk_schedule_ack(sk); + inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, + inet_csk(sk)->icsk_rto, + DCCP_RTO_MAX); + DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK; + } else if (dccp_ack_pending(sk)) { + DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATAACK; + } else { + DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_DATA; + } + + err = dccp_transmit_skb(sk, skb); + if (err) + dccp_pr_debug("transmit_skb() returned err=%d\n", err); + /* + * Register this one as sent even if an error occurred. To the remote + * end a local packet drop is indistinguishable from network loss, i.e. + * any local drop will eventually be reported via receiver feedback. + */ + ccid_hc_tx_packet_sent(dp->dccps_hc_tx_ccid, sk, len); + + /* + * If the CCID needs to transfer additional header options out-of-band + * (e.g. Ack Vectors or feature-negotiation options), it activates this + * flag to schedule a Sync. The Sync will automatically incorporate all + * currently pending header options, thus clearing the backlog. + */ + if (dp->dccps_sync_scheduled) + dccp_send_sync(sk, dp->dccps_gsr, DCCP_PKT_SYNC); +} + +/** + * dccp_flush_write_queue - Drain queue at end of connection + * Since dccp_sendmsg queues packets without waiting for them to be sent, it may + * happen that the TX queue is not empty at the end of a connection. We give the + * HC-sender CCID a grace period of up to @time_budget jiffies. If this function + * returns with a non-empty write queue, it will be purged later. + */ +void dccp_flush_write_queue(struct sock *sk, long *time_budget) +{ + struct dccp_sock *dp = dccp_sk(sk); + struct sk_buff *skb; + long delay, rc; + + while (*time_budget > 0 && (skb = skb_peek(&sk->sk_write_queue))) { + rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb); + + switch (ccid_packet_dequeue_eval(rc)) { + case CCID_PACKET_WILL_DEQUEUE_LATER: + /* + * If the CCID determines when to send, the next sending + * time is unknown or the CCID may not even send again + * (e.g. remote host crashes or lost Ack packets). + */ + DCCP_WARN("CCID did not manage to send all packets\n"); + return; + case CCID_PACKET_DELAY: + delay = msecs_to_jiffies(rc); + if (delay > *time_budget) + return; + rc = dccp_wait_for_ccid(sk, delay); + if (rc < 0) + return; + *time_budget -= (delay - rc); + /* check again if we can send now */ + break; + case CCID_PACKET_SEND_AT_ONCE: + dccp_xmit_packet(sk); + break; + case CCID_PACKET_ERR: + skb_dequeue(&sk->sk_write_queue); + kfree_skb(skb); + dccp_pr_debug("packet discarded due to err=%ld\n", rc); + } + } +} + +void dccp_write_xmit(struct sock *sk) +{ + struct dccp_sock *dp = dccp_sk(sk); + struct sk_buff *skb; + + while ((skb = dccp_qpolicy_top(sk))) { + int rc = ccid_hc_tx_send_packet(dp->dccps_hc_tx_ccid, sk, skb); + + switch (ccid_packet_dequeue_eval(rc)) { + case CCID_PACKET_WILL_DEQUEUE_LATER: + return; + case CCID_PACKET_DELAY: + sk_reset_timer(sk, &dp->dccps_xmit_timer, + jiffies + msecs_to_jiffies(rc)); + return; + case CCID_PACKET_SEND_AT_ONCE: + dccp_xmit_packet(sk); + break; + case CCID_PACKET_ERR: + dccp_qpolicy_drop(sk, skb); + dccp_pr_debug("packet discarded due to err=%d\n", rc); + } + } +} + +/** + * dccp_retransmit_skb - Retransmit Request, Close, or CloseReq packets + * There are only four retransmittable packet types in DCCP: + * - Request in client-REQUEST state (sec. 8.1.1), + * - CloseReq in server-CLOSEREQ state (sec. 8.3), + * - Close in node-CLOSING state (sec. 8.3), + * - Acks in client-PARTOPEN state (sec. 8.1.5, handled by dccp_delack_timer()). + * This function expects sk->sk_send_head to contain the original skb. + */ +int dccp_retransmit_skb(struct sock *sk) +{ + WARN_ON(sk->sk_send_head == NULL); + + if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk) != 0) + return -EHOSTUNREACH; /* Routing failure or similar. */ + + /* this count is used to distinguish original and retransmitted skb */ + inet_csk(sk)->icsk_retransmits++; + + return dccp_transmit_skb(sk, skb_clone(sk->sk_send_head, GFP_ATOMIC)); +} + +struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst, + struct request_sock *req) +{ + struct dccp_hdr *dh; + struct dccp_request_sock *dreq; + const u32 dccp_header_size = sizeof(struct dccp_hdr) + + sizeof(struct dccp_hdr_ext) + + sizeof(struct dccp_hdr_response); + struct sk_buff *skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1, + GFP_ATOMIC); + if (skb == NULL) + return NULL; + + /* Reserve space for headers. */ + skb_reserve(skb, sk->sk_prot->max_header); + + skb_dst_set(skb, dst_clone(dst)); + + dreq = dccp_rsk(req); + if (inet_rsk(req)->acked) /* increase GSS upon retransmission */ + dccp_inc_seqno(&dreq->dreq_gss); + DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE; + DCCP_SKB_CB(skb)->dccpd_seq = dreq->dreq_gss; + + /* Resolve feature dependencies resulting from choice of CCID */ + if (dccp_feat_server_ccid_dependencies(dreq)) + goto response_failed; + + if (dccp_insert_options_rsk(dreq, skb)) + goto response_failed; + + /* Build and checksum header */ + dh = dccp_zeroed_hdr(skb, dccp_header_size); + + dh->dccph_sport = htons(inet_rsk(req)->ir_num); + dh->dccph_dport = inet_rsk(req)->ir_rmt_port; + dh->dccph_doff = (dccp_header_size + + DCCP_SKB_CB(skb)->dccpd_opt_len) / 4; + dh->dccph_type = DCCP_PKT_RESPONSE; + dh->dccph_x = 1; + dccp_hdr_set_seq(dh, dreq->dreq_gss); + dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dreq->dreq_gsr); + dccp_hdr_response(skb)->dccph_resp_service = dreq->dreq_service; + + dccp_csum_outgoing(skb); + + /* We use `acked' to remember that a Response was already sent. */ + inet_rsk(req)->acked = 1; + DCCP_INC_STATS(DCCP_MIB_OUTSEGS); + return skb; +response_failed: + kfree_skb(skb); + return NULL; +} + +EXPORT_SYMBOL_GPL(dccp_make_response); + +/* answer offending packet in @rcv_skb with Reset from control socket @ctl */ +struct sk_buff *dccp_ctl_make_reset(struct sock *sk, struct sk_buff *rcv_skb) +{ + struct dccp_hdr *rxdh = dccp_hdr(rcv_skb), *dh; + struct dccp_skb_cb *dcb = DCCP_SKB_CB(rcv_skb); + const u32 dccp_hdr_reset_len = sizeof(struct dccp_hdr) + + sizeof(struct dccp_hdr_ext) + + sizeof(struct dccp_hdr_reset); + struct dccp_hdr_reset *dhr; + struct sk_buff *skb; + + skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC); + if (skb == NULL) + return NULL; + + skb_reserve(skb, sk->sk_prot->max_header); + + /* Swap the send and the receive. */ + dh = dccp_zeroed_hdr(skb, dccp_hdr_reset_len); + dh->dccph_type = DCCP_PKT_RESET; + dh->dccph_sport = rxdh->dccph_dport; + dh->dccph_dport = rxdh->dccph_sport; + dh->dccph_doff = dccp_hdr_reset_len / 4; + dh->dccph_x = 1; + + dhr = dccp_hdr_reset(skb); + dhr->dccph_reset_code = dcb->dccpd_reset_code; + + switch (dcb->dccpd_reset_code) { + case DCCP_RESET_CODE_PACKET_ERROR: + dhr->dccph_reset_data[0] = rxdh->dccph_type; + break; + case DCCP_RESET_CODE_OPTION_ERROR: /* fall through */ + case DCCP_RESET_CODE_MANDATORY_ERROR: + memcpy(dhr->dccph_reset_data, dcb->dccpd_reset_data, 3); + break; + } + /* + * From RFC 4340, 8.3.1: + * If P.ackno exists, set R.seqno := P.ackno + 1. + * Else set R.seqno := 0. + */ + if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ) + dccp_hdr_set_seq(dh, ADD48(dcb->dccpd_ack_seq, 1)); + dccp_hdr_set_ack(dccp_hdr_ack_bits(skb), dcb->dccpd_seq); + + dccp_csum_outgoing(skb); + return skb; +} + +EXPORT_SYMBOL_GPL(dccp_ctl_make_reset); + +/* send Reset on established socket, to close or abort the connection */ +int dccp_send_reset(struct sock *sk, enum dccp_reset_codes code) +{ + struct sk_buff *skb; + /* + * FIXME: what if rebuild_header fails? + * Should we be doing a rebuild_header here? + */ + int err = inet_csk(sk)->icsk_af_ops->rebuild_header(sk); + + if (err != 0) + return err; + + skb = sock_wmalloc(sk, sk->sk_prot->max_header, 1, GFP_ATOMIC); + if (skb == NULL) + return -ENOBUFS; + + /* Reserve space for headers and prepare control bits. */ + skb_reserve(skb, sk->sk_prot->max_header); + DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESET; + DCCP_SKB_CB(skb)->dccpd_reset_code = code; + + return dccp_transmit_skb(sk, skb); +} + +/* + * Do all connect socket setups that can be done AF independent. + */ +int dccp_connect(struct sock *sk) +{ + struct sk_buff *skb; + struct dccp_sock *dp = dccp_sk(sk); + struct dst_entry *dst = __sk_dst_get(sk); + struct inet_connection_sock *icsk = inet_csk(sk); + + sk->sk_err = 0; + sock_reset_flag(sk, SOCK_DONE); + + dccp_sync_mss(sk, dst_mtu(dst)); + + /* do not connect if feature negotiation setup fails */ + if (dccp_feat_finalise_settings(dccp_sk(sk))) + return -EPROTO; + + /* Initialise GAR as per 8.5; AWL/AWH are set in dccp_transmit_skb() */ + dp->dccps_gar = dp->dccps_iss; + + skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation); + if (unlikely(skb == NULL)) + return -ENOBUFS; + + /* Reserve space for headers. */ + skb_reserve(skb, sk->sk_prot->max_header); + + DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_REQUEST; + + dccp_transmit_skb(sk, dccp_skb_entail(sk, skb)); + DCCP_INC_STATS(DCCP_MIB_ACTIVEOPENS); + + /* Timer for repeating the REQUEST until an answer. */ + icsk->icsk_retransmits = 0; + inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, + icsk->icsk_rto, DCCP_RTO_MAX); + return 0; +} + +EXPORT_SYMBOL_GPL(dccp_connect); + +void dccp_send_ack(struct sock *sk) +{ + /* If we have been reset, we may not send again. */ + if (sk->sk_state != DCCP_CLOSED) { + struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, + GFP_ATOMIC); + + if (skb == NULL) { + 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, + DCCP_RTO_MAX); + return; + } + + /* Reserve space for headers */ + skb_reserve(skb, sk->sk_prot->max_header); + DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_ACK; + dccp_transmit_skb(sk, skb); + } +} + +EXPORT_SYMBOL_GPL(dccp_send_ack); + +#if 0 +/* FIXME: Is this still necessary (11.3) - currently nowhere used by DCCP. */ +void dccp_send_delayed_ack(struct sock *sk) +{ + struct inet_connection_sock *icsk = inet_csk(sk); + /* + * FIXME: tune this timer. elapsed time fixes the skew, so no problem + * with using 2s, and active senders also piggyback the ACK into a + * DATAACK packet, so this is really for quiescent senders. + */ + unsigned long timeout = jiffies + 2 * HZ; + + /* 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. + * + * FIXME: check the "about to expire" part + */ + if (icsk->icsk_ack.blocked) { + dccp_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); +} +#endif + +void dccp_send_sync(struct sock *sk, const u64 ackno, + const enum dccp_pkt_type pkt_type) +{ + /* + * We are not putting this on the write queue, so + * dccp_transmit_skb() will set the ownership to this + * sock. + */ + struct sk_buff *skb = alloc_skb(sk->sk_prot->max_header, GFP_ATOMIC); + + if (skb == NULL) { + /* FIXME: how to make sure the sync is sent? */ + DCCP_CRIT("could not send %s", dccp_packet_name(pkt_type)); + return; + } + + /* Reserve space for headers and prepare control bits. */ + skb_reserve(skb, sk->sk_prot->max_header); + DCCP_SKB_CB(skb)->dccpd_type = pkt_type; + DCCP_SKB_CB(skb)->dccpd_ack_seq = ackno; + + /* + * Clear the flag in case the Sync was scheduled for out-of-band data, + * such as carrying a long Ack Vector. + */ + dccp_sk(sk)->dccps_sync_scheduled = 0; + + dccp_transmit_skb(sk, skb); +} + +EXPORT_SYMBOL_GPL(dccp_send_sync); + +/* + * Send a DCCP_PKT_CLOSE/CLOSEREQ. The caller locks the socket for us. This + * cannot be allowed to fail queueing a DCCP_PKT_CLOSE/CLOSEREQ frame under + * any circumstances. + */ +void dccp_send_close(struct sock *sk, const int active) +{ + struct dccp_sock *dp = dccp_sk(sk); + struct sk_buff *skb; + const gfp_t prio = active ? GFP_KERNEL : GFP_ATOMIC; + + skb = alloc_skb(sk->sk_prot->max_header, prio); + if (skb == NULL) + return; + + /* Reserve space for headers and prepare control bits. */ + skb_reserve(skb, sk->sk_prot->max_header); + if (dp->dccps_role == DCCP_ROLE_SERVER && !dp->dccps_server_timewait) + DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSEREQ; + else + DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_CLOSE; + + if (active) { + skb = dccp_skb_entail(sk, skb); + /* + * Retransmission timer for active-close: RFC 4340, 8.3 requires + * to retransmit the Close/CloseReq until the CLOSING/CLOSEREQ + * state can be left. The initial timeout is 2 RTTs. + * Since RTT measurement is done by the CCIDs, there is no easy + * way to get an RTT sample. The fallback RTT from RFC 4340, 3.4 + * is too low (200ms); we use a high value to avoid unnecessary + * retransmissions when the link RTT is > 0.2 seconds. + * FIXME: Let main module sample RTTs and use that instead. + */ + inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, + DCCP_TIMEOUT_INIT, DCCP_RTO_MAX); + } + dccp_transmit_skb(sk, skb); +} |