Initial import

1 files changed, 2468 insertions, 0 deletions

diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
new file mode 100644
index 000000000..1e0ce4d7b
--- /dev/null
+++ b/net/ipv4/tcp_ipv4.c
@@ -0,0 +1,2468 @@
+/*
+ * 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).
+ *
+ *		IPv4 specific functions
+ *
+ *
+ *		code split from:
+ *		linux/ipv4/tcp.c
+ *		linux/ipv4/tcp_input.c
+ *		linux/ipv4/tcp_output.c
+ *
+ *		See tcp.c for author information
+ *
+ *	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.
+ */
+
+/*
+ * Changes:
+ *		David S. Miller	:	New socket lookup architecture.
+ *					This code is dedicated to John Dyson.
+ *		David S. Miller :	Change semantics of established hash,
+ *					half is devoted to TIME_WAIT sockets
+ *					and the rest go in the other half.
+ *		Andi Kleen :		Add support for syncookies and fixed
+ *					some bugs: ip options weren't passed to
+ *					the TCP layer, missed a check for an
+ *					ACK bit.
+ *		Andi Kleen :		Implemented fast path mtu discovery.
+ *	     				Fixed many serious bugs in the
+ *					request_sock handling and moved
+ *					most of it into the af independent code.
+ *					Added tail drop and some other bugfixes.
+ *					Added new listen semantics.
+ *		Mike McLagan	:	Routing by source
+ *	Juan Jose Ciarlante:		ip_dynaddr bits
+ *		Andi Kleen:		various fixes.
+ *	Vitaly E. Lavrov	:	Transparent proxy revived after year
+ *					coma.
+ *	Andi Kleen		:	Fix new listen.
+ *	Andi Kleen		:	Fix accept error reporting.
+ *	YOSHIFUJI Hideaki @USAGI and:	Support IPV6_V6ONLY socket option, which
+ *	Alexey Kuznetsov		allow both IPv4 and IPv6 sockets to bind
+ *					a single port at the same time.
+ */
+
+#define pr_fmt(fmt) "TCP: " fmt
+
+#include <linux/bottom_half.h>
+#include <linux/types.h>
+#include <linux/fcntl.h>
+#include <linux/module.h>
+#include <linux/random.h>
+#include <linux/cache.h>
+#include <linux/jhash.h>
+#include <linux/init.h>
+#include <linux/times.h>
+#include <linux/slab.h>
+
+#include <net/net_namespace.h>
+#include <net/icmp.h>
+#include <net/inet_hashtables.h>
+#include <net/tcp.h>
+#include <net/transp_v6.h>
+#include <net/ipv6.h>
+#include <net/inet_common.h>
+#include <net/timewait_sock.h>
+#include <net/xfrm.h>
+#include <net/secure_seq.h>
+#include <net/tcp_memcontrol.h>
+#include <net/busy_poll.h>
+#include <net/secure_seq.h>
+
+#include <linux/inet.h>
+#include <linux/ipv6.h>
+#include <linux/stddef.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+
+#include <linux/crypto.h>
+#include <linux/scatterlist.h>
+
+int sysctl_tcp_tw_reuse __read_mostly;
+int sysctl_tcp_low_latency __read_mostly;
+EXPORT_SYMBOL(sysctl_tcp_low_latency);
+
+#ifdef CONFIG_TCP_MD5SIG
+static int tcp_v4_md5_hash_hdr(char *md5_hash, const struct tcp_md5sig_key *key,
+			       __be32 daddr, __be32 saddr, const struct tcphdr *th);
+#endif
+
+struct inet_hashinfo tcp_hashinfo;
+EXPORT_SYMBOL(tcp_hashinfo);
+
+static  __u32 tcp_v4_init_sequence(const struct sk_buff *skb)
+{
+	return secure_tcp_sequence_number(ip_hdr(skb)->daddr,
+					  ip_hdr(skb)->saddr,
+					  tcp_hdr(skb)->dest,
+					  tcp_hdr(skb)->source);
+}
+
+int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp)
+{
+	const struct tcp_timewait_sock *tcptw = tcp_twsk(sktw);
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	/* With PAWS, it is safe from the viewpoint
+	   of data integrity. Even without PAWS it is safe provided sequence
+	   spaces do not overlap i.e. at data rates <= 80Mbit/sec.
+
+	   Actually, the idea is close to VJ's one, only timestamp cache is
+	   held not per host, but per port pair and TW bucket is used as state
+	   holder.
+
+	   If TW bucket has been already destroyed we fall back to VJ's scheme
+	   and use initial timestamp retrieved from peer table.
+	 */
+	if (tcptw->tw_ts_recent_stamp &&
+	    (!twp || (sysctl_tcp_tw_reuse &&
+			     get_seconds() - tcptw->tw_ts_recent_stamp > 1))) {
+		tp->write_seq = tcptw->tw_snd_nxt + 65535 + 2;
+		if (tp->write_seq == 0)
+			tp->write_seq = 1;
+		tp->rx_opt.ts_recent	   = tcptw->tw_ts_recent;
+		tp->rx_opt.ts_recent_stamp = tcptw->tw_ts_recent_stamp;
+		sock_hold(sktw);
+		return 1;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tcp_twsk_unique);
+
+/* This will initiate an outgoing connection. */
+int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len)
+{
+	struct sockaddr_in *usin = (struct sockaddr_in *)uaddr;
+	struct inet_sock *inet = inet_sk(sk);
+	struct tcp_sock *tp = tcp_sk(sk);
+	__be16 orig_sport, orig_dport;
+	__be32 daddr, nexthop;
+	struct flowi4 *fl4;
+	struct rtable *rt;
+	int err;
+	struct ip_options_rcu *inet_opt;
+
+	if (addr_len < sizeof(struct sockaddr_in))
+		return -EINVAL;
+
+	if (usin->sin_family != AF_INET)
+		return -EAFNOSUPPORT;
+
+	nexthop = daddr = usin->sin_addr.s_addr;
+	inet_opt = rcu_dereference_protected(inet->inet_opt,
+					     sock_owned_by_user(sk));
+	if (inet_opt && inet_opt->opt.srr) {
+		if (!daddr)
+			return -EINVAL;
+		nexthop = inet_opt->opt.faddr;
+	}
+
+	orig_sport = inet->inet_sport;
+	orig_dport = usin->sin_port;
+	fl4 = &inet->cork.fl.u.ip4;
+	rt = ip_route_connect(fl4, nexthop, inet->inet_saddr,
+			      RT_CONN_FLAGS(sk), sk->sk_bound_dev_if,
+			      IPPROTO_TCP,
+			      orig_sport, orig_dport, sk);
+	if (IS_ERR(rt)) {
+		err = PTR_ERR(rt);
+		if (err == -ENETUNREACH)
+			IP_INC_STATS(sock_net(sk), IPSTATS_MIB_OUTNOROUTES);
+		return err;
+	}
+
+	if (rt->rt_flags & (RTCF_MULTICAST | RTCF_BROADCAST)) {
+		ip_rt_put(rt);
+		return -ENETUNREACH;
+	}
+
+	if (!inet_opt || !inet_opt->opt.srr)
+		daddr = fl4->daddr;
+
+	if (!inet->inet_saddr)
+		inet->inet_saddr = fl4->saddr;
+	sk_rcv_saddr_set(sk, inet->inet_saddr);
+
+	if (tp->rx_opt.ts_recent_stamp && inet->inet_daddr != daddr) {
+		/* Reset inherited state */
+		tp->rx_opt.ts_recent	   = 0;
+		tp->rx_opt.ts_recent_stamp = 0;
+		if (likely(!tp->repair))
+			tp->write_seq	   = 0;
+	}
+
+	if (tcp_death_row.sysctl_tw_recycle &&
+	    !tp->rx_opt.ts_recent_stamp && fl4->daddr == daddr)
+		tcp_fetch_timewait_stamp(sk, &rt->dst);
+
+	inet->inet_dport = usin->sin_port;
+	sk_daddr_set(sk, daddr);
+
+	inet_csk(sk)->icsk_ext_hdr_len = 0;
+	if (inet_opt)
+		inet_csk(sk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
+
+	tp->rx_opt.mss_clamp = TCP_MSS_DEFAULT;
+
+	/* Socket identity is still unknown (sport may be zero).
+	 * However we set state to SYN-SENT and not releasing socket
+	 * lock select source port, enter ourselves into the hash tables and
+	 * complete initialization after this.
+	 */
+	tcp_set_state(sk, TCP_SYN_SENT);
+	err = inet_hash_connect(&tcp_death_row, sk);
+	if (err)
+		goto failure;
+
+	inet_set_txhash(sk);
+
+	rt = ip_route_newports(fl4, rt, orig_sport, orig_dport,
+			       inet->inet_sport, inet->inet_dport, sk);
+	if (IS_ERR(rt)) {
+		err = PTR_ERR(rt);
+		rt = NULL;
+		goto failure;
+	}
+	/* OK, now commit destination to socket.  */
+	sk->sk_gso_type = SKB_GSO_TCPV4;
+	sk_setup_caps(sk, &rt->dst);
+
+#ifdef CONFIG_TCP_STEALTH
+	/* If CONFIG_TCP_STEALTH is defined, we need to know the timestamp as
+	 * early as possible and thus move taking the snapshot of tcp_time_stamp
+	 * here.
+	 */
+	skb_mstamp_get(&tp->stealth.mstamp);
+
+	if (!tp->write_seq && likely(!tp->repair) &&
+	    unlikely(tp->stealth.mode & TCP_STEALTH_MODE_AUTH))
+		tp->write_seq = tcp_stealth_sequence_number(sk,
+					&inet->inet_daddr,
+					sizeof(inet->inet_daddr),
+					usin->sin_port);
+#endif
+
+	if (!tp->write_seq && likely(!tp->repair))
+		tp->write_seq = secure_tcp_sequence_number(inet->inet_saddr,
+							   inet->inet_daddr,
+							   inet->inet_sport,
+							   usin->sin_port);
+
+	inet->inet_id = tp->write_seq ^ jiffies;
+
+	err = tcp_connect(sk);
+
+	rt = NULL;
+	if (err)
+		goto failure;
+
+	return 0;
+
+failure:
+	/*
+	 * This unhashes the socket and releases the local port,
+	 * if necessary.
+	 */
+	tcp_set_state(sk, TCP_CLOSE);
+	ip_rt_put(rt);
+	sk->sk_route_caps = 0;
+	inet->inet_dport = 0;
+	return err;
+}
+EXPORT_SYMBOL(tcp_v4_connect);
+
+/*
+ * This routine reacts to ICMP_FRAG_NEEDED mtu indications as defined in RFC1191.
+ * It can be called through tcp_release_cb() if socket was owned by user
+ * at the time tcp_v4_err() was called to handle ICMP message.
+ */
+void tcp_v4_mtu_reduced(struct sock *sk)
+{
+	struct dst_entry *dst;
+	struct inet_sock *inet = inet_sk(sk);
+	u32 mtu = tcp_sk(sk)->mtu_info;
+
+	dst = inet_csk_update_pmtu(sk, mtu);
+	if (!dst)
+		return;
+
+	/* Something is about to be wrong... Remember soft error
+	 * for the case, if this connection will not able to recover.
+	 */
+	if (mtu < dst_mtu(dst) && ip_dont_fragment(sk, dst))
+		sk->sk_err_soft = EMSGSIZE;
+
+	mtu = dst_mtu(dst);
+
+	if (inet->pmtudisc != IP_PMTUDISC_DONT &&
+	    ip_sk_accept_pmtu(sk) &&
+	    inet_csk(sk)->icsk_pmtu_cookie > mtu) {
+		tcp_sync_mss(sk, mtu);
+
+		/* Resend the TCP packet because it's
+		 * clear that the old packet has been
+		 * dropped. This is the new "fast" path mtu
+		 * discovery.
+		 */
+		tcp_simple_retransmit(sk);
+	} /* else let the usual retransmit timer handle it */
+}
+EXPORT_SYMBOL(tcp_v4_mtu_reduced);
+
+static void do_redirect(struct sk_buff *skb, struct sock *sk)
+{
+	struct dst_entry *dst = __sk_dst_check(sk, 0);
+
+	if (dst)
+		dst->ops->redirect(dst, sk, skb);
+}
+
+
+/* handle ICMP messages on TCP_NEW_SYN_RECV request sockets */
+void tcp_req_err(struct sock *sk, u32 seq)
+{
+	struct request_sock *req = inet_reqsk(sk);
+	struct net *net = sock_net(sk);
+
+	/* ICMPs are not backlogged, hence we cannot get
+	 * an established socket here.
+	 */
+	WARN_ON(req->sk);
+
+	if (seq != tcp_rsk(req)->snt_isn) {
+		NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
+		reqsk_put(req);
+	} else {
+		/*
+		 * Still in SYN_RECV, just remove it silently.
+		 * There is no good way to pass the error to the newly
+		 * created socket, and POSIX does not want network
+		 * errors returned from accept().
+		 */
+		NET_INC_STATS_BH(net, LINUX_MIB_LISTENDROPS);
+		inet_csk_reqsk_queue_drop(req->rsk_listener, req);
+	}
+}
+EXPORT_SYMBOL(tcp_req_err);
+
+/*
+ * This routine is called by the ICMP module when it gets some
+ * sort of error condition.  If err < 0 then the socket should
+ * be closed and the error returned to the user.  If err > 0
+ * it's just the icmp type << 8 | icmp code.  After adjustment
+ * header points to the first 8 bytes of the tcp header.  We need
+ * to find the appropriate port.
+ *
+ * The locking strategy used here is very "optimistic". When
+ * someone else accesses the socket the ICMP is just dropped
+ * and for some paths there is no check at all.
+ * A more general error queue to queue errors for later handling
+ * is probably better.
+ *
+ */
+
+void tcp_v4_err(struct sk_buff *icmp_skb, u32 info)
+{
+	const struct iphdr *iph = (const struct iphdr *)icmp_skb->data;
+	struct tcphdr *th = (struct tcphdr *)(icmp_skb->data + (iph->ihl << 2));
+	struct inet_connection_sock *icsk;
+	struct tcp_sock *tp;
+	struct inet_sock *inet;
+	const int type = icmp_hdr(icmp_skb)->type;
+	const int code = icmp_hdr(icmp_skb)->code;
+	struct sock *sk;
+	struct sk_buff *skb;
+	struct request_sock *fastopen;
+	__u32 seq, snd_una;
+	__u32 remaining;
+	int err;
+	struct net *net = dev_net(icmp_skb->dev);
+
+	sk = __inet_lookup_established(net, &tcp_hashinfo, iph->daddr,
+				       th->dest, iph->saddr, ntohs(th->source),
+				       inet_iif(icmp_skb));
+	if (!sk) {
+		ICMP_INC_STATS_BH(net, ICMP_MIB_INERRORS);
+		return;
+	}
+	if (sk->sk_state == TCP_TIME_WAIT) {
+		inet_twsk_put(inet_twsk(sk));
+		return;
+	}
+	seq = ntohl(th->seq);
+	if (sk->sk_state == TCP_NEW_SYN_RECV)
+		return tcp_req_err(sk, seq);
+
+	bh_lock_sock(sk);
+	/* If too many ICMPs get dropped on busy
+	 * servers this needs to be solved differently.
+	 * We do take care of PMTU discovery (RFC1191) special case :
+	 * we can receive locally generated ICMP messages while socket is held.
+	 */
+	if (sock_owned_by_user(sk)) {
+		if (!(type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED))
+			NET_INC_STATS_BH(net, LINUX_MIB_LOCKDROPPEDICMPS);
+	}
+	if (sk->sk_state == TCP_CLOSE)
+		goto out;
+
+	if (unlikely(iph->ttl < inet_sk(sk)->min_ttl)) {
+		NET_INC_STATS_BH(net, LINUX_MIB_TCPMINTTLDROP);
+		goto out;
+	}
+
+	icsk = inet_csk(sk);
+	tp = tcp_sk(sk);
+	/* XXX (TFO) - tp->snd_una should be ISN (tcp_create_openreq_child() */
+	fastopen = tp->fastopen_rsk;
+	snd_una = fastopen ? tcp_rsk(fastopen)->snt_isn : tp->snd_una;
+	if (sk->sk_state != TCP_LISTEN &&
+	    !between(seq, snd_una, tp->snd_nxt)) {
+		NET_INC_STATS_BH(net, LINUX_MIB_OUTOFWINDOWICMPS);
+		goto out;
+	}
+
+	switch (type) {
+	case ICMP_REDIRECT:
+		do_redirect(icmp_skb, sk);
+		goto out;
+	case ICMP_SOURCE_QUENCH:
+		/* Just silently ignore these. */
+		goto out;
+	case ICMP_PARAMETERPROB:
+		err = EPROTO;
+		break;
+	case ICMP_DEST_UNREACH:
+		if (code > NR_ICMP_UNREACH)
+			goto out;
+
+		if (code == ICMP_FRAG_NEEDED) { /* PMTU discovery (RFC1191) */
+			/* We are not interested in TCP_LISTEN and open_requests
+			 * (SYN-ACKs send out by Linux are always <576bytes so
+			 * they should go through unfragmented).
+			 */
+			if (sk->sk_state == TCP_LISTEN)
+				goto out;
+
+			tp->mtu_info = info;
+			if (!sock_owned_by_user(sk)) {
+				tcp_v4_mtu_reduced(sk);
+			} else {
+				if (!test_and_set_bit(TCP_MTU_REDUCED_DEFERRED, &tp->tsq_flags))
+					sock_hold(sk);
+			}
+			goto out;
+		}
+
+		err = icmp_err_convert[code].errno;
+		/* check if icmp_skb allows revert of backoff
+		 * (see draft-zimmermann-tcp-lcd) */
+		if (code != ICMP_NET_UNREACH && code != ICMP_HOST_UNREACH)
+			break;
+		if (seq != tp->snd_una  || !icsk->icsk_retransmits ||
+		    !icsk->icsk_backoff || fastopen)
+			break;
+
+		if (sock_owned_by_user(sk))
+			break;
+
+		icsk->icsk_backoff--;
+		icsk->icsk_rto = tp->srtt_us ? __tcp_set_rto(tp) :
+					       TCP_TIMEOUT_INIT;
+		icsk->icsk_rto = inet_csk_rto_backoff(icsk, TCP_RTO_MAX);
+
+		skb = tcp_write_queue_head(sk);
+		BUG_ON(!skb);
+
+		remaining = icsk->icsk_rto -
+			    min(icsk->icsk_rto,
+				tcp_time_stamp - tcp_skb_timestamp(skb));
+
+		if (remaining) {
+			inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
+						  remaining, TCP_RTO_MAX);
+		} else {
+			/* RTO revert clocked out retransmission.
+			 * Will retransmit now */
+			tcp_retransmit_timer(sk);
+		}
+
+		break;
+	case ICMP_TIME_EXCEEDED:
+		err = EHOSTUNREACH;
+		break;
+	default:
+		goto out;
+	}
+
+	switch (sk->sk_state) {
+	case TCP_SYN_SENT:
+	case TCP_SYN_RECV:
+		/* Only in fast or simultaneous open. If a fast open socket is
+		 * is already accepted it is treated as a connected one below.
+		 */
+		if (fastopen && !fastopen->sk)
+			break;
+
+		if (!sock_owned_by_user(sk)) {
+			sk->sk_err = err;
+
+			sk->sk_error_report(sk);
+
+			tcp_done(sk);
+		} else {
+			sk->sk_err_soft = err;
+		}
+		goto out;
+	}
+
+	/* If we've already connected we will keep trying
+	 * until we time out, or the user gives up.
+	 *
+	 * rfc1122 4.2.3.9 allows to consider as hard errors
+	 * only PROTO_UNREACH and PORT_UNREACH (well, FRAG_FAILED too,
+	 * but it is obsoleted by pmtu discovery).
+	 *
+	 * Note, that in modern internet, where routing is unreliable
+	 * and in each dark corner broken firewalls sit, sending random
+	 * errors ordered by their masters even this two messages finally lose
+	 * their original sense (even Linux sends invalid PORT_UNREACHs)
+	 *
+	 * Now we are in compliance with RFCs.
+	 *							--ANK (980905)
+	 */
+
+	inet = inet_sk(sk);
+	if (!sock_owned_by_user(sk) && inet->recverr) {
+		sk->sk_err = err;
+		sk->sk_error_report(sk);
+	} else	{ /* Only an error on timeout */
+		sk->sk_err_soft = err;
+	}
+
+out:
+	bh_unlock_sock(sk);
+	sock_put(sk);
+}
+
+void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr)
+{
+	struct tcphdr *th = tcp_hdr(skb);
+
+	if (skb->ip_summed == CHECKSUM_PARTIAL) {
+		th->check = ~tcp_v4_check(skb->len, saddr, daddr, 0);
+		skb->csum_start = skb_transport_header(skb) - skb->head;
+		skb->csum_offset = offsetof(struct tcphdr, check);
+	} else {
+		th->check = tcp_v4_check(skb->len, saddr, daddr,
+					 csum_partial(th,
+						      th->doff << 2,
+						      skb->csum));
+	}
+}
+
+/* This routine computes an IPv4 TCP checksum. */
+void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb)
+{
+	const struct inet_sock *inet = inet_sk(sk);
+
+	__tcp_v4_send_check(skb, inet->inet_saddr, inet->inet_daddr);
+}
+EXPORT_SYMBOL(tcp_v4_send_check);
+
+/*
+ *	This routine will send an RST to the other tcp.
+ *
+ *	Someone asks: why I NEVER use socket parameters (TOS, TTL etc.)
+ *		      for reset.
+ *	Answer: if a packet caused RST, it is not for a socket
+ *		existing in our system, if it is matched to a socket,
+ *		it is just duplicate segment or bug in other side's TCP.
+ *		So that we build reply only basing on parameters
+ *		arrived with segment.
+ *	Exception: precedence violation. We do not implement it in any case.
+ */
+
+static void tcp_v4_send_reset(struct sock *sk, struct sk_buff *skb)
+{
+	const struct tcphdr *th = tcp_hdr(skb);
+	struct {
+		struct tcphdr th;
+#ifdef CONFIG_TCP_MD5SIG
+		__be32 opt[(TCPOLEN_MD5SIG_ALIGNED >> 2)];
+#endif
+	} rep;
+	struct ip_reply_arg arg;
+#ifdef CONFIG_TCP_MD5SIG
+	struct tcp_md5sig_key *key;
+	const __u8 *hash_location = NULL;
+	unsigned char newhash[16];
+	int genhash;
+	struct sock *sk1 = NULL;
+#endif
+	struct net *net;
+
+	/* Never send a reset in response to a reset. */
+	if (th->rst)
+		return;
+
+	/* If sk not NULL, it means we did a successful lookup and incoming
+	 * route had to be correct. prequeue might have dropped our dst.
+	 */
+	if (!sk && skb_rtable(skb)->rt_type != RTN_LOCAL)
+		return;
+
+	/* Swap the send and the receive. */
+	memset(&rep, 0, sizeof(rep));
+	rep.th.dest   = th->source;
+	rep.th.source = th->dest;
+	rep.th.doff   = sizeof(struct tcphdr) / 4;
+	rep.th.rst    = 1;
+
+	if (th->ack) {
+		rep.th.seq = th->ack_seq;
+	} else {
+		rep.th.ack = 1;
+		rep.th.ack_seq = htonl(ntohl(th->seq) + th->syn + th->fin +
+				       skb->len - (th->doff << 2));
+	}
+
+	memset(&arg, 0, sizeof(arg));
+	arg.iov[0].iov_base = (unsigned char *)&rep;
+	arg.iov[0].iov_len  = sizeof(rep.th);
+
+	net = sk ? sock_net(sk) : dev_net(skb_dst(skb)->dev);
+#ifdef CONFIG_TCP_MD5SIG
+	hash_location = tcp_parse_md5sig_option(th);
+	if (!sk && hash_location) {
+		/*
+		 * active side is lost. Try to find listening socket through
+		 * source port, and then find md5 key through listening socket.
+		 * we are not loose security here:
+		 * Incoming packet is checked with md5 hash with finding key,
+		 * no RST generated if md5 hash doesn't match.
+		 */
+		sk1 = __inet_lookup_listener(net,
+					     &tcp_hashinfo, ip_hdr(skb)->saddr,
+					     th->source, ip_hdr(skb)->daddr,
+					     ntohs(th->source), inet_iif(skb));
+		/* don't send rst if it can't find key */
+		if (!sk1)
+			return;
+		rcu_read_lock();
+		key = tcp_md5_do_lookup(sk1, (union tcp_md5_addr *)
+					&ip_hdr(skb)->saddr, AF_INET);
+		if (!key)
+			goto release_sk1;
+
+		genhash = tcp_v4_md5_hash_skb(newhash, key, NULL, skb);
+		if (genhash || memcmp(hash_location, newhash, 16) != 0)
+			goto release_sk1;
+	} else {
+		key = sk ? tcp_md5_do_lookup(sk, (union tcp_md5_addr *)
+					     &ip_hdr(skb)->saddr,
+					     AF_INET) : NULL;
+	}
+
+	if (key) {
+		rep.opt[0] = htonl((TCPOPT_NOP << 24) |
+				   (TCPOPT_NOP << 16) |
+				   (TCPOPT_MD5SIG << 8) |
+				   TCPOLEN_MD5SIG);
+		/* Update length and the length the header thinks exists */
+		arg.iov[0].iov_len += TCPOLEN_MD5SIG_ALIGNED;
+		rep.th.doff = arg.iov[0].iov_len / 4;
+
+		tcp_v4_md5_hash_hdr((__u8 *) &rep.opt[1],
+				     key, ip_hdr(skb)->saddr,
+				     ip_hdr(skb)->daddr, &rep.th);
+	}
+#endif
+	arg.csum = csum_tcpudp_nofold(ip_hdr(skb)->daddr,
+				      ip_hdr(skb)->saddr, /* XXX */
+				      arg.iov[0].iov_len, IPPROTO_TCP, 0);
+	arg.csumoffset = offsetof(struct tcphdr, check) / 2;
+	arg.flags = (sk && inet_sk(sk)->transparent) ? IP_REPLY_ARG_NOSRCCHECK : 0;
+	/* When socket is gone, all binding information is lost.
+	 * routing might fail in this case. No choice here, if we choose to force
+	 * input interface, we will misroute in case of asymmetric route.
+	 */
+	if (sk)
+		arg.bound_dev_if = sk->sk_bound_dev_if;
+
+	arg.tos = ip_hdr(skb)->tos;
+	ip_send_unicast_reply(*this_cpu_ptr(net->ipv4.tcp_sk),
+			      skb, &TCP_SKB_CB(skb)->header.h4.opt,
+			      ip_hdr(skb)->saddr, ip_hdr(skb)->daddr,
+			      &arg, arg.iov[0].iov_len);
+
+	TCP_INC_STATS_BH(net, TCP_MIB_OUTSEGS);
+	TCP_INC_STATS_BH(net, TCP_MIB_OUTRSTS);
+
+#ifdef CONFIG_TCP_MD5SIG
+release_sk1:
+	if (sk1) {
+		rcu_read_unlock();
+		sock_put(sk1);
+	}
+#endif
+}
+
+/* The code following below sending ACKs in SYN-RECV and TIME-WAIT states
+   outside socket context is ugly, certainly. What can I do?
+ */
+
+static void tcp_v4_send_ack(struct sk_buff *skb, u32 seq, u32 ack,
+			    u32 win, u32 tsval, u32 tsecr, int oif,
+			    struct tcp_md5sig_key *key,
+			    int reply_flags, u8 tos)
+{
+	const struct tcphdr *th = tcp_hdr(skb);
+	struct {
+		struct tcphdr th;
+		__be32 opt[(TCPOLEN_TSTAMP_ALIGNED >> 2)
+#ifdef CONFIG_TCP_MD5SIG
+			   + (TCPOLEN_MD5SIG_ALIGNED >> 2)
+#endif
+			];
+	} rep;
+	struct ip_reply_arg arg;
+	struct net *net = dev_net(skb_dst(skb)->dev);
+
+	memset(&rep.th, 0, sizeof(struct tcphdr));
+	memset(&arg, 0, sizeof(arg));
+
+	arg.iov[0].iov_base = (unsigned char *)&rep;
+	arg.iov[0].iov_len  = sizeof(rep.th);
+	if (tsecr) {
+		rep.opt[0] = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) |
+				   (TCPOPT_TIMESTAMP << 8) |
+				   TCPOLEN_TIMESTAMP);
+		rep.opt[1] = htonl(tsval);
+		rep.opt[2] = htonl(tsecr);
+		arg.iov[0].iov_len += TCPOLEN_TSTAMP_ALIGNED;
+	}
+
+	/* Swap the send and the receive. */
+	rep.th.dest    = th->source;
+	rep.th.source  = th->dest;
+	rep.th.doff    = arg.iov[0].iov_len / 4;
+	rep.th.seq     = htonl(seq);
+	rep.th.ack_seq = htonl(ack);
+	rep.th.ack     = 1;
+	rep.th.window  = htons(win);
+
+#ifdef CONFIG_TCP_MD5SIG
+	if (key) {
+		int offset = (tsecr) ? 3 : 0;
+
+		rep.opt[offset++] = htonl((TCPOPT_NOP << 24) |
+					  (TCPOPT_NOP << 16) |
+					  (TCPOPT_MD5SIG << 8) |
+					  TCPOLEN_MD5SIG);
+		arg.iov[0].iov_len += TCPOLEN_MD5SIG_ALIGNED;
+		rep.th.doff = arg.iov[0].iov_len/4;
+
+		tcp_v4_md5_hash_hdr((__u8 *) &rep.opt[offset],
+				    key, ip_hdr(skb)->saddr,
+				    ip_hdr(skb)->daddr, &rep.th);
+	}
+#endif
+	arg.flags = reply_flags;
+	arg.csum = csum_tcpudp_nofold(ip_hdr(skb)->daddr,
+				      ip_hdr(skb)->saddr, /* XXX */
+				      arg.iov[0].iov_len, IPPROTO_TCP, 0);
+	arg.csumoffset = offsetof(struct tcphdr, check) / 2;
+	if (oif)
+		arg.bound_dev_if = oif;
+	arg.tos = tos;
+	ip_send_unicast_reply(*this_cpu_ptr(net->ipv4.tcp_sk),
+			      skb, &TCP_SKB_CB(skb)->header.h4.opt,
+			      ip_hdr(skb)->saddr, ip_hdr(skb)->daddr,
+			      &arg, arg.iov[0].iov_len);
+
+	TCP_INC_STATS_BH(net, TCP_MIB_OUTSEGS);
+}
+
+static void tcp_v4_timewait_ack(struct sock *sk, struct sk_buff *skb)
+{
+	struct inet_timewait_sock *tw = inet_twsk(sk);
+	struct tcp_timewait_sock *tcptw = tcp_twsk(sk);
+
+	tcp_v4_send_ack(skb, tcptw->tw_snd_nxt, tcptw->tw_rcv_nxt,
+			tcptw->tw_rcv_wnd >> tw->tw_rcv_wscale,
+			tcp_time_stamp + tcptw->tw_ts_offset,
+			tcptw->tw_ts_recent,
+			tw->tw_bound_dev_if,
+			tcp_twsk_md5_key(tcptw),
+			tw->tw_transparent ? IP_REPLY_ARG_NOSRCCHECK : 0,
+			tw->tw_tos
+			);
+
+	inet_twsk_put(tw);
+}
+
+static void tcp_v4_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
+				  struct request_sock *req)
+{
+	/* sk->sk_state == TCP_LISTEN -> for regular TCP_SYN_RECV
+	 * sk->sk_state == TCP_SYN_RECV -> for Fast Open.
+	 */
+	tcp_v4_send_ack(skb, (sk->sk_state == TCP_LISTEN) ?
+			tcp_rsk(req)->snt_isn + 1 : tcp_sk(sk)->snd_nxt,
+			tcp_rsk(req)->rcv_nxt, req->rcv_wnd,
+			tcp_time_stamp,
+			req->ts_recent,
+			0,
+			tcp_md5_do_lookup(sk, (union tcp_md5_addr *)&ip_hdr(skb)->daddr,
+					  AF_INET),
+			inet_rsk(req)->no_srccheck ? IP_REPLY_ARG_NOSRCCHECK : 0,
+			ip_hdr(skb)->tos);
+}
+
+/*
+ *	Send a SYN-ACK after having received a SYN.
+ *	This still operates on a request_sock only, not on a big
+ *	socket.
+ */
+static int tcp_v4_send_synack(struct sock *sk, struct dst_entry *dst,
+			      struct flowi *fl,
+			      struct request_sock *req,
+			      u16 queue_mapping,
+			      struct tcp_fastopen_cookie *foc)
+{
+	const struct inet_request_sock *ireq = inet_rsk(req);
+	struct flowi4 fl4;
+	int err = -1;
+	struct sk_buff *skb;
+
+	/* First, grab a route. */
+	if (!dst && (dst = inet_csk_route_req(sk, &fl4, req)) == NULL)
+		return -1;
+
+	skb = tcp_make_synack(sk, dst, req, foc);
+
+	if (skb) {
+		__tcp_v4_send_check(skb, ireq->ir_loc_addr, ireq->ir_rmt_addr);
+
+		skb_set_queue_mapping(skb, queue_mapping);
+		err = ip_build_and_send_pkt(skb, sk, ireq->ir_loc_addr,
+					    ireq->ir_rmt_addr,
+					    ireq->opt);
+		err = net_xmit_eval(err);
+	}
+
+	return err;
+}
+
+/*
+ *	IPv4 request_sock destructor.
+ */
+static void tcp_v4_reqsk_destructor(struct request_sock *req)
+{
+	kfree(inet_rsk(req)->opt);
+}
+
+
+#ifdef CONFIG_TCP_MD5SIG
+/*
+ * RFC2385 MD5 checksumming requires a mapping of
+ * IP address->MD5 Key.
+ * We need to maintain these in the sk structure.
+ */
+
+/* Find the Key structure for an address.  */
+struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
+					 const union tcp_md5_addr *addr,
+					 int family)
+{
+	const struct tcp_sock *tp = tcp_sk(sk);
+	struct tcp_md5sig_key *key;
+	unsigned int size = sizeof(struct in_addr);
+	const struct tcp_md5sig_info *md5sig;
+
+	/* caller either holds rcu_read_lock() or socket lock */
+	md5sig = rcu_dereference_check(tp->md5sig_info,
+				       sock_owned_by_user(sk) ||
+				       lockdep_is_held(&sk->sk_lock.slock));
+	if (!md5sig)
+		return NULL;
+#if IS_ENABLED(CONFIG_IPV6)
+	if (family == AF_INET6)
+		size = sizeof(struct in6_addr);
+#endif
+	hlist_for_each_entry_rcu(key, &md5sig->head, node) {
+		if (key->family != family)
+			continue;
+		if (!memcmp(&key->addr, addr, size))
+			return key;
+	}
+	return NULL;
+}
+EXPORT_SYMBOL(tcp_md5_do_lookup);
+
+struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
+					 const struct sock *addr_sk)
+{
+	const union tcp_md5_addr *addr;
+
+	addr = (const union tcp_md5_addr *)&addr_sk->sk_daddr;
+	return tcp_md5_do_lookup(sk, addr, AF_INET);
+}
+EXPORT_SYMBOL(tcp_v4_md5_lookup);
+
+/* This can be called on a newly created socket, from other files */
+int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
+		   int family, const u8 *newkey, u8 newkeylen, gfp_t gfp)
+{
+	/* Add Key to the list */
+	struct tcp_md5sig_key *key;
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct tcp_md5sig_info *md5sig;
+
+	key = tcp_md5_do_lookup(sk, addr, family);
+	if (key) {
+		/* Pre-existing entry - just update that one. */
+		memcpy(key->key, newkey, newkeylen);
+		key->keylen = newkeylen;
+		return 0;
+	}
+
+	md5sig = rcu_dereference_protected(tp->md5sig_info,
+					   sock_owned_by_user(sk));
+	if (!md5sig) {
+		md5sig = kmalloc(sizeof(*md5sig), gfp);
+		if (!md5sig)
+			return -ENOMEM;
+
+		sk_nocaps_add(sk, NETIF_F_GSO_MASK);
+		INIT_HLIST_HEAD(&md5sig->head);
+		rcu_assign_pointer(tp->md5sig_info, md5sig);
+	}
+
+	key = sock_kmalloc(sk, sizeof(*key), gfp);
+	if (!key)
+		return -ENOMEM;
+	if (!tcp_alloc_md5sig_pool()) {
+		sock_kfree_s(sk, key, sizeof(*key));
+		return -ENOMEM;
+	}
+
+	memcpy(key->key, newkey, newkeylen);
+	key->keylen = newkeylen;
+	key->family = family;
+	memcpy(&key->addr, addr,
+	       (family == AF_INET6) ? sizeof(struct in6_addr) :
+				      sizeof(struct in_addr));
+	hlist_add_head_rcu(&key->node, &md5sig->head);
+	return 0;
+}
+EXPORT_SYMBOL(tcp_md5_do_add);
+
+int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr, int family)
+{
+	struct tcp_md5sig_key *key;
+
+	key = tcp_md5_do_lookup(sk, addr, family);
+	if (!key)
+		return -ENOENT;
+	hlist_del_rcu(&key->node);
+	atomic_sub(sizeof(*key), &sk->sk_omem_alloc);
+	kfree_rcu(key, rcu);
+	return 0;
+}
+EXPORT_SYMBOL(tcp_md5_do_del);
+
+static void tcp_clear_md5_list(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct tcp_md5sig_key *key;
+	struct hlist_node *n;
+	struct tcp_md5sig_info *md5sig;
+
+	md5sig = rcu_dereference_protected(tp->md5sig_info, 1);
+
+	hlist_for_each_entry_safe(key, n, &md5sig->head, node) {
+		hlist_del_rcu(&key->node);
+		atomic_sub(sizeof(*key), &sk->sk_omem_alloc);
+		kfree_rcu(key, rcu);
+	}
+}
+
+static int tcp_v4_parse_md5_keys(struct sock *sk, char __user *optval,
+				 int optlen)
+{
+	struct tcp_md5sig cmd;
+	struct sockaddr_in *sin = (struct sockaddr_in *)&cmd.tcpm_addr;
+
+	if (optlen < sizeof(cmd))
+		return -EINVAL;
+
+	if (copy_from_user(&cmd, optval, sizeof(cmd)))
+		return -EFAULT;
+
+	if (sin->sin_family != AF_INET)
+		return -EINVAL;
+
+	if (!cmd.tcpm_keylen)
+		return tcp_md5_do_del(sk, (union tcp_md5_addr *)&sin->sin_addr.s_addr,
+				      AF_INET);
+
+	if (cmd.tcpm_keylen > TCP_MD5SIG_MAXKEYLEN)
+		return -EINVAL;
+
+	return tcp_md5_do_add(sk, (union tcp_md5_addr *)&sin->sin_addr.s_addr,
+			      AF_INET, cmd.tcpm_key, cmd.tcpm_keylen,
+			      GFP_KERNEL);
+}
+
+static int tcp_v4_md5_hash_pseudoheader(struct tcp_md5sig_pool *hp,
+					__be32 daddr, __be32 saddr, int nbytes)
+{
+	struct tcp4_pseudohdr *bp;
+	struct scatterlist sg;
+
+	bp = &hp->md5_blk.ip4;
+
+	/*
+	 * 1. the TCP pseudo-header (in the order: source IP address,
+	 * destination IP address, zero-padded protocol number, and
+	 * segment length)
+	 */
+	bp->saddr = saddr;
+	bp->daddr = daddr;
+	bp->pad = 0;
+	bp->protocol = IPPROTO_TCP;
+	bp->len = cpu_to_be16(nbytes);
+
+	sg_init_one(&sg, bp, sizeof(*bp));
+	return crypto_hash_update(&hp->md5_desc, &sg, sizeof(*bp));
+}
+
+static int tcp_v4_md5_hash_hdr(char *md5_hash, const struct tcp_md5sig_key *key,
+			       __be32 daddr, __be32 saddr, const struct tcphdr *th)
+{
+	struct tcp_md5sig_pool *hp;
+	struct hash_desc *desc;
+
+	hp = tcp_get_md5sig_pool();
+	if (!hp)
+		goto clear_hash_noput;
+	desc = &hp->md5_desc;
+
+	if (crypto_hash_init(desc))
+		goto clear_hash;
+	if (tcp_v4_md5_hash_pseudoheader(hp, daddr, saddr, th->doff << 2))
+		goto clear_hash;
+	if (tcp_md5_hash_header(hp, th))
+		goto clear_hash;
+	if (tcp_md5_hash_key(hp, key))
+		goto clear_hash;
+	if (crypto_hash_final(desc, md5_hash))
+		goto clear_hash;
+
+	tcp_put_md5sig_pool();
+	return 0;
+
+clear_hash:
+	tcp_put_md5sig_pool();
+clear_hash_noput:
+	memset(md5_hash, 0, 16);
+	return 1;
+}
+
+int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
+			const struct sock *sk,
+			const struct sk_buff *skb)
+{
+	struct tcp_md5sig_pool *hp;
+	struct hash_desc *desc;
+	const struct tcphdr *th = tcp_hdr(skb);
+	__be32 saddr, daddr;
+
+	if (sk) { /* valid for establish/request sockets */
+		saddr = sk->sk_rcv_saddr;
+		daddr = sk->sk_daddr;
+	} else {
+		const struct iphdr *iph = ip_hdr(skb);
+		saddr = iph->saddr;
+		daddr = iph->daddr;
+	}
+
+	hp = tcp_get_md5sig_pool();
+	if (!hp)
+		goto clear_hash_noput;
+	desc = &hp->md5_desc;
+
+	if (crypto_hash_init(desc))
+		goto clear_hash;
+
+	if (tcp_v4_md5_hash_pseudoheader(hp, daddr, saddr, skb->len))
+		goto clear_hash;
+	if (tcp_md5_hash_header(hp, th))
+		goto clear_hash;
+	if (tcp_md5_hash_skb_data(hp, skb, th->doff << 2))
+		goto clear_hash;
+	if (tcp_md5_hash_key(hp, key))
+		goto clear_hash;
+	if (crypto_hash_final(desc, md5_hash))
+		goto clear_hash;
+
+	tcp_put_md5sig_pool();
+	return 0;
+
+clear_hash:
+	tcp_put_md5sig_pool();
+clear_hash_noput:
+	memset(md5_hash, 0, 16);
+	return 1;
+}
+EXPORT_SYMBOL(tcp_v4_md5_hash_skb);
+
+/* Called with rcu_read_lock() */
+static bool tcp_v4_inbound_md5_hash(struct sock *sk,
+				    const struct sk_buff *skb)
+{
+	/*
+	 * This gets called for each TCP segment that arrives
+	 * so we want to be efficient.
+	 * We have 3 drop cases:
+	 * o No MD5 hash and one expected.
+	 * o MD5 hash and we're not expecting one.
+	 * o MD5 hash and its wrong.
+	 */
+	const __u8 *hash_location = NULL;
+	struct tcp_md5sig_key *hash_expected;
+	const struct iphdr *iph = ip_hdr(skb);
+	const struct tcphdr *th = tcp_hdr(skb);
+	int genhash;
+	unsigned char newhash[16];
+
+	hash_expected = tcp_md5_do_lookup(sk, (union tcp_md5_addr *)&iph->saddr,
+					  AF_INET);
+	hash_location = tcp_parse_md5sig_option(th);
+
+	/* We've parsed the options - do we have a hash? */
+	if (!hash_expected && !hash_location)
+		return false;
+
+	if (hash_expected && !hash_location) {
+		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPMD5NOTFOUND);
+		return true;
+	}
+
+	if (!hash_expected && hash_location) {
+		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPMD5UNEXPECTED);
+		return true;
+	}
+
+	/* Okay, so this is hash_expected and hash_location -
+	 * so we need to calculate the checksum.
+	 */
+	genhash = tcp_v4_md5_hash_skb(newhash,
+				      hash_expected,
+				      NULL, skb);
+
+	if (genhash || memcmp(hash_location, newhash, 16) != 0) {
+		net_info_ratelimited("MD5 Hash failed for (%pI4, %d)->(%pI4, %d)%s\n",
+				     &iph->saddr, ntohs(th->source),
+				     &iph->daddr, ntohs(th->dest),
+				     genhash ? " tcp_v4_calc_md5_hash failed"
+				     : "");
+		return true;
+	}
+	return false;
+}
+#endif
+
+static void tcp_v4_init_req(struct request_sock *req, struct sock *sk_listener,
+			    struct sk_buff *skb)
+{
+	struct inet_request_sock *ireq = inet_rsk(req);
+
+	sk_rcv_saddr_set(req_to_sk(req), ip_hdr(skb)->daddr);
+	sk_daddr_set(req_to_sk(req), ip_hdr(skb)->saddr);
+	ireq->no_srccheck = inet_sk(sk_listener)->transparent;
+	ireq->opt = tcp_v4_save_options(skb);
+}
+
+static struct dst_entry *tcp_v4_route_req(struct sock *sk, struct flowi *fl,
+					  const struct request_sock *req,
+					  bool *strict)
+{
+	struct dst_entry *dst = inet_csk_route_req(sk, &fl->u.ip4, req);
+
+	if (strict) {
+		if (fl->u.ip4.daddr == inet_rsk(req)->ir_rmt_addr)
+			*strict = true;
+		else
+			*strict = false;
+	}
+
+	return dst;
+}
+
+struct request_sock_ops tcp_request_sock_ops __read_mostly = {
+	.family		=	PF_INET,
+	.obj_size	=	sizeof(struct tcp_request_sock),
+	.rtx_syn_ack	=	tcp_rtx_synack,
+	.send_ack	=	tcp_v4_reqsk_send_ack,
+	.destructor	=	tcp_v4_reqsk_destructor,
+	.send_reset	=	tcp_v4_send_reset,
+	.syn_ack_timeout =	tcp_syn_ack_timeout,
+};
+
+static const struct tcp_request_sock_ops tcp_request_sock_ipv4_ops = {
+	.mss_clamp	=	TCP_MSS_DEFAULT,
+#ifdef CONFIG_TCP_MD5SIG
+	.req_md5_lookup	=	tcp_v4_md5_lookup,
+	.calc_md5_hash	=	tcp_v4_md5_hash_skb,
+#endif
+	.init_req	=	tcp_v4_init_req,
+#ifdef CONFIG_SYN_COOKIES
+	.cookie_init_seq =	cookie_v4_init_sequence,
+#endif
+	.route_req	=	tcp_v4_route_req,
+	.init_seq	=	tcp_v4_init_sequence,
+	.send_synack	=	tcp_v4_send_synack,
+	.queue_hash_add =	inet_csk_reqsk_queue_hash_add,
+};
+
+int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
+{
+	/* Never answer to SYNs send to broadcast or multicast */
+	if (skb_rtable(skb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
+		goto drop;
+
+	return tcp_conn_request(&tcp_request_sock_ops,
+				&tcp_request_sock_ipv4_ops, sk, skb);
+
+drop:
+	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
+	return 0;
+}
+EXPORT_SYMBOL(tcp_v4_conn_request);
+
+
+/*
+ * The three way handshake has completed - we got a valid synack -
+ * now create the new socket.
+ */
+struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
+				  struct request_sock *req,
+				  struct dst_entry *dst)
+{
+	struct inet_request_sock *ireq;
+	struct inet_sock *newinet;
+	struct tcp_sock *newtp;
+	struct sock *newsk;
+#ifdef CONFIG_TCP_MD5SIG
+	struct tcp_md5sig_key *key;
+#endif
+	struct ip_options_rcu *inet_opt;
+
+	if (sk_acceptq_is_full(sk))
+		goto exit_overflow;
+
+	newsk = tcp_create_openreq_child(sk, req, skb);
+	if (!newsk)
+		goto exit_nonewsk;
+
+	newsk->sk_gso_type = SKB_GSO_TCPV4;
+	inet_sk_rx_dst_set(newsk, skb);
+
+	newtp		      = tcp_sk(newsk);
+	newinet		      = inet_sk(newsk);
+	ireq		      = inet_rsk(req);
+	sk_daddr_set(newsk, ireq->ir_rmt_addr);
+	sk_rcv_saddr_set(newsk, ireq->ir_loc_addr);
+	newinet->inet_saddr	      = ireq->ir_loc_addr;
+	inet_opt	      = ireq->opt;
+	rcu_assign_pointer(newinet->inet_opt, inet_opt);
+	ireq->opt	      = NULL;
+	newinet->mc_index     = inet_iif(skb);
+	newinet->mc_ttl	      = ip_hdr(skb)->ttl;
+	newinet->rcv_tos      = ip_hdr(skb)->tos;
+	inet_csk(newsk)->icsk_ext_hdr_len = 0;
+	inet_set_txhash(newsk);
+	if (inet_opt)
+		inet_csk(newsk)->icsk_ext_hdr_len = inet_opt->opt.optlen;
+	newinet->inet_id = newtp->write_seq ^ jiffies;
+
+	if (!dst) {
+		dst = inet_csk_route_child_sock(sk, newsk, req);
+		if (!dst)
+			goto put_and_exit;
+	} else {
+		/* syncookie case : see end of cookie_v4_check() */
+	}
+	sk_setup_caps(newsk, dst);
+
+	tcp_ca_openreq_child(newsk, dst);
+
+	tcp_sync_mss(newsk, dst_mtu(dst));
+	newtp->advmss = dst_metric_advmss(dst);
+	if (tcp_sk(sk)->rx_opt.user_mss &&
+	    tcp_sk(sk)->rx_opt.user_mss < newtp->advmss)
+		newtp->advmss = tcp_sk(sk)->rx_opt.user_mss;
+
+	tcp_initialize_rcv_mss(newsk);
+
+#ifdef CONFIG_TCP_MD5SIG
+	/* Copy over the MD5 key from the original socket */
+	key = tcp_md5_do_lookup(sk, (union tcp_md5_addr *)&newinet->inet_daddr,
+				AF_INET);
+	if (key) {
+		/*
+		 * We're using one, so create a matching key
+		 * on the newsk structure. If we fail to get
+		 * memory, then we end up not copying the key
+		 * across. Shucks.
+		 */
+		tcp_md5_do_add(newsk, (union tcp_md5_addr *)&newinet->inet_daddr,
+			       AF_INET, key->key, key->keylen, GFP_ATOMIC);
+		sk_nocaps_add(newsk, NETIF_F_GSO_MASK);
+	}
+#endif
+
+	if (__inet_inherit_port(sk, newsk) < 0)
+		goto put_and_exit;
+	__inet_hash_nolisten(newsk, NULL);
+
+	return newsk;
+
+exit_overflow:
+	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENOVERFLOWS);
+exit_nonewsk:
+	dst_release(dst);
+exit:
+	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_LISTENDROPS);
+	return NULL;
+put_and_exit:
+	inet_csk_prepare_forced_close(newsk);
+	tcp_done(newsk);
+	goto exit;
+}
+EXPORT_SYMBOL(tcp_v4_syn_recv_sock);
+
+static struct sock *tcp_v4_hnd_req(struct sock *sk, struct sk_buff *skb)
+{
+	const struct tcphdr *th = tcp_hdr(skb);
+	const struct iphdr *iph = ip_hdr(skb);
+	struct request_sock *req;
+	struct sock *nsk;
+
+	req = inet_csk_search_req(sk, th->source, iph->saddr, iph->daddr);
+	if (req) {
+		nsk = tcp_check_req(sk, skb, req, false);
+		if (!nsk)
+			reqsk_put(req);
+		return nsk;
+	}
+
+	nsk = inet_lookup_established(sock_net(sk), &tcp_hashinfo, iph->saddr,
+			th->source, iph->daddr, th->dest, inet_iif(skb));
+
+	if (nsk) {
+		if (nsk->sk_state != TCP_TIME_WAIT) {
+			bh_lock_sock(nsk);
+			return nsk;
+		}
+		inet_twsk_put(inet_twsk(nsk));
+		return NULL;
+	}
+
+#ifdef CONFIG_SYN_COOKIES
+	if (!th->syn)
+		sk = cookie_v4_check(sk, skb);
+#endif
+	return sk;
+}
+
+/* The socket must have it's spinlock held when we get
+ * here.
+ *
+ * We have a potential double-lock case here, so even when
+ * doing backlog processing we use the BH locking scheme.
+ * This is because we cannot sleep with the original spinlock
+ * held.
+ */
+int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+	struct tcphdr *th = tcp_hdr(skb);
+	struct sock *rsk;
+
+	if (sk->sk_state == TCP_ESTABLISHED) { /* Fast path */
+		struct dst_entry *dst = sk->sk_rx_dst;
+
+		sock_rps_save_rxhash(sk, skb);
+		sk_mark_napi_id(sk, skb);
+		if (dst) {
+			if (inet_sk(sk)->rx_dst_ifindex != skb->skb_iif ||
+			    !dst->ops->check(dst, 0)) {
+				dst_release(dst);
+				sk->sk_rx_dst = NULL;
+			}
+		}
+		tcp_rcv_established(sk, skb, tcp_hdr(skb), skb->len);
+		return 0;
+	}
+
+	if (skb->len < tcp_hdrlen(skb) || tcp_checksum_complete(skb))
+		goto csum_err;
+
+#ifdef CONFIG_TCP_STEALTH
+	if (sk->sk_state == TCP_LISTEN && th->syn && !th->fin &&
+	    unlikely(tp->stealth.mode & TCP_STEALTH_MODE_AUTH) &&
+	    tcp_stealth_do_auth(sk, skb)) {
+		rsk = sk;
+		goto reset;
+	}
+#endif
+
+	if (sk->sk_state == TCP_LISTEN) {
+		struct sock *nsk = tcp_v4_hnd_req(sk, skb);
+		if (!nsk)
+			goto discard;
+
+		if (nsk != sk) {
+			sock_rps_save_rxhash(nsk, skb);
+			sk_mark_napi_id(sk, skb);
+			if (tcp_child_process(sk, nsk, skb)) {
+				rsk = nsk;
+				goto reset;
+			}
+			return 0;
+		}
+	} else
+		sock_rps_save_rxhash(sk, skb);
+
+	if (tcp_rcv_state_process(sk, skb, tcp_hdr(skb), skb->len)) {
+		rsk = sk;
+		goto reset;
+	}
+	return 0;
+
+reset:
+	tcp_v4_send_reset(rsk, skb);
+discard:
+	kfree_skb(skb);
+	/* Be careful here. If this function gets more complicated and
+	 * gcc suffers from register pressure on the x86, sk (in %ebx)
+	 * might be destroyed here. This current version compiles correctly,
+	 * but you have been warned.
+	 */
+	return 0;
+
+csum_err:
+	TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_CSUMERRORS);
+	TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
+	goto discard;
+}
+EXPORT_SYMBOL(tcp_v4_do_rcv);
+
+void tcp_v4_early_demux(struct sk_buff *skb)
+{
+	const struct iphdr *iph;
+	const struct tcphdr *th;
+	struct sock *sk;
+
+	if (skb->pkt_type != PACKET_HOST)
+		return;
+
+	if (!pskb_may_pull(skb, skb_transport_offset(skb) + sizeof(struct tcphdr)))
+		return;
+
+	iph = ip_hdr(skb);
+	th = tcp_hdr(skb);
+
+	if (th->doff < sizeof(struct tcphdr) / 4)
+		return;
+
+	sk = __inet_lookup_established(dev_net(skb->dev), &tcp_hashinfo,
+				       iph->saddr, th->source,
+				       iph->daddr, ntohs(th->dest),
+				       skb->skb_iif);
+	if (sk) {
+		skb->sk = sk;
+		skb->destructor = sock_edemux;
+		if (sk_fullsock(sk)) {
+			struct dst_entry *dst = READ_ONCE(sk->sk_rx_dst);
+
+			if (dst)
+				dst = dst_check(dst, 0);
+			if (dst &&
+			    inet_sk(sk)->rx_dst_ifindex == skb->skb_iif)
+				skb_dst_set_noref(skb, dst);
+		}
+	}
+}
+
+/* Packet is added to VJ-style prequeue for processing in process
+ * context, if a reader task is waiting. Apparently, this exciting
+ * idea (VJ's mail "Re: query about TCP header on tcp-ip" of 07 Sep 93)
+ * failed somewhere. Latency? Burstiness? Well, at least now we will
+ * see, why it failed. 8)8)				  --ANK
+ *
+ */
+bool tcp_prequeue(struct sock *sk, struct sk_buff *skb)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	if (sysctl_tcp_low_latency || !tp->ucopy.task)
+		return false;
+
+	if (skb->len <= tcp_hdrlen(skb) &&
+	    skb_queue_len(&tp->ucopy.prequeue) == 0)
+		return false;
+
+	/* Before escaping RCU protected region, we need to take care of skb
+	 * dst. Prequeue is only enabled for established sockets.
+	 * For such sockets, we might need the skb dst only to set sk->sk_rx_dst
+	 * Instead of doing full sk_rx_dst validity here, let's perform
+	 * an optimistic check.
+	 */
+	if (likely(sk->sk_rx_dst))
+		skb_dst_drop(skb);
+	else
+		skb_dst_force(skb);
+
+	__skb_queue_tail(&tp->ucopy.prequeue, skb);
+	tp->ucopy.memory += skb->truesize;
+	if (tp->ucopy.memory > sk->sk_rcvbuf) {
+		struct sk_buff *skb1;
+
+		BUG_ON(sock_owned_by_user(sk));
+
+		while ((skb1 = __skb_dequeue(&tp->ucopy.prequeue)) != NULL) {
+			sk_backlog_rcv(sk, skb1);
+			NET_INC_STATS_BH(sock_net(sk),
+					 LINUX_MIB_TCPPREQUEUEDROPPED);
+		}
+
+		tp->ucopy.memory = 0;
+	} else if (skb_queue_len(&tp->ucopy.prequeue) == 1) {
+		wake_up_interruptible_sync_poll(sk_sleep(sk),
+					   POLLIN | POLLRDNORM | POLLRDBAND);
+		if (!inet_csk_ack_scheduled(sk))
+			inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK,
+						  (3 * tcp_rto_min(sk)) / 4,
+						  TCP_RTO_MAX);
+	}
+	return true;
+}
+EXPORT_SYMBOL(tcp_prequeue);
+
+/*
+ *	From tcp_input.c
+ */
+
+int tcp_v4_rcv(struct sk_buff *skb)
+{
+	const struct iphdr *iph;
+	const struct tcphdr *th;
+	struct sock *sk;
+	int ret;
+	struct net *net = dev_net(skb->dev);
+
+	if (skb->pkt_type != PACKET_HOST)
+		goto discard_it;
+
+	/* Count it even if it's bad */
+	TCP_INC_STATS_BH(net, TCP_MIB_INSEGS);
+
+	if (!pskb_may_pull(skb, sizeof(struct tcphdr)))
+		goto discard_it;
+
+	th = tcp_hdr(skb);
+
+	if (th->doff < sizeof(struct tcphdr) / 4)
+		goto bad_packet;
+	if (!pskb_may_pull(skb, th->doff * 4))
+		goto discard_it;
+
+	/* An explanation is required here, I think.
+	 * Packet length and doff are validated by header prediction,
+	 * provided case of th->doff==0 is eliminated.
+	 * So, we defer the checks. */
+
+	if (skb_checksum_init(skb, IPPROTO_TCP, inet_compute_pseudo))
+		goto csum_error;
+
+	th = tcp_hdr(skb);
+	iph = ip_hdr(skb);
+	/* This is tricky : We move IPCB at its correct location into TCP_SKB_CB()
+	 * barrier() makes sure compiler wont play fool^Waliasing games.
+	 */
+	memmove(&TCP_SKB_CB(skb)->header.h4, IPCB(skb),
+		sizeof(struct inet_skb_parm));
+	barrier();
+
+	TCP_SKB_CB(skb)->seq = ntohl(th->seq);
+	TCP_SKB_CB(skb)->end_seq = (TCP_SKB_CB(skb)->seq + th->syn + th->fin +
+				    skb->len - th->doff * 4);
+	TCP_SKB_CB(skb)->ack_seq = ntohl(th->ack_seq);
+	TCP_SKB_CB(skb)->tcp_flags = tcp_flag_byte(th);
+	TCP_SKB_CB(skb)->tcp_tw_isn = 0;
+	TCP_SKB_CB(skb)->ip_dsfield = ipv4_get_dsfield(iph);
+	TCP_SKB_CB(skb)->sacked	 = 0;
+
+	sk = __inet_lookup_skb(&tcp_hashinfo, skb, th->source, th->dest);
+	if (!sk)
+		goto no_tcp_socket;
+
+process:
+	if (sk->sk_state == TCP_TIME_WAIT)
+		goto do_time_wait;
+
+	if (unlikely(iph->ttl < inet_sk(sk)->min_ttl)) {
+		NET_INC_STATS_BH(net, LINUX_MIB_TCPMINTTLDROP);
+		goto discard_and_relse;
+	}
+
+	if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
+		goto discard_and_relse;
+
+#ifdef CONFIG_TCP_MD5SIG
+	/*
+	 * We really want to reject the packet as early as possible
+	 * if:
+	 *  o We're expecting an MD5'd packet and this is no MD5 tcp option
+	 *  o There is an MD5 option and we're not expecting one
+	 */
+	if (tcp_v4_inbound_md5_hash(sk, skb))
+		goto discard_and_relse;
+#endif
+
+	nf_reset(skb);
+
+	if (sk_filter(sk, skb))
+		goto discard_and_relse;
+
+	sk_incoming_cpu_update(sk);
+	skb->dev = NULL;
+
+	bh_lock_sock_nested(sk);
+	ret = 0;
+	if (!sock_owned_by_user(sk)) {
+		if (!tcp_prequeue(sk, skb))
+			ret = tcp_v4_do_rcv(sk, skb);
+	} else if (unlikely(sk_add_backlog(sk, skb,
+					   sk->sk_rcvbuf + sk->sk_sndbuf))) {
+		bh_unlock_sock(sk);
+		NET_INC_STATS_BH(net, LINUX_MIB_TCPBACKLOGDROP);
+		goto discard_and_relse;
+	}
+	bh_unlock_sock(sk);
+
+	sock_put(sk);
+
+	return ret;
+
+no_tcp_socket:
+	if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb))
+		goto discard_it;
+
+	if (skb->len < (th->doff << 2) || tcp_checksum_complete(skb)) {
+csum_error:
+		TCP_INC_STATS_BH(net, TCP_MIB_CSUMERRORS);
+bad_packet:
+		TCP_INC_STATS_BH(net, TCP_MIB_INERRS);
+	} else {
+		tcp_v4_send_reset(NULL, skb);
+	}
+
+discard_it:
+	/* Discard frame. */
+	kfree_skb(skb);
+	return 0;
+
+discard_and_relse:
+	sock_put(sk);
+	goto discard_it;
+
+do_time_wait:
+	if (!xfrm4_policy_check(NULL, XFRM_POLICY_IN, skb)) {
+		inet_twsk_put(inet_twsk(sk));
+		goto discard_it;
+	}
+
+	if (skb->len < (th->doff << 2)) {
+		inet_twsk_put(inet_twsk(sk));
+		goto bad_packet;
+	}
+	if (tcp_checksum_complete(skb)) {
+		inet_twsk_put(inet_twsk(sk));
+		goto csum_error;
+	}
+	switch (tcp_timewait_state_process(inet_twsk(sk), skb, th)) {
+	case TCP_TW_SYN: {
+		struct sock *sk2 = inet_lookup_listener(dev_net(skb->dev),
+							&tcp_hashinfo,
+							iph->saddr, th->source,
+							iph->daddr, th->dest,
+							inet_iif(skb));
+		if (sk2) {
+			inet_twsk_deschedule(inet_twsk(sk));
+			inet_twsk_put(inet_twsk(sk));
+			sk = sk2;
+			goto process;
+		}
+		/* Fall through to ACK */
+	}
+	case TCP_TW_ACK:
+		tcp_v4_timewait_ack(sk, skb);
+		break;
+	case TCP_TW_RST:
+		goto no_tcp_socket;
+	case TCP_TW_SUCCESS:;
+	}
+	goto discard_it;
+}
+
+static struct timewait_sock_ops tcp_timewait_sock_ops = {
+	.twsk_obj_size	= sizeof(struct tcp_timewait_sock),
+	.twsk_unique	= tcp_twsk_unique,
+	.twsk_destructor= tcp_twsk_destructor,
+};
+
+void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
+{
+	struct dst_entry *dst = skb_dst(skb);
+
+	if (dst) {
+		dst_hold(dst);
+		sk->sk_rx_dst = dst;
+		inet_sk(sk)->rx_dst_ifindex = skb->skb_iif;
+	}
+}
+EXPORT_SYMBOL(inet_sk_rx_dst_set);
+
+const struct inet_connection_sock_af_ops ipv4_specific = {
+	.queue_xmit	   = ip_queue_xmit,
+	.send_check	   = tcp_v4_send_check,
+	.rebuild_header	   = inet_sk_rebuild_header,
+	.sk_rx_dst_set	   = inet_sk_rx_dst_set,
+	.conn_request	   = tcp_v4_conn_request,
+	.syn_recv_sock	   = tcp_v4_syn_recv_sock,
+	.net_header_len	   = sizeof(struct iphdr),
+	.setsockopt	   = ip_setsockopt,
+	.getsockopt	   = ip_getsockopt,
+	.addr2sockaddr	   = inet_csk_addr2sockaddr,
+	.sockaddr_len	   = sizeof(struct sockaddr_in),
+	.bind_conflict	   = inet_csk_bind_conflict,
+#ifdef CONFIG_COMPAT
+	.compat_setsockopt = compat_ip_setsockopt,
+	.compat_getsockopt = compat_ip_getsockopt,
+#endif
+	.mtu_reduced	   = tcp_v4_mtu_reduced,
+};
+EXPORT_SYMBOL(ipv4_specific);
+
+#ifdef CONFIG_TCP_MD5SIG
+static const struct tcp_sock_af_ops tcp_sock_ipv4_specific = {
+	.md5_lookup		= tcp_v4_md5_lookup,
+	.calc_md5_hash		= tcp_v4_md5_hash_skb,
+	.md5_parse		= tcp_v4_parse_md5_keys,
+};
+#endif
+
+/* NOTE: A lot of things set to zero explicitly by call to
+ *       sk_alloc() so need not be done here.
+ */
+static int tcp_v4_init_sock(struct sock *sk)
+{
+	struct inet_connection_sock *icsk = inet_csk(sk);
+
+	tcp_init_sock(sk);
+
+	icsk->icsk_af_ops = &ipv4_specific;
+
+#ifdef CONFIG_TCP_MD5SIG
+	tcp_sk(sk)->af_specific = &tcp_sock_ipv4_specific;
+#endif
+
+	return 0;
+}
+
+void tcp_v4_destroy_sock(struct sock *sk)
+{
+	struct tcp_sock *tp = tcp_sk(sk);
+
+	tcp_clear_xmit_timers(sk);
+
+	tcp_cleanup_congestion_control(sk);
+
+	/* Cleanup up the write buffer. */
+	tcp_write_queue_purge(sk);
+
+	/* Cleans up our, hopefully empty, out_of_order_queue. */
+	__skb_queue_purge(&tp->out_of_order_queue);
+
+#ifdef CONFIG_TCP_MD5SIG
+	/* Clean up the MD5 key list, if any */
+	if (tp->md5sig_info) {
+		tcp_clear_md5_list(sk);
+		kfree_rcu(tp->md5sig_info, rcu);
+		tp->md5sig_info = NULL;
+	}
+#endif
+
+	/* Clean prequeue, it must be empty really */
+	__skb_queue_purge(&tp->ucopy.prequeue);
+
+	/* Clean up a referenced TCP bind bucket. */
+	if (inet_csk(sk)->icsk_bind_hash)
+		inet_put_port(sk);
+
+	BUG_ON(tp->fastopen_rsk);
+
+	/* If socket is aborted during connect operation */
+	tcp_free_fastopen_req(tp);
+
+	sk_sockets_allocated_dec(sk);
+	sock_release_memcg(sk);
+}
+EXPORT_SYMBOL(tcp_v4_destroy_sock);
+
+#ifdef CONFIG_PROC_FS
+/* Proc filesystem TCP sock list dumping. */
+
+/*
+ * Get next listener socket follow cur.  If cur is NULL, get first socket
+ * starting from bucket given in st->bucket; when st->bucket is zero the
+ * very first socket in the hash table is returned.
+ */
+static void *listening_get_next(struct seq_file *seq, void *cur)
+{
+	struct inet_connection_sock *icsk;
+	struct hlist_nulls_node *node;
+	struct sock *sk = cur;
+	struct inet_listen_hashbucket *ilb;
+	struct tcp_iter_state *st = seq->private;
+	struct net *net = seq_file_net(seq);
+
+	if (!sk) {
+		ilb = &tcp_hashinfo.listening_hash[st->bucket];
+		spin_lock_bh(&ilb->lock);
+		sk = sk_nulls_head(&ilb->head);
+		st->offset = 0;
+		goto get_sk;
+	}
+	ilb = &tcp_hashinfo.listening_hash[st->bucket];
+	++st->num;
+	++st->offset;
+
+	if (st->state == TCP_SEQ_STATE_OPENREQ) {
+		struct request_sock *req = cur;
+
+		icsk = inet_csk(st->syn_wait_sk);
+		req = req->dl_next;
+		while (1) {
+			while (req) {
+				if (req->rsk_ops->family == st->family) {
+					cur = req;
+					goto out;
+				}
+				req = req->dl_next;
+			}
+			if (++st->sbucket >= icsk->icsk_accept_queue.listen_opt->nr_table_entries)
+				break;
+get_req:
+			req = icsk->icsk_accept_queue.listen_opt->syn_table[st->sbucket];
+		}
+		sk	  = sk_nulls_next(st->syn_wait_sk);
+		st->state = TCP_SEQ_STATE_LISTENING;
+		spin_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
+	} else {
+		icsk = inet_csk(sk);
+		spin_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
+		if (reqsk_queue_len(&icsk->icsk_accept_queue))
+			goto start_req;
+		spin_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
+		sk = sk_nulls_next(sk);
+	}
+get_sk:
+	sk_nulls_for_each_from(sk, node) {
+		if (!net_eq(sock_net(sk), net))
+			continue;
+		if (sk->sk_family == st->family) {
+			cur = sk;
+			goto out;
+		}
+		icsk = inet_csk(sk);
+		spin_lock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
+		if (reqsk_queue_len(&icsk->icsk_accept_queue)) {
+start_req:
+			st->uid		= sock_i_uid(sk);
+			st->syn_wait_sk = sk;
+			st->state	= TCP_SEQ_STATE_OPENREQ;
+			st->sbucket	= 0;
+			goto get_req;
+		}
+		spin_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
+	}
+	spin_unlock_bh(&ilb->lock);
+	st->offset = 0;
+	if (++st->bucket < INET_LHTABLE_SIZE) {
+		ilb = &tcp_hashinfo.listening_hash[st->bucket];
+		spin_lock_bh(&ilb->lock);
+		sk = sk_nulls_head(&ilb->head);
+		goto get_sk;
+	}
+	cur = NULL;
+out:
+	return cur;
+}
+
+static void *listening_get_idx(struct seq_file *seq, loff_t *pos)
+{
+	struct tcp_iter_state *st = seq->private;
+	void *rc;
+
+	st->bucket = 0;
+	st->offset = 0;
+	rc = listening_get_next(seq, NULL);
+
+	while (rc && *pos) {
+		rc = listening_get_next(seq, rc);
+		--*pos;
+	}
+	return rc;
+}
+
+static inline bool empty_bucket(const struct tcp_iter_state *st)
+{
+	return hlist_nulls_empty(&tcp_hashinfo.ehash[st->bucket].chain);
+}
+
+/*
+ * Get first established socket starting from bucket given in st->bucket.
+ * If st->bucket is zero, the very first socket in the hash is returned.
+ */
+static void *established_get_first(struct seq_file *seq)
+{
+	struct tcp_iter_state *st = seq->private;
+	struct net *net = seq_file_net(seq);
+	void *rc = NULL;
+
+	st->offset = 0;
+	for (; st->bucket <= tcp_hashinfo.ehash_mask; ++st->bucket) {
+		struct sock *sk;
+		struct hlist_nulls_node *node;
+		spinlock_t *lock = inet_ehash_lockp(&tcp_hashinfo, st->bucket);
+
+		/* Lockless fast path for the common case of empty buckets */
+		if (empty_bucket(st))
+			continue;
+
+		spin_lock_bh(lock);
+		sk_nulls_for_each(sk, node, &tcp_hashinfo.ehash[st->bucket].chain) {
+			if (sk->sk_family != st->family ||
+			    !net_eq(sock_net(sk), net)) {
+				continue;
+			}
+			rc = sk;
+			goto out;
+		}
+		spin_unlock_bh(lock);
+	}
+out:
+	return rc;
+}
+
+static void *established_get_next(struct seq_file *seq, void *cur)
+{
+	struct sock *sk = cur;
+	struct hlist_nulls_node *node;
+	struct tcp_iter_state *st = seq->private;
+	struct net *net = seq_file_net(seq);
+
+	++st->num;
+	++st->offset;
+
+	sk = sk_nulls_next(sk);
+
+	sk_nulls_for_each_from(sk, node) {
+		if (sk->sk_family == st->family && net_eq(sock_net(sk), net))
+			return sk;
+	}
+
+	spin_unlock_bh(inet_ehash_lockp(&tcp_hashinfo, st->bucket));
+	++st->bucket;
+	return established_get_first(seq);
+}
+
+static void *established_get_idx(struct seq_file *seq, loff_t pos)
+{
+	struct tcp_iter_state *st = seq->private;
+	void *rc;
+
+	st->bucket = 0;
+	rc = established_get_first(seq);
+
+	while (rc && pos) {
+		rc = established_get_next(seq, rc);
+		--pos;
+	}
+	return rc;
+}
+
+static void *tcp_get_idx(struct seq_file *seq, loff_t pos)
+{
+	void *rc;
+	struct tcp_iter_state *st = seq->private;
+
+	st->state = TCP_SEQ_STATE_LISTENING;
+	rc	  = listening_get_idx(seq, &pos);
+
+	if (!rc) {
+		st->state = TCP_SEQ_STATE_ESTABLISHED;
+		rc	  = established_get_idx(seq, pos);
+	}
+
+	return rc;
+}
+
+static void *tcp_seek_last_pos(struct seq_file *seq)
+{
+	struct tcp_iter_state *st = seq->private;
+	int offset = st->offset;
+	int orig_num = st->num;
+	void *rc = NULL;
+
+	switch (st->state) {
+	case TCP_SEQ_STATE_OPENREQ:
+	case TCP_SEQ_STATE_LISTENING:
+		if (st->bucket >= INET_LHTABLE_SIZE)
+			break;
+		st->state = TCP_SEQ_STATE_LISTENING;
+		rc = listening_get_next(seq, NULL);
+		while (offset-- && rc)
+			rc = listening_get_next(seq, rc);
+		if (rc)
+			break;
+		st->bucket = 0;
+		st->state = TCP_SEQ_STATE_ESTABLISHED;
+		/* Fallthrough */
+	case TCP_SEQ_STATE_ESTABLISHED:
+		if (st->bucket > tcp_hashinfo.ehash_mask)
+			break;
+		rc = established_get_first(seq);
+		while (offset-- && rc)
+			rc = established_get_next(seq, rc);
+	}
+
+	st->num = orig_num;
+
+	return rc;
+}
+
+static void *tcp_seq_start(struct seq_file *seq, loff_t *pos)
+{
+	struct tcp_iter_state *st = seq->private;
+	void *rc;
+
+	if (*pos && *pos == st->last_pos) {
+		rc = tcp_seek_last_pos(seq);
+		if (rc)
+			goto out;
+	}
+
+	st->state = TCP_SEQ_STATE_LISTENING;
+	st->num = 0;
+	st->bucket = 0;
+	st->offset = 0;
+	rc = *pos ? tcp_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
+
+out:
+	st->last_pos = *pos;
+	return rc;
+}
+
+static void *tcp_seq_next(struct seq_file *seq, void *v, loff_t *pos)
+{
+	struct tcp_iter_state *st = seq->private;
+	void *rc = NULL;
+
+	if (v == SEQ_START_TOKEN) {
+		rc = tcp_get_idx(seq, 0);
+		goto out;
+	}
+
+	switch (st->state) {
+	case TCP_SEQ_STATE_OPENREQ:
+	case TCP_SEQ_STATE_LISTENING:
+		rc = listening_get_next(seq, v);
+		if (!rc) {
+			st->state = TCP_SEQ_STATE_ESTABLISHED;
+			st->bucket = 0;
+			st->offset = 0;
+			rc	  = established_get_first(seq);
+		}
+		break;
+	case TCP_SEQ_STATE_ESTABLISHED:
+		rc = established_get_next(seq, v);
+		break;
+	}
+out:
+	++*pos;
+	st->last_pos = *pos;
+	return rc;
+}
+
+static void tcp_seq_stop(struct seq_file *seq, void *v)
+{
+	struct tcp_iter_state *st = seq->private;
+
+	switch (st->state) {
+	case TCP_SEQ_STATE_OPENREQ:
+		if (v) {
+			struct inet_connection_sock *icsk = inet_csk(st->syn_wait_sk);
+			spin_unlock_bh(&icsk->icsk_accept_queue.syn_wait_lock);
+		}
+	case TCP_SEQ_STATE_LISTENING:
+		if (v != SEQ_START_TOKEN)
+			spin_unlock_bh(&tcp_hashinfo.listening_hash[st->bucket].lock);
+		break;
+	case TCP_SEQ_STATE_ESTABLISHED:
+		if (v)
+			spin_unlock_bh(inet_ehash_lockp(&tcp_hashinfo, st->bucket));
+		break;
+	}
+}
+
+int tcp_seq_open(struct inode *inode, struct file *file)
+{
+	struct tcp_seq_afinfo *afinfo = PDE_DATA(inode);
+	struct tcp_iter_state *s;
+	int err;
+
+	err = seq_open_net(inode, file, &afinfo->seq_ops,
+			  sizeof(struct tcp_iter_state));
+	if (err < 0)
+		return err;
+
+	s = ((struct seq_file *)file->private_data)->private;
+	s->family		= afinfo->family;
+	s->last_pos		= 0;
+	return 0;
+}
+EXPORT_SYMBOL(tcp_seq_open);
+
+int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo)
+{
+	int rc = 0;
+	struct proc_dir_entry *p;
+
+	afinfo->seq_ops.start		= tcp_seq_start;
+	afinfo->seq_ops.next		= tcp_seq_next;
+	afinfo->seq_ops.stop		= tcp_seq_stop;
+
+	p = proc_create_data(afinfo->name, S_IRUGO, net->proc_net,
+			     afinfo->seq_fops, afinfo);
+	if (!p)
+		rc = -ENOMEM;
+	return rc;
+}
+EXPORT_SYMBOL(tcp_proc_register);
+
+void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo)
+{
+	remove_proc_entry(afinfo->name, net->proc_net);
+}
+EXPORT_SYMBOL(tcp_proc_unregister);
+
+static void get_openreq4(const struct request_sock *req,
+			 struct seq_file *f, int i, kuid_t uid)
+{
+	const struct inet_request_sock *ireq = inet_rsk(req);
+	long delta = req->rsk_timer.expires - jiffies;
+
+	seq_printf(f, "%4d: %08X:%04X %08X:%04X"
+		" %02X %08X:%08X %02X:%08lX %08X %5u %8d %u %d %pK",
+		i,
+		ireq->ir_loc_addr,
+		ireq->ir_num,
+		ireq->ir_rmt_addr,
+		ntohs(ireq->ir_rmt_port),
+		TCP_SYN_RECV,
+		0, 0, /* could print option size, but that is af dependent. */
+		1,    /* timers active (only the expire timer) */
+		jiffies_delta_to_clock_t(delta),
+		req->num_timeout,
+		from_kuid_munged(seq_user_ns(f), uid),
+		0,  /* non standard timer */
+		0, /* open_requests have no inode */
+		0,
+		req);
+}
+
+static void get_tcp4_sock(struct sock *sk, struct seq_file *f, int i)
+{
+	int timer_active;
+	unsigned long timer_expires;
+	const struct tcp_sock *tp = tcp_sk(sk);
+	const struct inet_connection_sock *icsk = inet_csk(sk);
+	const struct inet_sock *inet = inet_sk(sk);
+	struct fastopen_queue *fastopenq = icsk->icsk_accept_queue.fastopenq;
+	__be32 dest = inet->inet_daddr;
+	__be32 src = inet->inet_rcv_saddr;
+	__u16 destp = ntohs(inet->inet_dport);
+	__u16 srcp = ntohs(inet->inet_sport);
+	int rx_queue;
+
+	if (icsk->icsk_pending == ICSK_TIME_RETRANS ||
+	    icsk->icsk_pending == ICSK_TIME_EARLY_RETRANS ||
+	    icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) {
+		timer_active	= 1;
+		timer_expires	= icsk->icsk_timeout;
+	} else if (icsk->icsk_pending == ICSK_TIME_PROBE0) {
+		timer_active	= 4;
+		timer_expires	= icsk->icsk_timeout;
+	} else if (timer_pending(&sk->sk_timer)) {
+		timer_active	= 2;
+		timer_expires	= sk->sk_timer.expires;
+	} else {
+		timer_active	= 0;
+		timer_expires = jiffies;
+	}
+
+	if (sk->sk_state == TCP_LISTEN)
+		rx_queue = sk->sk_ack_backlog;
+	else
+		/*
+		 * because we dont lock socket, we might find a transient negative value
+		 */
+		rx_queue = max_t(int, tp->rcv_nxt - tp->copied_seq, 0);
+
+	seq_printf(f, "%4d: %08X:%04X %08X:%04X %02X %08X:%08X %02X:%08lX "
+			"%08X %5u %8d %lu %d %pK %lu %lu %u %u %d",
+		i, src, srcp, dest, destp, sk->sk_state,
+		tp->write_seq - tp->snd_una,
+		rx_queue,
+		timer_active,
+		jiffies_delta_to_clock_t(timer_expires - jiffies),
+		icsk->icsk_retransmits,
+		from_kuid_munged(seq_user_ns(f), sock_i_uid(sk)),
+		icsk->icsk_probes_out,
+		sock_i_ino(sk),
+		atomic_read(&sk->sk_refcnt), sk,
+		jiffies_to_clock_t(icsk->icsk_rto),
+		jiffies_to_clock_t(icsk->icsk_ack.ato),
+		(icsk->icsk_ack.quick << 1) | icsk->icsk_ack.pingpong,
+		tp->snd_cwnd,
+		sk->sk_state == TCP_LISTEN ?
+		    (fastopenq ? fastopenq->max_qlen : 0) :
+		    (tcp_in_initial_slowstart(tp) ? -1 : tp->snd_ssthresh));
+}
+
+static void get_timewait4_sock(const struct inet_timewait_sock *tw,
+			       struct seq_file *f, int i)
+{
+	long delta = tw->tw_timer.expires - jiffies;
+	__be32 dest, src;
+	__u16 destp, srcp;
+
+	dest  = tw->tw_daddr;
+	src   = tw->tw_rcv_saddr;
+	destp = ntohs(tw->tw_dport);
+	srcp  = ntohs(tw->tw_sport);
+
+	seq_printf(f, "%4d: %08X:%04X %08X:%04X"
+		" %02X %08X:%08X %02X:%08lX %08X %5d %8d %d %d %pK",
+		i, src, srcp, dest, destp, tw->tw_substate, 0, 0,
+		3, jiffies_delta_to_clock_t(delta), 0, 0, 0, 0,
+		atomic_read(&tw->tw_refcnt), tw);
+}
+
+#define TMPSZ 150
+
+static int tcp4_seq_show(struct seq_file *seq, void *v)
+{
+	struct tcp_iter_state *st;
+	struct sock *sk = v;
+
+	seq_setwidth(seq, TMPSZ - 1);
+	if (v == SEQ_START_TOKEN) {
+		seq_puts(seq, "  sl  local_address rem_address   st tx_queue "
+			   "rx_queue tr tm->when retrnsmt   uid  timeout "
+			   "inode");
+		goto out;
+	}
+	st = seq->private;
+
+	switch (st->state) {
+	case TCP_SEQ_STATE_LISTENING:
+	case TCP_SEQ_STATE_ESTABLISHED:
+		if (sk->sk_state == TCP_TIME_WAIT)
+			get_timewait4_sock(v, seq, st->num);
+		else
+			get_tcp4_sock(v, seq, st->num);
+		break;
+	case TCP_SEQ_STATE_OPENREQ:
+		get_openreq4(v, seq, st->num, st->uid);
+		break;
+	}
+out:
+	seq_pad(seq, '\n');
+	return 0;
+}
+
+static const struct file_operations tcp_afinfo_seq_fops = {
+	.owner   = THIS_MODULE,
+	.open    = tcp_seq_open,
+	.read    = seq_read,
+	.llseek  = seq_lseek,
+	.release = seq_release_net
+};
+
+static struct tcp_seq_afinfo tcp4_seq_afinfo = {
+	.name		= "tcp",
+	.family		= AF_INET,
+	.seq_fops	= &tcp_afinfo_seq_fops,
+	.seq_ops	= {
+		.show		= tcp4_seq_show,
+	},
+};
+
+static int __net_init tcp4_proc_init_net(struct net *net)
+{
+	return tcp_proc_register(net, &tcp4_seq_afinfo);
+}
+
+static void __net_exit tcp4_proc_exit_net(struct net *net)
+{
+	tcp_proc_unregister(net, &tcp4_seq_afinfo);
+}
+
+static struct pernet_operations tcp4_net_ops = {
+	.init = tcp4_proc_init_net,
+	.exit = tcp4_proc_exit_net,
+};
+
+int __init tcp4_proc_init(void)
+{
+	return register_pernet_subsys(&tcp4_net_ops);
+}
+
+void tcp4_proc_exit(void)
+{
+	unregister_pernet_subsys(&tcp4_net_ops);
+}
+#endif /* CONFIG_PROC_FS */
+
+struct proto tcp_prot = {
+	.name			= "TCP",
+	.owner			= THIS_MODULE,
+	.close			= tcp_close,
+	.connect		= tcp_v4_connect,
+	.disconnect		= tcp_disconnect,
+	.accept			= inet_csk_accept,
+	.ioctl			= tcp_ioctl,
+	.init			= tcp_v4_init_sock,
+	.destroy		= tcp_v4_destroy_sock,
+	.shutdown		= tcp_shutdown,
+	.setsockopt		= tcp_setsockopt,
+	.getsockopt		= tcp_getsockopt,
+	.recvmsg		= tcp_recvmsg,
+	.sendmsg		= tcp_sendmsg,
+	.sendpage		= tcp_sendpage,
+	.backlog_rcv		= tcp_v4_do_rcv,
+	.release_cb		= tcp_release_cb,
+	.hash			= inet_hash,
+	.unhash			= inet_unhash,
+	.get_port		= inet_csk_get_port,
+	.enter_memory_pressure	= tcp_enter_memory_pressure,
+	.stream_memory_free	= tcp_stream_memory_free,
+	.sockets_allocated	= &tcp_sockets_allocated,
+	.orphan_count		= &tcp_orphan_count,
+	.memory_allocated	= &tcp_memory_allocated,
+	.memory_pressure	= &tcp_memory_pressure,
+	.sysctl_mem		= sysctl_tcp_mem,
+	.sysctl_wmem		= sysctl_tcp_wmem,
+	.sysctl_rmem		= sysctl_tcp_rmem,
+	.max_header		= MAX_TCP_HEADER,
+	.obj_size		= sizeof(struct tcp_sock),
+	.slab_flags		= SLAB_DESTROY_BY_RCU,
+	.twsk_prot		= &tcp_timewait_sock_ops,
+	.rsk_prot		= &tcp_request_sock_ops,
+	.h.hashinfo		= &tcp_hashinfo,
+	.no_autobind		= true,
+#ifdef CONFIG_COMPAT
+	.compat_setsockopt	= compat_tcp_setsockopt,
+	.compat_getsockopt	= compat_tcp_getsockopt,
+#endif
+#ifdef CONFIG_MEMCG_KMEM
+	.init_cgroup		= tcp_init_cgroup,
+	.destroy_cgroup		= tcp_destroy_cgroup,
+	.proto_cgroup		= tcp_proto_cgroup,
+#endif
+};
+EXPORT_SYMBOL(tcp_prot);
+
+static void __net_exit tcp_sk_exit(struct net *net)
+{
+	int cpu;
+
+	for_each_possible_cpu(cpu)
+		inet_ctl_sock_destroy(*per_cpu_ptr(net->ipv4.tcp_sk, cpu));
+	free_percpu(net->ipv4.tcp_sk);
+}
+
+static int __net_init tcp_sk_init(struct net *net)
+{
+	int res, cpu;
+
+	net->ipv4.tcp_sk = alloc_percpu(struct sock *);
+	if (!net->ipv4.tcp_sk)
+		return -ENOMEM;
+
+	for_each_possible_cpu(cpu) {
+		struct sock *sk;
+
+		res = inet_ctl_sock_create(&sk, PF_INET, SOCK_RAW,
+					   IPPROTO_TCP, net);
+		if (res)
+			goto fail;
+		*per_cpu_ptr(net->ipv4.tcp_sk, cpu) = sk;
+	}
+	net->ipv4.sysctl_tcp_ecn = 2;
+	net->ipv4.sysctl_tcp_base_mss = TCP_BASE_MSS;
+	net->ipv4.sysctl_tcp_probe_threshold = TCP_PROBE_THRESHOLD;
+	net->ipv4.sysctl_tcp_probe_interval = TCP_PROBE_INTERVAL;
+	return 0;
+
+fail:
+	tcp_sk_exit(net);
+
+	return res;
+}
+
+static void __net_exit tcp_sk_exit_batch(struct list_head *net_exit_list)
+{
+	inet_twsk_purge(&tcp_hashinfo, &tcp_death_row, AF_INET);
+}
+
+static struct pernet_operations __net_initdata tcp_sk_ops = {
+       .init	   = tcp_sk_init,
+       .exit	   = tcp_sk_exit,
+       .exit_batch = tcp_sk_exit_batch,
+};
+
+void __init tcp_v4_init(void)
+{
+	inet_hashinfo_init(&tcp_hashinfo);
+	if (register_pernet_subsys(&tcp_sk_ops))
+		panic("Failed to create the TCP control socket.\n");
+}