Patch "tcp: fix tcpi_segs_in after connection establishment" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

tcp: fix tcpi_segs_in after connection establishment

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
tcp-fix-tcpi_segs_in-after-connection-establishment.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Eric Dumazet <[email protected]>
Date: Sun, 6 Mar 2016 09:29:21 -0800
Subject: tcp: fix tcpi_segs_in after connection establishment

From: Eric Dumazet <[email protected]>

[ Upstream commit a9d99ce28ed359d68cf6f3c1a69038aefedf6d6a ]

If final packet (ACK) of 3WHS is lost, it appears we do not properly account the following incoming segment into tcpi_segs_in

While we are at it, starts segs_in with one, to count the SYN packet.

We do not yet count number of SYN we received for a request sock, we might add this someday.

packetdrill script showing proper behavior after fix :

// Tests tcpi_segs_in when 3rd packet (ACK) of 3WHS is lost 0.000 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 +0 bind(3, ..., ...) = 0
+0 listen(3, 1) = 0

+0 < S 0:0(0) win 32792 <mss 1000,sackOK,nop,nop> +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK>
+.020 < P. 1:1001(1000) ack 1 win 32792

+0 accept(3, ..., ...) = 4

+.000 %{ assert tcpi_segs_in == 2, 'tcpi_segs_in=%d' % tcpi_segs_in }%

---
 net/ipv4/tcp_minisocks.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

@@ -458,7 +458,7 @@ struct sock *tcp_create_openreq_child(co
 
 		newtp->rcv_wup = newtp->copied_seq =
 		newtp->rcv_nxt = treq->rcv_isn + 1;
-		newtp->segs_in = 0;
+		newtp->segs_in = 1;
 
 		newtp->snd_sml = newtp->snd_una =
 		newtp->snd_nxt = newtp->snd_up = treq->snt_isn + 1;

@@ -818,6 +818,7 @@ int tcp_child_process(struct sock *paren
 	int ret = 0;
 	int state = child->sk_state;
 
+	tcp_sk(child)->segs_in += max_t(u16, 1, skb_shinfo(skb)->gso_segs);
 	if (!sock_owned_by_user(child)) {
 		ret = tcp_rcv_state_process(child, skb);
 		/* Wakeup parent, send SIGIO */

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/tcp-fix-tcpi_segs_in-after-connection-establishment.patch queue-4.4/tcp-dccp-remove-obsolete-warn_on-in-icmp-handlers.patch queue-4.4/ipv6-udp-fix-udp_mib_ignoredmulti-updates.patch queue-4.4/net-fix-use-after-free-in-the-recvmmsg-exit-path.patch queue-4.4/bonding-fix-bond_get_stats.patch queue-4.4/net-bcmgenet-fix-dma-api-length-mismatch.patch