6.6-stable patches

added patches:
	net-tcp-accept-old-ack-during-closing.patch

diff --git a/queue-6.6/net-tcp-accept-old-ack-during-closing.patch b/queue-6.6/net-tcp-accept-old-ack-during-closing.patch
new file mode 100644 (file)
index 0000000..90c87a6
--- /dev/null
+++ b/queue-6.6/net-tcp-accept-old-ack-during-closing.patch
@@ -0,0 +1,75 @@
+From 795a7dfbc3d95e4c7c09569f319f026f8c7f5a9c Mon Sep 17 00:00:00 2001
+From: Menglong Dong <menglong8.dong@gmail.com>
+Date: Fri, 26 Jan 2024 12:05:19 +0800
+Subject: net: tcp: accept old ack during closing
+
+From: Menglong Dong <menglong8.dong@gmail.com>
+
+commit 795a7dfbc3d95e4c7c09569f319f026f8c7f5a9c upstream.
+
+For now, the packet with an old ack is not accepted if we are in
+FIN_WAIT1 state, which can cause retransmission. Taking the following
+case as an example:
+
+    Client                               Server
+      |                                    |
+  FIN_WAIT1(Send FIN, seq=10)          FIN_WAIT1(Send FIN, seq=20, ack=10)
+      |                                    |
+      |                                Send ACK(seq=21, ack=11)
+   Recv ACK(seq=21, ack=11)
+      |
+   Recv FIN(seq=20, ack=10)
+
+In the case above, simultaneous close is happening, and the FIN and ACK
+packet that send from the server is out of order. Then, the FIN will be
+dropped by the client, as it has an old ack. Then, the server has to
+retransmit the FIN, which can cause delay if the server has set the
+SO_LINGER on the socket.
+
+Old ack is accepted in the ESTABLISHED and TIME_WAIT state, and I think
+it should be better to keep the same logic.
+
+In this commit, we accept old ack in FIN_WAIT1/FIN_WAIT2/CLOSING/LAST_ACK
+states. Maybe we should limit it to FIN_WAIT1 for now?
+
+Signed-off-by: Menglong Dong <menglong8.dong@gmail.com>
+Reviewed-by: Simon Horman <horms@kernel.org>
+Reviewed-by: Eric Dumazet <edumazet@google.com>
+Link: https://lore.kernel.org/r/20240126040519.1846345-1-menglong8.dong@gmail.com
+Signed-off-by: Jakub Kicinski <kuba@kernel.org>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ net/ipv4/tcp_input.c |   18 +++++++++++-------
+ 1 file changed, 11 insertions(+), 7 deletions(-)
+
+--- a/net/ipv4/tcp_input.c
++++ b/net/ipv4/tcp_input.c
+@@ -6705,17 +6705,21 @@ int tcp_rcv_state_process(struct sock *s
+               return 0;
+ 
+       /* step 5: check the ACK field */
+-      acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH |
+-                                    FLAG_UPDATE_TS_RECENT |
+-                                    FLAG_NO_CHALLENGE_ACK) > 0;
++      reason = tcp_ack(sk, skb, FLAG_SLOWPATH |
++                                FLAG_UPDATE_TS_RECENT |
++                                FLAG_NO_CHALLENGE_ACK);
+ 
+-      if (!acceptable) {
++      if ((int)reason <= 0) {
+               if (sk->sk_state == TCP_SYN_RECV)
+                       return 1;       /* send one RST */
+-              tcp_send_challenge_ack(sk);
+-              SKB_DR_SET(reason, TCP_OLD_ACK);
+-              goto discard;
++              /* accept old ack during closing */
++              if ((int)reason < 0) {
++                      tcp_send_challenge_ack(sk);
++                      reason = -reason;
++                      goto discard;
++              }
+       }
++      SKB_DR_SET(reason, NOT_SPECIFIED);
+       switch (sk->sk_state) {
+       case TCP_SYN_RECV:
+               tp->delivered++; /* SYN-ACK delivery isn't tracked in tcp_ack */

diff --git a/queue-6.6/series b/queue-6.6/series
index 7a7daeff13e963ff68229770cdf18c0b8e6f0dd9..407311605c594b01ddd53b09ae026bfd18ee1701 100644 (file)
--- a/queue-6.6/series
+++ b/queue-6.6/series
@@ -183,3 +183,4 @@ xdp-produce-a-warning-when-calculated-tailroom-is-ne.patch
 selftest-arm64-fix-sve2p1_sigill-to-hwcap-test.patch
 tracing-add-null-pointer-check-to-trigger_data_free.patch
 net-sched-only-allow-act_ct-to-bind-to-clsact-ingress-qdiscs-and-shared-blocks.patch
+net-tcp-accept-old-ack-during-closing.patch