Patch "tcp: fix wrong RTO timeout when received SACK reneging" has been added to the 6.5-stable tree

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



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

    tcp: fix wrong RTO timeout when received SACK reneging

to the 6.5-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-wrong-rto-timeout-when-received-sack-renegin.patch
and it can be found in the queue-6.5 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 58a14745efbc88dcf599a39d1c2ceaa279c4a180
Author: Fred Chen <fred.chenchen03@xxxxxxxxx>
Date:   Sat Oct 21 08:19:47 2023 +0800

    tcp: fix wrong RTO timeout when received SACK reneging
    
    [ Upstream commit d2a0fc372aca561556e765d0a9ec365c7c12f0ad ]
    
    This commit fix wrong RTO timeout when received SACK reneging.
    
    When an ACK arrived pointing to a SACK reneging, tcp_check_sack_reneging()
    will rearm the RTO timer for min(1/2*srtt, 10ms) into to the future.
    
    But since the commit 62d9f1a6945b ("tcp: fix TLP timer not set when
    CA_STATE changes from DISORDER to OPEN") merged, the tcp_set_xmit_timer()
    is moved after tcp_fastretrans_alert()(which do the SACK reneging check),
    so the RTO timeout will be overwrited by tcp_set_xmit_timer() with
    icsk_rto instead of 1/2*srtt.
    
    Here is a packetdrill script to check this bug:
    0     socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
    +0    bind(3, ..., ...) = 0
    +0    listen(3, 1) = 0
    
    // simulate srtt to 100ms
    +0    < S 0:0(0) win 32792 <mss 1000, sackOK,nop,nop,nop,wscale 7>
    +0    > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 7>
    +.1    < . 1:1(0) ack 1 win 1024
    
    +0    accept(3, ..., ...) = 4
    
    +0    write(4, ..., 10000) = 10000
    +0    > P. 1:10001(10000) ack 1
    
    // inject sack
    +.1    < . 1:1(0) ack 1 win 257 <sack 1001:10001,nop,nop>
    +0    > . 1:1001(1000) ack 1
    
    // inject sack reneging
    +.1    < . 1:1(0) ack 1001 win 257 <sack 9001:10001,nop,nop>
    
    // we expect rto fired in 1/2*srtt (50ms)
    +.05    > . 1001:2001(1000) ack 1
    
    This fix remove the FLAG_SET_XMIT_TIMER from ack_flag when
    tcp_check_sack_reneging() set RTO timer with 1/2*srtt to avoid
    being overwrited later.
    
    Fixes: 62d9f1a6945b ("tcp: fix TLP timer not set when CA_STATE changes from DISORDER to OPEN")
    Signed-off-by: Fred Chen <fred.chenchen03@xxxxxxxxx>
    Reviewed-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
    Tested-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
    Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index a5781f86ac375..7d544f965b264 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -2202,16 +2202,17 @@ void tcp_enter_loss(struct sock *sk)
  * restore sanity to the SACK scoreboard. If the apparent reneging
  * persists until this RTO then we'll clear the SACK scoreboard.
  */
-static bool tcp_check_sack_reneging(struct sock *sk, int flag)
+static bool tcp_check_sack_reneging(struct sock *sk, int *ack_flag)
 {
-	if (flag & FLAG_SACK_RENEGING &&
-	    flag & FLAG_SND_UNA_ADVANCED) {
+	if (*ack_flag & FLAG_SACK_RENEGING &&
+	    *ack_flag & FLAG_SND_UNA_ADVANCED) {
 		struct tcp_sock *tp = tcp_sk(sk);
 		unsigned long delay = max(usecs_to_jiffies(tp->srtt_us >> 4),
 					  msecs_to_jiffies(10));
 
 		inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
 					  delay, TCP_RTO_MAX);
+		*ack_flag &= ~FLAG_SET_XMIT_TIMER;
 		return true;
 	}
 	return false;
@@ -2981,7 +2982,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const u32 prior_snd_una,
 		tp->prior_ssthresh = 0;
 
 	/* B. In all the states check for reneging SACKs. */
-	if (tcp_check_sack_reneging(sk, flag))
+	if (tcp_check_sack_reneging(sk, ack_flag))
 		return;
 
 	/* C. Check consistency of the current state. */



[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [Linux USB Devel]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]

  Powered by Linux