Files
linux/net
Yonglong Li fd35e34ece tcp: make retransmitted SKB fit into the send window
[ Upstream commit 536a6c8e05 ]

current code of __tcp_retransmit_skb only check TCP_SKB_CB(skb)->seq
in send window, and TCP_SKB_CB(skb)->seq_end maybe out of send window.
If receiver has shrunk his window, and skb is out of new window,  it
should retransmit a smaller portion of the payload.

test packetdrill script:
    0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
   +0 fcntl(3, F_GETFL) = 0x2 (flags O_RDWR)
   +0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0

   +0 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress)
   +0 > S 0:0(0)  win 65535 <mss 1460,sackOK,TS val 100 ecr 0,nop,wscale 8>
 +.05 < S. 0:0(0) ack 1 win 6000 <mss 1000,nop,nop,sackOK>
   +0 > . 1:1(0) ack 1

   +0 write(3, ..., 10000) = 10000

   +0 > . 1:2001(2000) ack 1 win 65535
   +0 > . 2001:4001(2000) ack 1 win 65535
   +0 > . 4001:6001(2000) ack 1 win 65535

 +.05 < . 1:1(0) ack 4001 win 1001

and tcpdump show:
192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 1:2001, ack 1, win 65535, length 2000
192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 2001:4001, ack 1, win 65535, length 2000
192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000
192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000
192.0.2.1.8080 > 192.168.226.67.55: Flags [.], ack 4001, win 1001, length 0
192.168.226.67.55 > 192.0.2.1.8080: Flags [.], seq 5001:6001, ack 1, win 65535, length 1000
192.168.226.67.55 > 192.0.2.1.8080: Flags [P.], seq 4001:5001, ack 1, win 65535, length 1000

when cient retract window to 1001, send window is [4001,5002],
but TLP send 5001-6001 packet which is out of send window.

Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: Yonglong Li <liyonglong@chinatelecom.cn>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/1657532838-20200-1-git-send-email-liyonglong@chinatelecom.cn
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-08-25 11:17:43 +02:00
..
2022-03-11 11:22:39 +01:00
2022-04-20 09:19:40 +02:00
2022-07-07 17:36:48 +02:00
2021-06-18 09:59:00 +02:00