From: Lu Wei <luwei32@huawei.com> maillist inclusion category: bugfix bugzilla: 187792, https://gitee.com/openeuler/kernel/issues/I5ZG7O Reference: https://www.spinics.net/lists/netdev/msg856902.html -------------------------------- If setsockopt with option name of TCP_REPAIR_OPTIONS and opt_code of TCPOPT_SACK_PERM is called to enable sack after data is sent and dupacks are received , it will trigger a warning in function tcp_verify_left_out() as follows: ============================================ WARNING: CPU: 8 PID: 0 at net/ipv4/tcp_input.c:2132 tcp_timeout_mark_lost+0x154/0x160 tcp_enter_loss+0x2b/0x290 tcp_retransmit_timer+0x50b/0x640 tcp_write_timer_handler+0x1c8/0x340 tcp_write_timer+0xe5/0x140 call_timer_fn+0x3a/0x1b0 __run_timers.part.0+0x1bf/0x2d0 run_timer_softirq+0x43/0xb0 __do_softirq+0xfd/0x373 __irq_exit_rcu+0xf6/0x140 The warning is caused in the following steps: 1. a socket named socketA is created 2. socketA enters repair mode without build a connection 3. socketA calls connect() and its state is changed to TCP_ESTABLISHED directly 4. socketA leaves repair mode 5. socketA calls sendmsg() to send data, packets_out and sack_outs(dup ack receives) increase 6. socketA enters repair mode again 7. socketA calls setsockopt with TCPOPT_SACK_PERM to enable sack 8. retransmit timer expires, it calls tcp_timeout_mark_lost(), lost_out increases 9. sack_outs + lost_out > packets_out triggers since lost_out and sack_outs increase repeatly In function tcp_timeout_mark_lost(), tp->sacked_out will be cleared if Step7 not happen and the warning will not be triggered. As suggested by Denis and Eric, TCP_REPAIR_OPTIONS should be prohibited if data was already sent. socket-tcp tests in CRIU has been tested as follows: $ sudo ./test/zdtm.py run -t zdtm/static/socket-tcp* --keep-going \ --ignore-taint socket-tcp* represent all socket-tcp tests in test/zdtm/static/. Fixes: b139ba4e90dc ("tcp: Repair connection-time negotiated parameters") Signed-off-by: Lu Wei <luwei32@huawei.com> Reviewed-by: Eric Dumazet <edumazet@google.com> Reviewed-by: Yue Haibing <yuehaibing@huawei.com> Signed-off-by: Yongqiang Liu <liuyongqiang13@huawei.com> --- net/ipv4/tcp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 094cd93e50c2..6f71b6cfc1b2 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -2916,7 +2916,7 @@ static int do_tcp_setsockopt(struct sock *sk, int level, case TCP_REPAIR_OPTIONS: if (!tp->repair) err = -EINVAL; - else if (sk->sk_state == TCP_ESTABLISHED) + else if (sk->sk_state == TCP_ESTABLISHED && !tp->bytes_sent) err = tcp_repair_options_est(sk, (struct tcp_repair_opt __user *)optval, optlen); -- 2.25.1