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 <[email protected]>
---
v5: modify the commit message
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 ef14efa1fb70..54836a6b81d6 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3647,7 +3647,7 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
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, optval, optlen);
else
err = -EPERM;
--
2.31.1
On Thu, Nov 3, 2022 at 6:22 PM Lu Wei <[email protected]> wrote:
>
> 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:
>
> 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 <[email protected]>
> ---
> v5: modify the commit message
> 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 ef14efa1fb70..54836a6b81d6 100644
> --- a/net/ipv4/tcp.c
> +++ b/net/ipv4/tcp.c
> @@ -3647,7 +3647,7 @@ int do_tcp_setsockopt(struct sock *sk, int level, int optname,
> 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, optval, optlen);
> else
> err = -EPERM;
> --
> 2.31.1
>
SGTM, thanks.
Reviewed-by: Eric Dumazet <[email protected]>
Hello:
This patch was applied to netdev/net.git (master)
by David S. Miller <[email protected]>:
On Fri, 4 Nov 2022 10:27:23 +0800 you wrote:
> 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
>
> [...]
Here is the summary with links:
- [net,v5] tcp: prohibit TCP_REPAIR_OPTIONS if data was already sent
https://git.kernel.org/netdev/net/c/0c175da7b037
You are awesome, thank you!
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