Messages in this thread Patch in this message | | | From | Eric Dumazet <> | Date | Tue, 24 May 2022 15:13:29 -0700 | Subject | Re: [RFC] EADDRINUSE from bind() on application restart after killing |
| |
On Tue, May 24, 2022 at 1:19 AM Muhammad Usama Anjum <usama.anjum@collabora.com> wrote: > > Hello, > > We have a set of processes which talk with each other through a local > TCP socket. If the process(es) are killed (through SIGKILL) and > restarted at once, the bind() fails with EADDRINUSE error. This error > only appears if application is restarted at once without waiting for 60 > seconds or more. It seems that there is some timeout of 60 seconds for > which the previous TCP connection remains alive waiting to get closed > completely. In that duration if we try to connect again, we get the error. > > We are able to avoid this error by adding SO_REUSEADDR attribute to the > socket in a hack. But this hack cannot be added to the application > process as we don't own it. > > I've looked at the TCP connection states after killing processes in > different ways. The TCP connection ends up in 2 different states with > timeouts: > > (1) Timeout associated with FIN_WAIT_1 state which is set through > `tcp_fin_timeout` in procfs (60 seconds by default) > > (2) Timeout associated with TIME_WAIT state which cannot be changed. It > seems like this timeout has come from RFC 1337. > > The timeout in (1) can be changed. Timeout in (2) cannot be changed. It > also doesn't seem feasible to change the timeout of TIME_WAIT state as > the RFC mentions several hazards. But we are talking about a local TCP > connection where maybe those hazards aren't applicable directly? Is it > possible to change timeout for TIME_WAIT state for only local > connections without any hazards? > > We have tested a hack where we replace timeout of TIME_WAIT state from a > value in procfs for local connections. This solves our problem and > application starts to work without any modifications to it. > > The question is that what can be the best possible solution here? Any > thoughts will be very helpful. >
One solution would be to extend TCP diag to support killing TIME_WAIT sockets. (This has been raised recently anyway)
Then you could zap all sockets, before re-starting your program.
ss -K -ta src :listen_port
Untested patch:
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 9984d23a7f3e1353d2e1fc9053d98c77268c577e..1b7bde889096aa800b2994c64a3a68edf3b62434 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -4519,6 +4519,15 @@ int tcp_abort(struct sock *sk, int err) local_bh_enable(); return 0; } + if (sk->sk_state == TCP_TIME_WAIT) { + struct inet_timewait_sock *tw = inet_twsk(sk); + + refcount_inc(&tw->tw_refcnt); + local_bh_disable(); + inet_twsk_deschedule_put(tw); + local_bh_enable(); + return 0; + } return -EOPNOTSUPP; }
| |