Messages in this thread | | | Date | Fri, 30 Sep 2022 18:24:00 +0500 | Subject | Re: [RFC] EADDRINUSE from bind() on application restart after killing | From | Muhammad Usama Anjum <> |
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Hi Eric,
RFC 1337 describes the TIME-WAIT Assassination Hazards in TCP. Because of this hazard we have 60 seconds timeout in TIME_WAIT state if connection isn't closed properly. From RFC 1337: > The TIME-WAIT delay allows all old duplicate segments time enough to die in the Internet before the connection is reopened.
As on localhost there is virtually no delay. I think the TIME-WAIT delay must be zero for localhost connections. I'm no expert here. On localhost there is no delay. So why should we wait for 60 seconds to mitigate a hazard which isn't there?
Zapping the sockets in TIME_WAIT and FIN_WAIT_2 does removes them. But zap is required from privileged (CAP_NET_ADMIN) process. We are having hard time finding a privileged process to do this.
Thanks, Usama
On 5/24/22 1:18 PM, Muhammad Usama Anjum 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. > > Regards, >
-- Muhammad Usama Anjum
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