Fw: [Bug 73021] New: TCP_USER_TIMEOUT not working when interface is taken down, e.g. cable unplugged

Fw: [Bug 73021] New: TCP_USER_TIMEOUT not working when interface is taken down, e.g. cable unplugged

[Stephen Hemminger]

Begin forwarded message:

Date: Thu, 27 Mar 2014 05:49:28 -0700
From: "bugzilla-daemon@bugzilla.kernel.org" <bugzilla-daemon@bugzilla.kernel.org>
To: "stephen@networkplumber.org" <stephen@networkplumber.org>
Subject: [Bug 73021] New: TCP_USER_TIMEOUT not working when interface is taken down, e.g. cable unplugged


https://bugzilla.kernel.org/show_bug.cgi?id=73021

            Bug ID: 73021
           Summary: TCP_USER_TIMEOUT not working when interface is taken
                    down, e.g. cable unplugged
           Product: Networking
           Version: 2.5
    Kernel Version: 3.4.24 and 3.11.0
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: IPV4
          Assignee: shemminger@linux-foundation.org
          Reporter: pelle.johnsen@gmail.com
        Regression: No

When the network interface is taken down (in this case eth0 plugging out cable)
an established socket goes to zero window probing state (netstat -o shows
unkn-4). This state ignores TCP_USER_TIMEOUT (and any keep-alive timeouts) and
result is that socket takes ~12 min. to timeout instead of what is specified
with TCP_USER_TIMEOUT.

There seems to be 2 'issues':

1. Why does socket go to zero window probing in this case?

2. Why does zero window probing not respect TCP_USER_TIMEOUT?

Expected behavior:

TCP_USER_TIMEOUT can be used to limit how long it takes a socket to timeout.

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