Package: netcat-openbsd
Version: 1.89-4
Tags: patch
In order to successfully bind() in AF_UNIX, the specified pathname
must not already exist. If it was previously bound, ie was a socket,
but no-one is listening any more, bind() will fail with EADDRINUSE.
This isn't helpful. In particular, it means that if you do this:
nc -v -l -U spong
^C
nc -v -l -U spong
the 2nd invocation is bound to fail.
This patch changes the behaviour so that we always call unlink().
That might cause unintended reuse of the socket pathname, but there is
no reliable way with an AF_UNIX socket to atomically tell whether the
socket is in use.
It is better to be optimistic (and succeed in multiple runs) and risk
unlinking a live socket. People who want some kind of locking can
arrange that themselves.
This patch doesn't have any error handling but then the error handling
in most of netcat is pretty shoddy and it's not clear that reporting
errors from unlink would be in keeping with the error handling
approach elsewhere.
Observed behaviour:
$ rm -f spong
$ nc.openbsd -U -l -v spong
[sits waiting for connection]
^C
$ nc.openbsd -U -l -v spong
nc.openbsd: Address already in use
$
Desired behaviour:
$ nc.openbsd -U -l -v spong
[sits waiting for connection]
^C
$ nc.openbsd -U -l -v spong
[sits waiting for connection]
Ian.
commit 28364d030822d3b5380383178d2e7cb31e395676
Author: Ian Jackson <i...@liberator.relativity.greenend.org.uk>
Date: Tue Apr 27 23:08:13 2010 +0100
remove paths supplied to unix_listen
diff --git a/netcat.c b/netcat.c
index eac43f8..8f2ac8e 100644
--- a/netcat.c
+++ b/netcat.c
@@ -504,6 +504,8 @@ unix_listen(char *path)
return (-1);
}
+ unlink(path);
+
if (bind(s, (struct sockaddr *)&sun, SUN_LEN(&sun)) < 0) {
close(s);
return (-1);
--
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