BUG/MINOR: sock_unix: match finalname with tempname in sock_unix_addrcmp()

In sock_unix_addrcmp(), named UNIX sockets paths are manually compared in
order to properly handle tempname paths (ending with ".XXXX.tmp") that result
from the 2-step bind implemented in sock_unix_bind_receiver().

However, this logic does not take into account "final" path names (without the
".XXXX.tmp" suffix).

Example:
  /tmp/test did not match with /tmp/test.1288.tmp prior to this patch

Indeed, depending on how the socket addr is retrieved, the same socket
could be designated either by its tempname or finalname.
socket addr is normally stored with its finalname within a receiver, but a
call to getsockname() on the same socket will return the tempname that was
used for the bind() call (sock_get_old_sockets() depends on getsockname()).

This causes sock_find_compatible_fd() to malfunction with named UNIX
sockets (ie: haproxy -x CLI option).

To fix this, we slightly modify the check around the temp suffix in
sock_unix_addrcmp(): we perform the suffix check even if one of the
paths is lacking the temp suffix (with proper precautions).

Now the function is able to match:
  - finalname x finalname
  - tempname  x tempname
  - finalname x tempname

That is: /tmp/test == /tmp/test.1288.tmp == /tmp/test.X.tmp

It should be backported up to 2.4

(cherry picked from commit 2a7903bbb2102867132d9821913c51cb1b938962)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit af3fa8c632abd425278bd8a8ae4ca89e41e92064)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit 985e257b1fa5534ef8cebd7a0aa075dd10327604)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
(cherry picked from commit af4bffa48915b33370715669bb4ae9fd7c5ed428)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>
diff --git a/src/sock_unix.c b/src/sock_unix.c
index 028dfb7..9b60a61 100644
--- a/src/sock_unix.c
+++ b/src/sock_unix.c
@@ -94,7 +94,21 @@
 
 	/* Now we have a difference. It's OK if they are within or after a
 	 * sequence of digits following a dot, and are followed by ".tmp".
+	 *
+	 * make sure to perform the check against tempname if the compared
+	 * string is in "final" format (does not end with ".XXXX.tmp").
+	 *
+	 * Examples:
+	 *     /tmp/test matches with /tmp/test.1822.tmp
+	 *     /tmp/test.1822.tmp matches with /tmp/test.XXXX.tmp
 	 */
+	if (au->sun_path[idx] == 0 || bu->sun_path[idx] == 0) {
+		if (au->sun_path[idx] == '.' || bu->sun_path[idx] == '.')
+			dot = idx; /* try to match against temp path */
+		else
+			return -1; /* invalid temp path */
+	}
+
 	if (!dot)
 		return -1;