Bugs item #764437, was opened at 2003-07-02 07:13
Message generated for change (Settings changed) made by gbrandl
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Category: Python Library
Group: Platform-specific
>Status: Closed
>Resolution: Fixed
Priority: 5
Submitted By: Pavel Pergamenshchik (ppergame)
Assigned to: Nobody/Anonymous (nobody)
Summary: AF_UNIX sockets do not handle Linux-specific addressing
Initial Comment:
As described in unix(7) manpage, Linux allows for
special "kernel namespace" AF_UNIX sockets defined.
With such sockets, the first byte of the path is \x00,
and the rest is the address. These sockets do not show
up in the filesystem.
socketmodule.c:makesockaddr (as called by recvfrom)
uses code like
PyString_FromString(a->sun_path)
to retrieve the address. This is incorrect -- on Linux, if
the first byte of a->sun_path is null, the function should
use PyString_FromStringAndSize to retrieve the full 108-
byte buffer.
I am not entirely sure that this is the only thing that
needs to be fixed, but bind() and sendto() work with
these sort of socket paths just fine.
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Comment By: Armin Rigo (arigo)
Date: 2006-04-13 20:03
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I'm about to check in a slightly different patch
(also at 1062014) which tries to preserve the length
of the abstract namespace addresses (the kernel saves
this length even though it is not zero-terminated,
so that the names '\x00abc' and '\x00abc\x00' and
'\x00abc\x00\x00' are all different in theory).
The patch no longer exposes UNIX_PATH_MAX because
I'm not sure it's useful any more. If anyone who
is relying on this Linux extension more than myself
has comments, now would be a good time :-)
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Comment By: Irmen de Jong (irmen)
Date: 2004-11-08 11:03
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Patch is at 1062014
The comments below state that UNIX_PATH_MAX is defined in
sys/un.h, but it isn't. The patch gets it in another
(hopefully portable) way (and also exposes it as a new
constant in the socket module)
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Comment By: Aaron Brady (insomnike)
Date: 2004-07-07 14:39
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It should use UNIX_PATH_MAX, but it should also check that
the length of the buffer supplied is correct, my bad.
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Comment By: Pavel Pergamenshchik (ppergame)
Date: 2004-07-07 14:37
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"""The sockets address in this namespace is given by the
rest of the bytes in sun_path. Note that names in the
abstract namespace are not zero‐terminated."""
The length would be UNIX_PATH_MAX in this case.
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Comment By: A.M. Kuchling (akuchling)
Date: 2004-07-07 14:04
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Should it use UNIX_PATH_MAX as the length of the string, or
1+ strlen(a->sun_path+1)? (The leading null byte, plus the
following null-terminated string?)
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Comment By: Aaron Brady (insomnike)
Date: 2004-06-05 19:16
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Also checks for "linux" to be defined, on Mondragon's
recommendation.
###
--- socketmodule.c 3 Jun 2004 09:24:42 -0000 1.291
+++ socketmodule.c 5 Jun 2004 18:17:51 -0000
@@ -942,6 +942,11 @@
case AF_UNIX:
{
struct sockaddr_un *a = (struct sockaddr_un
*) addr;
+#if defined(UNIX_PATH_MAX) && defined(linux)
+ if (*a->sun_path == 0) {
+ return
PyString_FromStringAndSize(a->sun_path, UNIX_PATH_MAX);
+ }
+#endif /* UNIX_PATH_MAX && linux */
return PyString_FromString(a->sun_path);
}
#endif /* AF_UNIX */
###
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Comment By: Aaron Brady (insomnike)
Date: 2004-06-05 19:06
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The below patch adds the functionality if UNIX_PATH_MAX is
defined (in Linux it's in sys/un.h).
###
--- socketmodule.c 3 Jun 2004 09:24:42 -0000 1.291
+++ socketmodule.c 5 Jun 2004 18:08:47 -0000
@@ -942,6 +942,11 @@
case AF_UNIX:
{
struct sockaddr_un *a = (struct sockaddr_un
*) addr;
+#if defined(UNIX_PATH_MAX)
+ if (*a->sun_path == 0) {
+ return
PyString_FromStringAndSize(a->sun_path, UNIX_PATH_MAX);
+ }
+#endif /* UNIX_PATH_MAX */
return PyString_FromString(a->sun_path);
}
#endif /* AF_UNIX */
###
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Comment By: Anthony Baxter (anthonybaxter)
Date: 2003-11-25 08:13
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Eek. What a totally mental design decision on the part of
the Linux kernel developers. Is there a magic C preprocessor
symbol we can use to detect that this insanity is available?
(FWIW, Perl also has problems with this:
http://www.alexhudson.com/code/abstract-sockets-and-perl
)
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