Bug with UNIX domain sockets on FreeBSD

[Maxime Soulé]

Hi,

I just submitted a bug report to perlbug concerning FreeBSD, so I copy 
it to the list too.

Best regards,

Max.

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Bug with UNIX domain sockets on FreeBSD (at least 7.0 until 7.2
RELEASE).

The unpack_sockaddr_un of perl-5.10.0/ext/Socket/Socket.xs does not
handle correctly struct sockaddr_un under FreeBSD in some cases.

It returns errors like:
    Bad arg length for Socket::unpack_sockaddr_un, length is 16,
    should be 106 at ...

When the system returns a struct sockaddr_un in getpeername(), it
returns the same structure the server gives to bind().

In some cases, servers (X for /tmp/.X11-unix/X0 and devd for
/var/run/devd.pipe, for example) give a shortest structure than
sizeof(struct sockaddr_un) but with a correct sun_len field. In these
cases, sun_path may not be '\0' terminated.

Then getpeername() returns a structure that Socket.xs
unpack_sockaddr_un() function think wrong sized. But it is not.

One can reproduce the problem with the following simple server and
client code.

Server side :
---------------------------------------
use strict;
use Socket;

my $name = $ARGV[0] or die "usage: $0 server_socket_file";

#my $sun = sockaddr_un($name);
# Use a shortest sockaddr_un as FreeBSD allows it for its daemons
my $sun = pack('CCA*', length($name)+2, 1, $name);

socket(my $fh, PF_UNIX, SOCK_STREAM, 0) or die "socket: $!\n";
bind($fh, $sun) or die "bind: $!\n";
listen($fh, 1) or die "listen: $!\n";
while (1)
{
    accept(my $new_fh, $fh) or die "accept: $!\n";
    sleep 1;
}
---------------------------------------

Client side (note that /var/run/devd.pipe socket is always available
on standard FreeBSD installation):
---------------------------------------
use strict;
use Socket;

my $name = $ARGV[0] // '/var/run/devd.pipe';

warn "*** Connecting to $name\n";
my $sun = sockaddr_un($name);

socket(my $fh, PF_UNIX, SOCK_STREAM, 0) or die "socket: $!\n";
connect($fh, $sun) or die "connect: $!\n";

my $sockaddr = getpeername($fh) or die "getpeername: $!\n";
my $warn;

($warn = $sockaddr) =~ s/([\x00-\x19\x7f-\xff])/sprintf("<%02x>",ord$1)/ge;
warn "hexdump: $warn--\n";
warn "real length: " . length($sockaddr) . "\n";
warn "sun_len field: " . unpack('C', $sockaddr) . "\n";
my $file = unpack_sockaddr_un($sockaddr);
warn "unpack: $file--\n";

close $fh;
---------------------------------------

I join a patch that correct the problem on FreeBSD.

Note that the version in the GIT repository have the same problem.

Perhaps the same problem occurs on other BSD (Open, Net, DragonFly),
but I don't have any of them to try...

Many thanks for your work, dont hesitate to contact me to do some
tests if you need...

Best regards,

Maxime Soulé.

Patch to perl-5.10.0/ext/Socket/Socket.xs :

--- perl-5.10.0/ext/Socket/Socket.xs.orig       2009-07-07 17:29:59.000000000 +0200
+++ perl-5.10.0/ext/Socket/Socket.xs    2009-07-07 18:25:57.000000000 +0200
@@ -351,19 +351,25 @@
 #ifdef I_SYS_UN
        struct sockaddr_un addr;
        STRLEN sockaddrlen;
+       STRLEN sockaddrmaxlen;
        char * sun_ad = SvPVbyte(sun_sv,sockaddrlen);
        char * e;
+#   ifdef __FreeBSD__
+       sockaddrmaxlen = addr.sun_len;
+#   else
+       sockaddrmaxlen = sizeof(addr);
+#   endif
 #   ifndef __linux__
        /* On Linux sockaddrlen on sockets returned by accept, recvfrom,
           getpeername and getsockname is not equal to sizeof(addr). */
-       if (sockaddrlen != sizeof(addr)) {
+       if (sockaddrlen != sockaddrmaxlen) {
            croak("Bad arg length for %s, length is %d, should be %d",
                        "Socket::unpack_sockaddr_un",
-                       sockaddrlen, sizeof(addr));
+                       sockaddrlen, sockaddrmaxlen);
        }
 #   endif
 
-       Copy( sun_ad, &addr, sizeof addr, char );
+       Copy( sun_ad, &addr, sockaddrmaxlen, char );
 
        if ( addr.sun_family != AF_UNIX ) {
            croak("Bad address family for %s, got %d, should be %d",
@@ -372,11 +378,18 @@
                        AF_UNIX);
        }
        e = (char*)addr.sun_path;
+#   ifdef __FreeBSD__
+       /* On FreeBSD sun_path ends not always with a '\0'.
+        * How do other BSDs work? */
+        while (e < (char*)&addr + sockaddrmaxlen && *e)
+           ++e;
+#   else
        /* On Linux, the name of abstract unix domain sockets begins
         * with a '\0', so allow this. */
        while ((*e || (e == addr.sun_path && e[1] && sockaddrlen > 1))
                && e < (char*)addr.sun_path + sizeof addr.sun_path)
            ++e;
+#   endif
        ST(0) = sv_2mortal(newSVpvn(addr.sun_path, e - (char*)addr.sun_path));
 #else
        ST(0) = (SV *) not_here("unpack_sockaddr_un");