Wireshark · Ethereal-users: Re: [Ethereal-users] capture on Unix Sockets ?

[jim cromie <jcromie@xxxxxxxxxx>]

jim cromie wrote:

> Guy Harris wrote:
>
> > > is there any way to capture Unix sockets or FIFOs ( using Ethereal) ? 
> >
> > No.  The reason why UNIX-domain sockets and FIFOs don't show up on
> > capture interface lists is that there's no network interface involved,
> > and libpcap can only capture on network interfaces.
> >
> > > if not, is it reasonable to write a small program to
> > > open such for reading, and echo stuff to UDP packets ? 

Ok, so I tried it. heres a 1st cut.
there are still lots of issues, but it did manage to open some of the 
available sockets,
and receive a message from 1 of them.



Frame 1 (50 on wire, 50 captured)
   Arrival Time: Feb 26, 2002 03:30:37.751026000
   Time delta from previous packet: 0.000000000 seconds
   Time relative to first packet: 0.000000000 seconds
   Frame Number: 1
   Packet Length: 50 bytes
   Capture Length: 50 bytes
Ethernet II
   Destination: 00:00:00:00:00:00 (XEROX_00:00:00)
   Source: 00:00:00:00:00:00 (XEROX_00:00:00)
   Type: IP (0x0800)
Internet Protocol, Src Addr: localhost.localdomain (127.0.0.1), Dst 
Addr: localhost.localdomain (127.0.0.1)
   Version: 4
   Header length: 20 bytes
   Differentiated Services Field: 0x00 (DSCP 0x00: Default; ECN: 0x00)
       0000 00.. = Differentiated Services Codepoint: Default (0x00)
       .... ..0. = ECN-Capable Transport (ECT): 0
       .... ...0 = ECN-CE: 0
   Total Length: 36
   Identification: 0xf316
   Flags: 0x04
       .1.. = Don't fragment: Set
       ..0. = More fragments: Not set
   Fragment offset: 0
   Time to live: 64
   Protocol: UDP (0x11)
   Header checksum: 0x49b0 (correct)
   Source: localhost.localdomain (127.0.0.1)
   Destination: localhost.localdomain (127.0.0.1)
User Datagram Protocol, Src Port: 20001 (20001), Dst Port: 20000 (20000)
   Source port: 20001 (20001)
   Destination port: 20000 (20000)
   Length: 16
   Checksum: 0x6549 (correct)
Data (8 bytes)

0000  00 01 00 40 00 00 00 00                           ...@....          


reply is ICMP destination unreachable
why ?  UDP is 'unreliable',


I had to drop the MSG_PEEK, cuz nobody else was reading it off the socket.
dunno whether Ive really tapped the line, or Ive replaced one receiver 
with another.

feedback welcome/encouraged.


#!/usr/bin/perl -w

use Getopt::Std;
use IO::Socket::UNIX;
use IO::Socket::INET;
use IO::Select;

getopts('l') or die "bad options\n";

if ($opt_l) {
   @endpoints = ("/dev/log", </tmp/*>, </tmp/.*/*>, </tmp/orbit-jimc/*>);

   foreach $fname (@endpoints) {
   if (-S $fname) {
       print "isa socket: $fname\n";
       push @socknames, $fname;
   }
   if (-p $fname) {
       print "isa fifo: $fname\n";
       push @fifonames, $fname;
   }
   }
}
print "found ", scalar @socknames,
   " sockets and ", scalar @fifonames, " fifos\n";

foreach my $sock (@socknames) {
   # print "opening $sock\n";
   $mon = IO::Socket::UNIX->new( Type => SOCK_STREAM,
                 #Local => $sock,
                 Peer => $sock,
                 );
   unless ($mon) {
   $mon = IO::Socket::UNIX->new( Type => SOCK_DGRAM,
                     #Local => $sock,
                     Peer => $sock,
                     );
   warn "bad socket open on $sock: $!\n";
   }
   if ($mon) {
   push @sockets, $mon;
   $sockname{$mon} = $sock;
   print "opening $sock\n";
   }
}

die "no sockets\n" unless @sockets;

print "process $$ opening sockets\n";
my $listener = IO::Select->new();
$listener->add(@sockets);

$out = IO::Socket::INET->new( Type => SOCK_DGRAM,
                 LocalHost => "127.0.0.1:20001",
                 PeerHost => "127.0.0.1:20000",
                 Proto => "udp",
                 )
   or warn "UDP socket failed: $!\n";

my $sr; # sockets ready
# ENTER service loop
while (1) {
   my ($rd,$wr,$err) = IO::Select->select ($listener,undef,undef,undef);
   print "got ", scalar @$rd, " ready\n";

   foreach my $r (@$rd) {
   $r->recv($buf, 10000, MSG_PEEK) or warn "recv: $!\n";
   $r->recv($buf, 10000) or warn "recv: $!\n";
   $out->send($buf);
   print("$sockname{$r} got <$buf> len ", length $buf,
         " val ", unpack("C*", $buf), "\n");

   print stat($sockname{$r});
   }
   foreach my $r (@$wr) {
   print "$r ready to write\n";
   }
   foreach my $r (@$err) {
   print "$r has errs\n";
   }
}
print("server closing\n");