mdw@git.distorted.org.uk Git - secnet/blob - polypath-interface-monitor-linux

   1 #!/usr/bin/perl -w
   2
   3 # This file is part of secnet.
   4 # See README for full list of copyright holders.
   5 #
   6 # secnet is free software; you can redistribute it and/or modify it
   7 # under the terms of the GNU General Public License as published by
   8 # the Free Software Foundation; either version 3 of the License, or
   9 # (at your option) any later version.
  10 #
  11 # secnet is distributed in the hope that it will be useful, but
  12 # WITHOUT ANY WARRANTY; without even the implied warranty of
  13 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 # General Public License for more details.
  15 #
  16 # You should have received a copy of the GNU General Public License
  17 # version 3 along with secnet; if not, see
  18 # https://www.gnu.org/licenses/gpl.html.
  19
  20 use strict;
  21 use IO::Handle;
  22
  23 my $us = $0;
  24 $us =~ s{.*/}{};
  25
  26 open DEBUG, ">/dev/null" or die $!;
  27
  28 if (@ARGV && $ARGV[0] eq '-D') {
  29     shift @ARGV;
  30     open DEBUG, ">&STDERR" or die $!;
  31 }
  32
  33 die "$us: no arguments permitted\n" if @ARGV;
  34
  35 our ($monh,$monchild);
  36
  37 our %reported;
  38 #  no entry: not reported, does not exist
  39 #  /ry+/: reported, entry exists
  40 # during processing only:
  41 #  /r/: reported, may not still exist
  42 #  /y+/: not reported, entry exists
  43
  44 sub killmonitor () {
  45     return unless $monchild;
  46     kill 9, $monchild
  47         or warn "$us: cannot kill monitor child [$monchild]: $!\n";
  48     $monchild=undef;
  49     close $monh;
  50 }
  51
  52 END { killmonitor(); }
  53
  54 my $restart;
  55
  56 for (;;) {
  57     my $o;
  58     eval {
  59         if (!$monh) {
  60             killmonitor();
  61             $monh = new IO::File;
  62             $monchild = open $monh, "-|", qw(ip -o monitor addr)
  63                 or die "spawn monitor: $!\n";
  64             sleep(1) if $restart++;
  65         } else {
  66             my $discard;
  67             my $got = sysread $monh, $discard, 4096;
  68             die "read monitor: $!\n" unless defined $got;
  69             die "monitor failed\n" unless $got;
  70         }
  71         $_='r' foreach values %reported;
  72         print DEBUG "#########################################\n";
  73         foreach my $ip (qw(4 6)) {
  74             print DEBUG "###### $ip:\n";
  75             my $addrh = new IO::File;
  76             open $addrh, "-|", qw(ip -o), "-$ip", qw(addr show)
  77                 or die "spawn addr $ip show: $!\n";
  78             my $afstr = $ip==4 ? 'inet' : $ip==6 ? 'inet6' : die;
  79             while (<$addrh>) {
  80                 print DEBUG "#$_";
  81                 if (m{^\d+\:\s*(\S+)\s+$afstr\s+([0-9a-z.:]+)(?:/\d+)?\s}) {
  82                     my $rhs=$'; #';
  83                     my $outline = "$ip $1 $2";
  84                     # "ip -o addr show" has a ridiculous output format.  In
  85                     # particular, it mixes output keywords which introduce
  86                     # values with ones which don't, and there seems to be
  87                     # no way to tell without knowing all the possible
  88                     # keywords.  We hope that before the \ there is nothing
  89                     # which contains arbitrary text (specifically, which
  90                     # might be `tentative' other than to specify IPv6
  91                     # tentativeness).  We have to do this for IPv6 only
  92                     # because in the IPv4 output, the interface name
  93                     # appears here!
  94                     next if $ip==6 && $rhs=~m{[^\\]* tentative\s};
  95                     $reported{$outline} .= "y";
  96                 } else {
  97                     chomp;
  98                     warn "unexpected output from addr $ip show: $_\n";
  99                 }
 100             }
 101             my $r = close $addrh;
 102             die "addr $ip show failed $!\n" unless $r;
 103             $o = '';
 104         }
 105         foreach my $k (keys %reported) {
 106             local $_ = $reported{$k};
 107             if (m/^r$/) {
 108                 $o .= "-$k\n";
 109                 delete $reported{$k};
 110             } elsif (m/^y/) {
 111                 $o .= "+$k\n";
 112             }
 113         }
 114     };
 115     if ($@) {
 116         print STDERR "$us: $@";
 117         sleep 5;
 118         next;
 119     }
 120     print $o or die $!;
 121     STDOUT->flush or die $!;
 122 }