gen_hosts.pl

gen_hosts.pl

#!/usr/bin/env perl

# NO FITNESS FOR A PARTICULAR PURPOSE.  NO MERCHANTABILITY.

unless ($ARGV[0]) {
    die "Usage: gen_hosts.pl <hosts_file>\n";
}

my $hosts_file = $ARGV[0];
my $hostmap;

# load existing entries into the host map
if (-e $hosts_file) {
    open my $hf, '<', $hosts_file;
    while (my $line = <$hf>) {
        next if $line =~ /^#/;
        my @cols = split(/\s+/, $line);
        push(@{$hostmap->{$cols[0]}}, @cols[1..$#cols]);
    }
    close($hf);
}

# get the hosts data out of the nodeinfo database, must be connected to hyperboria!
my $hosts_url = "http://[fc5d:baa5:61fc:6ffd:9554:67f0:e290:7535]/nodes/list.perl";
my $data = `curl -s -g $hosts_url`;
if ($data =~ /^\[/ && $data =~ /\]$/) {
    my $ar = eval($data);
    foreach my $entry (@$ar) {
        # don't include entries that have the same name as the IP or are just the las
        # 4 of the ipv6 or names that contain illegal chars.
        if (length($entry->{name}) => 3 && 
          $entry->{ip} ne $entry->{name} && 
          $entry->{name} !~ /(?:^[0-9a-f]{4}$|[_\s]+|^-)/) {
            $hostmap->{$entry->{ip}} = [$entry->{name}];
        }
    }

    open my $hf, '>', $hosts_file;
    print $hf "# hosts file automatically generated by gen_hosts.pl\n\n";
    foreach my $addr (keys %$hostmap) {
        # one name for every line.
        foreach my $col (@{$hostmap->{$addr}}) {
            print $hf "$addr $col\n";
        }
    }

    print "[done]: wrote " . scalar(keys %$hostmap) . " entries\n";
} else {
    die "[fatal]: bad data\n";
}