generate an id based on a block device's iscsi target name and lun number

iscsi-blockdev-uid.pl

#!/usr/bin/perl
use strict;
use warnings;

use Getopt::Long;
use Digest::SHA1 qw(sha1_base64);

my $hash;
GetOptions("hash" => \$hash);

my $dev = shift or die "Need a block device";

my $devs = `echo /sys/class/iscsi_session/*/device/target*/*/scsi_device:*/device/block:*`;
chomp $devs;

my @devs = split m/ /, $devs;
my %block_dev;
foreach (@devs) {
    my ($session, $lun, $bd) = m!^(/sys/class/iscsi_session/[^/]+)/.*scsi_device:\d+:\d+:\d+:(\d+)/device/block:(\w+)$!;
    $bd or die "Couldn't parse $_";
    $block_dev{$bd}{lun} = $lun;
    my $tgt = `cat $session/targetname`;
    chomp $tgt;
    $block_dev{$bd}{target} = $tgt;
}
my $bd = $block_dev{$dev} or die "$dev: invalid block device";
print "dev: $dev\n" unless $hash;
my $s;
foreach (qw/target lun/) {
    $s .= "$_: " . $bd->{$_} . "\n";
}
chomp $s;
$s = sha1_base64($s) if $hash;
print "$s\n";