#! /usr/bin/perl

# **** License ****
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# This code was originally developed by Vyatta, Inc.
# Portions created by Vyatta are Copyright (C) 2007 Vyatta, Inc.
# All Rights Reserved.
#
# Author: Stephen Hemminger
# Date: October 2010
# Description: script is run as net-snmp extension to read interface alias
#
# **** End License ****

use strict;
use warnings;
use feature "switch";
no warnings 'experimental::smartmatch';

# Collect interface all alias values
sub get_alias {
    my @interfaces;

    open (my $ip, '-|', 'ip li')
       or die "Can't run ip command\n";
    my $index;
    while(<$ip>) {
       if (/^(\d+): ([^:]*): /) {
	   $index = $1;
	   $interfaces[$index] = $2;
       } elsif (/^ +alias (.*)$/) {
	   $interfaces[$index] = $1;
       }
    }
    close $ip;
    return @interfaces;
}

sub get_oid {
    my $oid = shift;
    die "Not a valid Object ID: $oid"
	unless ($oid =~ /.(\d+)$/);

    my $ifindex = $1;
    my @interfaces = get_alias();

    my $ifalias = $interfaces[$ifindex];
    print "$oid\nstring\n$ifalias\n" if $ifalias;
}

# OID of ifAlias [RFC2863]
my $BASE = '.1.3.6.1.2.1.31.1.1.1.18';

sub get_next {
    my $oid = shift;

    return get_next("$BASE.0")
	if ($oid eq $BASE);

    die "Not a valid Object ID: $oid"
	unless ($oid =~ /^(\S*)\.(\d+)$/);

    my $base = $1;
    my $ifindex = $2;
    my @interfaces = get_alias();

    while (++$ifindex <= $#interfaces) {
	my $ifalias = $interfaces[$ifindex];
	if ($ifalias) {
	    print "$base.$ifindex\nstring\n$ifalias\n";
	    last;
	}
    }
}

sub ifindextoname {
    my $ifindex = shift;

    open (my $ip, '-|', 'ip li')
	or die "Can't run ip command\n";
    my $index;
    while(<$ip>) {
	next unless (/^(\d+): ([^:]*): /);
	return $2 if ($1 == $ifindex);
    }
    return;
}

sub set_oid {
    my ($oid, $target, $value) = @_;
    die "Not a valid Object ID: $oid"
	unless ($oid =~ /\.(\d+)$/);
    my $ifindex = $1;
    unless ($target eq 'string') {
	print "wrong-type\n";
	return;
    }

    my $ifname = ifindextoname($ifindex);
    if ($ifname) {
	system("ip li set $ifname alias '$value' >/dev/null 2>&1");
	print "not-writeable\n"	if ($? != 0);
    }
}

sub usage {
    warn "Usage: $0 {-g|-n} OID\n";
    warn "       $0 -s OID TARGET VALUE\n";
    exit 1;
}

usage unless $#ARGV >= 1;

given ($ARGV[0]) {
    when ('-g') { get_oid ($ARGV[1]); }
    when ('-n') { get_next ($ARGV[1]); }
    when ('-s') { set_oid ($ARGV[1], $ARGV[2], $ARGV[3]); }
    default {
	warn "$ARGV[0] unknown flag\n";
	usage;
    }
}