#!/usr/bin/perl

# Modify the grub config file on the node to boot the specified kernel and initrd.
# This script is meant to be run on the node via xdsh -e.
# Currently requires that dns on the mn be configured and working to resolve the short node names.

use strict;
use Getopt::Long;
use Data::Dumper;
use Socket;

# Globals - these are set once and then only read.
my $HELP;
my $VERBOSE;
my $WAITTIME;
my $XCATNETBOOTTITLE = 'xCAT network boot kernel and initrd';

my $usage = sub {
   	my $exitcode = shift @_;
   	print "Usage: modifygrub [-?|-h|--help] [-v|--verbose] [-w waittime] <kernel-path> <initrd-path> <kernel-parms> <mn-ip>\n\n";
   	if (!$exitcode) {
   		print "Modify the grub config file on the node to boot the specified kernel and initrd.\n";
   	}
	exit $exitcode;
};

if (-f '/etc/os-release') { die "This script doesn't support ubuntu yet.\n"; }

# Process the cmd line args
Getopt::Long::Configure("bundling");
#Getopt::Long::Configure("pass_through");
Getopt::Long::Configure("no_pass_through");
if (!GetOptions('h|?|help'  => \$HELP, 'v|verbose' => \$VERBOSE, 'w|waittime' => \$WAITTIME)) { $usage->(1); }

if ($HELP) { $usage->(0); }
if (scalar(@ARGV) != 4) { $usage->(1); }
if (!defined($WAITTIME)) { $WAITTIME = 90; }	# seconds to wait after configuring the nic (to let the switch handle the state change)
my %args;
$args{kernelpath} = $ARGV[0];
$args{initrdpath} = $ARGV[1];
$args{kernelparms} = $ARGV[2];
$args{mnip} = $ARGV[3];

addKernelParms(\%args);		# replace and add some parms to args{kernelparms}
updateGrub(\%args);			# update the grub config with an entry filled with the info in args
	
exit(0);


# Add ip and net info to the kernel parms.  Modifies the kernelparms value of the args hash passed in.
sub addKernelParms {
	my $args = shift @_;

	# replace '!myipfn!' with the mn ip
	my $mnip = $args->{mnip};
	$args->{kernelparms} =~ s/!myipfn!/$mnip/g;

	# replace <nodename> with the nodename
	my $nodename = $ENV{NODE};			# this env var is set by xdsh
	$args->{kernelparms} =~ s/<nodename>/$nodename/g;

	# get node ip and add it to the kernel parms
	my ($nic, $ip, $netmask, $gateway) = getNodeIpInfo($args);
	if (!$ip) { die "Error: could not find the NIC that would connect to the xCAT mgmt node's IP (".$args->{mnip}.").\n"; }
	$args->{kernelparms} .= " hostip=$ip netmask=$netmask gateway=$gateway netdevice=$nic netwait=$WAITTIME";
}


# get this nodes nic, ip, netmask, and gateway.  Returns them in a 4 element array.
sub getNodeIpInfo {
	my $args = shift @_;
	my ($ipprefix) = $args->{mnip}=~m/^(\d+\.\d+)\./;		#todo: this is a hack, just using the 1st 2 octets of the mn ip addr
	verbose("using IP prefix $ipprefix");

	# parse ip addr show output, looking for ipprefix, to determine nic and ip
	my @output = runcmd("ip addr show");
	my ($nic, $ipandmask);
	foreach my $line (@output) {
		my ($nictmp, $iptmp);
		if (($nictmp) = $line=~m/^\d+:\s+(\S+): /) { $nic = $nictmp; }		# new stanza, remember it
		if (($iptmp) = $line=~m/^\s+inet\s+($ipprefix\S+) /) { $ipandmask = $iptmp; last; }		# got ip, we are done
	}
	my ($ip, $netmask) = convertIpAndMask($ipandmask);

	# if the nic is a bonded nic (common on sl), then find the 1st real nic that is part of it
	my $realnic = $nic;
	if ($nic =~ /^bond/) {
		my @nics = grep(m/\s+master\s+$nic\s+/, @output);
		if (!scalar(@nics)) { die "Error: can't find the NICs that are part of $nic.\n"; }
		($realnic) = $nics[0]=~m/^\d+:\s+(\S+): /;
	}

	# finally, find the gateway
	my $gateway;
	my @output = runcmd("ip route");
	# we are looking for a line like: 10.0.0.0/8 via 10.54.51.1 dev bond0
	my @networks = grep(m/ via .* $nic\s*$/, @output);
	if (scalar(@networks)) { ($gateway) = $networks[0]=~m/ via\s+(\S+)/; }
	else {
		# use the mn ip as a fall back
		$gateway = $args->{mnip};
		verbose("using xCAT mgmt node IP as the fall back gateway.");
	}

	verbose("IP info: realnic=$realnic, ip=$ip, netmask=$netmask, gateway=$gateway");
	return ($realnic, $ip, $netmask, $gateway);
}


# Convert an ip/mask in slash notation (like 10.0.0.1/26) to separate ip and netmask like 10.0.0.1 and 255.255.255.192
sub convertIpAndMask {
	my $ipandmask = shift @_;
	my ($ip, $masknum) = split('/', $ipandmask);
	my $netbin = oct("0b" . '1' x $masknum . '0' x (32-$masknum));	# create a str like '1111100', then convert to binary
	my @netarr=unpack('C4',pack('N',$netbin));		# separate into the 4 octets
	my $netmask=join('.',@netarr);			# put them together into the normal looking netmask
	return ($ip, $netmask);
}


# not used - resolve the hostname to an ip addr
sub getipaddr {
	my $hostname = shift @_;
	my $packed_ip;
    $packed_ip = inet_aton($hostname);
    if (!$packed_ip) { return undef; }
    return inet_ntoa($packed_ip);
}


# Update the grub config file with a new stanza for booting our kernel and initrd
sub updateGrub {
	my $args = shift @_;

	# this is the entry we want in the grub file
	my @entry = (
		"title $XCATNETBOOTTITLE\n",
		"\troot (hd0,0)\n",
		"\tkernel " . $args->{kernelpath} . ' ' . $args->{kernelparms} . "\n",
		"\tinitrd " . $args->{initrdpath} . "\n",
		);

	# open the grub file and see if it is in there or if we have to add it
	my $grubfile = findGrubPath();
	verbose("reading $grubfile");
	open(FILE, $grubfile) || die "Error: can not open config file $grubfile for reading: $!\n";
	my @lines = <FILE>;
	close FILE;

	my $needtowritefile = 1;
	if (grep(/^title\s+$XCATNETBOOTTITLE/, @lines)) { $needtowritefile = updateGrubEntry(\@lines, \@entry); }		# there is already an entry in there
	else { addGrubEntry (\@lines, \@entry); }

	# write the file with the new/updated xcat entry
	if ($needtowritefile) {
		verbose("updating $grubfile");
		open(FILE, '>', $grubfile) || die "Error: can not open config file $grubfile for writinging: $!\n";
		print FILE @lines;
		close FILE;
	}
	else { print "Info: $grubfile did not need modifying. It was already up to date.\n"; }
}


# add our entry as the 1st one in the grub file
sub addGrubEntry {
	my ($lines, $entry) = @_;
	# find the index of the 1st stanza (it starts with 'title')
	my $i;
	for ($i=0; $i<scalar(@$lines); $i++) {
		if ($lines->[$i] =~ m/^title\s+/) { verbose('adding xcat entry before:'.$lines->[$i]); last; }		# found it
	}
	
	# splice the entry right before the i-th line (which may also be 1 past the end)
	splice(@$lines, $i, 0, @$entry);
}


# check the xcat entry in the grub file and see if it needs to be updated.  Return 1 if it does.
sub updateGrubEntry {
	my ($lines, $entry) = @_;
	# find the index of the xcat stanza
	my $i;
	for ($i=0; $i++; $i<scalar(@$lines)) {
		if ($lines->[$i] =~ m/^title\s+$XCATNETBOOTTITLE/) { last; }		# found it
	}

	# compare the next few lines with the corresponding line in @$entries and replace if different
	my $replaced = 0;
	for (my $j=0; $j++; $j<scalar(@$entry)) {
		if ($lines->[$i+$j] ne $entry->[$j]) {		# this line was different
			$lines->[$i+$j] = $entry->[$j];
			$replaced = 1;
		}
	}
	
	return $replaced;
}


# depending on the distro, find the correct grub file and return its path
sub findGrubPath {
	# for rhel/centos it is /boot/grub/grub.conf, for sles it is /boot/grub/menu.lst
	my @paths = qw(/boot/grub/grub.conf /boot/grub/menu.lst);
	foreach my $p (@paths) {
		if (-f $p) { return $p; }
	}
	
	die "Error: Can't find grub config file.\n";

	#todo: support ubuntu: you add an executable file in /etc/grub.d named 06_xcatnetboot that prints out the
	#		entry to add.  Then run grub-mkconfig.
}


# Pring msg only if -v was specified
sub verbose { if ($VERBOSE) { print shift, "\n"; } }



# Run a command.  If called in the context of return an array, it will capture the output
# of the cmd and return it.  Otherwise, it will display the output to stdout.
# If the cmd has a non-zero rc, this function will die with a msg.
sub runcmd
{
    my ($cmd) = @_;
    my $rc;

    $cmd .= ' 2>&1' ;
    verbose($cmd);

   	my @output;
   	if (wantarray) {
		@output = `$cmd`;
		$rc = $?;
	}
	else {
		system($cmd);
		$rc = $?;
	}

    if ($rc) {
        $rc = $rc >> 8;
        if ($rc > 0) { die "Error: rc $rc return from cmd: $cmd\n"; }
        else { die "Error: system error returned from cmd: $cmd\n"; }
    }
    elsif (wantarray) { return @output; }
}