scripts/lcp_rtt_dump: dump the LCP RTT log

Signed-off-by: Marco d'Itri <md@linux.it>

diff --git a/scripts/lcp_rtt_dump b/scripts/lcp_rtt_dump
new file mode 100755 (executable)
index 0000000..7898f08
--- /dev/null
+++ b/scripts/lcp_rtt_dump
@@ -0,0 +1,81 @@
+#!/usr/bin/perl
+# vim: shiftwidth=4 tabstop=4
+#
+# This program dumps to standard output the content of the file written
+# by pppd's lcp-rtt-file configuration option.
+#
+# Copyright (C) Marco d'Itri <md@linux.it>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+
+use v5.14;
+use warnings;
+use autodie;
+
+use POSIX qw(strftime);
+
+{
+       my $data = read_data($ARGV[0] || '/run/ppp-rtt.data');
+       die "The data file is invalid!\n" if not $data;
+       dump_data($data);
+}
+
+sub dump_data {
+       my ($s) = @_;
+
+       say "status:   $s->{status}";
+       say "interval: $s->{echo_interval}";
+       say "position: $s->{position}";
+       say 'elements: ' . scalar(@{ $s->{data} });
+       say '';
+
+       foreach (my $i= 0; $i < @{ $s->{data} }; $i++) {
+               my $date = strftime('%F %T', localtime($s->{data}->[$i]->[0]));
+               print "$i\t$date\t$s->{data}->[$i]->[1]\t$s->{data}->[$i]->[2]\n";
+       }
+}
+
+sub read_data {
+       my ($file) = @_;
+
+       my $data;
+       open(my $fh, '<', $file);
+       binmode($fh);
+       my $bytes_read;
+       do {
+               $bytes_read = sysread($fh, $data, 8192, length($data));
+       } while ($bytes_read == 8192);
+       close($fh);
+
+       my ($magic, $status, $position, $echo_interval, $rest)
+               = unpack('NNNN a*', $data);
+       return undef if $magic != 0x19450425;
+
+       # the position is relative to the C array, not to the logical entries
+       $position /= 2;
+
+       my @rawdata = unpack('(N C a3)*', $rest);
+       my @data;
+       while (my ($time, $loss, $rtt) = splice(@rawdata, 0, 3)) {
+               push(@data, [ $time, unpack('N', "\000$rtt"), $loss ]);
+       }
+
+       if (0) {
+       @data =
+               # skip any "empty" (null) entries
+               grep { $_->[0] }
+               # rearrange the list in chronological order
+               (@data[$position+1 .. $#data], @data[0 .. $position]);
+       }
+
+       return {
+               status                  => $status,
+               echo_interval   => $echo_interval,
+               position                => $position,
+               data                    => \@data,
+       };
+}
+