tcp-sack-retrans.pl

#!/usr/bin/perl
use strict;

sub netstat {
    my %stats;
    {
        open my $fh, '<', '/proc/net/snmp' or die "$!\n";
        my @keys;
       while (<$fh>) {
            chomp;
            if (/^Tcp\:/ && ! @keys) {
                @keys = split / /;
            } elsif ( /^Tcp\:/ ) {
                for my $v (split / /) {
                    $stats{shift @keys} = $v;
                }
            }
        }
    }

    {
        open my $fh, '<', '/proc/net/netstat' or die "$!\n";
        my @keys;
        while (<$fh>) {
            chomp;
            if (/^TcpExt\:/ && ! @keys) {
                @keys = split / /;
            } elsif ( /^TcpExt\:/ ) {
                for my $v (split / /) {
                    $stats{shift @keys} = $v;
                }
            }
        }
    }
    return \%stats;
}

my $prev = netstat();
my @keys = keys %$prev;
sleep 1;
while (1) {
    my $cur = netstat();
    my @stats;
    for my $k (@keys) {
        next unless $k =~ m!(sack|retrans)!i;
        push @stats, sprintf("%s:%s",$k, $cur->{$k} - $prev->{$k});
    }
    print join("\t", @stats),"\n";
    $prev = $cur;
    sleep 1;
}