NAME

Linux::Proc::Net::TCP - Parser for Linux /proc/net/tcp and /proc/net/tcp6

SYNOPSIS

use Linux::Proc::Net::TCP;
my $table = Linux::Proc::Net::TCP->read;

for my $entry (@$table) {
  printf("%s:%d --> %s:%d, %s\n",
         $entry->local_address, $entry->local_port,
         $entry->rem_address, $entry->rem_port,
         $entry->st );
}

DESCRIPTION

This module can read and parse the information available from /proc/net/tcp in Linux systems.

API

The table object

$table = Linux::Proc::Net::TCP->read

$table = Linux::Proc::Net::TCP->read(%opts)

reads /proc/net/tcp and /proc/net/tcp6 and returns an object representing a table of the connections.

Individual entries in the table can be accessed just dereferencing the returned object. For instance:

for my $entry (@$table) {
  # do something with $entry
}

The table entries are of class Linux::Proc::Net::TCP::Entry described below.

This method accepts the following optional arguments:

ip4 => 0

disables parsing of the file /proc/net/tcp containing state information for TCP over IP4 connections

ip6 => 0

disables parsing of the file /proc/net/tcp6 containing state information for TCP over IP6 connections

mnt => $procfs_mount_point

overrides the default mount point for the procfs at /proc.

$table->listeners

returns a list of the entries that are listeners:

for my $entry ($table->listeners) {
  printf "listener: %s:%d\n", $entry->local_address, $entry->local_port;
}

$table->listener_ports

returns the list of TCP ports where there are some service listening.

This method can be used to find some unused port:

my @used_ports = Linux::Proc::Net::TCP->read->listener_ports;
my %used_port = map { $_ => 1 } @used_ports;
my $port = $start;
$port++ while $used_port{$port};

The entry object

The entries in the table are of class Linux::Proc::Net::TCP::Entry and implement the following read only accessors:

sl local_address local_port rem_address rem_port st tx_queue
rx_queue timer tm_when retrnsmt uid timeout inode reference_count
memory_address retransmit_timeout predicted_tick ack_quick
ack_pingpong sending_congestion_window slow_start_size_threshold
ip4 ip6

The /proc/net/tcp documentation

This is the documentation about /proc/net/tcp available from the Linux kernel source distribution:

This document describes the interfaces /proc/net/tcp and
/proc/net/tcp6.  Note that these interfaces are deprecated in favor
of tcp_diag.

These /proc interfaces provide information about currently active TCP
connections, and are implemented by tcp4_seq_show() in
net/ipv4/tcp_ipv4.c and tcp6_seq_show() in net/ipv6/tcp_ipv6.c,
respectively.

It will first list all listening TCP sockets, and next list all
established TCP connections. A typical entry of /proc/net/tcp would
look like this (split up into 3 parts because of the length of the
line):

  46: 010310AC:9C4C 030310AC:1770 01 
  |      |      |      |      |   |--> connection state
  |      |      |      |      |------> remote TCP port number
  |      |      |      |-------------> remote IPv4 address
  |      |      |--------------------> local TCP port number
  |      |---------------------------> local IPv4 address
  |----------------------------------> number of entry

  00000150:00000000 01:00000019 00000000  
     |        |     |     |       |--> number of unrecovered RTO timeouts
     |        |     |     |----------> number of jiffies until timer expires
     |        |     |----------------> timer_active (see below)
     |        |----------------------> receive-queue
     |-------------------------------> transmit-queue

  1000        0 54165785 4 cd1e6040 25 4 27 3 -1
   |          |    |     |    |     |  | |  | |--> slow start size threshold, 
   |          |    |     |    |     |  | |  |      or -1 if the threshold
   |          |    |     |    |     |  | |  |      is >= 0xFFFF
   |          |    |     |    |     |  | |  |----> sending congestion window
   |          |    |     |    |     |  | |-------> (ack.quick<<1)|ack.pingpong
   |          |    |     |    |     |  |---------> Predicted tick of soft clock
   |          |    |     |    |     |              (delayed ACK control data)
   |          |    |     |    |     |------------> retransmit timeout
   |          |    |     |    |------------------> location of socket in memory
   |          |    |     |-----------------------> socket reference count
   |          |    |-----------------------------> inode
   |          |----------------------------------> unanswered 0-window probes
   |---------------------------------------------> uid

timer_active:
 0  no timer is pending
 1  retransmit-timer is pending
 2  another timer (e.g. delayed ack or keepalive) is pending
 3  this is a socket in TIME_WAIT state. Not all fields will contain 
    data (or even exist)
 4  zero window probe timer is pending

AUTHOR

Salvador Fandiño <sfandino@yahoo.com>

COPYRIGHT AND LICENSE

Copyright (C) 2010, 2012, 2014 by Qindel Formación y Servicios S.L.

This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself, either Perl version 5.10.1 or, at your option, any later version of Perl 5 you may have available.