Documentation/networking/proc_net_tcp.txt

   1 This document describes the interfaces /proc/net/tcp and /proc/net/tcp6.
   2 Note that these interfaces are deprecated in favor of tcp_diag.
   3
   4 These /proc interfaces provide information about currently active TCP
   5 connections, and are implemented by tcp4_seq_show() in net/ipv4/tcp_ipv4.c
   6 and tcp6_seq_show() in net/ipv6/tcp_ipv6.c, respectively.
   7
   8 It will first list all listening TCP sockets, and next list all established
   9 TCP connections. A typical entry of /proc/net/tcp would look like this (split
  10 up into 3 parts because of the length of the line):
  11
  12    46: 010310AC:9C4C 030310AC:1770 01
  13    |      |      |      |      |   |--> connection state
  14    |      |      |      |      |------> remote TCP port number
  15    |      |      |      |-------------> remote IPv4 address
  16    |      |      |--------------------> local TCP port number
  17    |      |---------------------------> local IPv4 address
  18    |----------------------------------> number of entry
  19
  20    00000150:00000000 01:00000019 00000000
  21       |        |     |     |       |--> number of unrecovered RTO timeouts
  22       |        |     |     |----------> number of jiffies until timer expires
  23       |        |     |----------------> timer_active (see below)
  24       |        |----------------------> receive-queue
  25       |-------------------------------> transmit-queue
  26
  27    1000        0 54165785 4 cd1e6040 25 4 27 3 -1
  28     |          |    |     |    |     |  | |  | |--> slow start size threshold,
  29     |          |    |     |    |     |  | |  |      or -1 if the threshold
  30     |          |    |     |    |     |  | |  |      is >= 0xFFFF
  31     |          |    |     |    |     |  | |  |----> sending congestion window
  32     |          |    |     |    |     |  | |-------> (ack.quick<<1)|ack.pingpong
  33     |          |    |     |    |     |  |---------> Predicted tick of soft clock
  34     |          |    |     |    |     |              (delayed ACK control data)
  35     |          |    |     |    |     |------------> retransmit timeout
  36     |          |    |     |    |------------------> location of socket in memory
  37     |          |    |     |-----------------------> socket reference count
  38     |          |    |-----------------------------> inode
  39     |          |----------------------------------> unanswered 0-window probes
  40     |---------------------------------------------> uid
  41
  42 timer_active:
  43   0  no timer is pending
  44   1  retransmit-timer is pending
  45   2  another timer (e.g. delayed ack or keepalive) is pending
  46   3  this is a socket in TIME_WAIT state. Not all fields will contain
  47      data (or even exist)
  48   4  zero window probe timer is pending