0001 .. SPDX-License-Identifier: GPL-2.0
0002
0003 ============================================
0004 The proc/net/tcp and proc/net/tcp6 variables
0005 ============================================
0006
0007 This document describes the interfaces /proc/net/tcp and /proc/net/tcp6.
0008 Note that these interfaces are deprecated in favor of tcp_diag.
0009
0010 These /proc interfaces provide information about currently active TCP
0011 connections, and are implemented by tcp4_seq_show() in net/ipv4/tcp_ipv4.c
0012 and tcp6_seq_show() in net/ipv6/tcp_ipv6.c, respectively.
0013
0014 It will first list all listening TCP sockets, and next list all established
0015 TCP connections. A typical entry of /proc/net/tcp would look like this (split
0016 up into 3 parts because of the length of the line)::
0017
0018 46: 010310AC:9C4C 030310AC:1770 01
0019 | | | | | |--> connection state
0020 | | | | |------> remote TCP port number
0021 | | | |-------------> remote IPv4 address
0022 | | |--------------------> local TCP port number
0023 | |---------------------------> local IPv4 address
0024 |----------------------------------> number of entry
0025
0026 00000150:00000000 01:00000019 00000000
0027 | | | | |--> number of unrecovered RTO timeouts
0028 | | | |----------> number of jiffies until timer expires
0029 | | |----------------> timer_active (see below)
0030 | |----------------------> receive-queue
0031 |-------------------------------> transmit-queue
0032
0033 1000 0 54165785 4 cd1e6040 25 4 27 3 -1
0034 | | | | | | | | | |--> slow start size threshold,
0035 | | | | | | | | | or -1 if the threshold
0036 | | | | | | | | | is >= 0xFFFF
0037 | | | | | | | | |----> sending congestion window
0038 | | | | | | | |-------> (ack.quick<<1)|ack.pingpong
0039 | | | | | | |---------> Predicted tick of soft clock
0040 | | | | | | (delayed ACK control data)
0041 | | | | | |------------> retransmit timeout
0042 | | | | |------------------> location of socket in memory
0043 | | | |-----------------------> socket reference count
0044 | | |-----------------------------> inode
0045 | |----------------------------------> unanswered 0-window probes
0046 |---------------------------------------------> uid
0047
0048 timer_active:
0049
0050 == ================================================================
0051 0 no timer is pending
0052 1 retransmit-timer is pending
0053 2 another timer (e.g. delayed ack or keepalive) is pending
0054 3 this is a socket in TIME_WAIT state. Not all fields will contain
0055 data (or even exist)
0056 4 zero window probe timer is pending
0057 == ================================================================
