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1.. SPDX-License-Identifier: GPL-2.02 3============================================4The proc/net/tcp and proc/net/tcp6 variables5============================================6 7This document describes the interfaces /proc/net/tcp and /proc/net/tcp6.8Note that these interfaces are deprecated in favor of tcp_diag.9 10These /proc interfaces provide information about currently active TCP11connections, and are implemented by tcp4_seq_show() in net/ipv4/tcp_ipv4.c12and tcp6_seq_show() in net/ipv6/tcp_ipv6.c, respectively.13 14It will first list all listening TCP sockets, and next list all established15TCP connections. A typical entry of /proc/net/tcp would look like this (split16up into 3 parts because of the length of the line)::17 18 46: 010310AC:9C4C 030310AC:1770 0119 | | | | | |--> connection state20 | | | | |------> remote TCP port number21 | | | |-------------> remote IPv4 address22 | | |--------------------> local TCP port number23 | |---------------------------> local IPv4 address24 |----------------------------------> number of entry25 26 00000150:00000000 01:00000019 0000000027 | | | | |--> number of unrecovered RTO timeouts28 | | | |----------> number of jiffies until timer expires29 | | |----------------> timer_active (see below)30 | |----------------------> receive-queue31 |-------------------------------> transmit-queue32 33 1000 0 54165785 4 cd1e6040 25 4 27 3 -134 | | | | | | | | | |--> slow start size threshold,35 | | | | | | | | | or -1 if the threshold36 | | | | | | | | | is >= 0xFFFF37 | | | | | | | | |----> sending congestion window38 | | | | | | | |-------> (ack.quick<<1)|ack.pingpong39 | | | | | | |---------> Predicted tick of soft clock40 | | | | | | (delayed ACK control data)41 | | | | | |------------> retransmit timeout42 | | | | |------------------> location of socket in memory43 | | | |-----------------------> socket reference count44 | | |-----------------------------> inode45 | |----------------------------------> unanswered 0-window probes46 |---------------------------------------------> uid47 48timer_active:49 50 == ================================================================51 0 no timer is pending52 1 retransmit-timer is pending53 2 another timer (e.g. delayed ack or keepalive) is pending54 3 this is a socket in TIME_WAIT state. Not all fields will contain55 data (or even exist)56 4 zero window probe timer is pending57 == ================================================================58