1 .. SPDX-License-Identifier: GPL-2.0 1 .. SPDX-License-Identifier: GPL-2.0
2 2
3 ============================================ 3 ============================================
4 The proc/net/tcp and proc/net/tcp6 variables 4 The proc/net/tcp and proc/net/tcp6 variables
5 ============================================ 5 ============================================
6 6
7 This document describes the interfaces /proc/n 7 This document describes the interfaces /proc/net/tcp and /proc/net/tcp6.
8 Note that these interfaces are deprecated in f 8 Note that these interfaces are deprecated in favor of tcp_diag.
9 9
10 These /proc interfaces provide information abo 10 These /proc interfaces provide information about currently active TCP
11 connections, and are implemented by tcp4_seq_s 11 connections, and are implemented by tcp4_seq_show() in net/ipv4/tcp_ipv4.c
12 and tcp6_seq_show() in net/ipv6/tcp_ipv6.c, re 12 and tcp6_seq_show() in net/ipv6/tcp_ipv6.c, respectively.
13 13
14 It will first list all listening TCP sockets, 14 It will first list all listening TCP sockets, and next list all established
15 TCP connections. A typical entry of /proc/net/ 15 TCP connections. A typical entry of /proc/net/tcp would look like this (split
16 up into 3 parts because of the length of the l 16 up into 3 parts because of the length of the line)::
17 17
18 46: 010310AC:9C4C 030310AC:1770 01 18 46: 010310AC:9C4C 030310AC:1770 01
19 | | | | | |--> connec 19 | | | | | |--> connection state
20 | | | | |------> remote 20 | | | | |------> remote TCP port number
21 | | | |-------------> remote 21 | | | |-------------> remote IPv4 address
22 | | |--------------------> local 22 | | |--------------------> local TCP port number
23 | |---------------------------> local 23 | |---------------------------> local IPv4 address
24 |----------------------------------> number 24 |----------------------------------> number of entry
25 25
26 00000150:00000000 01:00000019 00000000 26 00000150:00000000 01:00000019 00000000
27 | | | | |--> number 27 | | | | |--> number of unrecovered RTO timeouts
28 | | | |----------> number 28 | | | |----------> number of jiffies until timer expires
29 | | |----------------> timer_ 29 | | |----------------> timer_active (see below)
30 | |----------------------> receiv 30 | |----------------------> receive-queue
31 |-------------------------------> transm 31 |-------------------------------> transmit-queue
32 32
33 1000 0 54165785 4 cd1e6040 25 4 27 3 33 1000 0 54165785 4 cd1e6040 25 4 27 3 -1
34 | | | | | | | | | 34 | | | | | | | | | |--> slow start size threshold,
35 | | | | | | | | | 35 | | | | | | | | | or -1 if the threshold
36 | | | | | | | | | 36 | | | | | | | | | is >= 0xFFFF
37 | | | | | | | | | 37 | | | | | | | | |----> sending congestion window
38 | | | | | | | |--- 38 | | | | | | | |-------> (ack.quick<<1)|ack.pingpong
39 | | | | | | |----- 39 | | | | | | |---------> Predicted tick of soft clock
40 | | | | | | 40 | | | | | | (delayed ACK control data)
41 | | | | | |-------- 41 | | | | | |------------> retransmit timeout
42 | | | | |-------------- 42 | | | | |------------------> location of socket in memory
43 | | | |------------------- 43 | | | |-----------------------> socket reference count
44 | | |------------------------- 44 | | |-----------------------------> inode
45 | |------------------------------ 45 | |----------------------------------> unanswered 0-window probes
46 |----------------------------------------- 46 |---------------------------------------------> uid
47 47
48 timer_active: 48 timer_active:
49 49
50 == ========================================= 50 == ================================================================
51 0 no timer is pending 51 0 no timer is pending
52 1 retransmit-timer is pending 52 1 retransmit-timer is pending
53 2 another timer (e.g. delayed ack or keepal 53 2 another timer (e.g. delayed ack or keepalive) is pending
54 3 this is a socket in TIME_WAIT state. Not 54 3 this is a socket in TIME_WAIT state. Not all fields will contain
55 data (or even exist) 55 data (or even exist)
56 4 zero window probe timer is pending 56 4 zero window probe timer is pending
57 == ========================================= 57 == ================================================================
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