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1 | .. SPDX-License-Identifier: GPL-2.0 |
2 | ||
3 | ============================================ | |
4 | The proc/net/tcp and proc/net/tcp6 variables | |
5 | ============================================ | |
6 | ||
1da177e4 | 7 | This document describes the interfaces /proc/net/tcp and /proc/net/tcp6. |
d603d0ab | 8 | Note that these interfaces are deprecated in favor of tcp_diag. |
1da177e4 | 9 | |
83261901 | 10 | These /proc interfaces provide information about currently active TCP |
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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, respectively. | |
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13 | |
14 | It will first list all listening TCP sockets, and next list all established | |
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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 line):: | |
1da177e4 | 17 | |
83261901 | 18 | 46: 010310AC:9C4C 030310AC:1770 01 |
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19 | | | | | | |--> connection state |
20 | | | | | |------> remote TCP port number | |
21 | | | | |-------------> remote IPv4 address | |
22 | | | |--------------------> local TCP port number | |
23 | | |---------------------------> local IPv4 address | |
24 | |----------------------------------> number of entry | |
25 | ||
83261901 | 26 | 00000150:00000000 01:00000019 00000000 |
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27 | | | | | |--> number of unrecovered RTO timeouts |
28 | | | | |----------> number of jiffies until timer expires | |
29 | | | |----------------> timer_active (see below) | |
30 | | |----------------------> receive-queue | |
31 | |-------------------------------> transmit-queue | |
32 | ||
33 | 1000 0 54165785 4 cd1e6040 25 4 27 3 -1 | |
83261901 | 34 | | | | | | | | | | |--> slow start size threshold, |
fa00e7e1 | 35 | | | | | | | | | | or -1 if the threshold |
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36 | | | | | | | | | | is >= 0xFFFF |
37 | | | | | | | | | |----> sending congestion window | |
38 | | | | | | | | |-------> (ack.quick<<1)|ack.pingpong | |
39 | | | | | | | |---------> Predicted tick of soft clock | |
40 | | | | | | | (delayed ACK control data) | |
41 | | | | | | |------------> retransmit timeout | |
42 | | | | | |------------------> location of socket in memory | |
43 | | | | |-----------------------> socket reference count | |
44 | | | |-----------------------------> inode | |
45 | | |----------------------------------> unanswered 0-window probes | |
46 | |---------------------------------------------> uid | |
47 | ||
48 | timer_active: | |
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49 | |
50 | == ================================================================ | |
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51 | 0 no timer is pending |
52 | 1 retransmit-timer is pending | |
53 | 2 another timer (e.g. delayed ack or keepalive) is pending | |
83261901 | 54 | 3 this is a socket in TIME_WAIT state. Not all fields will contain |
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55 | data (or even exist) |
56 | 4 zero window probe timer is pending | |
83261901 | 57 | == ================================================================ |