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/Documentation/networking/proc_net_tcp.txt

https://bitbucket.org/evzijst/gittest
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 1This document describes the interfaces /proc/net/tcp and /proc/net/tcp6.
 2
 3These /proc interfaces provide information about currently active TCP 
 4connections, and are implemented by tcp_get_info() in net/ipv4/tcp_ipv4.c and
 5tcp6_get_info() in net/ipv6/tcp_ipv6.c, respectively.
 6
 7It will first list all listening TCP sockets, and next list all established
 8TCP connections. A typical entry of /proc/net/tcp would look like this (split 
 9up into 3 parts because of the length of the line):
10
11   46: 010310AC:9C4C 030310AC:1770 01 
12   |      |      |      |      |   |--> connection state
13   |      |      |      |      |------> remote TCP port number
14   |      |      |      |-------------> remote IPv4 address
15   |      |      |--------------------> local TCP port number
16   |      |---------------------------> local IPv4 address
17   |----------------------------------> number of entry
18
19   00000150:00000000 01:00000019 00000000  
20      |        |     |     |       |--> number of unrecovered RTO timeouts
21      |        |     |     |----------> number of jiffies until timer expires
22      |        |     |----------------> timer_active (see below)
23      |        |----------------------> receive-queue
24      |-------------------------------> transmit-queue
25
26   1000        0 54165785 4 cd1e6040 25 4 27 3 -1
27    |          |    |     |    |     |  | |  | |--> slow start size threshold, 
28    |          |    |     |    |     |  | |  |      or -1 if the treshold
29    |          |    |     |    |     |  | |  |      is >= 0xFFFF
30    |          |    |     |    |     |  | |  |----> sending congestion window
31    |          |    |     |    |     |  | |-------> (ack.quick<<1)|ack.pingpong
32    |          |    |     |    |     |  |---------> Predicted tick of soft clock
33    |          |    |     |    |     |              (delayed ACK control data)
34    |          |    |     |    |     |------------> retransmit timeout
35    |          |    |     |    |------------------> location of socket in memory
36    |          |    |     |-----------------------> socket reference count
37    |          |    |-----------------------------> inode
38    |          |----------------------------------> unanswered 0-window probes
39    |---------------------------------------------> uid
40
41timer_active:
42  0  no timer is pending
43  1  retransmit-timer is pending
44  2  another timer (e.g. delayed ack or keepalive) is pending
45  3  this is a socket in TIME_WAIT state. Not all fields will contain 
46     data (or even exist)
47  4  zero window probe timer is pending