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+This document describes the interfaces /proc/net/tcp and /proc/net/tcp6.
+Note that these interfaces are deprecated in favor of tcp_diag.
+
+These /proc interfaces provide information about currently active TCP
+connections, and are implemented by tcp4_seq_show() in net/ipv4/tcp_ipv4.c
+and tcp6_seq_show() in net/ipv6/tcp_ipv6.c, respectively.
+
+It will first list all listening TCP sockets, and next list all established
+TCP connections. A typical entry of /proc/net/tcp would look like this (split
+up into 3 parts because of the length of the line):
+
+ 46: 010310AC:9C4C 030310AC:1770 01
+ | | | | | |--> connection state
+ | | | | |------> remote TCP port number
+ | | | |-------------> remote IPv4 address
+ | | |--------------------> local TCP port number
+ | |---------------------------> local IPv4 address
+ |----------------------------------> number of entry
+
+ 00000150:00000000 01:00000019 00000000
+ | | | | |--> number of unrecovered RTO timeouts
+ | | | |----------> number of jiffies until timer expires
+ | | |----------------> timer_active (see below)
+ | |----------------------> receive-queue
+ |-------------------------------> transmit-queue
+
+ 1000 0 54165785 4 cd1e6040 25 4 27 3 -1
+ | | | | | | | | | |--> slow start size threshold,
+ | | | | | | | | | or -1 if the threshold
+ | | | | | | | | | is >= 0xFFFF
+ | | | | | | | | |----> sending congestion window
+ | | | | | | | |-------> (ack.quick<<1)|ack.pingpong
+ | | | | | | |---------> Predicted tick of soft clock
+ | | | | | | (delayed ACK control data)
+ | | | | | |------------> retransmit timeout
+ | | | | |------------------> location of socket in memory
+ | | | |-----------------------> socket reference count
+ | | |-----------------------------> inode
+ | |----------------------------------> unanswered 0-window probes
+ |---------------------------------------------> uid
+
+timer_active:
+ 0 no timer is pending
+ 1 retransmit-timer is pending
+ 2 another timer (e.g. delayed ack or keepalive) is pending
+ 3 this is a socket in TIME_WAIT state. Not all fields will contain
+ data (or even exist)
+ 4 zero window probe timer is pending