The meaning of the connection state constants in /proc/net/tcp

networkingproc

I'm creating a parser for /proc/net/tcp, and I would like to know what are all the possible constants for the connection states (fourth column)? I know 0A means LISTENING, but Google results don't give me the rest of the answers I need. 

  sl  local_address rem_address   st tx_queue rx_queue tr tm->when retrnsmt   uid  timeout inode
  0: 3500007F:0035 00000000:0000 0A 00000000:00000000 00:00000000 00000000   101        0 21384 1 ffff987636718000 100 0 0 10 0                     
  1: 0100007F:0277 00000000:0000 0A 00000000:00000000 00:00000000 00000000     0        0 78109 1 ffff98762c4dd000 100 0 0 10 0                     
  2: 800AA8C0:B9CC 70FD1EC0:0016 06 00000000:00000000 03:000005EF 00000000     0        0 0 3 ffff987518bb7cf0

Best Answer

The state contants correspond to the entries in the first enum in net/tcp_states.h:

enum {
    TCP_ESTABLISHED = 1,
    TCP_SYN_SENT,
    TCP_SYN_RECV,
    TCP_FIN_WAIT1,
    TCP_FIN_WAIT2,
    TCP_TIME_WAIT,
    TCP_CLOSE,
    TCP_CLOSE_WAIT,
    TCP_LAST_ACK,
    TCP_LISTEN,
    TCP_CLOSING,    /* Now a valid state */
    TCP_NEW_SYN_RECV,

    TCP_MAX_STATES  /* Leave at the end! */
};

The values are currently as follows:

  1. established;
  2. syn sent;
  3. syn received;
  4. fin wait 1;
  5. fin wait 2;
  6. time wait;
  7. close;
  8. close wait;
  9. last acknowledgment;
  10. listening;
  11. closing;
  12. new syn received.

Most of these correspond to states in the TCP/IP state machine.

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