linux – TCP_NEW_SYN_RECV的含义是什么？

2023年3月12日 245次阅读

我知道TCP_SYN_RECV,但TCP_NEW_SYN_RECV的含义是什么？他们之间有什么区别？

https://github.com/torvalds/linux/blob/5924bbecd0267d87c24110cbe2041b5075173a25/include/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! */
};

另外我看到以下代码“sk-> sk_state == TCP_NEW_SYN_RECV”,为什么不使用“sk-> sk_state == TCP_SYN_RECV”？

https://github.com/torvalds/linux/blob/8fa3b6f9392bf6d90cb7b908e07bd90166639f0a/net/ipv4/tcp_ipv4.c#L16485

if (sk->sk_state == TCP_NEW_SYN_RECV) {
    struct request_sock *req = inet_reqsk(sk);
    struct sock *nsk;

最佳答案 我发现了这个：

TCP_SYN_RECV state is currently used by fast open sockets.

Initial TCP requests (the pseudo sockets created when a SYN is received)
are not yet associated to a state. They are attached to their parent,
and the parent is in TCP_LISTEN state.

This commit adds TCP_NEW_SYN_RECV state, so that we can convert
TCP stack to a different schem gradually.

来源,作者承诺：http://git.kernel.org/linus/10feb428a504

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