tcp连接建立过程
一、server
1. 接收syn
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| tcp_v4_do_rcv {
nsk = tcp_v4_hnd_req(sk, skb);
nsk == sk
tcp_rcv_state_process {
icsk->icsk_af_ops->conn_request(sk, skb)
tcp_v4_conn_request {
__tcp_v4_send_synack {
2. 发送syn/ack
}
}
}
}
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2. 接收ack
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| tcp_v4_do_rcv {
nsk = tcp_v4_hnd_req(sk, skb) {
req = inet_csk_search_req
nsk = tcp_check_req {
tcp_v4_syn_recv_sock {
tcp_create_openreq_child {
inet_csk_clone {
newsk->sk_state = TCP_SYN_RECV;
}
}
}
}
}
nsk != sk {
tcp_child_process {
tcp_rcv_state_process {
if (!tcp_validate_incoming(sk, skb, th, 0))
return 0;
/* step 5: check the ACK field */
if (th->ack) {
int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH) > 0;
switch (sk->sk_state) {
case TCP_SYN_RECV:
tcp_set_state(sk, TCP_ESTABLISHED);
}
case TCP_ESTABLISHED:
tcp_data_queue(sk, skb);
queued = 1;
break;
}
}
}
}
}
}
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二、client
1. 发送syn
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| tcp_v4_connect {
tcp_set_state(sk, TCP_SYN_SENT);
tcp_connect {
__tcp_add_write_queue_tail
tcp_transmit_skb
inet_csk_reset_xmit_timer
}
}
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2. 接收syn/ack
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| tcp_v4_do_rcv {
sk->sk_state == TCP_SYN_SENT
tcp_rcv_state_process {
queued = tcp_rcv_synsent_state_process(sk, skb, th, len) {
tcp_set_state(sk, TCP_ESTABLISHED);
tcp_send_ack(sk); // 发送ack
}
}
}
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