📄 2_4网络代码阅读笔(4) - china linux forum.htm
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<BR><BR>/* <BR>* Accept a pending connection. The TCP layer now
gives BSD semantics. <BR>*/ <BR>int inet_accept(struct socket *sock,
struct socket *newsock, int flags) <BR>{ <BR>struct sock *sk1 =
sock->sk; <BR>struct sock *sk2; <BR>int err = -EINVAL;
<BR>>>>>调用INET层的accept,即为tcp_accept,返回一个新的struct sock指针
<BR>>>>>这个新的struct sock是当三路握手完成之后,系统建立的, <BR>if((sk2 =
sk1->prot->accept(sk1,flags,&err)) == NULL) <BR>goto
do_err; <BR>lock_sock(sk2);
<BR>BUG_TRAP((1<<SK2->state)&(TCPF_ESTABLISHED|TCPF_CLOSE_WAIT|TCPF_CLOSE));
<BR>>>>>建立sk2与newsock之间的键接关系 <BR>>>>>static
inline void sock_graft(struct sock *sk, struct socket *parent)
<BR>>>>>{ <BR>>>>>
write_lock_bh(&sk->callback_lock); <BR>>>>>
sk->sleep = &parent->wait; <BR>>>>>
parent->sk = sk; <BR>>>>> sk->socket = parent;
<BR>>>>> write_unlock_bh(&sk->callback_lock);
<BR>>>>>} <BR>>>>>这样 struct soket newsock 与
struct sock sk2就是一个完整的内核套接字结构了 <BR>sock_graft(sk2, newsock);
<BR>>>>>置socket的状态为SS_CONNECTED <BR>newsock->state =
SS_CONNECTED; <BR>release_sock(sk2); <BR>return 0; <BR>do_err:
<BR>return err; <BR>} <BR><BR>/* <BR>* This will accept the next
outstanding connection. <BR>*/ <BR>struct sock *tcp_accept(struct
sock *sk, int flags, int *err) <BR>{ <BR>struct tcp_opt *tp =
&sk->tp_pinfo.af_tcp; <BR>struct open_request *req;
<BR>struct sock *newsk; <BR>int error; <BR>lock_sock(sk); <BR>/* We
need to make sure that this socket is listening, <BR>* and that it
has something pending. <BR>*/ <BR>error = -EINVAL; <BR>if
(sk->state != TCP_LISTEN) <BR>goto out; <BR>/* Find already
established connection */
<BR>>>>>对连接已经建立的s套接对，放入accept_queue队列中
<BR>>>>>（以结构struct open_request表示）
<BR>>>>>如果还没有建立连接 <BR>if (!tp->accept_queue) {
<BR>long timeo = sock_rcvtimeo(sk, flags & O_NONBLOCK); <BR>/*
If this is a non blocking socket don't sleep */ <BR>error = -EAGAIN;
<BR>if (!timeo) <BR>goto out;
<BR>>>>>则等待建立连接,wait_for_connect是在分析connect时在说 <BR>error
= wait_for_connect(sk, timeo); <BR>if (error) <BR>goto out; <BR>}
<BR>req = tp->accept_queue;
<BR>>>>>将accept_queue置为下一个open_request。如果只有一个连接，则accept_queue
<BR>>>>>和accept_queue_tail均置为NULL。 <BR>if
((tp->accept_queue = req->dl_next) == NULL)
<BR>tp->accept_queue_tail = NULL;
<BR>>>>>这里req->sk是连接建立的时候分配的struct sock结构 <BR>newsk =
req->sk; <BR><BR>>>>>sk->ack_backlog--;
<BR>tcp_acceptq_removed(sk);
<BR>>>>>kmem_cache_free(tcp_openreq_cachep, req)
<BR>tcp_openreq_fastfree(req); <BR>BUG_TRAP(newsk->state !=
TCP_SYN_RECV); <BR>release_sock(sk); <BR>return newsk; <BR>out:
<BR>release_sock(sk); <BR>*err = error; <BR>return NULL; <BR>}
<BR><BR>※ 修改:·ysqcn 於 07月29日16:47:11 修改本文·[FROM: 202.114.2.11]
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