📄 2_4网络代码阅读笔(3) - china linux forum.htm
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<TD class=darktable rowSpan=2 vAlign=top width="17%"><A
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<TD align=left width="70%"><IMG height=15
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<P class=post>发信人: ysqcn (岁月无声), 信区: llkm <BR>标 题: 2.4网络代码阅读笔(3)
<BR>发信站: UNIX编程 (2001年06月13日15:04:42 星期三), 站内信件
<BR><BR>在就是sys_listen了,这个函数更简单: <BR>asmlinkage long sys_listen(int
fd, int backlog) <BR>{ <BR>struct socket *sock; <BR>int err;
<BR><BR>if ((sock = sockfd_lookup(fd, &err)) != NULL) { <BR>if
((unsigned) backlog > SOMAXCONN) <BR>backlog = SOMAXCONN;
<BR>>>>>这里调用BSD层的inet_listen
<BR>err=sock->ops->listen(sock, backlog);
<BR>sockfd_put(sock); <BR>} <BR>return err; <BR>} <BR><BR>int
inet_listen(struct socket *sock, int backlog) <BR>{ <BR>struct sock
*sk = sock->sk; <BR>unsigned char old_state; <BR>int err;
<BR>lock_sock(sk); <BR>err = -EINVAL; <BR>if (sock->state !=
SS_UNCONNECTED || sock->type != SOCK_STREAM) <BR>goto out;
<BR>old_state = sk->state; <BR>if
(!((1<<OLD_STATE)&(TCPF_CLOSE|TCPF_LISTEN))) <br> goto out;
<BR>/* Really, if the socket is already in listen state <BR>* we can
only allow the backlog to be adjusted. <BR>*/ <BR>if (old_state !=
TCP_LISTEN) { <BR>err = tcp_listen_start(sk); <BR>if (err) <BR>goto
out; <BR>} <BR>>>>>保存backlog到struct sock结构中去
<BR>sk->max_ack_backlog = backlog; <BR>err = 0; <BR>out:
<BR>release_sock(sk); <BR>return err; <BR>} <BR><BR>int
tcp_listen_start(struct sock *sk) <BR>{ <BR>struct tcp_opt *tp =
&(sk->tp_pinfo.af_tcp); <BR>struct tcp_listen_opt *lopt;
<BR>>>>>先做一些初始化 <BR>sk->max_ack_backlog = 0;
<BR>sk->ack_backlog = 0; <BR>tp->accept_queue =
tp->accept_queue_tail = NULL; <BR>tp->syn_wait_lock =
RW_LOCK_UNLOCKED; <BR>>>>>memset(&tp->ack, 0,
sizeof(tp->ack)); <BR>tcp_delack_init(tp); <BR>lopt =
kmalloc(sizeof(struct tcp_listen_opt), GFP_KERNEL); <BR>if (!lopt)
<BR>return -ENOMEM; <BR>memset(lopt, 0, sizeof(struct
tcp_listen_opt)); <BR>for (lopt->max_qlen_log = 6; ;
lopt->max_qlen_log++) <BR>if ((1<<LOPT->max_qlen_log) >=
sysctl_max_syn_backlog) <BR>break;
<BR>write_lock_bh(&tp->syn_wait_lock); <BR>tp->listen_opt
= lopt; <BR>write_unlock_bh(&tp->syn_wait_lock); <BR>/* There
is race window here: we announce ourselves listening, <BR>* but this
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