📄 2_4网络代码阅读笔(3) - china linux forum.htm
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transition is still not validated by get_port(). <BR>* It is OK,
because this socket enters to hash table only <BR>* after validation
is complete. <BR>*/ <BR>>>>>更改状态 <BR>sk->state =
TCP_LISTEN; <BR>>>>>如果没有对端口赋值,则查找一个合适的端口,
<BR>>>>>这里调用的函数是tcp_v4_get_port,我们已经详细分析了 <BR>if
(sk->prot->get_port(sk, sk->num) == 0) { <BR>sk->sport =
htons(sk->num);
<BR>>>>>得到sk->dst_cache的指针,然后将其置为NULL,然后将sk->dst_cache
<BR>>>>>所指的路由缓存使用计数减1 <BR>sk_dst_reset(sk);
<BR>>>>>调用tcp_v4_hash,见下面分析
<BR>sk->prot->hash(sk); <BR>return 0; <BR>} <BR>sk->state =
TCP_CLOSE; <BR>write_lock_bh(&tp->syn_wait_lock);
<BR>tp->listen_opt = NULL;
<BR>write_unlock_bh(&tp->syn_wait_lock); <BR>kfree(lopt);
<BR>return -EADDRINUSE; <BR>} <BR>tcp_v4_hash调用__tcp_v4_hash：
<BR>static __inline__ void __tcp_v4_hash(struct sock *sk) <BR>{
<BR>struct sock **skp; <BR>rwlock_t *lock;
<BR>BUG_TRAP(sk->pprev==NULL); <BR>if(sk->state == TCP_LISTEN)
{ <BR>>>>>如果是倾听状态,则将其链入到tcp_listening_hash表中,hash值根据端口
<BR>>>>>号计算. <BR>skp =
&tcp_listening_hash[tcp_sk_listen_hashfn(sk)]; <BR>lock =
&tcp_lhash_lock; <BR>tcp_listen_wlock(); <BR>} else {
<BR>>>>>否则,则将其链入到tcp_ehash链表中,什么时候会将其连接到tcp_ehash中
<BR>>>>>有待于后面的分析. <BR>skp =
&tcp_ehash[(sk->hashent = tcp_sk_hashfn(sk))].chain; <BR>lock
= &tcp_ehash[sk->hashent].lock; <BR>write_lock(lock); <BR>}
<BR>>>>>将它连到hash表的前面,如果后面还有其它的hash值相同的元素,则将这个元素的
<BR>>>>>的前向指针指向我们这个sock的next域 <BR>if((sk->next =
*skp) != NULL) <BR>(*skp)->pprev = &sk->next; <BR>*skp =
sk; <BR>>>>>我们这个sock的前向指针指向hash表头. <BR>sk->pprev =
skp; <BR>sock_prot_inc_use(sk->prot); <BR>write_unlock(lock);
<BR>if (sk->state == TCP_LISTEN)
<BR>wake_up(&tcp_lhash_wait); <BR>} <BR><BR>到目前为止,我们已经遇到了struct
sock如下的指针: <BR><BR>第一组: <BR>/* Local port binding hash linkage. */
<BR>>>>>将绑定到相同端口的sock连接起来的指针 <BR>struct sock *bind_next;
<BR>struct sock **bind_pprev;
<BR>>>>>这个指针指向所在的tcp_bind_bucket结构 <BR>struct sock
*prev; <BR>第二组: <BR>/* Main hash linkage for various protocol lookup
tables. */ <BR>>>>>将处于同一状态的sock连接起来的指针,例如倾听状态,连接建立状态
<BR>struct sock *next; <BR>struct sock **pprev;
<BR><BR>还遇到了两个hash表,它们是: <BR>struct tcp_hashinfo __cacheline_aligned
tcp_hashinfo = { <BR>__tcp_ehash: NULL, <BR>__tcp_bhash: NULL,
<BR>__tcp_bhash_size: 0, <BR>__tcp_ehash_size: 0,
<BR>__tcp_listening_hash: { NULL, }, <BR>__tcp_lhash_lock:
RW_LOCK_UNLOCKED, <BR>__tcp_lhash_users: ATOMIC_INIT(0),
<BR>__tcp_lhash_wait:
<BR>__WAIT_QUEUE_HEAD_INITIALIZER(tcp_hashinfo.__tcp_lhash_wait),
<BR>__tcp_portalloc_lock: SPIN_LOCK_UNLOCKED <BR>};
<BR><BR><BR>#define tcp_bhash (tcp_hashinfo.__tcp_bhash) <BR>#define
tcp_ehash_size (tcp_hashinfo.__tcp_ehash_size) <BR>#define
tcp_listening_hash (tcp_hashinfo.__tcp_listening_hash)
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