?? 2_4網絡代碼閱讀筆(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>>>>>更改狀態 <BR>sk->state =
TCP_LISTEN; <BR>>>>>如果沒有對端口賦值,則查找一個合適的端口,
<BR>>>>>這里調用的函數是tcp_v4_get_port,我們已經詳細分析了 <BR>if
(sk->prot->get_port(sk, sk->num) == 0) { <BR>sk->sport =
htons(sk->num);
<BR>>>>>得到sk->dst_cache的指針,然后將其置為NULL,然后將sk->dst_cache
<BR>>>>>所指的路由緩存使用計數減1 <BR>sk_dst_reset(sk);
<BR>>>>>調用tcp_v4_hash,見下面分析
<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調用__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>>>>>如果是傾聽狀態,則將其鏈入到tcp_listening_hash表中,hash值根據端口
<BR>>>>>號計算. <BR>skp =
&tcp_listening_hash[tcp_sk_listen_hashfn(sk)]; <BR>lock =
&tcp_lhash_lock; <BR>tcp_listen_wlock(); <BR>} else {
<BR>>>>>否則,則將其鏈入到tcp_ehash鏈表中,什么時候會將其連接到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>>>>>將它連到hash表的前面,如果后面還有其它的hash值相同的元素,則將這個元素的
<BR>>>>>的前向指針指向我們這個sock的next域 <BR>if((sk->next =
*skp) != NULL) <BR>(*skp)->pprev = &sk->next; <BR>*skp =
sk; <BR>>>>>我們這個sock的前向指針指向hash表頭. <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>到目前為止,我們已經遇到了struct
sock如下的指針: <BR><BR>第一組: <BR>/* Local port binding hash linkage. */
<BR>>>>>將綁定到相同端口的sock連接起來的指針 <BR>struct sock *bind_next;
<BR>struct sock **bind_pprev;
<BR>>>>>這個指針指向所在的tcp_bind_bucket結構 <BR>struct sock
*prev; <BR>第二組: <BR>/* Main hash linkage for various protocol lookup
tables. */ <BR>>>>>將處于同一狀態的sock連接起來的指針,例如傾聽狀態,連接建立狀態
<BR>struct sock *next; <BR>struct sock **pprev;
<BR><BR>還遇到了兩個hash表,它們是: <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)
<BR><BR><BR><BR>歡迎訪問"Unix編程" <BR>telnet apue.dhs.org 2323 <BR>or
http://apue.dhs.org
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