论坛徽章:: 0

发表于 2009-02-20 15:42 |显示全部楼层

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贴出代码如下

static int inet_create(struct socket *sock, int protocol)
{
      struct sock *sk;
      struct list_head *p;
      struct inet_protosw *answer;
      struct inet_sock *inet;
      struct proto *answer_prot;
      unsigned char answer_flags;
      char answer_no_check;
      int try_loading_module = 0;
      int err;

      sock->state = SS_UNCONNECTED;

      /* Look for the requested type/protocol pair. */
      answer = NULL;
lookup_protocol:
      err = -ESOCKTNOSUPPORT;
      rcu_read_lock();
      list_for_each_rcu(p, &inetsw[sock->type]) {
            answer = list_entry(p, struct inet_protosw, list);

            /* Check the non-wild match. */
            if (protocol == answer->protocol) {
                     if (protocol != IPPROTO_IP)
                              break;
            } else {
                     /* Check for the two wild cases. */
                     if (IPPROTO_IP == protocol) {
                              protocol = answer->protocol;
                              break;
                     }
                     if (IPPROTO_IP == answer->protocol)
                              break;
            }
            err = -EPROTONOSUPPORT;
            answer = NULL;
      }

      if (unlikely(answer == NULL)) {
            if (try_loading_module < 2) {
                     rcu_read_unlock();
                     /*
                     * Be more specific, e.g. net-pf-2-proto-132-type-1
                     * (net-pf-PF_INET-proto-IPPROTO_SCTP-type-SOCK_STREAM)
                     */
                     if (++try_loading_module == 1)
                              request_module("net-pf-%d-proto-%d-type-%d",
                                             PF_INET, protocol, sock->type);
                     /*
                     * Fall back to generic, e.g. net-pf-2-proto-132
                     * (net-pf-PF_INET-proto-IPPROTO_SCTP)
                     */
                     else
                              request_module("net-pf-%d-proto-%d",
                                             PF_INET, protocol);
                     goto lookup_protocol;
            } else
                     goto out_rcu_unlock;
      } err = -EPERM;
      if (answer->capability > 0 && !capable(answer->capability))
            goto out_rcu_unlock;

      sock->ops = answer->ops;
      answer_prot = answer->prot;
      answer_no_check = answer->no_check;
      answer_flags = answer->flags;
      rcu_read_unlock();

      BUG_TRAP(answer_prot->slab != NULL);

      err = -ENOBUFS;
      sk = sk_alloc(PF_INET, GFP_KERNEL, answer_prot, 1);
      if (sk == NULL)
            goto out;

      err = 0;
      sk->sk_no_check = answer_no_check;
      if (INET_PROTOSW_REUSE & answer_flags)
            sk->sk_reuse = 1;

      inet = inet_sk(sk);
      inet->is_icsk = INET_PROTOSW_ICSK & answer_flags;

      if (SOCK_RAW == sock->type) {
            inet->num = protocol;
            if (IPPROTO_RAW == protocol)
                     inet->hdrincl = 1;
      }

      if (ipv4_config.no_pmtu_disc)
            inet->pmtudisc = IP_PMTUDISC_DONT;
      else
            inet->pmtudisc = IP_PMTUDISC_WANT;

      inet->id = 0;

      sock_init_data(sock, sk);

      sk->sk_destruct = inet_sock_destruct;
      sk->sk_family = PF_INET;
      sk->sk_protocol = protocol;
      sk->sk_backlog_rcv = sk->sk_prot->backlog_rcv;

      inet->uc_ttl = -1;
      inet->mc_loop = 1;
      inet->mc_ttl = 1;
      inet->mc_index = 0;
      inet->mc_list = NULL;

      sk_refcnt_debug_inc(sk);

      if (inet->num) {
            /* It assumes that any protocol which allows
               * the user to assign a number at socket
               * creation time automatically
               * shares.
               */
            inet->sport = htons(inet->num);
            /* Add to protocol hash chains. */
            sk->sk_prot->hash(sk);
      }

      if (sk->sk_prot->init) {
            err = sk->sk_prot->init(sk);
            if (err)
                     sk_common_release(sk);
      }
out:
      return err;
out_rcu_unlock:
      rcu_read_unlock();
      goto out;
}

主要想详细了解 lookupproto这段遍历是如何完成的
以及下方模块如何加载的

/*
                     * Be more specific, e.g. net-pf-2-proto-132-type-1
                     * (net-pf-PF_INET-proto-IPPROTO_SCTP-type-SOCK_STREAM)
                     */
                     if (++try_loading_module == 1)
                              request_module("net-pf-%d-proto-%d-type-%d",
                                             PF_INET, protocol, sock->type);
                     /*
                     * Fall back to generic, e.g. net-pf-2-proto-132
                     * (net-pf-PF_INET-proto-IPPROTO_SCTP)
                     */
                     else
                              request_module("net-pf-%d-proto-%d",
                                             PF_INET, protocol);
                     goto lookup_protocol;

尤其是这两个注释想表达的意思。不太明白啊。

[ 本帖最后由 talentyxc 于 2009-2-20 17:32 编辑 ]