An issue on one network development.

[Zhikui Chen <zhikui.chen@xxxxxxxxxxxxxxxxxxxx>]

Dear all,

HELP!

I am writing a DCCP code in Linux kernel 2.6.6,  I met a problem, which 
bored me about two weeks. Hope you to give me some hints, thanks in 
advance. The problem is on structure sock in dccp_lookup_listen of 
dccp_lookup.
When dccp_rcv (similar to udp_rcv and TCP_*_rcv) called dccp_v4_lookup( 
similar to TCP_v4_lookup),  the dccp_v4_lookup will call 
dccp_v4_lookup_listen. Running is dead when the 7th line is implemented, 
I checked, problem is from sk=__sk_head(head).  And I also checked the 
printed value of __sk_head(head) is correct.
The other way, I changed the first line as struct sock *sk; (remove 
"=NULL"), running is dead here. I doubt the problem belongs to memory.
My dccp_v4_lookup is so that:
static inline struct sock *dccp_v4_lookup_listen(u32 daddr, u16 
dport,int dif)
{
  struct sock *sk = NULL;
  struct hlist_head *head;

 read_lock(&dccp_lhash_lock);
head = &dccp_hash[ntohs(dport) & (DCCP_HTABLE_SIZE - 1)];
  if (!hlist_empty(head)) {
      struct inet_opt *inet = inet_sk(sk  = __sk_head(head));

      if (inet->num == ntohs(dport) && !(sk->sk_node.next &&
          (!inet->rcv_saddr || inet->rcv_saddr == daddr) &&
          (sk->sk_family == PF_INET || !ipv6_only_sock(sk)) &&
          !sk->sk_bound_dev_if)
          goto sherry_cache;
  printk("dccp_v4_lookup_listen: sk:%x\n",(__sk_head(head)));
      //sk = __dccp_v4_lookup_listen(head, daddr, ntohs(dport), dif);
  }
  if (sk) {
sherry_cache:
      sock_hold(sk);
  }
  read_unlock(&dccp_lhash_lock);
  return (sk);

}

Best regards,

Zhikui Chen
In stuttgart university.