转:http://blog.csdn.net/nerdx/article/details/12656987
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1.1 static inline struct ipq *ip_find(struct iphdr *iph, u32 user)
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{
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__u16 id = iph->id;
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__u32 saddr = iph->saddr;
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__u32 daddr = iph->daddr;
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__u8 protocol = iph->protocol;
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unsigned int hash = ipqhashfn(id, saddr, daddr, protocol);
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struct ipq *qp;
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read_lock(&ipfrag_lock);
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for(qp = ipq_hash[hash]; qp; qp = qp->next) {
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if(qp->id == id &&
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qp->saddr == saddr &&
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qp->daddr == daddr &&
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qp->protocol == protocol &&
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qp->user == user) {
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atomic_inc(&qp->refcnt);
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read_unlock(&ipfrag_lock);
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return qp;
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}
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}
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read_unlock(&ipfrag_lock);
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return ip_frag_create(hash, iph, user);
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}
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1.2 static struct ipq *ip_frag_create(unsigned hash, struct iphdr *iph, u32 user)
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{
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struct ipq *qp;
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if ((qp = frag_alloc_queue()) == NULL)
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goto out_nomem;
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qp->protocol = iph->protocol;
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qp->last_in = 0;
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qp->id = iph->id;
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qp->saddr = iph->saddr;
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qp->daddr = iph->daddr;
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qp->user = user;
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qp->len = 0;
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qp->meat = 0;
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qp->fragments = NULL;
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qp->iif = 0;
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init_timer(&qp->timer);
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qp->timer.data = (unsigned long) qp;
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qp->timer.function = ip_expire;
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spin_lock_init(&qp->lock);
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atomic_set(&qp->refcnt, 1);
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return ip_frag_intern(hash, qp);
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out_nomem:
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NETDEBUG(if (net_ratelimit()) printk(KERN_ERR "ip_frag_create: no memory left !\n"));
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return NULL;
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}
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1.3 static struct ipq *ip_frag_intern(unsigned int hash, struct ipq *qp_in)
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{
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struct ipq *qp;
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write_lock(&ipfrag_lock);
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qp = qp_in;
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if (!mod_timer(&qp->timer, jiffies + sysctl_ipfrag_time))
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atomic_inc(&qp->refcnt);
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atomic_inc(&qp->refcnt);
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if((qp->next = ipq_hash[hash]) != NULL)
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qp->next->pprev = &qp->next;
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ipq_hash[hash] = qp;
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qp->pprev = &ipq_hash[hash];
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INIT_LIST_HEAD(&qp->lru_list);
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list_add_tail(&qp->lru_list, &ipq_lru_list);
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ip_frag_nqueues++;
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write_unlock(&ipfrag_lock);
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return qp;
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}
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1.4 static void ip_expire(unsigned long arg)
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{
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struct ipq *qp = (struct ipq *) arg;
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spin_lock(&qp->lock);
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if (qp->last_in & COMPLETE)
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goto out;
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ipq_kill(qp);
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if ((qp->last_in&FIRST_IN) && qp->fragments != NULL) {
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struct sk_buff *head = qp->fragments;
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if ((head->dev = dev_get_by_index(qp->iif)) != NULL) {
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icmp_send(head, ICMP_TIME_EXCEEDED, ICMP_EXC_FRAGTIME, 0);
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dev_put(head->dev);
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}
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}
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out:
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spin_unlock(&qp->lock);
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ipq_put(qp, NULL);
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}
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