dev_add_pack函数

内核版本：2.6.18

inet_init函数调用dev_add_pack函数：

/*
 *    Called once on startup.
 */

static struct packet_type arp_packet_type = {
    .type =    __constant_htons(ETH_P_ARP),
    .func =    arp_rcv,
}

以太网帧类型为ARP的数据帧。

/*
 *    IP protocol layer initialiser
 */

static struct packet_type ip_packet_type = {
    .type = __constant_htons(ETH_P_IP), //转化为网络字节序
    .func = ip_rcv,
    .gso_send_check = inet_gso_send_check,
    .gso_segment = inet_gso_segment,
};

以太网帧类型为IP的数据帧。

dev_add_pack(&ip_packet_type)

把处理ETH_P_IP数据的handler加入到相应的链表中。

static struct list_head ptype_base[16];    /* 16 way hashed list */
static struct list_head ptype_all;        /* Taps */

/**
 *    dev_add_pack - add packet handler
 *    @pt: packet type declaration
 *
 *    Add a protocol handler to the networking stack. The passed &packet_type
 *    is linked into kernel lists and may not be freed until it has been
 *    removed from the kernel lists.
 *
 *    This call does not sleep therefore it can not
 *    guarantee all CPU's that are in middle of receiving packets
 *    will see the new packet type (until the next received packet).
 */

void dev_add_pack(struct packet_type *pt)
{
    int hash;

    spin_lock_bh(&ptype_lock);
    if (pt->type == htons(ETH_P_ALL)) {
        netdev_nit++;
        list_add_rcu(&pt->list, &ptype_all);
    } else {
        hash = ntohs(pt->type) & 15;
        list_add_rcu(&pt->list, &ptype_base[hash]);
    }
    spin_unlock_bh(&ptype_lock);
}