inet_init函数中的inet_add_protocol()函数

内核版本：2.6.18

if (inet_add_protocol(&icmp_protocol, IPPROTO_ICMP) < 0)
        printk(KERN_CRIT "inet_init: Cannot add ICMP protocol\n");
    if (inet_add_protocol(&udp_protocol, IPPROTO_UDP) < 0)
        printk(KERN_CRIT "inet_init: Cannot add UDP protocol\n");
    if (inet_add_protocol(&tcp_protocol, IPPROTO_TCP) < 0)
        printk(KERN_CRIT "inet_init: Cannot add TCP protocol\n");
#ifdef CONFIG_IP_MULTICAST
    if (inet_add_protocol(&igmp_protocol, IPPROTO_IGMP) < 0)
        printk(KERN_CRIT "inet_init: Cannot add IGMP protocol\n");
#endif

#ifdef CONFIG_IP_MULTICAST
static struct net_protocol igmp_protocol = {
    .handler =    igmp_rcv, //icmp协议接收处理函数
};
#endif

static struct net_protocol tcp_protocol = {
    .handler =    tcp_v4_rcv,
    .err_handler =    tcp_v4_err,
    .gso_send_check = tcp_v4_gso_send_check,
    .gso_segment =    tcp_tso_segment,
    .no_policy =    1,
};

static struct net_protocol udp_protocol = {
    .handler =    udp_rcv,
    .err_handler =    udp_err,
    .no_policy =    1,
};

static struct net_protocol icmp_protocol = {
    .handler =    icmp_rcv,
}

inet_add_protocol()作用：把igmp_protocol,icmp_protocol,tcp_protocol,udp_protocol放到inet_protos(全局hash table)上。

源代码:

int inet_add_protocol(struct net_protocol *prot, unsigned char protocol)
{
    int hash, ret;

    hash = protocol & (MAX_INET_PROTOS - 1);//计算hash

    spin_lock_bh(&inet_proto_lock);
    if (inet_protos[hash]) {
        ret = -1;
    } else {
        inet_protos[hash] = prot;
        ret = 0;
    }
    spin_unlock_bh(&inet_proto_lock);

    return ret;
}