linux 协议栈初始化（一）

以下是协议栈初始化函数调用层次结构

socket.c ：BSD socket层，属于表示层，为应用层系统调用提供接口；

af_inet.c ：INET Socket层，属于会话层，屏蔽底层协议

以下是sock_init()函数

void sock_init(void)
{
    int i;

    printk("Swansea University Computer Society NET3.019\n");

    /*
     *    Initialize all address (protocol) families. 
     */
     
    for (i = 0; i < NPROTO; ++i) pops[i] = NULL;

    /*
     *    Initialize the protocols module. 
     */

    proto_init();

#ifdef CONFIG_NET
    /* 
     *    Initialize the DEV module. 
     */

    dev_init();
  
    /*
     *    And the bottom half handler 
     */

    bh_base[NET_BH].routine= net_bh;
    enable_bh(NET_BH);
#endif  
}

for (i = 0; i < NPROTO; ++i) pops[i] = NULL;

pops[]定义如下： 

static struct proto_ops *pops[NPROTO];

proto_ops结构体定义如下：

struct proto_ops {
  int    family;

  int    (*create)    (struct socket *sock, int protocol);
  int    (*dup)        (struct socket *newsock, struct socket *oldsock);
  int    (*release)    (struct socket *sock, struct socket *peer);
  int    (*bind)        (struct socket *sock, struct sockaddr *umyaddr,
             int sockaddr_len);
  int    (*connect)    (struct socket *sock, struct sockaddr *uservaddr,
             int sockaddr_len, int flags);
  int    (*socketpair)    (struct socket *sock1, struct socket *sock2);
  int    (*accept)    (struct socket *sock, struct socket *newsock,
             int flags);
  int    (*getname)    (struct socket *sock, struct sockaddr *uaddr,
             int *usockaddr_len, int peer);
  int    (*read)        (struct socket *sock, char *ubuf, int size,
             int nonblock);
  int    (*write)    (struct socket *sock, char *ubuf, int size,
             int nonblock);
  int    (*select)    (struct socket *sock, int sel_type,
             select_table *wait);
  int    (*ioctl)    (struct socket *sock, unsigned int cmd,
             unsigned long arg);
  int    (*listen)    (struct socket *sock, int len);
  int    (*send)        (struct socket *sock, void *buff, int len, int nonblock,
             unsigned flags);
  int    (*recv)        (struct socket *sock, void *buff, int len, int nonblock,
             unsigned flags);
  int    (*sendto)    (struct socket *sock, void *buff, int len, int nonblock,
             unsigned flags, struct sockaddr *, int addr_len);
  int    (*recvfrom)    (struct socket *sock, void *buff, int len, int nonblock,
             unsigned flags, struct sockaddr *, int *addr_len);
  int    (*shutdown)    (struct socket *sock, int flags);
  int    (*setsockopt)    (struct socket *sock, int level, int optname,
             char *optval, int optlen);
  int    (*getsockopt)    (struct socket *sock, int level, int optname,
             char *optval, int *optlen);
  int    (*fcntl)    (struct socket *sock, unsigned int cmd,
             unsigned long arg);    
};