socket学习

使用socket(AF_INET, SOCK_STREAM, 0)创建socket
struct proto tcp_prot = {
.name = "TCP",
......
.init = tcp_v4_init_sock,
......
};

/* NOTE: A lot of things set to zero explicitly by call to
 *       sk_alloc() so need not be done here.
 */
static int tcp_v4_init_sock(struct sock *sk)
{
struct inet_connection_sock *icsk = inet_csk(sk);

tcp_init_sock(sk);
icsk->icsk_af_ops = &ipv4_specific;
 ......
}

/* Upon startup we insert all the elements in inetsw_array[] into
 * the linked list inetsw.
 */
static struct inet_protosw inetsw_array[] =
{
{
.type =       SOCK_STREAM,
.protocol =   IPPROTO_TCP,
.prot =       &tcp_prot,
.ops =        &inet_stream_ops,
.no_check =   0,
.flags =      INET_PROTOSW_PERMANENT |
      INET_PROTOSW_ICSK,
},
 ......
 {
  .type =       SOCK_RAW,
  .protocol =   IPPROTO_IP, /* wild card */
  .prot =       &raw_prot,
  .ops =        &inet_sockraw_ops,
  .no_check =   UDP_CSUM_DEFAULT,
  .flags =      INET_PROTOSW_REUSE,
 }
};

static int __init inet_init(void)
{
 ......
/* Register the socket-side information for inet_create. */
for (r = &inetsw[0]; r < &inetsw[SOCK_MAX]; ++r)
INIT_LIST_HEAD(r);

for (q = inetsw_array; q < &inetsw_array[INETSW_ARRAY_LEN]; ++q)
inet_register_protosw(q);
.....
}

static const struct net_proto_family inet_family_ops = {
.family = PF_INET,
.create = inet_create,
.owner = THIS_MODULE,
};

static int inet_create(struct net *net, struct socket *sock, int protocol,
       int kern)
{
......
 list_for_each_entry_rcu(answer, &inetsw[sock->type], list){......}
......
 sock->ops = answer->ops;
 answer_prot = answer->prot;
 ......
sk = sk_alloc(net, PF_INET, GFP_KERNEL, answer_prot);
......
if (sk->sk_prot->init) 
err = sk->sk_prot->init(sk);
......
}

---------------------------------------------------------------------------
sys_socket():
#define AF_INET 2 /* Internet IP Protocol  */
#define PF_INET AF_INET //include.h/linux/socket.h

1.sys_socket()
SYSCALL_DEFINE3(socket, int, family, int, type, int, protocol)
{
int retval;
struct socket *sock;
int flags;
 ......

retval = sock_create(family, type, protocol, &sock);
if (retval < 0)
goto out;

retval = sock_map_fd(sock, flags & (O_CLOEXEC | O_NONBLOCK));
 ......
}

2.sock_create()
int sock_create(int family, int type, int protocol, struct socket **res)
{
return __sock_create(current->nsproxy->net_ns, family, type, protocol, res, 0);
}
EXPORT_SYMBOL(sock_create);

int __sock_create(struct net *net, int family, int type, int protocol,
 struct socket **res, int kern)
{
......
/*
 * Allocate the socket and allow the family to set things up. if
 * the protocol is 0, the family is instructed to select an appropriate
 * default.
 */
sock = sock_alloc();
 sock->type = type;
 ......
pf = rcu_dereference(net_families[family]);
err = pf->create(net, sock, protocol, kern);
......
}

Note:三组操作数组：
1.struct proto_ops  //socket
2.struct proto         //sock
3.struct inet_connection_sock_af_ops //inet_connection_sock