static int sock_bind(int fd, struct sockaddr *umyaddr, int addrlen)
{struct socket *sock;int i;char address[MAX_SOCK_ADDR];int err;if (fd < 0 || fd >= NR_OPEN || current->files->fd[fd] == NULL)return(-EBADF);// 通过文件描述符找到对应的socket，见socket函数源码分析的视图if (!(sock = sockfd_lookup(fd, NULL))) return(-ENOTSOCK);if((err=move_addr_to_kernel(umyaddr,addrlen,address))<0)return err;if ((i = sock->ops->bind(sock, (struct sockaddr *)address, addrlen)) < 0) {return(i);}return(0);
}
```
可见bind函数是直接调用底层af_inet.c的inet_bind
```c
// 给socket绑定一个地址
static int inet_bind(struct socket *sock, struct sockaddr *uaddr,int addr_len)
{struct sockaddr_in *addr=(struct sockaddr_in *)uaddr;struct sock *sk=(struct sock *)sock->data, *sk2;unsigned short snum = 0 /* Stoopid compiler.. this IS ok */;int chk_addr_ret;/* check this error. */if (sk->state != TCP_CLOSE)return(-EIO);if(addr_len<sizeof(struct sockaddr_in))return -EINVAL;// raw是链路层，不需要端口    if(sock->type != SOCK_RAW){ // 已经绑定了端口if (sk->num != 0) return(-EINVAL);snum = ntohs(addr->sin_port);/** We can't just leave the socket bound wherever it is, it might* be bound to a privileged port. However, since there seems to* be a bug here, we will leave it if the port is not privileged.*/// 端口无效则随机获取一个非root才能使用的端口if (snum == 0) {snum = get_new_socknum(sk->prot, 0);}// 小于1024的端口需要超级用户权限if (snum < PROT_SOCK && !suser()) return(-EACCES);}// 判断ipchk_addr_ret = ip_chk_addr(addr->sin_addr.s_addr);if (addr->sin_addr.s_addr != 0 && chk_addr_ret != IS_MYADDR && chk_addr_ret != IS_MULTICAST)return(-EADDRNOTAVAIL);    /* Source address MUST be ours! */if (chk_addr_ret || addr->sin_addr.s_addr == 0)sk->saddr = addr->sin_addr.s_addr;if(sock->type != SOCK_RAW){/* Make sure we are allowed to bind here. */cli();for(sk2 = sk->prot->sock_array[snum & (SOCK_ARRAY_SIZE -1)];sk2 != NULL; sk2 = sk2->next) {/* should be below! */if (sk2->num != snum) continue;// 端口已经被使用，没有设置可重用标记，比如断开了解后在2msl内是否可以重用if (!sk->reuse){sti();return(-EADDRINUSE);}if (sk2->num != snum) continue;     /* more than one */if (sk2->saddr != sk->saddr) continue;    /* socket per slot ! -FB */// 被监听的端口不能同时被使用if (!sk2->reuse || sk2->state==TCP_LISTEN) {sti();return(-EADDRINUSE);}}sti();// 保证该sk不在sock_array队列里remove_sock(sk);// 挂载到sock_array里put_sock(snum, sk);// tcp头中的源端口sk->dummy_th.source = ntohs(sk->num);sk->daddr = 0;sk->dummy_th.dest = 0;}return(0);
}
复制代码

由代码中可以看到，bind函数主要做的事情是判断一下端口和ip和可用性，然后把sock结构体挂载到协议对应的sock_array哈希列表中。