SYSCALL_DEFINE5 setsockopt 代码流程_syscall.setsockoptint-优快云博客

本文链接：https://blog.youkuaiyun.com/already_skb/article/details/85003526

本文深入探讨了Linux系统中socket选项的设置过程，包括setsockopt函数的实现细节，以及TCP和IP选项的处理流程。通过分析内核源码，解释了如何为套接字设置不同级别的选项，并展示了socket选项的安全性和功能性验证。

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SYSCALL_DEFINE5(setsockopt, int, fd, int, level, int, optname,
       char __user *, optval, int, optlen)
{
   int err, fput_needed;
   struct socket *sock;

if (optlen < 0)
return -EINVAL;

   sock = sockfd_lookup_light(fd, &err, &fput_needed);
   if (sock != NULL) {
       err = security_socket_setsockopt(sock, level, optname);
       if (err)
           goto out_put;

       if (level == SOL_SOCKET)
           err =
           sock_setsockopt(sock, level, optname, optval,
                   optlen);
       else
           err =
           sock->ops->setsockopt(sock, level, optname, optval,
                       optlen);
out_put:
       fput_light(sock->file, fput_needed);
   }
   return err;
}

const struct proto_ops inet_stream_ops = {
   .family       = PF_INET,
   .owner       = THIS_MODULE,
   .release   = inet_release,
   .bind       = inet_bind,
   .connect   = inet_stream_connect,
   .socketpair   = sock_no_socketpair,
   .accept       = inet_accept,
   .getname   = inet_getname,
   .poll       = tcp_poll,
   .ioctl       = inet_ioctl,
   .listen       = inet_listen,
   .shutdown   = inet_shutdown,
   .setsockopt   = sock_common_setsockopt,
   .getsockopt   = sock_common_getsockopt,

   err = -ENOBUFS;
   sk = sk_alloc(net, PF_INET, GFP_KERNEL, answer_prot);
   if (sk == NULL)
       goto out;

   /*
*   Set socket options on an inet socket.
*/
int sock_common_setsockopt(struct socket *sock, int level, int optname,
           char __user *optval, unsigned int optlen)
{
   struct sock *sk = sock->sk;

//call tcp_prot setsockopt api
return sk->sk_prot->setsockopt(sk, level, optname, optval, optlen);
}

int tcp_setsockopt(struct sock *sk, int level, int optname, char __user *optval,
unsigned int optlen)
{
const struct inet_connection_sock *icsk = inet_csk(sk);

   //IP option handler
   if (level != SOL_TCP)
       return icsk->icsk_af_ops->setsockopt(sk, level, optname,
                       optval, optlen);

   //TCP option handler
   return do_tcp_setsockopt(sk, level, optname, optval, optlen);
}
EXPORT_SYMBOL(tcp_setsockopt);