tun: support receiving skb through msg_control

This patch makes tun_recvmsg() can receive from skb from its caller
through msg_control. Vhost_net will be the first user.

Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 3cbfc5c707e3b1e7db78cfb645d161af260615f9..f8041f9c7e6535deb2b883fc8f579aeb940830de 100644 (file)
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1510,9 +1510,8 @@ out:
 
 static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
                           struct iov_iter *to,
-                          int noblock)
+                          int noblock, struct sk_buff *skb)
 {
-       struct sk_buff *skb;
        ssize_t ret;
        int err;
 
@@ -1521,10 +1520,12 @@ static ssize_t tun_do_read(struct tun_struct *tun, struct tun_file *tfile,
        if (!iov_iter_count(to))
                return 0;
 
-       /* Read frames from ring */
-       skb = tun_ring_recv(tfile, noblock, &err);
-       if (!skb)
-               return err;
+       if (!skb) {
+               /* Read frames from ring */
+               skb = tun_ring_recv(tfile, noblock, &err);
+               if (!skb)
+                       return err;
+       }
 
        ret = tun_put_user(tun, tfile, skb, to);
        if (unlikely(ret < 0))
@@ -1544,7 +1545,7 @@ static ssize_t tun_chr_read_iter(struct kiocb *iocb, struct iov_iter *to)
 
        if (!tun)
                return -EBADFD;
-       ret = tun_do_read(tun, tfile, to, file->f_flags & O_NONBLOCK);
+       ret = tun_do_read(tun, tfile, to, file->f_flags & O_NONBLOCK, NULL);
        ret = min_t(ssize_t, ret, len);
        if (ret > 0)
                iocb->ki_pos = ret;
@@ -1646,7 +1647,8 @@ static int tun_recvmsg(struct socket *sock, struct msghdr *m, size_t total_len,
                                         SOL_PACKET, TUN_TX_TIMESTAMP);
                goto out;
        }
-       ret = tun_do_read(tun, tfile, &m->msg_iter, flags & MSG_DONTWAIT);
+       ret = tun_do_read(tun, tfile, &m->msg_iter, flags & MSG_DONTWAIT,
+                         m->msg_control);
        if (ret > (ssize_t)total_len) {
                m->msg_flags |= MSG_TRUNC;
                ret = flags & MSG_TRUNC ? ret : total_len;