tap: support receiving skb from msg_control

This patch makes tap_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>

1 files changed, 8 insertions, 4 deletions

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index abdaf867774d..9af3239d6ad5 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -824,15 +824,17 @@ done:
 
 static ssize_t tap_do_read(struct tap_queue *q,
                            struct iov_iter *to,
-                           int noblock)
+                           int noblock, struct sk_buff *skb)
 {
         DEFINE_WAIT(wait);
-        struct sk_buff *skb;
         ssize_t ret = 0;
 
         if (!iov_iter_count(to))
                 return 0;
 
+        if (skb)
+                goto put;
+
         while (1) {
                 if (!noblock)
                         prepare_to_wait(sk_sleep(&q->sk), &wait,
@@ -856,6 +858,7 @@ static ssize_t tap_do_read(struct tap_queue *q,
         if (!noblock)
                 finish_wait(sk_sleep(&q->sk), &wait);
 
+put:
         if (skb) {
                 ret = tap_put_user(q, skb, to);
                 if (unlikely(ret < 0))
@@ -872,7 +875,7 @@ static ssize_t tap_read_iter(struct kiocb *iocb, struct iov_iter *to)
         struct tap_queue *q = file->private_data;
         ssize_t len = iov_iter_count(to), ret;
 
-        ret = tap_do_read(q, to, file->f_flags & O_NONBLOCK);
+        ret = tap_do_read(q, to, file->f_flags & O_NONBLOCK, NULL);
         ret = min_t(ssize_t, ret, len);
         if (ret > 0)
                 iocb->ki_pos = ret;
@@ -1155,7 +1158,8 @@ static int tap_recvmsg(struct socket *sock, struct msghdr *m,
         int ret;
         if (flags & ~(MSG_DONTWAIT|MSG_TRUNC))
                 return -EINVAL;
-        ret = tap_do_read(q, &m->msg_iter, flags & MSG_DONTWAIT);
+        ret = tap_do_read(q, &m->msg_iter, flags & MSG_DONTWAIT,
+                          m->msg_control);
         if (ret > total_len) {
                 m->msg_flags |= MSG_TRUNC;
                 ret = flags & MSG_TRUNC ? ret : total_len;