[PATCH V2 net-next 6/7] tap: support receiving skb from msg_control

[Jason Wang]

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 <jasow...@redhat.com>
---
 drivers/net/tap.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/net/tap.c b/drivers/net/tap.c
index abdaf86..07d9174 100644
--- a/drivers/net/tap.c
+++ b/drivers/net/tap.c
@@ -824,15 +824,17 @@ static ssize_t tap_put_user(struct tap_queue *q,
 
 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 done;
+
        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);
 
+done:
        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;
-- 
2.7.4