Commit 2f3ab622 authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
Browse files

tuntap: correctly set SOCKWQ_ASYNC_NOSPACE 



When link is down, writes to the device might fail with
-EIO. Userspace needs an indication when the status is resolved.  As a
fix, tun_net_open() attempts to wake up writers - but that is only
effective if SOCKWQ_ASYNC_NOSPACE has been set in the past. This is
not the case of vhost_net which only poll for EPOLLOUT after it meets
errors during sendmsg().

This patch fixes this by making sure SOCKWQ_ASYNC_NOSPACE is set when
socket is not writable or device is down to guarantee EPOLLOUT will be
raised in either tun_chr_poll() or tun_sock_write_space() after device
is up.

Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Eric Dumazet <edumazet@google.com>
Fixes: 1bd4978a ("tun: honor IFF_UP in tun_get_user()")
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a43ad59a

drivers/net/tun.c

+15 −4
Original line number Diff line number Diff line
@@ -1423,6 +1423,13 @@ static void tun_net_init(struct net_device *dev) 
	dev->max_mtu = MAX_MTU - dev->hard_header_len;

}



static bool tun_sock_writeable(struct tun_struct *tun, struct tun_file *tfile)

{

	struct sock *sk = tfile->socket.sk;



	return (tun->dev->flags & IFF_UP) && sock_writeable(sk);

}



/* Character device part */



/* Poll */
@@ -1445,10 +1452,14 @@ static __poll_t tun_chr_poll(struct file *file, poll_table *wait) 
	if (!ptr_ring_empty(&tfile->tx_ring))

		mask |= EPOLLIN | EPOLLRDNORM;



	if (tun->dev->flags & IFF_UP &&

	    (sock_writeable(sk) ||

	/* Make sure SOCKWQ_ASYNC_NOSPACE is set if not writable to

	 * guarantee EPOLLOUT to be raised by either here or

	 * tun_sock_write_space(). Then process could get notification

	 * after it writes to a down device and meets -EIO.

	 */

	if (tun_sock_writeable(tun, tfile) ||

	    (!test_and_set_bit(SOCKWQ_ASYNC_NOSPACE, &sk->sk_socket->flags) &&

	      sock_writeable(sk))))

	     tun_sock_writeable(tun, tfile)))

		mask |= EPOLLOUT | EPOLLWRNORM;



	if (tun->dev->reg_state != NETREG_REGISTERED)

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