lkml.org 
[lkml]   [2018]   [May]   [18]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH net] tuntap: raise EPOLLOUT on device up
    On Fri, May 18, 2018 at 09:00:43PM +0800, Jason Wang wrote:
    > We return -EIO on device down but can not raise EPOLLOUT after it was
    > up. This may confuse user like vhost which expects tuntap to raise
    > EPOLLOUT to re-enable its TX routine after tuntap is down. This could
    > be easily reproduced by transmitting packets from VM while down and up
    > the tap device. Fixing this by set SOCKWQ_ASYNC_NOSPACE on -EIO.
    >
    > Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
    > Cc: Eric Dumazet <edumazet@google.com>
    > Fixes: 1bd4978a88ac2 ("tun: honor IFF_UP in tun_get_user()")
    > Signed-off-by: Jason Wang <jasowang@redhat.com>
    > ---
    > drivers/net/tun.c | 4 +++-
    > 1 file changed, 3 insertions(+), 1 deletion(-)
    >
    > diff --git a/drivers/net/tun.c b/drivers/net/tun.c
    > index d45ac37..1b29761 100644
    > --- a/drivers/net/tun.c
    > +++ b/drivers/net/tun.c
    > @@ -1734,8 +1734,10 @@ static ssize_t tun_get_user(struct tun_struct *tun, struct tun_file *tfile,
    > int skb_xdp = 1;
    > bool frags = tun_napi_frags_enabled(tun);
    >
    > - if (!(tun->dev->flags & IFF_UP))
    > + if (!(tun->dev->flags & IFF_UP)) {

    Isn't this racy? What if flag is cleared at this point?

    > + set_bit(SOCKWQ_ASYNC_NOSPACE, &tfile->socket.flags);
    > return -EIO;
    > + }
    >
    > if (!(tun->flags & IFF_NO_PI)) {
    > if (len < sizeof(pi))
    > --
    > 2.7.4

    \
     
     \ /
      Last update: 2018-05-18 15:14    [W:2.165 / U:0.360 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site