On 2018年05月18日 21:13, Michael S. Tsirkin wrote:
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 <han...@stressinduktion.org> Cc: Eric Dumazet <eduma...@google.com> Fixes: 1bd4978a88ac2 ("tun: honor IFF_UP in tun_get_user()") Signed-off-by: Jason Wang <jasow...@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?
I think you mean "set at this point"? Then yes, so we probably need to set the bit during tun_net_close().
Thanks
+ set_bit(SOCKWQ_ASYNC_NOSPACE, &tfile->socket.flags); return -EIO; + }if (!(tun->flags & IFF_NO_PI)) {if (len < sizeof(pi)) -- 2.7.4
