Hello! I'm sending new patch, with proper formatting and signed tag 2017-03-08 23:29 GMT+03:00 Yaroslav Isakov <yaroslav.isa...@gmail.com>: > Hello! > I've found a bug in TUN/TAP driver with offloads - when Qemu is trying > to set offloads on tap device, there is no error, but offloads are not > appied. > > The cause of this is that udev in recent systemd is using ethtool to > disable offloads. So, udev is setting tun->dev->wanted_features via > ethtool ioctl to disable TSO, but when qemu is trying to set offloads, > it's using TUN/TAP ioctl which is not setting wanted_features, so > netdev_update_features will not see features qemu wants. > > This can be easily reproduced - just run qemu with > guest_tso4=on,guest_tso6=on on systemd with systemd>=226 and after > booting the VM, ethtool -k tap0 will show that TSO4 is disabled and > TSO6 is enabled (systemd is not touching TSO6, that's why it's not > affected at all) > I've attached pretty trivial patch to fix this problem.
From 12a5079ef6172c32ac19b606310db151c7ca3e5d Mon Sep 17 00:00:00 2001 From: Yaroslav Isakov <yaroslav.isa...@gmail.com> Date: Thu, 16 Mar 2017 21:08:37 +0300 Subject: [PATCH] tun: fix inability to set offloads after disabling them via ethtool
From: Yaroslav Isakov <yaroslav.isa...@gmail.com> Added missing logic in tun driver, which prevents apps to set offloads using tun ioctl, if offloads were previously disabled via ethtool Signed-off-by: Yaroslav Isakov <yaroslav.isa...@gmail.com> --- drivers/net/tun.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/drivers/net/tun.c b/drivers/net/tun.c index 34cc3c5..cc88cd7 100644 --- a/drivers/net/tun.c +++ b/drivers/net/tun.c @@ -1931,6 +1931,8 @@ static int set_offload(struct tun_struct *tun, unsigned long arg) return -EINVAL; tun->set_features = features; + tun->dev->wanted_features &= ~TUN_USER_FEATURES; + tun->dev->wanted_features |= features; netdev_update_features(tun->dev); return 0; -- 2.10.2
