netdev - Re: tap/bridge: Dropping NETIF_F_GSO/NETIF_F

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20110504232854.GA11687@rere.qmqm.pl>
Date:	Thu, 5 May 2011 01:28:54 +0200
From:	Michał Mirosław <mirq-linux@...e.qmqm.pl>
To:	Herbert Xu <herbert@...dor.apana.org.au>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>, netdev@...r.kernel.org,
	Ben Hutchings <bhutchings@...arflare.com>
Subject: Re: tap/bridge: Dropping NETIF_F_GSO/NETIF_F_SG

On Thu, May 05, 2011 at 08:34:15AM +1000, Herbert Xu wrote:
> On Wed, May 04, 2011 at 09:18:14PM +0300, Michael S. Tsirkin wrote:
> > BTW, I just noticed that net-next spits out
> > many of the following when I run any VMs:
> > 
> > tap0: Dropping NETIF_F_SG since no checksum feature.
> > tap0: Dropping NETIF_F_GSO since no SG feature.
> > tap0: Features changed: 0x401b4849 -> 0x40004040
> > device msttap0 entered promiscuous mode
> > br0: Dropping NETIF_F_GSO since no SG feature.
> > br0: port 1(msttap0) entering forwarding state
> > br0: port 1(msttap0) entering forwarding state
> > tap0: Features changed: 0x40004040 -> 0x40024849
> > tap0: Dropping NETIF_F_SG since no checksum feature.
> > tap0: Dropping NETIF_F_GSO since no SG feature.
> > tap0: Features changed: 0x40024849 -> 0x40004040
> > br0: Dropping NETIF_F_GSO since no SG feature.
> > tap0: Dropping NETIF_F_SG since no checksum feature.
> > tap0: Dropping NETIF_F_GSO since no SG feature.
> > tap0: Dropping NETIF_F_SG since no checksum feature.
> > tap0: Dropping NETIF_F_GSO since no SG feature.
> > tap0: Dropping NETIF_F_SG since no checksum feature.
> > tap0: Dropping NETIF_F_GSO since no SG feature.
> > tap0: Dropping NETIF_F_SG since no checksum feature.
> > tap0: Dropping NETIF_F_GSO since no SG feature.
> > tap0: Features changed: 0x40004040 -> 0x401b4849
> > tap0: Dropping NETIF_F_SG since no checksum feature.
> > tap0: Dropping NETIF_F_GSO since no SG feature.
> > tap0: Features changed: 0x401b4849 -> 0x40004040
> > br0: Dropping NETIF_F_GSO since no SG feature.
> > 
> > My problem is not primarily with warnings:
> > 
> > will that linearize all packets and disable GSO
> > for tap and bridge? If yes it can't be good
> > for performance...
> I think so.  So the question is why is checksum off?

Whatever application is creating the tap0 device is not calling
ioctl(TUNSETOFFLOAD) with TUN_F_CSUM set. This is userspace bug/feature
exposed by recent changes to netdev features handling.

Best Regards,
Michał Mirosław
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html