From: Eric Dumazet <edumazet@google.com>
To: Cong Wang <xiyou.wangcong@gmail.com>
Cc: netdev <netdev@vger.kernel.org>, Saeed Mahameed <saeedm@mellanox.com>
Subject: Re: [Patch net v2] mlx5: fixup checksum for short ethernet frame padding
Date: Wed, 28 Nov 2018 20:09:03 -0800 [thread overview]
Message-ID: <CANn89i+oyQRa3f=3V=hbs4xzGttXLuHVS7wG3qEFqaHJyLtpSQ@mail.gmail.com> (raw)
In-Reply-To: <CAM_iQpVPy2sSz53wiF=fFVm=PPRudsnc58bAn2YX156D0-TRyg@mail.gmail.com>
On Wed, Nov 28, 2018 at 7:53 PM Cong Wang <xiyou.wangcong@gmail.com> wrote:
>
> On Wed, Nov 28, 2018 at 7:50 PM Eric Dumazet <edumazet@google.com> wrote:
> >
> > On Wed, Nov 28, 2018 at 7:40 PM Cong Wang <xiyou.wangcong@gmail.com> wrote:
> > >
> > > On Wed, Nov 28, 2018 at 4:07 PM Eric Dumazet <edumazet@google.com> wrote:
> > > >
> > > > A NIC is supposed to deliver frames, even the ones that 'seem' bad.
> > >
> > > A quick test shows this is not the case for mlx5.
> > >
> > > With the trafgen script you gave to me, with tot_len==40, the dest host
> > > could receive all the packets. Changing tot_len to 80, tcpdump could no
> > > longer see any packet. (Both sender and receiver are mlx5.)
> > >
> > > So, packets with tot_len > skb->len are clearly dropped before tcpdump
> > > could see it, that is likely by mlx5 hardware.
> >
> > Or a router, or a switch.
> >
> > Are your two hosts connected back to back ?
>
> Both should be plugged into a same switch. I fail to see why a
> switch could parse IP header as the packet is nothing of interest,
> like a IGMP snooping.
Well, _something_ is dropping the frames.
It can be mlx5, or something else.
Does ethtool -S show any increasing counter ?
next prev parent reply other threads:[~2018-11-29 15:13 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-28 6:10 [Patch net v2] mlx5: fixup checksum for short ethernet frame padding Cong Wang
2018-11-28 15:00 ` Eric Dumazet
2018-11-28 22:16 ` Cong Wang
2018-11-28 23:50 ` Eric Dumazet
2018-11-28 23:57 ` Cong Wang
2018-11-29 0:05 ` Cong Wang
2018-11-29 0:14 ` Eric Dumazet
2018-11-30 0:03 ` Saeed Mahameed
2018-11-29 0:07 ` Eric Dumazet
2018-11-29 3:40 ` Cong Wang
2018-11-29 3:49 ` Eric Dumazet
2018-11-29 3:53 ` Cong Wang
2018-11-29 4:09 ` Eric Dumazet [this message]
2018-11-30 0:30 ` Saeed Mahameed
2018-12-03 23:17 ` David Miller
2018-12-03 23:45 ` Cong Wang
2018-12-04 19:21 ` Saeed Mahameed
2018-12-04 20:50 ` Cong Wang
2018-12-05 1:06 ` Saeed Mahameed
2018-12-05 2:15 ` Cong Wang
2018-12-13 8:40 ` Nikola Ciprich
2018-12-13 17:08 ` Saeed Mahameed
2018-12-14 9:33 ` Nikola Ciprich
2019-01-05 18:35 ` Nikola Ciprich
2019-01-06 11:10 ` Saeed Mahameed
2019-01-18 1:19 ` Christoph Paasch
2019-01-19 0:45 ` Saeed Mahameed
2019-01-22 11:35 ` David Laight
2018-12-05 2:52 ` Cong Wang
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