From: Joseph Gasparakis <joseph.gasparakis@intel•com>
To: Jerry Chu <hkchu@google•com>
Cc: Joseph Gasparakis <joseph.gasparakis@intel•com>,
Or Gerlitz <ogerlitz@mellanox•com>,
David Miller <davem@davemloft•net>,
Pravin B Shelar <pshelar@nicira•com>,
Eric Dumazet <edumazet@google•com>,
"netdev@vger•kernel.org" <netdev@vger•kernel.org>,
Tom Herbert <therbert@google•com>
Subject: Re: [PATCH] net-gre-gro: Fix a bug that breaks the forwarding path
Date: Tue, 4 Mar 2014 17:01:06 -0800 (PST) [thread overview]
Message-ID: <alpine.LFD.2.03.1403041641430.19558@intel.com> (raw)
In-Reply-To: <CAPshTChzL5f5SD2ofH4frhX8QJBgbkw9+qStCMdg2u=WQ8Trqg@mail.gmail.com>
On Tue, 4 Mar 2014, Jerry Chu wrote:
> On Tue, Mar 4, 2014 at 2:53 PM, Joseph Gasparakis
> <joseph.gasparakis@intel•com> wrote:
> >
> >
> > On Tue, 4 Mar 2014, Jerry Chu wrote:
> >
> >> Hi Or,
> >>
> >> Thanks for writing this up.
> >>
> >> On Tue, Mar 4, 2014 at 8:13 AM, Or Gerlitz <ogerlitz@mellanox•com> wrote:
> >> > On 28/02/2014 23:56, David Miller wrote:
> >> >>
> >> >> The topic of the skb->encapsulation semantics has come up several times in
> >> >> the past few weeks. We cannot move forward on any changes in this area until
> >> >> the semantics are well defined, and documented. Can someone work on a patch
> >> >> which documents skb->encapsulation properly, and then we can come back to
> >> >> fixing this bug? Thanks.
> >> >
> >> >
> >> > Lets try... the skb->encapsulation flag was introduced and used in 3.8 by
> >> > the
> >> > sequence of these three commits
> >> >
> >> > 0afb166 vxlan: Add capability of Rx checksum offload for inner packet
> >> > d6727fe vxlan: capture inner headers during encapsulation
> >> > 6a674e9 net: Add support for hardware-offloaded encapsulation
> >> >
> >> > When discussed earlier on the list in the context of the skb->ip_summed
> >> > field,
> >> > Tom Herbert came with the following interpretation for the semantics which
> >> > Joseph confirmed
> >> >
> >> > "when skb->encapsulation is set the ip_summed is valid for both the inner
> >> > and outer header
> >> > (e.g. CHECKSUM_COMPLETE is always assumed okay for both layers). If
> >> > skb->encapsulation is not set then ip_summed is only valid for outer header"
> >>
> >> For GRE encapped pkts is the following interpretation correct?
> >>
> >> 1) ip_summed == CHECKSUM_COMPLETE
> >> => csum covers IP payload csum of the outer IP datagram
> >>
> >> 2) ip_summed == CHECKSUM_UNNECESSARY
> >> 2.1. skb->encapsulation is on => both GRE csum (if one is present) and TCP/UDP
> >> csum have been validated (assuming inner is a TCP or UDP pkt)
> >
> > i40e also supports SCTP csumming for the inner packet, too.
> >
> >>
> >> 2.2. skb->encapsulation is off => only GRE csum (if one is present) is
> >> validated.
> >>
> >
> > Apart for the SCTP request for inclusion, it looks reasonable to me.
> >
> >> >
> >> > As for the TX side of things, the change-log of commit 6a674e9 states
> >> >
> >> > "For Tx encapsulation offload, the driver will need to set the right bits in
> >> > netdev->hw_enc_features. The protocol driver will have to set the
> >> > skb->encapsulation bit and populate the inner headers, so the NIC driver
> >> > will use those inner headers to calculate the csum in hardware."
> >>
> >> So we only support/care about csum offload for the inner pkts, which
> >> makes sense.
> >
> > Well, we care about outer too. It is just that the inner headers are for
> > the inner csum, the outer headers are for the outer csum. The outer
> > headers will be always there anyway, so the patch introduced the inner
> > ones. But I guess this is what you meant, right?
>
> Actually i was wondering that since there is only one set csum_start/csum_offset
> fields per skb, which would you support CHECKSUM_PARTIAL for both inner
> and outer? You can only support one, right? (I haven't checked the UDP encap
> code to see how this works though.)
>
> Jerry
I am not sure I understand the question, Jerry... Are you asking in Tx
path if the ip_summed==CHECKSUM_PARTIAL, which headers will the
csum_start/csum_offset refer to?
> >
> >>
> >> >
> >> > So in higher level, it seems that the role of the skb->encapsulation field
> >> > is to mark the skb to carry encapsulated packet for the code path between
> >> > the time the packet is encapsulated by the protocol driver (e.g vxlan/ipip)
> >> > to the time driver xmit is called. Or from the time driver rx code runs till
> >> > the the time the packet is decapsulated.
> >> >
> >> > Further, my personal interpretation was that on the rx path, skb should
> >> > carry the encapsulation flag **only** if the HW was able to offload the
> >> > inner checksum.
> >>
> >> SGTM.
> >>
> >> Jerry
> >>
> >> >
> >> > Joseph, what's your thinking here?
> >> >
> >> > Or.
> >> >
> >> >
> >>
>
next prev parent reply other threads:[~2014-03-05 0:41 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-02-27 21:26 [PATCH] net-gre-gro: Fix a bug that breaks the forwarding path H.K. Jerry Chu
2014-02-27 22:25 ` Or Gerlitz
2014-02-27 23:39 ` Jerry Chu
2014-02-28 21:56 ` David Miller
2014-03-03 9:30 ` Or Gerlitz
2014-03-04 16:13 ` Or Gerlitz
2014-03-04 22:13 ` Jerry Chu
2014-03-04 22:53 ` Joseph Gasparakis
2014-03-04 23:11 ` Jerry Chu
2014-03-05 1:01 ` Joseph Gasparakis [this message]
2014-03-05 0:54 ` Jerry Chu
2014-03-05 1:27 ` Joseph Gasparakis
2014-03-05 1:14 ` Alexei Starovoitov
2014-03-04 22:36 ` Joseph Gasparakis
2014-03-05 0:50 ` Tom Herbert
2014-03-05 1:46 ` Joseph Gasparakis
2014-03-05 20:47 ` Or Gerlitz
2014-03-06 16:42 ` Joseph Gasparakis
2014-03-06 16:30 ` Hannes Frederic Sowa
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=alpine.LFD.2.03.1403041641430.19558@intel.com \
--to=joseph.gasparakis@intel$(echo .)com \
--cc=davem@davemloft$(echo .)net \
--cc=edumazet@google$(echo .)com \
--cc=hkchu@google$(echo .)com \
--cc=netdev@vger$(echo .)kernel.org \
--cc=ogerlitz@mellanox$(echo .)com \
--cc=pshelar@nicira$(echo .)com \
--cc=therbert@google$(echo .)com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox