Re: Death by extension header

[Toerless Eckert <[e-mail]>]

Brian,

Slowpath/fastpath predate ASIC/FPGA, otherwise you're right.

On Wed, Jul 15, 2020 at 12:14:29PM +1200, Brian E Carpenter wrote:
> On 15-Jul-20 12:04, Jeff Tantsura wrote:
> > slow path usually means - punted to the central CPU (that runs control plane)
> 
> And isn't it true to say that the punting occurs when the packet header is such that it cannot be processed by whatever ASIC or FPGA happens to be present in the particular box? In other words, it is *not* because the header contains an option that is specified to be "slow path" by nature; it's dependent on the exact design of the router model.
> 
>    Brian
> 
> > 
> > Cheers,
> > Jeff
> > On Jul 14, 2020, 5:01 PM -0700, Gyan Mishra <[e-mail]>, wrote:
> >> Sorry I was thinking ???cisco fast switching??? 
> >>
> >> My fault I am good with those fast and slow and agree that is industry standard nomenclature.
> >>
> >> Fast path = line rate processing in hardware data plane path 
> >>
> >> Slow path = requires extra NPU control plane packet processing and is processed In software and can impact control plane 
> >>
> >>
> >>
> >> On Tue, Jul 14, 2020 at 3:36 AM Toerless Eckert <[e-mail] <mailto:[e-mail]>> wrote:
> >>
> >>     Hi Gyan,
> >>
> >>     On Tue, Jul 14, 2020 at 02:37:12AM -0400, Gyan Mishra wrote:
> >>     > >From a historical perspective the slow path and fast path has some vendor
> >>     > connotations into it ???cxxxx???.
> >>
> >>     I think its used pretty consistently throughout the industry.
> >>     If you have an example of a router that has something other vendors
> >>     would call slowpath but calls it differently, i would be interested to
> >>     know such alternative terms.
> >>
> >>     > I think any document within the IETF  should stay clear of anything that is
> >>     > a vendor terminology.
> >>
> >>     Definitely agreed if something is really specific to a subset of vendors
> >>     instead of the most widely used term. I think its the most widely used term..
> >>
> >>     > The concept of ???punt??? meanIng send to control plane also has vendor
> >>     > connotation and should not be used.
> >>
> >>     I think the same applies here as what i said above for slow/fast path.
> >>
> >>     Btw: these are just comments about my best understanding about terminology.
> >>     Not an endorsement to base any upcoming work on those terms. I already
> >>     sent emails as to the opposite.
> >>
> >>     > I personally like control plane and data plane processing of extension
> >>     > headers.
> >>
> >>     Do you have a good definition for control-plane and data-plane processing ?
> >>     E.g.: inband-signaling, is that decidedly control-plane for data-plane
> >>     to you ?
> >>
> >>     Cheers
> >>        Toerless
> >>
> >>     > Gyan
> >>     >
> >>     > On Mon, Jul 13, 2020 at 11:35 PM Pengshuping (Peng Shuping) <
> >>     > [e-mail] <mailto:[e-mail]>> wrote:
> >>     >
> >>     > >
> >>     > >
> >>     > > > -----Original Message-----
> >>     > > > From: ipv6 [mailto:[e-mail] <mailto:[e-mail]>] On Behalf Of Tom Herbert
> >>     > > > Sent: Tuesday, July 14, 2020 3:31 AM
> >>     > > > To: Toerless Eckert <[e-mail] <mailto:[e-mail]>>
> >>     > > > Cc: Ron Bonica <rbonica=[e-mail] <mailto:[e-mail]>>; [e-mail] <mailto:[e-mail]>
> >>     > > > Subject: Re: Death by extension header (was:RE: New Version Notification
> >>     > > > for draft-li-6man-hbh-fwd-hdr-00.txt)
> >>     > > >
> >>     > > > On Mon, Jul 13, 2020 at 12:18 PM Toerless Eckert <[e-mail] <mailto:[e-mail]>> wrote:
> >>     > > > >
> >>     > > > > And now find me any single IETF RFC that even uses the term slow-path
> >>     > > > > and fast-path to formalize requirements against them. We are just not
> >>     > > > > explicit enough about this. Hence my example of redooing router-alert
> >>     > > > > as the most simple example. Not that i think this would be most
> >>     > > > > important, but just to make the community consider that we need to be
> >>     > > > > more diligent about protocol specs in this respect.
> >>     > > > >
> >>     > > >
> >>     > > > Toerless,
> >>     > > >
> >>     > > > I wouldn't expect any IETF to use the term "slow path" and "fast path".
> >>     > > RFCs
> >>     > > > tend to describe protocol behavior and generally themselves don't care
> >>     > > > whether they are processed in a slow path or fast path as long as the
> >>     > > > external behavior is conformant. If you want to make these terms
> >>     > > explicit it
> >>     > > > seems like we would need to quantify in exact terms what a slow path is
> >>     > > and
> >>     > > > exactly what a fast path is-- that is, they need normative definitions
> >>     > > if we are
> >>     > > > to set normative requirements around them.
> >>     > >
> >>     > > But do we still need to differentiate "control plane" and "forwarding
> >>     > > plane"? The processing capability in bps and pps of the two planes are
> >>     > > different, so the corresponding terms are used as "slow path" and "fast
> >>     > > path", respectively.
> >>     > >
> >>     > > There are some HBH options such as RA* that carry the information that
> >>     > > need to be consumed by the "control plane", so they will be sent to the
> >>     > > "control plane" anyway. While other HBH options carry the information that
> >>     > > will not be consumed by the "control plane" but still sent to the "control
> >>     > > plane" / "slow path", which cause problems.
> >>     > >
> >>     > > *
> >>     > > https://www.iana.org/assignments/ipv6-routeralert-values/ipv6-routeralert-values.xhtml#ipv6-routeralert-values-1
> >>     > >
> >>     > > Shuping
> >>     > >
> >>     > > >
> >>     > > > Tom
> >>     > > >
> >>     > > > > Some maximum amount of fast-path extensions is already in specs as an
> >>     > > > > example, but it too is not comprehensive enough to feel more confident
> >>     > > > > about safe extensibility.
> >>     > > > >
> >>     > > > > And we need to break free of the rfc8200 constraints whenever we
> >>     > > > > deploy the network protocol in controlled networks. rfc8200 is such a
> >>     > > > > career limiter when comparing IPv6 with MPLS for this type of
> >>     > > > > use-cases. Not to speak of the unnecessary long addresses.
> >>     > > > >
> >>     > > > > Oh well...
> >>     > > > >
> >>     > > > > Cheers
> >>     > > > >     Toerless
> >>     > > > >
> >>     > > > > On Fri, Jul 10, 2020 at 06:43:59PM +0000, Ron Bonica wrote:
> >>     > > > > > Tom,
> >>     > > > > >
> >>     > > > > > Given that you parse the extension header chain on the fast path, HBH
> >>     > > > and destination options can be categorized as follows:
> >>     > > > > >
> >>     > > > > > 1) unrecognized (ACT 00, 01, 10, and 11)
> >>     > > > > > 2) recognized and processed on the fast path
> >>     > > > > > 3) recognized and processed on the slow path
> >>     > > > > >
> >>     > > > > > Types 1 and 2 cannot be used in a DoS attack, because they are never
> >>     > > > sent to the slow path. Type 3 is the dangerous one.
> >>     > > > > >
> >>     > > > > > I think that an implementation is safe if it only recognizes options
> >>     > > that it
> >>     > > > can process on the fast path. It may also be safe if it severely rate
> >>     > > limits
> >>     > > > packets as it sends them to the slow path.
> >>     > > > > >
> >>     > > > > >
> >>     > > > > > Ron
> >>     > > > > >
> >>     > > > > >
> >>     > > > > >
> >>     > > > > >
> >>     > > > > >
> >>     > > > > > Juniper Business Use Only
> >>     > > > > >
> >>     > > > > > -----Original Message-----
> >>     > > > > > From: Tom Herbert <[e-mail] <mailto:[e-mail]>>
> >>     > > > > > Sent: Friday, July 10, 2020 2:29 PM
> >>     > > > > > To: Ron Bonica <[e-mail] <mailto:[e-mail]>>
> >>     > > > > > Cc: Pengshuping (Peng Shuping) <[e-mail] <mailto:[e-mail]>>;
> >>     > > > > > [e-mail] <mailto:[e-mail]>
> >>     > > > > > Subject: Re: Death by extension header (was:RE: New Version
> >>     > > > > > Notification for draft-li-6man-hbh-fwd-hdr-00.txt)
> >>     > > > > >
> >>     > > > > > [External Email. Be cautious of content]
> >>     > > > > >
> >>     > > > > >
> >>     > > > > > On Fri, Jul 10, 2020 at 11:18 AM Ron Bonica <[e-mail] <mailto:[e-mail]>>
> >>     > > > wrote:
> >>     > > > > > >
> >>     > > > > > > Tom,
> >>     > > > > > >
> >>     > > > > > > I am forking a new thread since this is not directly related to
> >>     > > Shuping's
> >>     > > > draft.
> >>     > > > > > >
> >>     > > > > > > Any variable length extension header can be used in a DoS attack.
> >>     > > So, if
> >>     > > > a node encounters a packet that satisfies any of the following criteria,
> >>     > > it
> >>     > > > should discard the packet and send an ICMP message as described in
> >>     > > >
> >>     > > https://urldefense.com/v3/__https://tools.ietf.org/html/draft-herbert-6ma <https://urldefense.com/v3/__https://tools.ietf..org/html/draft-herbert-6ma>
> >>     > > > n-icmp-limits-03__;!!NEt6yMaO-gk!XnKPvkz9vBtVNlSCx0SqcojVpo2uBgeSDJ
> >>     > > > zZEJa2fLd1NTKb53H0w3Ue2Xxv7iGB$ .
> >>     > > > > > >
> >>     > > > > > > - The extension header chain is longer than the node can process
> >>     > > > > > > - An individual extension header is longer than the node can
> >>     > > > > > > process
> >>     > > > > > > - The total number of options contained by all instances of the
> >>     > > HBH and
> >>     > > > Destination Options header exceeds the number or options that the node
> >>     > > > can process.
> >>     > > > > > >
> >>     > > > > >
> >>     > > > > > Ron,
> >>     > > > > >
> >>     > > > > > Right, those are the ICMP errors for the allowance to drop or ignore
> >>     > > > extension headers in section 5.3 of RFC8504, there's also default limits
> >>     > > > suggested in that doc. Do you think this is sufficient in routers to get
> >>     > > past the
> >>     > > > DOS concern?
> >>     > > > > >
> >>     > > > > > Tom
> >>     > > > > >
> >>     > > > > > >
> >>     > > > > > > Ron
> >>     > > > > > >
> >>     > > > > > >
> >>     > > > > > >
> >>     > > > > > > Juniper Business Use Only
> >>     > > > > > >
> >>     > > > > > > -----Original Message-----
> >>     > > > > > > From: Tom Herbert <[e-mail] <mailto:[e-mail]>>
> >>     > > > > > > Sent: Friday, July 10, 2020 1:13 PM
> >>     > > > > > > To: Ron Bonica <[e-mail] <mailto:[e-mail]>>
> >>     > > > > > > Cc: Pengshuping (Peng Shuping) <[e-mail] <mailto:[e-mail]>>;
> >>     > > > > > > [e-mail] <mailto:[e-mail]>
> >>     > > > > > > Subject: Re: New Version Notification for
> >>     > > > > > > draft-li-6man-hbh-fwd-hdr-00.txt
> >>     > > > > > >
> >>     > > > > > > [External Email. Be cautious of content]
> >>     > > > > > >
> >>     > > > > > >
> >>     > > > > > > On Fri, Jul 10, 2020 at 7:59 AM Ron Bonica
> >>     > > > <rbonica=[e-mail] <mailto:[e-mail]>> wrote:
> >>     > > > > > > >
> >>     > > > > > > > Peng,
> >>     > > > > > > >
> >>     > > > > > > > While your solution may require refinement, I think that you have
> >>     > > > latched on to a problem that needs to be solved. HBH Options, as they
> >>     > > were
> >>     > > > originally conceived in RFC 1883, are very useful.
> >>     > > > > > > >
> >>     > > > > > > > When IPv6 was first implemented on high-speed routers (circa
> >>     > > 2000),
> >>     > > > HBH options were not yet well-understood and ASICs were not so capable as
> >>     > > > they are today. So, early IPv6 implementation dispatched all packet that
> >>     > > > contain HBH options to their slow path. In these implementations, a large
> >>     > > > flow of IPv6 packets could congest the slow path, causing other critical
> >>     > > > functions that are executed on the slow path to fail. These critical
> >>     > > functions
> >>     > > > include routing and network management.
> >>     > > > > > > >
> >>     > > > > > > > To mitigate this DoS vulnerability, many operators deployed
> >>     > > Access
> >>     > > > Control Lists (ACLs) that discard all packets containing HBH Options.
> >>     > > This
> >>     > > > introduced a circular problem:
> >>     > > > > > > >
> >>     > > > > > > > - An implementation problem caused HBH to become a DoS vector
> >>     > > > > > > > - Because HBH was a DoS vector, network operators deployed ACLs
> >>     > > > > > > > that discard packets containing HBH
> >>     > > > > > > > - Because network operators deployed ACLs that discard packets
> >>     > > > > > > > containing HBH, network designers stopped defining new HBH
> >>     > > > > > > > Options
> >>     > > > > > > > - Because network designers stopped defining new HBH Options,
> >>     > > > > > > > the community was not motivated to fix the implementation
> >>     > > > > > > > problem that cause HBH to become a DoS vector
> >>     > > > > > > >
> >>     > > > > > > > If we can fix the implementation problem that caused HBH to
> >>     > > > become a DoS vector, we can break this cycle and start using HBH Options.
> >>     > > > > > > >
> >>     > > > > > > Ron,
> >>     > > > > > >
> >>     > > > > > > I think there were "protocol problems" in the original design of
> >>     > > HBH.
> >>     > > > > > > The requirement that _all_ routers in the path process Hop-by-Hop
> >>     > > > options was in retrospect too austere, and the possibility that an
> >>     > > attacker
> >>     > > > could stuff a packet with hundreds of bogus options, only limited by MTU,
> >>     > > > was, again in retrospect, a pretty obvious DOS vector.
> >>     > > > > > > I believe these problems have been addressed in RFC8200 and
> >>     > > > RFC8504.
> >>     > > > > > > We certainly welcome the feedback from router vendors whether these
> >>     > > > mitigations are sufficient to make HBH options deployable.
> >>     > > > > > >
> >>     > > > > > > Tom
> >>     > > > > > >
> >>     > > > > > > > Let's continue to work on a solution..
> >>     > > > > > > >
> >>     > > > > > > >
> >>     > > > Ron
> >>     > > > > > > >
> >>     > > > > > > >
> >>     > > > > > > >
> >>     > > > > > > > Juniper Business Use Only
> >>     > > > > > > >
> >>     > > > > > > > -----Original Message-----
> >>     > > > > > > > From: ipv6 <[e-mail] <mailto:[e-mail]>> On Behalf Of Pengshuping
> >>     > > > > > > > (Peng
> >>     > > > > > > > Shuping)
> >>     > > > > > > > Sent: Thursday, July 2, 2020 12:07 PM
> >>     > > > > > > > To: [e-mail] <mailto:[e-mail]>
> >>     > > > > > > > Subject: FW: New Version Notification for
> >>     > > > > > > > draft-li-6man-hbh-fwd-hdr-00.txt
> >>     > > > > > > >
> >>     > > > > > > > [External Email. Be cautious of content]
> >>     > > > > > > >
> >>     > > > > > > >
> >>     > > > > > > > Hi Folks,
> >>     > > > > > > >
> >>     > > > > > > > We have just uploaded a new draft aiming to analyze and tackle
> >>     > > the
> >>     > > > issues faced by the Hop-by-Hop Options Header, which has been sparsely
> >>     > > > used without any form of large scale deployment.
> >>     > > > > > > >
> >>     > > > > > > > However, as IPv6 is being rapidly and widely deployed worldwide,
> >>     > > > more and more new services that requires hop-by-hop forwarding process
> >>     > > > behavior are emerging, and also the already defined over ten HBH Options
> >>     > > > are going to be used widely in practice.
> >>     > > > > > > >
> >>     > > > > > > > We look forward to hearing your feedback and comments, and try to
> >>     > > > release the benefits that could be provided by HBH Options header
> >>     > > > altogether.
> >>     > > > > > > >
> >>     > > > > > > > Best regards,
> >>     > > > > > > > Shuping
> >>     > > > > > > >
> >>     > > > > > > > -----Original Message-----
> >>     > > > > > > > From: [e-mail] <mailto:[e-mail]> [mailto:[e-mail] <mailto:[e-mail]>]
> >>     > > > > > > > Sent: Thursday, July 2, 2020 11:31 PM
> >>     > > > > > > > To: Lizhenbin <[e-mail] <mailto:[e-mail]>>; Pengshuping (Peng Shuping)
> >>     > > > > > > > <[e-mail] <mailto:pengshuping@huawei..com>>
> >>     > > > > > > > Subject: New Version Notification for
> >>     > > > > > > > draft-li-6man-hbh-fwd-hdr-00.txt
> >>     > > > > > > >
> >>     > > > > > > >
> >>     > > > > > > > A new version of I-D, draft-li-6man-hbh-fwd-hdr-00.txt has been
> >>     > > > successfully submitted by Shuping Peng and posted to the IETF repository.
> >>     > > > > > > >
> >>     > > > > > > > Name:           draft-li-6man-hbh-fwd-hdr
> >>     > > > > > > > Revision:       00
> >>     > > > > > > > Title:          Hop-by-Hop Forwarding Options Header
> >>     > > > > > > > Document date:  2020-07-03
> >>     > > > > > > > Group:          Individual Submission
> >>     > > > > > > > Pages:          10
> >>     > > > > > > > URL:
> >>     > > >
> >>     > > https://urldefense.com/v3/__https://www.ietf.org/internet-drafts/draft-li-6
> >>     > > > man-hbh-fwd-hdr-00.txt__;!!NEt6yMaO-gk!QoInpMGHwaC7LsKAVISa9A00d
> >>     > > > bzuCmO7S4CG2fZYHGYeOXYwVmtNTFnzgB-bqLrg$
> >>     > > > > > > > Status:
> >>     > > >
> >>     > > https://urldefense.com/v3/__https://datatracker.ietf.org/doc/draft-li-6man-
> >>     > > > hbh-fwd-hdr/__;!!NEt6yMaO-gk!QoInpMGHwaC7LsKAVISa9A00dbzuCmO7S
> >>     > > > 4CG2fZYHGYeOXYwVmtNTFnzgM5iPE22$
> >>     > > > > > > > Htmlized:
> >>     > > >
> >>     > > https://urldefense.com/v3/__https://tools.ietf.org/html/draft-li-6man-hbh-f <https://urldefense.com/v3/__https://tools.ietf..org/html/draft-li-6man-hbh-f>
> >>     > > > wd-hdr-00__;!!NEt6yMaO-gk!QoInpMGHwaC7LsKAVISa9A00dbzuCmO7S4C
> >>     > > > G2fZYHGYeOXYwVmtNTFnzgPvsH43l$
> >>     > > > > > > > Htmlized:
> >>     > > >
> >>     > > https://urldefense.com/v3/__https://datatracker.ietf.org/doc/html/draft-li-
> >>     > > > 6man-hbh-fwd-hdr__;!!NEt6yMaO-gk!QoInpMGHwaC7LsKAVISa9A00dbzuC
> >>     > > > mO7S4CG2fZYHGYeOXYwVmtNTFnzgBQxbwZb$
> >>     > > > > > > >
> >>     > > > > > > >
> >>     > > > > > > > Abstract:
> >>     > > > > > > >    RFC8200 specifies the HBH header that is assumed to be
> >>     > > > processed by
> >>     > > > > > > >    each hop in the delivery path of the packet.  However, RFC8200
> >>     > > > also
> >>     > > > > > > >    expects that nodes processing the HBH header have been
> >>     > > > explicitly
> >>     > > > > > > >    configured to do so.  Therefore, it cannot be assumed that a
> >>     > > > HBH
> >>     > > > > > > >    header present in the packet is processed.  It all depends on
> >>     > > the
> >>     > > > > > > >    configuration of each node across the path.  Moreover, in most
> >>     > > > of
> >>     > > > > > > >    networks today, the processing of the HBH header is done in
> >>     > > the
> >>     > > > > > > >    control plane (slow processing path) which incurs several
> >>     > > > limitations
> >>     > > > > > > >    among which resources consumption and security risk.
> >>     > > > > > > >
> >>     > > > > > > >    For these reasons, over time, the Hop-by-Hop Options header
> >>     > > > has been
> >>     > > > > > > >    sparsely used without any form of large scale deployment.
> >>     > > Also,
> >>     > > > most
> >>     > > > > > > >    of already defined HBH options are forwarding options which
> >>     > > > contain
> >>     > > > > > > >    forwarding plane information that needs not to be sent to the
> >>     > > > control
> >>     > > > > > > >    plane.
> >>     > > > > > > >
> >>     > > > > > > >    This document proposes a new Hop-by-Hop Forwarding Options
> >>     > > > Header in
> >>     > > > > > > >    order to carry Hop-by-Hop options that are solely intended to
> >>     > > > and
> >>     > > > > > > >    processed by the forwarding plane.  This new HBH header is
> >>     > > > confined
> >>     > > > > > > >    in and dedicated to the forwarding plane while the current HBH
> >>     > > > header
> >>     > > > > > > >    can still be used for control plane options.
> >>     > > > > > > >
> >>     > > > > > > >
> >>     > > > > > > >
> >>     > > > > > > >
> >>     > > > > > > >
> >>     > > > > > > > Please note that it may take a couple of minutes from the time of
> >>     > > > submission until the htmlized version and diff are available at
> >>     > > tools.ietf.org <http://tools.ietf.org>.
> >>     > > > > > > >
> >>     > > > > > > > The IETF Secretariat
> >>     > > > > > > >
> >>     > > > > > > >
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> >>     > > > > > > > v6
> >>     > > > > > > >
> >>     > > > __;!!NEt6yMaO-gk!QoInpMGHwaC7LsKAVISa9A00dbzuCmO7S4CG2fZYHGYe
> >>     > > > OXY
> >>     > > > > > > > wVmt
> >>     > > > > > > > NT
> >>     > > > > > > > FnzgEBbFhyl$
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> >>     > > > __;!!NEt6yMaO-gk!Qu9y9Ou2SvlYIZjMQa3hBXcu08HG3W4BBIcFoOHCfp41H
> >>     > > > tk
> >>     > > > > > > > dIYu
> >>     > > > > > > > Ds
> >>     > > > > > > > XM8uyxPWt9N$
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> >>     > > > > > Requests: https://www.ietf.org/mailman/listinfo/ipv6
> >>     > > > > > --------------------------------------------------------------------
> >>     > > > >
> >>     > > > > --
> >>     > > > > ---
> >>     > > > > [e-mail] <mailto:[e-mail]>
> >>     > > >
> >>     > > > --------------------------------------------------------------------
> >>     > > > IETF IPv6 working group mailing list
> >>     > > > ipv6@ietf..org <mailto:[e-mail]>
> >>     > > > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> >>     > > > --------------------------------------------------------------------
> >>     > >
> >>     > > --------------------------------------------------------------------
> >>     > > IETF IPv6 working group mailing list
> >>     > > [e-mail] <mailto:[e-mail]>
> >>     > > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> >>     > > --------------------------------------------------------------------
> >>     > >
> >>     > --
> >>     >
> >>     > <http://www.verizon.com/>
> >>     >
> >>     > *Gyan Mishra*
> >>     >
> >>     > *Network Solutions A**rchitect *
> >>     >
> >>     >
> >>     >
> >>     > *M 301 502-134713101 Columbia Pike *Silver Spring, MD
> >>
> >>     --
> >>     ---
> >>     [e-mail] <mailto:[e-mail]>
> >>
> >> --
> >>
> >> <http://www.verizon.com/>
> >>
> >> *Gyan Mishra*
> >>
> >> /Network Solutions A//rchitect /
> >>
> >> /M 301 502-1347
> >> 13101 Columbia Pike 
> >> /Silver Spring, MD
> >>
> >>
> >> --------------------------------------------------------------------
> >> IETF IPv6 working group mailing list
> >> [e-mail]
> >> Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> >> --------------------------------------------------------------------
> > 
> > --------------------------------------------------------------------
> > IETF IPv6 working group mailing list
> > [e-mail]
> > Administrative Requests: https://www.ietf.org/mailman/listinfo/ipv6
> > --------------------------------------------------------------------
> > 

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