Internet DRAFT - draft-elkins-v6ops-eh-deepdive-fw
draft-elkins-v6ops-eh-deepdive-fw
IPv6 Operations N. Elkins
Internet-Draft M. Ackermann
Intended status: Best Current Practice INT Council
Expires: 24 April 2023 D. Dhody
India Internet Engineering Society
21 October 2022
Deep Dive into IPv6 Extension Header Testing
draft-elkins-v6ops-eh-deepdive-fw-01
Abstract
IPv6 Extension Header testing is a complex area. Studies have shown
varying results. This document proposes a methodology for isolating
the location and reasons for IPv6 Extension Headers blockage. This
document outlines the basic framework and set of documents which will
follow.
Discussion Venues
This note is to be removed before publishing as an RFC.
Discussion of this document takes place on the IPv6 Operations
Working Group mailing list (v6ops@ietf.org), which is archived at
https://mailarchive.ietf.org/arch/browse/v6ops/.
Source for this draft and an issue tracker can be found at
https://github.com/dhruvdhody/draft-elkins-v6ops-eh-deepdive-fw.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 24 April 2023.
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Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Problem Description . . . . . . . . . . . . . . . . . . . 2
1.2. Fundamental Premises . . . . . . . . . . . . . . . . . . 3
1.3. Diagnostic Methodology Overview . . . . . . . . . . . . . 5
2. EH Enabled Server / Client / Router . . . . . . . . . . . . . 7
2.1. Modifications to send EHs with application data . . . . . 7
2.2. Crafting packets with EH headers . . . . . . . . . . . . 7
2.3. How to Add EH . . . . . . . . . . . . . . . . . . . . . . 8
2.4. Which EH to Use . . . . . . . . . . . . . . . . . . . . . 9
3. Rate of sending and sampling . . . . . . . . . . . . . . . . 9
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. Privacy Considerations . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. Normative References . . . . . . . . . . . . . . . . . . 9
7.2. Informative References . . . . . . . . . . . . . . . . . 10
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 10
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
1.1. Problem Description
IPv6 [RFC8200] Extension Headers (EHs) may be blocked at various
points yet show the same symptom. That is, if an EH is blocked at a
router, it will appear to the client or measurement technique that
the packet is dropped. If an EH is blocked at a load balancer or
CDN, the client will see the same symptom -- the packet is dropped.
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This is a problem because when the same symptom can be the due to
multiple factors, incorrect conclusions may be drawn from the
results. That is, if, for example, loss of the sense of taste of
sweetness can be due either to a brain tumor or a minor neurological
problem, then if someone has a tendency towards hypochondria, they
may incorrectly bemoan their impending death from a brain tumor when
it may really be only a minor issue.
This is the same for EH testing. If a packet is seen to be dropped
in measurement, it may only be that there is a bug in the load
balancer code (for example) and not that EH transmission does not
work writ large.
This document proposes a framework to isolate the problem of where
the packet is being dropped. This is, however, more easily said than
done. There are many components and devices in a network. Each may
require a different isolation technique.
We propose a methdology which starts with the simplest topology and
grows towards more and more complex, real-world networks. For
example, in today's networks, if one attempts to access a well-known
site such as Facebook.com, one is likely to access a cache server
managed by a Content Delivery Network (CDN) rather than the origin
server managed by Facebook. It is important to isolate the testing
so that we can determine the exact component which may be blocking
the EH and why.
We additionally discuss the potential issues with the type of data
sent as well as how the way the data is sent for testing may impact
test results.
1.2. Fundamental Premises
Yet, there are some overriding principles.
The blockage may be:
* in the source network
* in the destination network
* in a transit network
Then:
* it may be blocked intentionally
* it may be blocked unintentionally
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Intentional blocks are easier to assess. The block is an
administrator or network policy. Of course, the policy may come
about as a result of a misunderstanding of the function of EHs or
lack of effective guidance but nonetheless, this is an understandable
decision.
The more troubling causes of EH blocks include:
* bugs
* default configurations or policies by the vendor
* lack of support of EH or IPv6 itself
As far as the blocking component itself (whether intentional or
unintentional):
* may be a router
* may be a firewall
* may be a load balancer
* may be a proxy
* may be a Host OS
* may be a DNS or other configuration setting
Note: A DNS or other configuration setting may block IPv6 or prefer
IPv4. If not tested correctly, lack of support for IPv6 itself may
incorrectly appear as lack of support for EHs.
Finally, the blockage or source may differ based on the type of EH.
Some EHs are limited to an administrative domain, some EHs are
processed at every hop, still others are from the source and
destination. Problem isolation techniques will differ for the
various classes of EH.
Our final document in this series will be a BCP to indicate which EH
should be allowed, blocked, encrypted, or authenticated and at which
component or platform.
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Note: [RFC9288] "Recommendations on the Filtering of IPv6 Packets
Containing IPv6 Extension Headers at Transit Routers" focuses on the
IPv6 EH handling at transit routers only. Our approach is to produce
a final BCP with various recommendations across network segments,
once the nature of the problems and techniques for isolation are well
known.
1.3. Diagnostic Methodology Overview
The diagnostic methodology to follow depends on what is being tested.
For example, the problem isolation for a CDN would be different than
the problem isolation for an internal network.
This framework proposes the following set of documents:
* EH problem isolation for owned client / server
* EH problem isolation in a network using a CDN
* EH problem isolation in a network using a cloud provider
* EH problem isolation for routers
* EH problem isolation for load balancers
* EH problem isolation for proxies
* EH problem isolation for host OSs
* EH problem isolation for transit networks
* EH problem isolation for ISPs (multiple components / networks)
* BCP for EH Permissions, Encryption and Authentication
Note that the server can be owned and operated by the administrator
themselves (on-prem) Figure 1, or they could hosted behind a CDN
Figure 2, or hosted by the cloud provider Figure 3.
+--------------------------+
| |
+--------+ | | +---------+
| client |---------| Internet |-----| server |
+--------+ | | +---------+
| |
+--------------------------+
Figure 1: Owned client / server
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+-----------------+
+--------------------------+ +-----------------+ |
| | | CDN Network | |
+--------+ | | | +---------+ | |
| client |---------| Internet |-----| | Edge | | |
+--------+ | | | | Server | | |
| | | +---------+ | |
+--------------------------+ | | |
| (LB, Firewall | |
| Cache etc) | |
| | |
| | |
| | |
| |-+
+-----------------+
|
| (*)
|
+---------+
| Origin |
| server |
+---------+
(*) - can be over the internet
Figure 2: Server behind CDN
+--------------------------+ +-----------------+
| | | |
+--------+ | | | |
| client |---------| Internet |-----| Cloud Network |
+--------+ | | | (LB, Firewall, |
| | | Gateways etc) |
+--------------------------+ | |
| |
| |
| +---------+ |
| | Virtual | |
| | server | |
| +---------+ |
+-----------------+
Figure 3: Cloud-hosted server
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2. EH Enabled Server / Client / Router
The first step for all testing is to have a test server, client and /
or router enabled to send EHs. There are two basic options to do
this, each with its own set of advantages and drawbacks.
The options fall broadly into two categories:
* Modifications to the OS / interface / socket / driver to send EHs
with application data
* Using a package which crafts EHs (multiple exist)
If crafting packets, then the question arises of which packets to
craft. This will be discussed in Section 2.2.
For either methodology, the rate of sending may influence results.
This will be discussed in Section 3.
2.1. Modifications to send EHs with application data
Possibly the best way to isolate problems with EHs may be to have a
server, client or router which has modifications to the OS,
interface, driver or other to send real EHs with real application
data. This carries the initial cost of creating such modifications
since, unfortunately, the current set of host OSs do not natively
support this.
The reason we find this to be the best method is because the problem
of what packet to craft is a field which is rife with land mines.
See Section 2.2 for a further discussion of the exact nature of the
aforesaid land mines.
2.2. Crafting packets with EH headers
A number of packages exist which can craft a packet with an EH
header. The more interesting and fraught problem may be which exact
packet to craft and then which EH to craft.
Let's discuss first the options for the type of packet to craft.
These include:
* A TCP packet
* A UDP packet
* An ICMPv6 packet
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* A QUIC packet
If crafting a TCP packet, then it is likely that some middlebox will
drop a TCP packet which does not have the appropriate ACK and
SEQUENCE numbers. One may get around this problem by sending a
packet with the SYN flag on and directed to some well-known port such
as 443 or 80. But, if many firewalls and other devices such as IDS /
IPS, and even some OSs have SYN Flood protection. So, if more than a
certain number of these packets, say 10, in some short interval are
sent, then they are likely to be dropped for reasons other than
blockage of EH headers.
One may choose to use UDP, QUIC, or ICMPv6 to attempt to bypass the
complexities of TCP. Some enterprise networks are likely to drop UDP
and / or QUIC. Testing should be done without EH to make sure that
such packets do indeed pass.
Certainly, if you have access to all the middleboxes in your domain,
you may be able to bypass or stop SYN Flood, UDP, ICMPv6 or other
transport layer blocks at all the middleboxes. But, it may be a more
difficult effort than might be imagined.
You may wish to test in a lab environment first to validate your
approach.
2.3. How to Add EH
There are two ways to add an EH to a packet:
* use a "real" EH
* craft an EH
The best method may be to use an EH which is actually processed at
the client, server, and any associated router. This leaves us with a
sparse set to choose from. The problem with crafting an EH is that
if the data is not "real", one may not be able to fault a network
component for blocking it.
Having said that, let's discuss crafting an EH. An EH may be crafted
by simply using multiple PADN options. One should be careful not to
use too many PADNs because then this type of header may be dropped by
a middlebox or OS as being a flawed packet. This is likely to
distort the results.
An EH with all 0's or other data patterns that could be perceived as
not "real" may also be dropped by middleboxes which are trying to be
helpful.
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It is also possible that the length of the EH may have some effect on
what EHs get dropped and where.
You may wish to try this in a lab environment first. If the test
suceeds, then you may test on your network.
2.4. Which EH to Use
Next, there is a consideration that the type of EH, for example,
Destination Options, Hop-by-hop, etc. could get processed differently
and may be dropped at different frequencies, by different devices.
You may wish to test one at a time and note the results.
You may wish to try this in a lab environment first. If the test
suceeds, then you may test on your network.
3. Rate of sending and sampling
Whether you have chosen to send real application data or to craft
packets, the rate of sending and sampling may create a false
indication of blockage. That is, if you send a great deal of data at
frequent intervals, some middlebox in the network is likely to see
this traffic as a Denial of Service (DoS) attack and block it. This
is more likely if a great many crafted packets are sent but even with
real application data such as FTP or HTTP, overly aggressive sending
is likely to be counterproductive.
You may wish to send only a few packets or one or two CURL or FTPs at
any one test.
4. Security Considerations
This document has no security considerations.
5. Privacy Considerations
This document has no privacy considerations.
6. IANA Considerations
This document has no IANA actions.
7. References
7.1. Normative References
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[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/rfc/rfc8200>.
7.2. Informative References
[RFC9288] Gont, F. and W. Liu, "Recommendations on the Filtering of
IPv6 Packets Containing IPv6 Extension Headers at Transit
Routers", RFC 9288, DOI 10.17487/RFC9288, August 2022,
<https://www.rfc-editor.org/rfc/rfc9288>.
Acknowledgments
TODO acknowledge.
Contributors
TODO contributors.
Authors' Addresses
Nalini Elkins
Industry Network Technology Council
United States of America
Phone: +1 831 234 4232
Email: nalini.elkins@insidethestack.com
Michael Ackermann
Industry Network Technology Council
United States of America
Phone: +1 248 703 3600
Email: mackermann@bcbsm.com
URI: https://www.bcbsm.com
Dhruv Dhody
India Internet Engineering Society
India
Email: dhruv.ietf@gmail.com
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