Extension headers are the mechanism of extensibility for the IPv6
protocol, however to date they have only seen limited deployment.
The reasons for that are because intermediate devices don't handle
them well, and there haven't really be any useful extension headers
defined. In particular, Destination and Hop-by-Hop options have
not been deployed to any extent.
The landscape may be changing as there are now a number of serious
efforts to define and deploy extension headers. In particular, a number
of uses for Hop-by-Hop Options are currently being proposed, Some of
these are from router vendors so there is hope that they might start
start to fix their brokenness. These proposals include IOAM, Path MTU,
Firewall and Service Tickets, SRv6, CRH, etc.
Assuming that IPv6 extension headers gain traction, that leaves a
noticeable gap in IPv4 support. IPv4 options have long been considered a
non-starter for deployment. An alternative being proposed is to enable
use of IPv6 options with IPv4 (draft-herbert-ipv4-eh-00).
This series of patch sets endeavours to make extension headers and
related options useful and easy to use. The following items will be
addressed:
- Reorganize extension header files
- Allow registration of TLV handlers
- Elaborate on the TLV tables to include more characteristics
- Add a netlink interface to set TLV parameters (such as
alignment requirements, authorization to send, etc.)
- Enhance validation of TLVs being sent. Validation is strict
(unless overridden by admin) following that sending clause
of the robustness principle
- Allow non-privileged users to set Hop-by-Hop and Destination
Options if authorized by the admin
- Add an API that allows individual Hop-by-Hop and Destination
Options to be set or removed for a connected socket. The
backend end enforces permissions on what TLVs may be set and
merges set TLVs per following the rules in the TLV parameter table
(for instance, TLV parameters include a preferred sending order
that merging adheres to)
- Support for some of the aforementioned options
- Enable IPv4 extension headers
------
In this series:
- Create exhdrs_options.c. Move options specific processing to this
file from exthdrs.c (for RA, Jumbo, Calipso, and HAO)
- Allow modules to register TLV handlers for Destination and HBH
options.
- Add parameters block to TLV type entries that describe characteristics
related to the TLV. For the most part, these encode rules about
sending each TLV (TLV alignment requirements for instance).
- Add a netlink interface to manage parameters in the TLV table.
- Add validation of HBH and Destination Options that are set on a
socket or in ancillary data in sendmsg. The validation applies the
rules that are encoded in the TLV parameters.
- TLV parameters includes permissions that may allow non-privileged
users to set specific TLVs on a socket HBH options or Destination
options. Strong validation can be enabled for this to constrain
what the non-privileged user is able to do.
v2:
- Don't rename extension header files with IPv6 specific code before
code for IPv4 extension headers is present
- Added patches for creating TLV parameters and validation
Tested:
Set Hop-by-Hop options on TCP/UDP socket and verified to be functional.
Tom Herbert (6):
exthdrs: Create exthdrs_options.c
exthdrs: Move generic EH functions to exthdrs_core.c
exthdrs: Registration of TLV handlers and parameters
exthdrs: Add TX parameters
ip6tlvs: Add netlink interface
ip6tlvs: Validation of TX Destination and Hop-by-Hop options
include/net/ipv6.h | 109 +++++
include/uapi/linux/in6.h | 49 ++
net/ipv6/Makefile | 2 +-
net/ipv6/datagram.c | 30 +-
net/ipv6/exthdrs.c | 388 +--------------
net/ipv6/exthdrs_core.c | 1162 ++++++++++++++++++++++++++++++++++++++++++++
net/ipv6/exthdrs_options.c | 271 +++++++++++
net/ipv6/ipv6_sockglue.c | 35 +-
8 files changed, 1643 insertions(+), 403 deletions(-)
create mode 100644 net/ipv6/exthdrs_options.c
--
2.7.4
