Re: [PATCH net-next v4 0/5] Support for the IOAM Pre-allocated Trace with IPv6

On 5/27/21 9:16 AM, Justin Iurman wrote:

v4:
 - Address warnings from checkpatch (ignore errors related to unnamed bitfields
   in the first patch)
 - Use of hweight32 (thanks Jakub)
 - Remove inline keyword from static functions in C files and let the compiler
   decide what to do (thanks Jakub)

v3:
 - Fix warning "unused label 'out_unregister_genl'" by adding conditional macro
 - Fix lwtunnel output redirect bug: dst cache useless in this case, use
   orig_output instead

v2:
 - Fix warning with static for __ioam6_fill_trace_data
 - Fix sparse warning with __force when casting __be64 to __be32
 - Fix unchecked dereference when removing IOAM namespaces or schemas
 - exthdrs.c: Don't drop by default (now: ignore) to match the act bits "00"
 - Add control plane support for the inline insertion (lwtunnel)
 - Provide uapi structures
 - Use __net_timestamp if skb->tstamp is empty
 - Add note about the temporary IANA allocation
 - Remove support for "removable" TLVs
 - Remove support for virtual/anonymous tunnel decapsulation

In-situ Operations, Administration, and Maintenance (IOAM) records
operational and telemetry information in a packet while it traverses
a path between two points in an IOAM domain. It is defined in
draft-ietf-ippm-ioam-data [1]. IOAM data fields can be encapsulated
into a variety of protocols. The IPv6 encapsulation is defined in
draft-ietf-ippm-ioam-ipv6-options [2], via extension headers. IOAM
can be used to complement OAM mechanisms based on e.g. ICMP or other
types of probe packets.

This patchset implements support for the Pre-allocated Trace, carried
by a Hop-by-Hop. Therefore, a new IPv6 Hop-by-Hop TLV option is
introduced, see IANA [3]. The three other IOAM options are not included
in this patchset (Incremental Trace, Proof-of-Transit and Edge-to-Edge).
The main idea behind the IOAM Pre-allocated Trace is that a node
pre-allocates some room in packets for IOAM data. Then, each IOAM node
on the path will insert its data. There exist several interesting use-
cases, e.g. Fast failure detection/isolation or Smart service selection.
Another killer use-case is what we have called Cross-Layer Telemetry,
see the demo video on its repository [4], that aims to make the entire
stack (L2/L3 -> L7) visible for distributed tracing tools (e.g. Jaeger),
instead of the current L5 -> L7 limited view. So, basically, this is a
nice feature for the Linux Kernel.

This patchset also provides support for the control plane part, but only for the
inline insertion (host-to-host use case), through lightweight tunnels. Indeed,
for in-transit traffic, the solution is to have an IPv6-in-IPv6 encapsulation,
which brings some difficulties and still requires a little bit of work and
discussion (ie anonymous tunnel decapsulation and multi egress resolution).

- Patch 1: IPv6 IOAM headers definition
- Patch 2: Data plane support for Pre-allocated Trace
- Patch 3: IOAM Generic Netlink API
- Patch 4: Support for IOAM injection with lwtunnels
- Patch 5: Documentation for new IOAM sysctls

  [1] https://tools.ietf.org/html/draft-ietf-ippm-ioam-data
  [2] https://tools.ietf.org/html/draft-ietf-ippm-ioam-ipv6-options
  [3] https://www.iana.org/assignments/ipv6-parameters/ipv6-parameters.xhtml#ipv6-parameters-2
  [4] https://github.com/iurmanj/cross-layer-telemetry

These are draft documents from February 2021. Good to have RFC patches
for others to try the proposed feature, but is really early to be
committing code to Linux. I think we should wait and see how that
proposal develops.