ipv6: ioam: Data plane support for Pre-allocated Trace

Implement support for processing the IOAM Pre-allocated Trace with IPv6,
see [1] and [2]. Introduce a new IPv6 Hop-by-Hop TLV option, see IANA [3].

A new per-interface sysctl is introduced. The value is a boolean to accept (=1)
or ignore (=0, by default) IPv6 IOAM options on ingress for an interface:
 - net.ipv6.conf.XXX.ioam6_enabled

Two other sysctls are introduced to define IOAM IDs, represented by an integer.
They are respectively per-namespace and per-interface:
 - net.ipv6.ioam6_id
 - net.ipv6.conf.XXX.ioam6_id

The value of the first one represents the IOAM ID of the node itself (u32; max
and default value = U32_MAX>>8, due to hop limit concatenation) while the other
represents the IOAM ID of an interface (u16; max and default value = U16_MAX).

Each "ioam6_id" sysctl has a "_wide" equivalent:
 - net.ipv6.ioam6_id_wide
 - net.ipv6.conf.XXX.ioam6_id_wide

The value of the first one represents the wide IOAM ID of the node itself (u64;
max and default value = U64_MAX>>8, due to hop limit concatenation) while the
other represents the wide IOAM ID of an interface (u32; max and default value
= U32_MAX).

The use of short and wide equivalents is not exclusive, a deployment could
choose to leverage both. For example, net.ipv6.conf.XXX.ioam6_id (short format)
could be an identifier for a physical interface, whereas
net.ipv6.conf.XXX.ioam6_id_wide (wide format) could be an identifier for a
logical sub-interface. Documentation about new sysctls is provided at the end
of this patchset.

Two relativistic hash tables are used: one for IOAM namespaces, the other for
IOAM schemas. A namespace can only have a single active schema and a schema
can only be attached to a single namespace (1:1 relationship).

  [1] https://tools.ietf.org/html/draft-ietf-ippm-ioam-ipv6-options
  [2] https://tools.ietf.org/html/draft-ietf-ippm-ioam-data
  [3] https://www.iana.org/assignments/ipv6-parameters/ipv6-parameters.xhtml#ipv6-parameters-2

Signed-off-by: Justin Iurman <justin.iurman@uliege.be>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 13 insertions, 0 deletions

diff --git a/include/uapi/linux/in6.h b/include/uapi/linux/in6.h
index 5ad396a57eb3..c4c53a9ab959 100644
--- a/include/uapi/linux/in6.h
+++ b/include/uapi/linux/in6.h
@@ -145,6 +145,7 @@ struct in6_flowlabel_req {
 #define IPV6_TLV_PADN		1
 #define IPV6_TLV_ROUTERALERT	5
 #define IPV6_TLV_CALIPSO	7	/* RFC 5570 */
+#define IPV6_TLV_IOAM		49	/* TEMPORARY IANA allocation for IOAM */
 #define IPV6_TLV_JUMBO		194
 #define IPV6_TLV_HAO		201	/* home address option */
 
diff --git a/include/uapi/linux/ioam6.h b/include/uapi/linux/ioam6.h
index 2177e4e49566..23ba6e85582f 100644
--- a/include/uapi/linux/ioam6.h
+++ b/include/uapi/linux/ioam6.h
@@ -12,6 +12,15 @@
 #include <asm/byteorder.h>
 #include <linux/types.h>
 
+#define IOAM6_U16_UNAVAILABLE U16_MAX
+#define IOAM6_U32_UNAVAILABLE U32_MAX
+#define IOAM6_U64_UNAVAILABLE U64_MAX
+
+#define IOAM6_DEFAULT_ID (IOAM6_U32_UNAVAILABLE >> 8)
+#define IOAM6_DEFAULT_ID_WIDE (IOAM6_U64_UNAVAILABLE >> 8)
+#define IOAM6_DEFAULT_IF_ID IOAM6_U16_UNAVAILABLE
+#define IOAM6_DEFAULT_IF_ID_WIDE IOAM6_U32_UNAVAILABLE
+
 /*
  * IPv6 IOAM Option Header
  */
diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
index 70603775fe91..b243a53fa985 100644
--- a/include/uapi/linux/ipv6.h
+++ b/include/uapi/linux/ipv6.h
@@ -190,6 +190,9 @@ enum {
 	DEVCONF_NDISC_TCLASS,
 	DEVCONF_RPL_SEG_ENABLED,
 	DEVCONF_RA_DEFRTR_METRIC,
+	DEVCONF_IOAM6_ENABLED,
+	DEVCONF_IOAM6_ID,
+	DEVCONF_IOAM6_ID_WIDE,
 	DEVCONF_MAX
 };