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>

1 files changed, 61 insertions, 0 deletions

diff --git a/net/ipv6/exthdrs.c b/net/ipv6/exthdrs.c
index 26882e165c9e..d897faa4e9e6 100644
--- a/net/ipv6/exthdrs.c
+++ b/net/ipv6/exthdrs.c
@@ -49,6 +49,9 @@
 #include <net/seg6_hmac.h>
 #endif
 #include <net/rpl.h>
+#include <linux/ioam6.h>
+#include <net/ioam6.h>
+#include <net/dst_metadata.h>
 
 #include <linux/uaccess.h>
 
@@ -928,6 +931,60 @@ static bool ipv6_hop_ra(struct sk_buff *skb, int optoff)
 	return false;
 }
 
+/* IOAM */
+
+static bool ipv6_hop_ioam(struct sk_buff *skb, int optoff)
+{
+	struct ioam6_trace_hdr *trace;
+	struct ioam6_namespace *ns;
+	struct ioam6_hdr *hdr;
+
+	/* Bad alignment (must be 4n-aligned) */
+	if (optoff & 3)
+		goto drop;
+
+	/* Ignore if IOAM is not enabled on ingress */
+	if (!__in6_dev_get(skb->dev)->cnf.ioam6_enabled)
+		goto ignore;
+
+	/* Truncated Option header */
+	hdr = (struct ioam6_hdr *)(skb_network_header(skb) + optoff);
+	if (hdr->opt_len < 2)
+		goto drop;
+
+	switch (hdr->type) {
+	case IOAM6_TYPE_PREALLOC:
+		/* Truncated Pre-allocated Trace header */
+		if (hdr->opt_len < 2 + sizeof(*trace))
+			goto drop;
+
+		/* Malformed Pre-allocated Trace header */
+		trace = (struct ioam6_trace_hdr *)((u8 *)hdr + sizeof(*hdr));
+		if (hdr->opt_len < 2 + sizeof(*trace) + trace->remlen * 4)
+			goto drop;
+
+		/* Ignore if the IOAM namespace is unknown */
+		ns = ioam6_namespace(ipv6_skb_net(skb), trace->namespace_id);
+		if (!ns)
+			goto ignore;
+
+		if (!skb_valid_dst(skb))
+			ip6_route_input(skb);
+
+		ioam6_fill_trace_data(skb, ns, trace);
+		break;
+	default:
+		break;
+	}
+
+ignore:
+	return true;
+
+drop:
+	kfree_skb(skb);
+	return false;
+}
+
 /* Jumbo payload */
 
 static bool ipv6_hop_jumbo(struct sk_buff *skb, int optoff)
@@ -1000,6 +1057,10 @@ static const struct tlvtype_proc tlvprochopopt_lst[] = {
 		.func	= ipv6_hop_ra,
 	},
 	{
+		.type	= IPV6_TLV_IOAM,
+		.func	= ipv6_hop_ioam,
+	},
+	{
 		.type	= IPV6_TLV_JUMBO,
 		.func	= ipv6_hop_jumbo,
 	},