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>

include/linux/ioam6.h

@@ -0,0 +1,13 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ *  IPv6 IOAM
+ *
+ *  Author:
+ *  Justin Iurman <justin.iurman@uliege.be>
+ */
+#ifndef _LINUX_IOAM6_H
+#define _LINUX_IOAM6_H
+
+#include <uapi/linux/ioam6.h>
+
+#endif /* _LINUX_IOAM6_H */

include/linux/ipv6.h

@@ -76,6 +76,9 @@ struct ipv6_devconf {
 	__s32		disable_policy;
 	__s32           ndisc_tclass;
 	__s32		rpl_seg_enabled;
+	__u32		ioam6_id;
+	__u32		ioam6_id_wide;
+	__u8		ioam6_enabled;
 
 	struct ctl_table_header *sysctl_header;
 };

include/net/ioam6.h

@@ -0,0 +1,64 @@
+/* SPDX-License-Identifier: GPL-2.0+ */
+/*
+ *  IPv6 IOAM implementation
+ *
+ *  Author:
+ *  Justin Iurman <justin.iurman@uliege.be>
+ */
+
+#ifndef _NET_IOAM6_H
+#define _NET_IOAM6_H
+
+#include <linux/net.h>
+#include <linux/ipv6.h>
+#include <linux/ioam6.h>
+#include <linux/rhashtable-types.h>
+
+struct ioam6_namespace {
+	struct rhash_head head;
+	struct rcu_head rcu;
+
+	struct ioam6_schema __rcu *schema;
+
+	__be16 id;
+	__be32 data;
+	__be64 data_wide;
+};
+
+struct ioam6_schema {
+	struct rhash_head head;
+	struct rcu_head rcu;
+
+	struct ioam6_namespace __rcu *ns;
+
+	u32 id;
+	int len;
+	__be32 hdr;
+
+	u8 data[0];
+};
+
+struct ioam6_pernet_data {
+	struct mutex lock;
+	struct rhashtable namespaces;
+	struct rhashtable schemas;
+};
+
+static inline struct ioam6_pernet_data *ioam6_pernet(struct net *net)
+{
+#if IS_ENABLED(CONFIG_IPV6)
+	return net->ipv6.ioam6_data;
+#else
+	return NULL;
+#endif
+}
+
+struct ioam6_namespace *ioam6_namespace(struct net *net, __be16 id);
+void ioam6_fill_trace_data(struct sk_buff *skb,
+			   struct ioam6_namespace *ns,
+			   struct ioam6_trace_hdr *trace);
+
+int ioam6_init(void);
+void ioam6_exit(void);
+
+#endif /* _NET_IOAM6_H */

include/net/netns/ipv6.h

@@ -51,6 +51,8 @@ struct netns_sysctl_ipv6 {
 	int max_dst_opts_len;
 	int max_hbh_opts_len;
 	int seg6_flowlabel;
+	u32 ioam6_id;
+	u64 ioam6_id_wide;
 	bool skip_notify_on_dev_down;
 	u8 fib_notify_on_flag_change;
 };
@@ -110,6 +112,7 @@ struct netns_ipv6 {
 		spinlock_t	lock;
 		u32		seq;
 	} ip6addrlbl_table;
+	struct ioam6_pernet_data *ioam6_data;
 };
 
 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV6)

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 */
 

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
  */

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
 };