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, 333 insertions, 0 deletions

diff --git a/net/ipv6/ioam6.c b/net/ipv6/ioam6.c
new file mode 100644
index 000000000000..ba629e1b9408
--- /dev/null
+++ b/net/ipv6/ioam6.c
@@ -0,0 +1,333 @@
+// SPDX-License-Identifier: GPL-2.0+
+/*
+ *  IPv6 IOAM implementation
+ *
+ *  Author:
+ *  Justin Iurman <justin.iurman@uliege.be>
+ */
+
+#include <linux/errno.h>
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/net.h>
+#include <linux/ioam6.h>
+#include <linux/rhashtable.h>
+
+#include <net/addrconf.h>
+#include <net/ioam6.h>
+
+static void ioam6_ns_release(struct ioam6_namespace *ns)
+{
+	kfree_rcu(ns, rcu);
+}
+
+static void ioam6_sc_release(struct ioam6_schema *sc)
+{
+	kfree_rcu(sc, rcu);
+}
+
+static void ioam6_free_ns(void *ptr, void *arg)
+{
+	struct ioam6_namespace *ns = (struct ioam6_namespace *)ptr;
+
+	if (ns)
+		ioam6_ns_release(ns);
+}
+
+static void ioam6_free_sc(void *ptr, void *arg)
+{
+	struct ioam6_schema *sc = (struct ioam6_schema *)ptr;
+
+	if (sc)
+		ioam6_sc_release(sc);
+}
+
+static int ioam6_ns_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
+{
+	const struct ioam6_namespace *ns = obj;
+
+	return (ns->id != *(__be16 *)arg->key);
+}
+
+static int ioam6_sc_cmpfn(struct rhashtable_compare_arg *arg, const void *obj)
+{
+	const struct ioam6_schema *sc = obj;
+
+	return (sc->id != *(u32 *)arg->key);
+}
+
+static const struct rhashtable_params rht_ns_params = {
+	.key_len		= sizeof(__be16),
+	.key_offset		= offsetof(struct ioam6_namespace, id),
+	.head_offset		= offsetof(struct ioam6_namespace, head),
+	.automatic_shrinking	= true,
+	.obj_cmpfn		= ioam6_ns_cmpfn,
+};
+
+static const struct rhashtable_params rht_sc_params = {
+	.key_len		= sizeof(u32),
+	.key_offset		= offsetof(struct ioam6_schema, id),
+	.head_offset		= offsetof(struct ioam6_schema, head),
+	.automatic_shrinking	= true,
+	.obj_cmpfn		= ioam6_sc_cmpfn,
+};
+
+struct ioam6_namespace *ioam6_namespace(struct net *net, __be16 id)
+{
+	struct ioam6_pernet_data *nsdata = ioam6_pernet(net);
+
+	return rhashtable_lookup_fast(&nsdata->namespaces, &id, rht_ns_params);
+}
+
+static void __ioam6_fill_trace_data(struct sk_buff *skb,
+				    struct ioam6_namespace *ns,
+				    struct ioam6_trace_hdr *trace,
+				    struct ioam6_schema *sc,
+				    u8 sclen)
+{
+	struct __kernel_sock_timeval ts;
+	u64 raw64;
+	u32 raw32;
+	u16 raw16;
+	u8 *data;
+	u8 byte;
+
+	data = trace->data + trace->remlen * 4 - trace->nodelen * 4 - sclen * 4;
+
+	/* hop_lim and node_id */
+	if (trace->type.bit0) {
+		byte = ipv6_hdr(skb)->hop_limit;
+		if (skb->dev)
+			byte--;
+
+		raw32 = dev_net(skb->dev)->ipv6.sysctl.ioam6_id;
+
+		*(__be32 *)data = cpu_to_be32((byte << 24) | raw32);
+		data += sizeof(__be32);
+	}
+
+	/* ingress_if_id and egress_if_id */
+	if (trace->type.bit1) {
+		if (!skb->dev)
+			raw16 = IOAM6_U16_UNAVAILABLE;
+		else
+			raw16 = (__force u16)__in6_dev_get(skb->dev)->cnf.ioam6_id;
+
+		*(__be16 *)data = cpu_to_be16(raw16);
+		data += sizeof(__be16);
+
+		if (skb_dst(skb)->dev->flags & IFF_LOOPBACK)
+			raw16 = IOAM6_U16_UNAVAILABLE;
+		else
+			raw16 = (__force u16)__in6_dev_get(skb_dst(skb)->dev)->cnf.ioam6_id;
+
+		*(__be16 *)data = cpu_to_be16(raw16);
+		data += sizeof(__be16);
+	}
+
+	/* timestamp seconds */
+	if (trace->type.bit2) {
+		if (!skb->tstamp)
+			__net_timestamp(skb);
+
+		skb_get_new_timestamp(skb, &ts);
+
+		*(__be32 *)data = cpu_to_be32((u32)ts.tv_sec);
+		data += sizeof(__be32);
+	}
+
+	/* timestamp subseconds */
+	if (trace->type.bit3) {
+		if (!skb->tstamp)
+			__net_timestamp(skb);
+
+		if (!trace->type.bit2)
+			skb_get_new_timestamp(skb, &ts);
+
+		*(__be32 *)data = cpu_to_be32((u32)ts.tv_usec);
+		data += sizeof(__be32);
+	}
+
+	/* transit delay */
+	if (trace->type.bit4) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* namespace data */
+	if (trace->type.bit5) {
+		*(__be32 *)data = ns->data;
+		data += sizeof(__be32);
+	}
+
+	/* queue depth */
+	if (trace->type.bit6) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* checksum complement */
+	if (trace->type.bit7) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* hop_lim and node_id (wide) */
+	if (trace->type.bit8) {
+		byte = ipv6_hdr(skb)->hop_limit;
+		if (skb->dev)
+			byte--;
+
+		raw64 = dev_net(skb->dev)->ipv6.sysctl.ioam6_id_wide;
+
+		*(__be64 *)data = cpu_to_be64(((u64)byte << 56) | raw64);
+		data += sizeof(__be64);
+	}
+
+	/* ingress_if_id and egress_if_id (wide) */
+	if (trace->type.bit9) {
+		if (!skb->dev)
+			raw32 = IOAM6_U32_UNAVAILABLE;
+		else
+			raw32 = __in6_dev_get(skb->dev)->cnf.ioam6_id_wide;
+
+		*(__be32 *)data = cpu_to_be32(raw32);
+		data += sizeof(__be32);
+
+		if (skb_dst(skb)->dev->flags & IFF_LOOPBACK)
+			raw32 = IOAM6_U32_UNAVAILABLE;
+		else
+			raw32 = __in6_dev_get(skb_dst(skb)->dev)->cnf.ioam6_id_wide;
+
+		*(__be32 *)data = cpu_to_be32(raw32);
+		data += sizeof(__be32);
+	}
+
+	/* namespace data (wide) */
+	if (trace->type.bit10) {
+		*(__be64 *)data = ns->data_wide;
+		data += sizeof(__be64);
+	}
+
+	/* buffer occupancy */
+	if (trace->type.bit11) {
+		*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE);
+		data += sizeof(__be32);
+	}
+
+	/* opaque state snapshot */
+	if (trace->type.bit22) {
+		if (!sc) {
+			*(__be32 *)data = cpu_to_be32(IOAM6_U32_UNAVAILABLE >> 8);
+		} else {
+			*(__be32 *)data = sc->hdr;
+			data += sizeof(__be32);
+
+			memcpy(data, sc->data, sc->len);
+		}
+	}
+}
+
+/* called with rcu_read_lock() */
+void ioam6_fill_trace_data(struct sk_buff *skb,
+			   struct ioam6_namespace *ns,
+			   struct ioam6_trace_hdr *trace)
+{
+	struct ioam6_schema *sc;
+	u8 sclen = 0;
+
+	/* Skip if Overflow flag is set OR
+	 * if an unknown type (bit 12-21) is set
+	 */
+	if (trace->overflow ||
+	    trace->type.bit12 | trace->type.bit13 | trace->type.bit14 |
+	    trace->type.bit15 | trace->type.bit16 | trace->type.bit17 |
+	    trace->type.bit18 | trace->type.bit19 | trace->type.bit20 |
+	    trace->type.bit21) {
+		return;
+	}
+
+	/* NodeLen does not include Opaque State Snapshot length. We need to
+	 * take it into account if the corresponding bit is set (bit 22) and
+	 * if the current IOAM namespace has an active schema attached to it
+	 */
+	sc = rcu_dereference(ns->schema);
+	if (trace->type.bit22) {
+		sclen = sizeof_field(struct ioam6_schema, hdr) / 4;
+
+		if (sc)
+			sclen += sc->len / 4;
+	}
+
+	/* If there is no space remaining, we set the Overflow flag and we
+	 * skip without filling the trace
+	 */
+	if (!trace->remlen || trace->remlen < trace->nodelen + sclen) {
+		trace->overflow = 1;
+		return;
+	}
+
+	__ioam6_fill_trace_data(skb, ns, trace, sc, sclen);
+	trace->remlen -= trace->nodelen + sclen;
+}
+
+static int __net_init ioam6_net_init(struct net *net)
+{
+	struct ioam6_pernet_data *nsdata;
+	int err = -ENOMEM;
+
+	nsdata = kzalloc(sizeof(*nsdata), GFP_KERNEL);
+	if (!nsdata)
+		goto out;
+
+	mutex_init(&nsdata->lock);
+	net->ipv6.ioam6_data = nsdata;
+
+	err = rhashtable_init(&nsdata->namespaces, &rht_ns_params);
+	if (err)
+		goto free_nsdata;
+
+	err = rhashtable_init(&nsdata->schemas, &rht_sc_params);
+	if (err)
+		goto free_rht_ns;
+
+out:
+	return err;
+free_rht_ns:
+	rhashtable_destroy(&nsdata->namespaces);
+free_nsdata:
+	kfree(nsdata);
+	net->ipv6.ioam6_data = NULL;
+	goto out;
+}
+
+static void __net_exit ioam6_net_exit(struct net *net)
+{
+	struct ioam6_pernet_data *nsdata = ioam6_pernet(net);
+
+	rhashtable_free_and_destroy(&nsdata->namespaces, ioam6_free_ns, NULL);
+	rhashtable_free_and_destroy(&nsdata->schemas, ioam6_free_sc, NULL);
+
+	kfree(nsdata);
+}
+
+static struct pernet_operations ioam6_net_ops = {
+	.init = ioam6_net_init,
+	.exit = ioam6_net_exit,
+};
+
+int __init ioam6_init(void)
+{
+	int err = register_pernet_subsys(&ioam6_net_ops);
+
+	if (err)
+		return err;
+
+	pr_info("In-situ OAM (IOAM) with IPv6\n");
+	return 0;
+}
+
+void ioam6_exit(void)
+{
+	unregister_pernet_subsys(&ioam6_net_ops);
+}