Merge branch 'seg6-add-next-c-sid-support-for-srv6-end-behavior'

Andrea Mayer says:

====================
seg6: add NEXT-C-SID support for SRv6 End behavior

The Segment Routing (SR) architecture is based on loose source routing.
A list of instructions, called segments, can be added to the packet headers to
influence the forwarding and processing of the packets in an SR enabled
network.
In SRv6 (Segment Routing over IPv6 data plane) [1], the segment identifiers
(SIDs) are IPv6 addresses (128 bits) and the segment list (SID List) is carried
in the Segment Routing Header (SRH). A segment may correspond to a "behavior"
that is executed by a node when the packet is received.
The Linux kernel currently supports a large subset of the behaviors described
in [2] (e.g., End, End.X, End.T and so on).

Some SRv6 scenarios (i.e.: traffic-engineering, fast-rerouting, VPN, mobile
network backhaul, etc.) may require a large number of segments (i.e. up to 15).
Therefore, reducing the size of the SID List is useful to minimize the impact
on MTU (Maximum Transfer Unit) and to enable SRv6 on legacy hardware devices
with limited processing power that can suffer from long IPv6 headers.

Draft-ietf-spring-srv6-srh-compression [3] extends the SRv6 architecture by
providing different mechanisms for the efficient representation (i.e.
compression) of the SID List.

The NEXT-C-SID mechanism described in [3] offers the possibility of encoding
several SRv6 segments within a single 128 bit SID address. Such a SID address
is called a Compressed SID Container. In this way, the length of the SID List
can be drastically reduced. In some cases, the SRH can be omitted, as the IPv6
Destination Address can carry the whole Segment List, using its compressed
representation.

The NEXT-C-SID mechanism relies on the "flavors" framework defined in [2].
The flavors represent additional operations that can modify or extend a subset
of the existing behaviors.

In this patchset we extend the SRv6 Subsystem in order to support the
NEXT-C-SID mechanism.

In details the patchset is made of:
 - patch 1/3: add netlink_ext_ack support in parsing SRv6 behavior attributes;
 - patch 2/3: add NEXT-C-SID support for SRv6 End behavior;
 - patch 3/3: add selftest for NEXT-C-SID in SRv6 End behavior.

The corresponding iproute2 patch for supporting the NEXT-C-SID in SRv6 End
behavior is provided in a separated patchset.

Comments, improvements and suggestions are always appreciated.

[1] - https://datatracker.ietf.org/doc/html/rfc8754
[2] - https://datatracker.ietf.org/doc/html/rfc8986
[3] - https://datatracker.ietf.org/doc/html/draft-ietf-spring-srv6-srh-compression

====================

Link: https://lore.kernel.org/r/20220912171619.16943-1-andrea.mayer@uniroma2.itSigned-off-by: Paolo Abeni <pabeni@redhat.com>

include/uapi/linux/seg6_local.h

@@ -28,6 +28,7 @@ enum {
 	SEG6_LOCAL_BPF,
 	SEG6_LOCAL_VRFTABLE,
 	SEG6_LOCAL_COUNTERS,
+	SEG6_LOCAL_FLAVORS,
 	__SEG6_LOCAL_MAX,
 };
 #define SEG6_LOCAL_MAX (__SEG6_LOCAL_MAX - 1)
@@ -110,4 +111,27 @@ enum {
 
 #define SEG6_LOCAL_CNT_MAX (__SEG6_LOCAL_CNT_MAX - 1)
 
+/* SRv6 End* Flavor attributes */
+enum {
+	SEG6_LOCAL_FLV_UNSPEC,
+	SEG6_LOCAL_FLV_OPERATION,
+	SEG6_LOCAL_FLV_LCBLOCK_BITS,
+	SEG6_LOCAL_FLV_LCNODE_FN_BITS,
+	__SEG6_LOCAL_FLV_MAX,
+};
+
+#define SEG6_LOCAL_FLV_MAX (__SEG6_LOCAL_FLV_MAX - 1)
+
+/* Designed flavor operations for SRv6 End* Behavior */
+enum {
+	SEG6_LOCAL_FLV_OP_UNSPEC,
+	SEG6_LOCAL_FLV_OP_PSP,
+	SEG6_LOCAL_FLV_OP_USP,
+	SEG6_LOCAL_FLV_OP_USD,
+	SEG6_LOCAL_FLV_OP_NEXT_CSID,
+	__SEG6_LOCAL_FLV_OP_MAX
+};
+
+#define SEG6_LOCAL_FLV_OP_MAX (__SEG6_LOCAL_FLV_OP_MAX - 1)
+
 #endif

net/ipv6/seg6_local.c

@@ -73,6 +73,55 @@ struct bpf_lwt_prog {
 	char *name;
 };
 
+/* default length values (expressed in bits) for both Locator-Block and
+ * Locator-Node Function.
+ *
+ * Both SEG6_LOCAL_LCBLOCK_DBITS and SEG6_LOCAL_LCNODE_FN_DBITS *must* be:
+ *    i) greater than 0;
+ *   ii) evenly divisible by 8. In other terms, the lengths of the
+ *	 Locator-Block and Locator-Node Function must be byte-aligned (we can
+ *	 relax this constraint in the future if really needed).
+ *
+ * Moreover, a third condition must hold:
+ *  iii) SEG6_LOCAL_LCBLOCK_DBITS + SEG6_LOCAL_LCNODE_FN_DBITS <= 128.
+ *
+ * The correctness of SEG6_LOCAL_LCBLOCK_DBITS and SEG6_LOCAL_LCNODE_FN_DBITS
+ * values are checked during the kernel compilation. If the compilation stops,
+ * check the value of these parameters to see if they meet conditions (i), (ii)
+ * and (iii).
+ */
+#define SEG6_LOCAL_LCBLOCK_DBITS	32
+#define SEG6_LOCAL_LCNODE_FN_DBITS	16
+
+/* The following next_csid_chk_{cntr,lcblock,lcblock_fn}_bits macros can be
+ * used directly to check whether the lengths (in bits) of Locator-Block and
+ * Locator-Node Function are valid according to (i), (ii), (iii).
+ */
+#define next_csid_chk_cntr_bits(blen, flen)		\
+	((blen) + (flen) > 128)
+
+#define next_csid_chk_lcblock_bits(blen)		\
+({							\
+	typeof(blen) __tmp = blen;			\
+	(!__tmp || __tmp > 120 || (__tmp & 0x07));	\
+})
+
+#define next_csid_chk_lcnode_fn_bits(flen)		\
+	next_csid_chk_lcblock_bits(flen)
+
+/* Supported Flavor operations are reported in this bitmask */
+#define SEG6_LOCAL_FLV_SUPP_OPS	(BIT(SEG6_LOCAL_FLV_OP_NEXT_CSID))
+
+struct seg6_flavors_info {
+	/* Flavor operations */
+	__u32 flv_ops;
+
+	/* Locator-Block length, expressed in bits */
+	__u8 lcblock_bits;
+	/* Locator-Node Function length, expressed in bits*/
+	__u8 lcnode_func_bits;
+};
+
 enum seg6_end_dt_mode {
 	DT_INVALID_MODE	= -EINVAL,
 	DT_LEGACY_MODE	= 0,
@@ -136,6 +185,8 @@ struct seg6_local_lwt {
 #ifdef CONFIG_NET_L3_MASTER_DEV
 	struct seg6_end_dt_info dt_info;
 #endif
+	struct seg6_flavors_info flv_info;
+
 	struct pcpu_seg6_local_counters __percpu *pcpu_counters;
 
 	int headroom;
@@ -271,8 +322,50 @@ int seg6_lookup_nexthop(struct sk_buff *skb,
 	return seg6_lookup_any_nexthop(skb, nhaddr, tbl_id, false);
 }
 
-/* regular endpoint function */
-static int input_action_end(struct sk_buff *skb, struct seg6_local_lwt *slwt)
+static __u8 seg6_flv_lcblock_octects(const struct seg6_flavors_info *finfo)
+{
+	return finfo->lcblock_bits >> 3;
+}
+
+static __u8 seg6_flv_lcnode_func_octects(const struct seg6_flavors_info *finfo)
+{
+	return finfo->lcnode_func_bits >> 3;
+}
+
+static bool seg6_next_csid_is_arg_zero(const struct in6_addr *addr,
+				       const struct seg6_flavors_info *finfo)
+{
+	__u8 fnc_octects = seg6_flv_lcnode_func_octects(finfo);
+	__u8 blk_octects = seg6_flv_lcblock_octects(finfo);
+	__u8 arg_octects;
+	int i;
+
+	arg_octects = 16 - blk_octects - fnc_octects;
+	for (i = 0; i < arg_octects; ++i) {
+		if (addr->s6_addr[blk_octects + fnc_octects + i] != 0x00)
+			return false;
+	}
+
+	return true;
+}
+
+/* assume that DA.Argument length > 0 */
+static void seg6_next_csid_advance_arg(struct in6_addr *addr,
+				       const struct seg6_flavors_info *finfo)
+{
+	__u8 fnc_octects = seg6_flv_lcnode_func_octects(finfo);
+	__u8 blk_octects = seg6_flv_lcblock_octects(finfo);
+
+	/* advance DA.Argument */
+	memmove(&addr->s6_addr[blk_octects],
+		&addr->s6_addr[blk_octects + fnc_octects],
+		16 - blk_octects - fnc_octects);
+
+	memset(&addr->s6_addr[16 - fnc_octects], 0x00, fnc_octects);
+}
+
+static int input_action_end_core(struct sk_buff *skb,
+				 struct seg6_local_lwt *slwt)
 {
 	struct ipv6_sr_hdr *srh;
 
@@ -291,6 +384,38 @@ static int input_action_end(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 	return -EINVAL;
 }
 
+static int end_next_csid_core(struct sk_buff *skb, struct seg6_local_lwt *slwt)
+{
+	const struct seg6_flavors_info *finfo = &slwt->flv_info;
+	struct in6_addr *daddr = &ipv6_hdr(skb)->daddr;
+
+	if (seg6_next_csid_is_arg_zero(daddr, finfo))
+		return input_action_end_core(skb, slwt);
+
+	/* update DA */
+	seg6_next_csid_advance_arg(daddr, finfo);
+
+	seg6_lookup_nexthop(skb, NULL, 0);
+
+	return dst_input(skb);
+}
+
+static bool seg6_next_csid_enabled(__u32 fops)
+{
+	return fops & BIT(SEG6_LOCAL_FLV_OP_NEXT_CSID);
+}
+
+/* regular endpoint function */
+static int input_action_end(struct sk_buff *skb, struct seg6_local_lwt *slwt)
+{
+	const struct seg6_flavors_info *finfo = &slwt->flv_info;
+
+	if (seg6_next_csid_enabled(finfo->flv_ops))
+		return end_next_csid_core(skb, slwt);
+
+	return input_action_end_core(skb, slwt);
+}
+
 /* regular endpoint, and forward to specified nexthop */
 static int input_action_end_x(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 {
@@ -951,7 +1076,8 @@ static struct seg6_action_desc seg6_action_table[] = {
 	{
 		.action		= SEG6_LOCAL_ACTION_END,
 		.attrs		= 0,
-		.optattrs	= SEG6_F_LOCAL_COUNTERS,
+		.optattrs	= SEG6_F_LOCAL_COUNTERS |
+				  SEG6_F_ATTR(SEG6_LOCAL_FLAVORS),
 		.input		= input_action_end,
 	},
 	{
@@ -1132,9 +1258,11 @@ static const struct nla_policy seg6_local_policy[SEG6_LOCAL_MAX + 1] = {
 	[SEG6_LOCAL_OIF]	= { .type = NLA_U32 },
 	[SEG6_LOCAL_BPF]	= { .type = NLA_NESTED },
 	[SEG6_LOCAL_COUNTERS]	= { .type = NLA_NESTED },
+	[SEG6_LOCAL_FLAVORS]	= { .type = NLA_NESTED },
 };
 
-static int parse_nla_srh(struct nlattr **attrs, struct seg6_local_lwt *slwt)
+static int parse_nla_srh(struct nlattr **attrs, struct seg6_local_lwt *slwt,
+			 struct netlink_ext_ack *extack)
 {
 	struct ipv6_sr_hdr *srh;
 	int len;
@@ -1191,7 +1319,8 @@ static void destroy_attr_srh(struct seg6_local_lwt *slwt)
 	kfree(slwt->srh);
 }
 
-static int parse_nla_table(struct nlattr **attrs, struct seg6_local_lwt *slwt)
+static int parse_nla_table(struct nlattr **attrs, struct seg6_local_lwt *slwt,
+			   struct netlink_ext_ack *extack)
 {
 	slwt->table = nla_get_u32(attrs[SEG6_LOCAL_TABLE]);
 
@@ -1225,7 +1354,8 @@ seg6_end_dt_info *seg6_possible_end_dt_info(struct seg6_local_lwt *slwt)
 }
 
 static int parse_nla_vrftable(struct nlattr **attrs,
-			      struct seg6_local_lwt *slwt)
+			      struct seg6_local_lwt *slwt,
+			      struct netlink_ext_ack *extack)
 {
 	struct seg6_end_dt_info *info = seg6_possible_end_dt_info(slwt);
 
@@ -1261,7 +1391,8 @@ static int cmp_nla_vrftable(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
 	return 0;
 }
 
-static int parse_nla_nh4(struct nlattr **attrs, struct seg6_local_lwt *slwt)
+static int parse_nla_nh4(struct nlattr **attrs, struct seg6_local_lwt *slwt,
+			 struct netlink_ext_ack *extack)
 {
 	memcpy(&slwt->nh4, nla_data(attrs[SEG6_LOCAL_NH4]),
 	       sizeof(struct in_addr));
@@ -1287,7 +1418,8 @@ static int cmp_nla_nh4(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
 	return memcmp(&a->nh4, &b->nh4, sizeof(struct in_addr));
 }
 
-static int parse_nla_nh6(struct nlattr **attrs, struct seg6_local_lwt *slwt)
+static int parse_nla_nh6(struct nlattr **attrs, struct seg6_local_lwt *slwt,
+			 struct netlink_ext_ack *extack)
 {
 	memcpy(&slwt->nh6, nla_data(attrs[SEG6_LOCAL_NH6]),
 	       sizeof(struct in6_addr));
@@ -1313,7 +1445,8 @@ static int cmp_nla_nh6(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
 	return memcmp(&a->nh6, &b->nh6, sizeof(struct in6_addr));
 }
 
-static int parse_nla_iif(struct nlattr **attrs, struct seg6_local_lwt *slwt)
+static int parse_nla_iif(struct nlattr **attrs, struct seg6_local_lwt *slwt,
+			 struct netlink_ext_ack *extack)
 {
 	slwt->iif = nla_get_u32(attrs[SEG6_LOCAL_IIF]);
 
@@ -1336,7 +1469,8 @@ static int cmp_nla_iif(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
 	return 0;
 }
 
-static int parse_nla_oif(struct nlattr **attrs, struct seg6_local_lwt *slwt)
+static int parse_nla_oif(struct nlattr **attrs, struct seg6_local_lwt *slwt,
+			 struct netlink_ext_ack *extack)
 {
 	slwt->oif = nla_get_u32(attrs[SEG6_LOCAL_OIF]);
 
@@ -1366,7 +1500,8 @@ static const struct nla_policy bpf_prog_policy[SEG6_LOCAL_BPF_PROG_MAX + 1] = {
 				       .len = MAX_PROG_NAME },
 };
 
-static int parse_nla_bpf(struct nlattr **attrs, struct seg6_local_lwt *slwt)
+static int parse_nla_bpf(struct nlattr **attrs, struct seg6_local_lwt *slwt,
+			 struct netlink_ext_ack *extack)
 {
 	struct nlattr *tb[SEG6_LOCAL_BPF_PROG_MAX + 1];
 	struct bpf_prog *p;
@@ -1444,7 +1579,8 @@ nla_policy seg6_local_counters_policy[SEG6_LOCAL_CNT_MAX + 1] = {
 };
 
 static int parse_nla_counters(struct nlattr **attrs,
-			      struct seg6_local_lwt *slwt)
+			      struct seg6_local_lwt *slwt,
+			      struct netlink_ext_ack *extack)
 {
 	struct pcpu_seg6_local_counters __percpu *pcounters;
 	struct nlattr *tb[SEG6_LOCAL_CNT_MAX + 1];
@@ -1542,8 +1678,195 @@ static void destroy_attr_counters(struct seg6_local_lwt *slwt)
 	free_percpu(slwt->pcpu_counters);
 }
 
+static const
+struct nla_policy seg6_local_flavors_policy[SEG6_LOCAL_FLV_MAX + 1] = {
+	[SEG6_LOCAL_FLV_OPERATION]	= { .type = NLA_U32 },
+	[SEG6_LOCAL_FLV_LCBLOCK_BITS]	= { .type = NLA_U8 },
+	[SEG6_LOCAL_FLV_LCNODE_FN_BITS]	= { .type = NLA_U8 },
+};
+
+/* check whether the lengths of the Locator-Block and Locator-Node Function
+ * are compatible with the dimension of a C-SID container.
+ */
+static int seg6_chk_next_csid_cfg(__u8 block_len, __u8 func_len)
+{
+	/* Locator-Block and Locator-Node Function cannot exceed 128 bits
+	 * (i.e. C-SID container lenghts).
+	 */
+	if (next_csid_chk_cntr_bits(block_len, func_len))
+		return -EINVAL;
+
+	/* Locator-Block length must be greater than zero and evenly divisible
+	 * by 8. There must be room for a Locator-Node Function, at least.
+	 */
+	if (next_csid_chk_lcblock_bits(block_len))
+		return -EINVAL;
+
+	/* Locator-Node Function length must be greater than zero and evenly
+	 * divisible by 8. There must be room for the Locator-Block.
+	 */
+	if (next_csid_chk_lcnode_fn_bits(func_len))
+		return -EINVAL;
+
+	return 0;
+}
+
+static int seg6_parse_nla_next_csid_cfg(struct nlattr **tb,
+					struct seg6_flavors_info *finfo,
+					struct netlink_ext_ack *extack)
+{
+	__u8 func_len = SEG6_LOCAL_LCNODE_FN_DBITS;
+	__u8 block_len = SEG6_LOCAL_LCBLOCK_DBITS;
+	int rc;
+
+	if (tb[SEG6_LOCAL_FLV_LCBLOCK_BITS])
+		block_len = nla_get_u8(tb[SEG6_LOCAL_FLV_LCBLOCK_BITS]);
+
+	if (tb[SEG6_LOCAL_FLV_LCNODE_FN_BITS])
+		func_len = nla_get_u8(tb[SEG6_LOCAL_FLV_LCNODE_FN_BITS]);
+
+	rc = seg6_chk_next_csid_cfg(block_len, func_len);
+	if (rc < 0) {
+		NL_SET_ERR_MSG(extack,
+			       "Invalid Locator Block/Node Function lengths");
+		return rc;
+	}
+
+	finfo->lcblock_bits = block_len;
+	finfo->lcnode_func_bits = func_len;
+
+	return 0;
+}
+
+static int parse_nla_flavors(struct nlattr **attrs, struct seg6_local_lwt *slwt,
+			     struct netlink_ext_ack *extack)
+{
+	struct seg6_flavors_info *finfo = &slwt->flv_info;
+	struct nlattr *tb[SEG6_LOCAL_FLV_MAX + 1];
+	unsigned long fops;
+	int rc;
+
+	rc = nla_parse_nested_deprecated(tb, SEG6_LOCAL_FLV_MAX,
+					 attrs[SEG6_LOCAL_FLAVORS],
+					 seg6_local_flavors_policy, NULL);
+	if (rc < 0)
+		return rc;
+
+	/* this attribute MUST always be present since it represents the Flavor
+	 * operation(s) to be carried out.
+	 */
+	if (!tb[SEG6_LOCAL_FLV_OPERATION])
+		return -EINVAL;
+
+	fops = nla_get_u32(tb[SEG6_LOCAL_FLV_OPERATION]);
+	if (fops & ~SEG6_LOCAL_FLV_SUPP_OPS) {
+		NL_SET_ERR_MSG(extack, "Unsupported Flavor operation(s)");
+		return -EOPNOTSUPP;
+	}
+
+	finfo->flv_ops = fops;
+
+	if (seg6_next_csid_enabled(fops)) {
+		/* Locator-Block and Locator-Node Function lengths can be
+		 * provided by the user space. Otherwise, default values are
+		 * applied.
+		 */
+		rc = seg6_parse_nla_next_csid_cfg(tb, finfo, extack);
+		if (rc < 0)
+			return rc;
+	}
+
+	return 0;
+}
+
+static int seg6_fill_nla_next_csid_cfg(struct sk_buff *skb,
+				       struct seg6_flavors_info *finfo)
+{
+	if (nla_put_u8(skb, SEG6_LOCAL_FLV_LCBLOCK_BITS, finfo->lcblock_bits))
+		return -EMSGSIZE;
+
+	if (nla_put_u8(skb, SEG6_LOCAL_FLV_LCNODE_FN_BITS,
+		       finfo->lcnode_func_bits))
+		return -EMSGSIZE;
+
+	return 0;
+}
+
+static int put_nla_flavors(struct sk_buff *skb, struct seg6_local_lwt *slwt)
+{
+	struct seg6_flavors_info *finfo = &slwt->flv_info;
+	__u32 fops = finfo->flv_ops;
+	struct nlattr *nest;
+	int rc;
+
+	nest = nla_nest_start(skb, SEG6_LOCAL_FLAVORS);
+	if (!nest)
+		return -EMSGSIZE;
+
+	if (nla_put_u32(skb, SEG6_LOCAL_FLV_OPERATION, fops)) {
+		rc = -EMSGSIZE;
+		goto err;
+	}
+
+	if (seg6_next_csid_enabled(fops)) {
+		rc = seg6_fill_nla_next_csid_cfg(skb, finfo);
+		if (rc < 0)
+			goto err;
+	}
+
+	return nla_nest_end(skb, nest);
+
+err:
+	nla_nest_cancel(skb, nest);
+	return rc;
+}
+
+static int seg6_cmp_nla_next_csid_cfg(struct seg6_flavors_info *finfo_a,
+				      struct seg6_flavors_info *finfo_b)
+{
+	if (finfo_a->lcblock_bits != finfo_b->lcblock_bits)
+		return 1;
+
+	if (finfo_a->lcnode_func_bits != finfo_b->lcnode_func_bits)
+		return 1;
+
+	return 0;
+}
+
+static int cmp_nla_flavors(struct seg6_local_lwt *a, struct seg6_local_lwt *b)
+{
+	struct seg6_flavors_info *finfo_a = &a->flv_info;
+	struct seg6_flavors_info *finfo_b = &b->flv_info;
+
+	if (finfo_a->flv_ops != finfo_b->flv_ops)
+		return 1;
+
+	if (seg6_next_csid_enabled(finfo_a->flv_ops)) {
+		if (seg6_cmp_nla_next_csid_cfg(finfo_a, finfo_b))
+			return 1;
+	}
+
+	return 0;
+}
+
+static int encap_size_flavors(struct seg6_local_lwt *slwt)
+{
+	struct seg6_flavors_info *finfo = &slwt->flv_info;
+	int nlsize;
+
+	nlsize = nla_total_size(0) +	/* nest SEG6_LOCAL_FLAVORS */
+		 nla_total_size(4);	/* SEG6_LOCAL_FLV_OPERATION */
+
+	if (seg6_next_csid_enabled(finfo->flv_ops))
+		nlsize += nla_total_size(1) + /* SEG6_LOCAL_FLV_LCBLOCK_BITS */
+			  nla_total_size(1); /* SEG6_LOCAL_FLV_LCNODE_FN_BITS */
+
+	return nlsize;
+}
+
 struct seg6_action_param {
-	int (*parse)(struct nlattr **attrs, struct seg6_local_lwt *slwt);
+	int (*parse)(struct nlattr **attrs, struct seg6_local_lwt *slwt,
+		     struct netlink_ext_ack *extack);
 	int (*put)(struct sk_buff *skb, struct seg6_local_lwt *slwt);
 	int (*cmp)(struct seg6_local_lwt *a, struct seg6_local_lwt *b);
 
@@ -1593,6 +1916,10 @@ static struct seg6_action_param seg6_action_params[SEG6_LOCAL_MAX + 1] = {
 				    .put = put_nla_counters,
 				    .cmp = cmp_nla_counters,
 				    .destroy = destroy_attr_counters },
+
+	[SEG6_LOCAL_FLAVORS]	= { .parse = parse_nla_flavors,
+				    .put = put_nla_flavors,
+				    .cmp = cmp_nla_flavors },
 };
 
 /* call the destroy() callback (if available) for each set attribute in
@@ -1636,7 +1963,8 @@ static void destroy_attrs(struct seg6_local_lwt *slwt)
 }
 
 static int parse_nla_optional_attrs(struct nlattr **attrs,
-				    struct seg6_local_lwt *slwt)
+				    struct seg6_local_lwt *slwt,
+				    struct netlink_ext_ack *extack)
 {
 	struct seg6_action_desc *desc = slwt->desc;
 	unsigned long parsed_optattrs = 0;
@@ -1652,7 +1980,7 @@ static int parse_nla_optional_attrs(struct nlattr **attrs,
 		 */
 		param = &seg6_action_params[i];
 
-		err = param->parse(attrs, slwt);
+		err = param->parse(attrs, slwt, extack);
 		if (err < 0)
 			goto parse_optattrs_err;
 
@@ -1705,7 +2033,8 @@ static void seg6_local_lwtunnel_destroy_state(struct seg6_local_lwt *slwt)
 	ops->destroy_state(slwt);
 }
 
-static int parse_nla_action(struct nlattr **attrs, struct seg6_local_lwt *slwt)
+static int parse_nla_action(struct nlattr **attrs, struct seg6_local_lwt *slwt,
+			    struct netlink_ext_ack *extack)
 {
 	struct seg6_action_param *param;
 	struct seg6_action_desc *desc;
@@ -1749,14 +2078,14 @@ static int parse_nla_action(struct nlattr **attrs, struct seg6_local_lwt *slwt)
 
 			param = &seg6_action_params[i];
 
-			err = param->parse(attrs, slwt);
+			err = param->parse(attrs, slwt, extack);
 			if (err < 0)
 				goto parse_attrs_err;
 		}
 	}
 
 	/* parse the optional attributes, if any */
-	err = parse_nla_optional_attrs(attrs, slwt);
+	err = parse_nla_optional_attrs(attrs, slwt, extack);
 	if (err < 0)
 		goto parse_attrs_err;
 
@@ -1800,7 +2129,7 @@ static int seg6_local_build_state(struct net *net, struct nlattr *nla,
 	slwt = seg6_local_lwtunnel(newts);
 	slwt->action = nla_get_u32(tb[SEG6_LOCAL_ACTION]);
 
-	err = parse_nla_action(tb, slwt);
+	err = parse_nla_action(tb, slwt, extack);
 	if (err < 0)
 		goto out_free;
 
@@ -1904,6 +2233,9 @@ static int seg6_local_get_encap_size(struct lwtunnel_state *lwt)
 			  /* SEG6_LOCAL_CNT_ERRORS */
 			  nla_total_size_64bit(sizeof(__u64));
 
+	if (attrs & SEG6_F_ATTR(SEG6_LOCAL_FLAVORS))
+		nlsize += encap_size_flavors(slwt);
+
 	return nlsize;
 }
 
@@ -1959,6 +2291,15 @@ int __init seg6_local_init(void)
 	 */
 	BUILD_BUG_ON(SEG6_LOCAL_MAX + 1 > BITS_PER_TYPE(unsigned long));
 
+	/* If the default NEXT-C-SID Locator-Block/Node Function lengths (in
+	 * bits) have been changed with invalid values, kernel build stops
+	 * here.
+	 */
+	BUILD_BUG_ON(next_csid_chk_cntr_bits(SEG6_LOCAL_LCBLOCK_DBITS,
+					     SEG6_LOCAL_LCNODE_FN_DBITS));
+	BUILD_BUG_ON(next_csid_chk_lcblock_bits(SEG6_LOCAL_LCBLOCK_DBITS));
+	BUILD_BUG_ON(next_csid_chk_lcnode_fn_bits(SEG6_LOCAL_LCNODE_FN_DBITS));
+
 	return lwtunnel_encap_add_ops(&seg6_local_ops,
 				      LWTUNNEL_ENCAP_SEG6_LOCAL);
 }

tools/testing/selftests/net/Makefile

@@ -37,6 +37,7 @@ TEST_PROGS += srv6_end_dt4_l3vpn_test.sh
 TEST_PROGS += srv6_end_dt6_l3vpn_test.sh
 TEST_PROGS += srv6_hencap_red_l3vpn_test.sh
 TEST_PROGS += srv6_hl2encap_red_l2vpn_test.sh
+TEST_PROGS += srv6_end_next_csid_l3vpn_test.sh
 TEST_PROGS += vrf_strict_mode_test.sh
 TEST_PROGS += arp_ndisc_evict_nocarrier.sh
 TEST_PROGS += ndisc_unsolicited_na_test.sh

tools/testing/selftests/net/srv6_end_next_csid_l3vpn_test.sh

+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# author: Andrea Mayer <andrea.mayer@uniroma2.it>
+#
+# This script is designed for testing the support of NEXT-C-SID flavor for SRv6
+# End behavior.
+# A basic knowledge of SRv6 architecture [1] and of the compressed SID approach
+# [2] is assumed for the reader.
+#
+# The network topology used in the selftest is depicted hereafter, composed by
+# two hosts and four routers. Hosts hs-1 and hs-2 are connected through an
+# IPv4/IPv6 L3 VPN service, offered by routers rt-1, rt-2, rt-3 and rt-4 using
+# the NEXT-C-SID flavor. The key components for such VPNs are:
+#
+#    i) The SRv6 H.Encaps/H.Encaps.Red behaviors [1] apply SRv6 Policies on
+#       traffic received by connected hosts, initiating the VPN tunnel;
+#
+#   ii) The SRv6 End behavior [1] advances the active SID in the SID List
+#       carried by the SRH;
+#
+#  iii) The NEXT-C-SID mechanism [2] offers the possibility of encoding several
+#       SRv6 segments within a single 128-bit SID address, referred to as a
+#       Compressed SID (C-SID) container. In this way, the length of the SID
+#       List can be drastically reduced.
+#       The NEXT-C-SID is provided as a "flavor" of the SRv6 End behavior
+#       which advances the current C-SID (i.e. the Locator-Node Function defined
+#       in [2]) with the next one carried in the Argument, if available.
+#       When no more C-SIDs are available in the Argument, the SRv6 End behavior
+#       will apply the End function selecting the next SID in the SID List.
+#
+#   iv) The SRv6 End.DT46 behavior [1] is used for removing the SRv6 Policy and,
+#       thus, it terminates the VPN tunnel. Such a behavior is capable of
+#       handling, at the same time, both tunneled IPv4 and IPv6 traffic.
+#
+# [1] https://datatracker.ietf.org/doc/html/rfc8986
+# [2] https://datatracker.ietf.org/doc/html/draft-ietf-spring-srv6-srh-compression
+#
+#
+#               cafe::1                      cafe::2
+#              10.0.0.1                     10.0.0.2
+#             +--------+                   +--------+
+#             |        |                   |        |
+#             |  hs-1  |                   |  hs-2  |
+#             |        |                   |        |
+#             +---+----+                   +----+---+
+#    cafe::/64    |                             |      cafe::/64
+#  10.0.0.0/24    |                             |    10.0.0.0/24
+#             +---+----+                   +----+---+
+#             |        |  fcf0:0:1:2::/64  |        |
+#             |  rt-1  +-------------------+  rt-2  |
+#             |        |                   |        |
+#             +---+----+                   +----+---+
+#                 |      .               .      |
+#                 |  fcf0:0:1:3::/64   .        |
+#                 |          .       .          |
+#                 |            .   .            |
+# fcf0:0:1:4::/64 |              .              | fcf0:0:2:3::/64
+#                 |            .   .            |
+#                 |          .       .          |
+#                 |  fcf0:0:2:4::/64   .        |
+#                 |      .               .      |
+#             +---+----+                   +----+---+
+#             |        |                   |        |
+#             |  rt-4  +-------------------+  rt-3  |
+#             |        |  fcf0:0:3:4::/64  |        |
+#             +---+----+                   +----+---+
+#
+# Every fcf0:0:x:y::/64 network interconnects the SRv6 routers rt-x with rt-y in
+# the selftest network.
+#
+# Local SID/C-SID table
+# =====================
+#
+# Each SRv6 router is configured with a Local SID/C-SID table in which
+# SIDs/C-SIDs are stored. Considering an SRv6 router rt-x, SIDs/C-SIDs are
+# configured in the Local SID/C-SIDs table as follows:
+#
+#   Local SID/C-SID table for SRv6 router rt-x
+#   +-----------------------------------------------------------+
+#   |fcff:x::d46 is associated with the non-compressed SRv6     |
+#   |   End.DT46 behavior                                       |
+#   +-----------------------------------------------------------+
+#   |fcbb:0:0x00::/48 is associated with the NEXT-C-SID flavor  |
+#   |   of SRv6 End behavior                                    |
+#   +-----------------------------------------------------------+
+#   |fcbb:0:0x00:d46::/64 is associated with the SRv6 End.DT46  |
+#   |   behavior when NEXT-C-SID compression is turned on       |
+#   +-----------------------------------------------------------+
+#
+# The fcff::/16 prefix is reserved for implementing SRv6 services with regular
+# (non compressed) SIDs. Reachability of SIDs is ensured by proper configuration
+# of the IPv6 routing tables in the routers.
+# Similarly, the fcbb:0::/32 prefix is reserved for implementing SRv6 VPN
+# services leveraging the NEXT-C-SID compression mechanism. Indeed, the
+# fcbb:0::/32 is used for encoding the Locator-Block while the Locator-Node
+# Function is encoded with 16 bits.
+#
+# Incoming traffic classification and application of SRv6 Policies
+# ================================================================
+#
+# An SRv6 ingress router applies different SRv6 Policies to the traffic received
+# from a connected host, considering the IPv4 or IPv6 destination address.
+# SRv6 policy enforcement consists of encapsulating the received traffic into a
+# new IPv6 packet with a given SID List contained in the SRH.
+# When the SID List contains only one SID, the SRH could be omitted completely
+# and that SID is stored directly in the IPv6 Destination Address (DA) (this is
+# called "reduced" encapsulation).
+#
+# Test cases for NEXT-C-SID
+# =========================
+#
+# We consider two test cases for NEXT-C-SID: i) single SID and ii) double SID.
+#
+# In the single SID test case we have a number of segments that are all
+# contained in a single Compressed SID (C-SID) container. Therefore the
+# resulting SID List has only one SID. Using the reduced encapsulation format
+# this will result in a packet with no SRH.
+#
+# In the double SID test case we have one segment carried in a Compressed SID
+# (C-SID) container, followed by a regular (non compressed) SID. The resulting
+# SID List has two segments and it is possible to test the advance to the next
+# SID when all the C-SIDs in a C-SID container have been processed. Using the
+# reduced encapsulation format this will result in a packet with an SRH
+# containing 1 segment.
+#
+# For the single SID test case, we use the IPv4 addresses of hs-1 and hs-2, for
+# the double SID test case, we use their IPv6 addresses. This is only done to
+# simplify the test setup and avoid adding other hosts or multiple addresses on
+# the same interface of a host.
+#
+# Traffic from hs-1 to hs-2
+# -------------------------
+#
+# Packets generated from hs-1 and directed towards hs-2 are handled by rt-1
+# which applies the SRv6 Policies as follows:
+#
+#   i) IPv6 DA=cafe::2, H.Encaps.Red with SID List=fcbb:0:0400:0300:0200:d46::
+#  ii) IPv4 DA=10.0.0.2, H.Encaps.Red with SID List=fcbb:0:0300::,fcff:2::d46
+#
+# ### i) single SID
+#
+# The router rt-1 is configured to enforce the given Policy through the SRv6
+# H.Encaps.Red behavior which avoids the presence of the SRH at all, since it
+# pushes the single SID directly in the IPv6 DA. Such a SID encodes a whole
+# C-SID container carrying several C-SIDs (e.g. 0400, 0300, etc).
+#
+# As the packet reaches the router rt-4, the enabled NEXT-C-SID SRv6 End
+# behavior (associated with fcbb:0:0400::/48) is triggered. This behavior
+# analyzes the IPv6 DA and checks whether the Argument of the C-SID container
+# is zero or not. In this case, the Argument is *NOT* zero and the IPv6 DA is
+# updated as follows:
+#
+# +---------------------------------------------------------------+
+# | Before applying the rt-4 enabled NEXT-C-SID SRv6 End behavior |
+# +---------------------------------------------------------------+
+# |                            +---------- Argument               |
+# |                     vvvvvvvvvvvvvvvv                          |
+# | IPv6 DA fcbb:0:0400:0300:0200:d46::                           |
+# |                ^^^^    <-- shifting                           |
+# |                  |                                            |
+# |          Locator-Node Function                                |
+# +---------------------------------------------------------------+
+# | After applying the rt-4 enabled NEXT-C-SID SRv6 End behavior  |
+# +---------------------------------------------------------------+
+# |                          +---------- Argument                 |
+# |                    vvvvvvvvvvvv                               |
+# | IPv6 DA fcbb:0:0300:0200:d46::                                |
+# |                ^^^^                                           |
+# |                  |                                            |
+# |          Locator-Node Function                                |
+# +---------------------------------------------------------------+
+#
+# After having applied the enabled NEXT-C-SID SRv6 End behavior, the packet is
+# sent to the next node, i.e. rt-3.
+#
+# The enabled NEXT-C-SID SRv6 End behavior on rt-3 is executed as the packet is
+# received. This behavior processes the packet and updates the IPv6 DA with
+# fcbb:0:0200:d46::, since the Argument is *NOT* zero. Then, the packet is sent
+# to the router rt-2.
+#
+# The router rt-2 is configured for decapsulating the inner IPv6 packet and,
+# for this reason, it applies the SRv6 End.DT46 behavior on the received
+# packet. It is worth noting that the SRv6 End.DT46 behavior does not require
+# the presence of the SRH: it is fully capable to operate properly on
+# IPv4/IPv6-in-IPv6 encapsulations.
+# At the end of the decap operation, the packet is sent to the
+# host hs-2.
+#
+# ### ii) double SID
+#
+# The router rt-1 is configured to enforce the given Policy through the SRv6
+# H.Encaps.Red. As a result, the first SID fcbb:0:0300:: is stored into the
+# IPv6 DA, while the SRH pushed into the packet is made of only one SID, i.e.
+# fcff:2::d46. Hence, the packet sent by hs-1 to hs-2 is encapsulated in an
+# outer IPv6 header plus the SRH.
+#
+# As the packet reaches the node rt-3, the router applies the enabled NEXT-C-SID
+# SRv6 End behavior.
+#
+# +---------------------------------------------------------------+
+# | Before applying the rt-3 enabled NEXT-C-SID SRv6 End behavior |
+# +---------------------------------------------------------------+
+# |                            +---------- Argument               |
+# |                      vvvv (Argument is all filled with zeros) |
+# | IPv6 DA fcbb:0:0300::                                         |
+# |                ^^^^                                           |
+# |                  |                                            |
+# |          Locator-Node Function                                |
+# +---------------------------------------------------------------+
+# | After applying the rt-3 enabled NEXT-C-SID SRv6 End behavior  |
+# +---------------------------------------------------------------+
+# |                                                               |
+# | IPv6 DA fcff:2::d46                                           |
+# |         ^^^^^^^^^^^                                           |
+# |              |                                                |
+# |        SID copied from the SID List contained in the SRH      |
+# +---------------------------------------------------------------+
+#
+# Since the Argument of the C-SID container is zero, the behavior can not
+# update the Locator-Node function with the next C-SID carried in the Argument
+# itself. Thus, the enabled NEXT-C-SID SRv6 End behavior operates as the
+# traditional End behavior: it updates the IPv6 DA by copying the next
+# available SID in the SID List carried by the SRH. After that, the packet is
+# sent to the node rt-2.
+#
+# Once the packet is received by rt-2, the router decapsulates the inner IPv6
+# packet using the SRv6 End.DT46 behavior (associated with the SID fcff:2::d46)
+# and sends it to the host hs-2.
+#
+# Traffic from hs-2 to hs-1
+# -------------------------
+#
+# Packets generated from hs-2 and directed towards hs-1 are handled by rt-2
+# which applies the SRv6 Policies as follows:
+#
+#   i) IPv6 DA=cafe::1, SID List=fcbb:0:0300:0400:0100:d46::
+#  ii) IPv4 DA=10.0.0.1, SID List=fcbb:0:0300::,fcff:1::d46
+#
+# For simplicity, such SRv6 Policies were chosen so that, in both use cases (i)
+# and (ii), the network paths crossed by traffic from hs-2 to hs-1 are the same
+# as those taken by traffic from hs-1 to hs-2.
+# In this way, traffic from hs-2 to hs-1 is processed similarly to traffic from
+# hs-1 to hs-2. So, the traffic processing scheme turns out to be the same as
+# that adopted in the use cases already examined (of course, it is necessary to
+# consider the different SIDs/C-SIDs).
+
+# Kselftest framework requirement - SKIP code is 4.
+readonly ksft_skip=4
+
+readonly RDMSUFF="$(mktemp -u XXXXXXXX)"
+readonly DUMMY_DEVNAME="dum0"
+readonly VRF_TID=100
+readonly VRF_DEVNAME="vrf-${VRF_TID}"
+readonly RT2HS_DEVNAME="veth-t${VRF_TID}"
+readonly LOCALSID_TABLE_ID=90
+readonly IPv6_RT_NETWORK=fcf0:0
+readonly IPv6_HS_NETWORK=cafe
+readonly IPv4_HS_NETWORK=10.0.0
+readonly VPN_LOCATOR_SERVICE=fcff
+readonly DT46_FUNC=0d46
+readonly HEADEND_ENCAP="encap.red"
+
+# do not add ':' as separator
+readonly LCBLOCK_ADDR=fcbb0000
+readonly LCBLOCK_BLEN=32
+# do not add ':' as separator
+readonly LCNODEFUNC_FMT="0%d00"
+readonly LCNODEFUNC_BLEN=16
+
+readonly LCBLOCK_NODEFUNC_BLEN=$((LCBLOCK_BLEN + LCNODEFUNC_BLEN))
+
+readonly CSID_CNTR_PREFIX="dead:beaf::/32"
+# ID of the router used for testing the C-SID container cfgs
+readonly CSID_CNTR_RT_ID_TEST=1
+# Routing table used for testing the C-SID container cfgs
+readonly CSID_CNTR_RT_TABLE=91
+
+# C-SID container configurations to be tested
+#
+# An entry of the array is defined as "a,b,c" where:
+# - 'a' and 'b' elements represent respectively the Locator-Block length
+#   (lblen) in bits and the Locator-Node Function length (nflen) in bits.
+#   'a' and 'b' can be set to default values using the placeholder "d" which
+#   indicates the default kernel values (32 for lblen and 16 for nflen);
+#   otherwise, any numeric value is accepted;
+# - 'c' indicates whether the C-SID configuration provided by the values 'a'
+#   and 'b' should be considered valid ("y") or invalid ("n").
+declare -ra CSID_CONTAINER_CFGS=(
+	"d,d,y"
+	"d,16,y"
+	"16,d,y"
+	"16,32,y"
+	"32,16,y"
+	"48,8,y"
+	"8,48,y"
+	"d,0,n"
+	"0,d,n"
+	"32,0,n"
+	"0,32,n"
+	"17,d,n"
+	"d,17,n"
+	"120,16,n"
+	"16,120,n"
+	"0,128,n"
+	"128,0,n"
+	"130,0,n"
+	"0,130,n"
+	"0,0,n"
+)
+
+PING_TIMEOUT_SEC=4
+PAUSE_ON_FAIL=${PAUSE_ON_FAIL:=no}
+
+# IDs of routers and hosts are initialized during the setup of the testing
+# network
+ROUTERS=''
+HOSTS=''
+
+SETUP_ERR=1
+
+ret=${ksft_skip}
+nsuccess=0
+nfail=0
+
+log_test()
+{
+	local rc="$1"
+	local expected="$2"
+	local msg="$3"
+
+	if [ "${rc}" -eq "${expected}" ]; then
+		nsuccess=$((nsuccess+1))
+		printf "\n    TEST: %-60s  [ OK ]\n" "${msg}"
+	else
+		ret=1
+		nfail=$((nfail+1))
+		printf "\n    TEST: %-60s  [FAIL]\n" "${msg}"
+		if [ "${PAUSE_ON_FAIL}" = "yes" ]; then
+			echo
+			echo "hit enter to continue, 'q' to quit"
+			read a
+			[ "$a" = "q" ] && exit 1
+		fi
+	fi
+}
+
+print_log_test_results()
+{
+	printf "\nTests passed: %3d\n" "${nsuccess}"
+	printf "Tests failed: %3d\n"   "${nfail}"
+
+	# when a test fails, the value of 'ret' is set to 1 (error code).
+	# Conversely, when all tests are passed successfully, the 'ret' value
+	# is set to 0 (success code).
+	if [ "${ret}" -ne 1 ]; then
+		ret=0
+	fi
+}
+
+log_section()
+{
+	echo
+	echo "################################################################################"
+	echo "TEST SECTION: $*"
+	echo "################################################################################"
+}
+
+test_command_or_ksft_skip()
+{
+	local cmd="$1"
+
+	if [ ! -x "$(command -v "${cmd}")" ]; then
+		echo "SKIP: Could not run test without \"${cmd}\" tool";
+		exit "${ksft_skip}"
+	fi
+}
+
+get_nodename()
+{
+	local name="$1"
+
+	echo "${name}-${RDMSUFF}"
+}
+
+get_rtname()
+{
+	local rtid="$1"
+
+	get_nodename "rt-${rtid}"
+}
+
+get_hsname()
+{
+	local hsid="$1"
+
+	get_nodename "hs-${hsid}"
+}
+
+__create_namespace()
+{
+	local name="$1"
+
+	ip netns add "${name}"
+}
+
+create_router()
+{
+	local rtid="$1"
+	local nsname
+
+	nsname="$(get_rtname "${rtid}")"
+
+	__create_namespace "${nsname}"
+}
+
+create_host()
+{
+	local hsid="$1"
+	local nsname
+
+	nsname="$(get_hsname "${hsid}")"
+
+	__create_namespace "${nsname}"
+}
+
+cleanup()
+{
+	local nsname
+	local i
+
+	# destroy routers
+	for i in ${ROUTERS}; do
+		nsname="$(get_rtname "${i}")"
+
+		ip netns del "${nsname}" &>/dev/null || true
+	done
+
+	# destroy hosts
+	for i in ${HOSTS}; do
+		nsname="$(get_hsname "${i}")"
+
+		ip netns del "${nsname}" &>/dev/null || true
+	done
+
+	# check whether the setup phase was completed successfully or not. In
+	# case of an error during the setup phase of the testing environment,
+	# the selftest is considered as "skipped".
+	if [ "${SETUP_ERR}" -ne 0 ]; then
+		echo "SKIP: Setting up the testing environment failed"
+		exit "${ksft_skip}"
+	fi
+
+	exit "${ret}"
+}
+
+add_link_rt_pairs()
+{
+	local rt="$1"
+	local rt_neighs="$2"
+	local neigh
+	local nsname
+	local neigh_nsname
+
+	nsname="$(get_rtname "${rt}")"
+
+	for neigh in ${rt_neighs}; do
+		neigh_nsname="$(get_rtname "${neigh}")"
+
+		ip link add "veth-rt-${rt}-${neigh}" netns "${nsname}" \
+			type veth peer name "veth-rt-${neigh}-${rt}" \
+			netns "${neigh_nsname}"
+	done
+}
+
+get_network_prefix()
+{
+	local rt="$1"
+	local neigh="$2"
+	local p="${rt}"
+	local q="${neigh}"
+
+	if [ "${p}" -gt "${q}" ]; then
+		p="${q}"; q="${rt}"
+	fi
+
+	echo "${IPv6_RT_NETWORK}:${p}:${q}"
+}
+
+# Setup the basic networking for the routers
+setup_rt_networking()
+{
+	local rt="$1"
+	local rt_neighs="$2"
+	local nsname
+	local net_prefix
+	local devname
+	local neigh
+
+	nsname="$(get_rtname "${rt}")"
+
+	for neigh in ${rt_neighs}; do
+		devname="veth-rt-${rt}-${neigh}"
+
+		net_prefix="$(get_network_prefix "${rt}" "${neigh}")"
+
+		ip -netns "${nsname}" addr \
+			add "${net_prefix}::${rt}/64" dev "${devname}" nodad
+
+		ip -netns "${nsname}" link set "${devname}" up
+	done
+
+        ip -netns "${nsname}" link add "${DUMMY_DEVNAME}" type dummy
+
+        ip -netns "${nsname}" link set "${DUMMY_DEVNAME}" up
+	ip -netns "${nsname}" link set lo up
+
+	ip netns exec "${nsname}" sysctl -wq net.ipv6.conf.all.accept_dad=0
+	ip netns exec "${nsname}" sysctl -wq net.ipv6.conf.default.accept_dad=0
+	ip netns exec "${nsname}" sysctl -wq net.ipv6.conf.all.forwarding=1
+
+	ip netns exec "${nsname}" sysctl -wq net.ipv4.conf.all.rp_filter=0
+	ip netns exec "${nsname}" sysctl -wq net.ipv4.conf.default.rp_filter=0
+	ip netns exec "${nsname}" sysctl -wq net.ipv4.ip_forward=1
+}
+
+# build an ipv6 prefix/address based on the input string
+# Note that the input string does not contain ':' and '::' which are considered
+# to be implicit.
+# e.g.:
+#  - input:  fbcc00000400300
+#  - output: fbcc:0000:0400:0300:0000:0000:0000:0000
+#                                ^^^^^^^^^^^^^^^^^^^
+#                              fill the address with 0s
+build_ipv6_addr()
+{
+	local addr="$1"
+	local out=""
+	local strlen="${#addr}"
+	local padn
+	local i
+
+	# add ":" every 4 digits (16 bits)
+	for (( i = 0; i < strlen; i++ )); do
+		if (( i > 0 && i < 32 && (i % 4) == 0 )); then
+			out="${out}:"
+		fi
+
+		out="${out}${addr:$i:1}"
+	done
+
+	# fill the remaining bits of the address with 0s
+	padn=$((32 - strlen))
+	for (( i = padn; i > 0; i-- )); do
+		if (( i > 0 && i < 32 && (i % 4) == 0 )); then
+			out="${out}:"
+		fi
+
+		out="${out}0"
+	done
+
+	printf "${out}"
+}
+
+build_csid()
+{
+	local nodeid="$1"
+
+	printf "${LCNODEFUNC_FMT}" "${nodeid}"
+}
+
+build_lcnode_func_prefix()
+{
+	local nodeid="$1"
+	local lcnodefunc
+	local prefix
+	local out
+
+	lcnodefunc="$(build_csid "${nodeid}")"
+	prefix="$(build_ipv6_addr "${LCBLOCK_ADDR}${lcnodefunc}")"
+
+	out="${prefix}/${LCBLOCK_NODEFUNC_BLEN}"
+
+	echo "${out}"
+}
+
+# Setup local SIDs for an SRv6 router
+setup_rt_local_sids()
+{
+	local rt="$1"
+	local rt_neighs="$2"
+	local net_prefix
+	local devname
+	local nsname
+	local neigh
+	local lcnode_func_prefix
+	local lcblock_prefix
+
+	nsname="$(get_rtname "${rt}")"
+
+	for neigh in ${rt_neighs}; do
+		devname="veth-rt-${rt}-${neigh}"
+
+		net_prefix="$(get_network_prefix "${rt}" "${neigh}")"
+
+		# set underlay network routes for SIDs reachability
+		ip -netns "${nsname}" -6 route \
+			add "${VPN_LOCATOR_SERVICE}:${neigh}::/32" \
+			table "${LOCALSID_TABLE_ID}" \
+			via "${net_prefix}::${neigh}" dev "${devname}"
+
+		# set the underlay network for C-SIDs reachability
+		lcnode_func_prefix="$(build_lcnode_func_prefix "${neigh}")"
+
+		ip -netns "${nsname}" -6 route \
+			add "${lcnode_func_prefix}" \
+			table "${LOCALSID_TABLE_ID}" \
+			via "${net_prefix}::${neigh}" dev "${devname}"
+	done
+
+	lcnode_func_prefix="$(build_lcnode_func_prefix "${rt}")"
+
+	# enabled NEXT-C-SID SRv6 End behavior (note that "dev" is the dummy
+	# dum0 device chosen for the sake of simplicity).
+	ip -netns "${nsname}" -6 route \
+		add "${lcnode_func_prefix}" \
+		table "${LOCALSID_TABLE_ID}" \
+		encap seg6local action End flavors next-csid \
+		lblen "${LCBLOCK_BLEN}" nflen "${LCNODEFUNC_BLEN}" \
+		dev "${DUMMY_DEVNAME}"
+
+	# all SIDs for VPNs start with a common locator. Routes and SRv6
+	# Endpoint behavior instaces are grouped together in the 'localsid'
+	# table.
+	ip -netns "${nsname}" -6 rule \
+		add to "${VPN_LOCATOR_SERVICE}::/16" \
+		lookup "${LOCALSID_TABLE_ID}" prio 999
+
+	# common locator block for NEXT-C-SIDS compression mechanism.
+	lcblock_prefix="$(build_ipv6_addr "${LCBLOCK_ADDR}")"
+	ip -netns "${nsname}" -6 rule \
+		add to "${lcblock_prefix}/${LCBLOCK_BLEN}" \
+		lookup "${LOCALSID_TABLE_ID}" prio 999
+}
+
+# build and install the SRv6 policy into the ingress SRv6 router as well as the
+# decap SID in the egress one.
+# args:
+#  $1 - src host (evaluate automatically the ingress router)
+#  $2 - dst host (evaluate automatically the egress router)
+#  $3 - SRv6 routers configured for steering traffic (End behaviors)
+#  $4 - single SID or double SID
+#  $5 - traffic type (IPv6 or IPv4)
+__setup_l3vpn()
+{
+	local src="$1"
+	local dst="$2"
+	local end_rts="$3"
+	local mode="$4"
+	local traffic="$5"
+	local nsname
+	local policy
+	local container
+	local decapsid
+	local lcnfunc
+	local dt
+	local n
+	local rtsrc_nsname
+	local rtdst_nsname
+
+	rtsrc_nsname="$(get_rtname "${src}")"
+	rtdst_nsname="$(get_rtname "${dst}")"
+
+	container="${LCBLOCK_ADDR}"
+
+	# build first SID (C-SID container)
+	for n in ${end_rts}; do
+		lcnfunc="$(build_csid "${n}")"
+
+		container="${container}${lcnfunc}"
+	done
+
+	if [ "${mode}" -eq 1 ]; then
+		# single SID policy
+		dt="$(build_csid "${dst}")${DT46_FUNC}"
+		container="${container}${dt}"
+		# build the full ipv6 address for the container
+		policy="$(build_ipv6_addr "${container}")"
+
+		# build the decap SID used in the decap node
+		container="${LCBLOCK_ADDR}${dt}"
+		decapsid="$(build_ipv6_addr "${container}")"
+	else
+		# double SID policy
+		decapsid="${VPN_LOCATOR_SERVICE}:${dst}::${DT46_FUNC}"
+
+		policy="$(build_ipv6_addr "${container}"),${decapsid}"
+	fi
+
+	# apply encap policy
+	if [ "${traffic}" -eq 6 ]; then
+		ip -netns "${rtsrc_nsname}" -6 route \
+			add "${IPv6_HS_NETWORK}::${dst}" vrf "${VRF_DEVNAME}" \
+			encap seg6 mode "${HEADEND_ENCAP}" segs "${policy}" \
+			dev "${VRF_DEVNAME}"
+
+		ip -netns "${rtsrc_nsname}" -6 neigh \
+			add proxy "${IPv6_HS_NETWORK}::${dst}" \
+			dev "${RT2HS_DEVNAME}"
+	else
+		# "dev" must be different from the one where the packet is
+		# received, otherwise the proxy arp does not work.
+		ip -netns "${rtsrc_nsname}" -4 route \
+			add "${IPv4_HS_NETWORK}.${dst}" vrf "${VRF_DEVNAME}" \
+			encap seg6 mode "${HEADEND_ENCAP}" segs "${policy}" \
+			dev "${VRF_DEVNAME}"
+	fi
+
+	# apply decap
+	# Local End.DT46 behavior (decap)
+	ip -netns "${rtdst_nsname}" -6 route \
+		add "${decapsid}" \
+		table "${LOCALSID_TABLE_ID}" \
+		encap seg6local action End.DT46 vrftable "${VRF_TID}" \
+		dev "${VRF_DEVNAME}"
+}
+
+# see __setup_l3vpn()
+setup_ipv4_vpn_2sids()
+{
+	__setup_l3vpn "$1" "$2" "$3" 2 4
+}
+
+# see __setup_l3vpn()
+setup_ipv6_vpn_1sid()
+{
+	__setup_l3vpn "$1" "$2" "$3" 1 6
+}
+
+setup_hs()
+{
+	local hs="$1"
+	local rt="$2"
+	local hsname
+	local rtname
+
+	hsname="$(get_hsname "${hs}")"
+	rtname="$(get_rtname "${rt}")"
+
+	ip netns exec "${hsname}" sysctl -wq net.ipv6.conf.all.accept_dad=0
+	ip netns exec "${hsname}" sysctl -wq net.ipv6.conf.default.accept_dad=0
+
+	ip -netns "${hsname}" link add veth0 type veth \
+		peer name "${RT2HS_DEVNAME}" netns "${rtname}"
+
+	ip -netns "${hsname}" addr \
+		add "${IPv6_HS_NETWORK}::${hs}/64" dev veth0 nodad
+	ip -netns "${hsname}" addr add "${IPv4_HS_NETWORK}.${hs}/24" dev veth0
+
+	ip -netns "${hsname}" link set veth0 up
+	ip -netns "${hsname}" link set lo up
+
+	# configure the VRF on the router which is directly connected to the
+	# source host.
+	ip -netns "${rtname}" link \
+		add "${VRF_DEVNAME}" type vrf table "${VRF_TID}"
+	ip -netns "${rtname}" link set "${VRF_DEVNAME}" up
+
+	# enslave the veth interface connecting the router with the host to the
+	# VRF in the access router
+	ip -netns "${rtname}" link \
+		set "${RT2HS_DEVNAME}" master "${VRF_DEVNAME}"
+
+	# set default routes to unreachable for both ipv6 and ipv4
+	ip -netns "${rtname}" -6 route \
+		add unreachable default metric 4278198272 \
+		vrf "${VRF_DEVNAME}"
+	ip -netns "${rtname}" -4 route \
+		add unreachable default metric 4278198272 \
+		vrf "${VRF_DEVNAME}"
+
+	ip -netns "${rtname}" addr \
+		add "${IPv6_HS_NETWORK}::254/64" dev "${RT2HS_DEVNAME}" nodad
+	ip -netns "${rtname}" addr \
+		add "${IPv4_HS_NETWORK}.254/24" dev "${RT2HS_DEVNAME}"
+
+	ip -netns "${rtname}" link set "${RT2HS_DEVNAME}" up
+
+	ip netns exec "${rtname}" \
+		sysctl -wq net.ipv6.conf."${RT2HS_DEVNAME}".proxy_ndp=1
+	ip netns exec "${rtname}" \
+		sysctl -wq net.ipv4.conf."${RT2HS_DEVNAME}".proxy_arp=1
+
+	# disable the rp_filter otherwise the kernel gets confused about how
+	# to route decap ipv4 packets.
+	ip netns exec "${rtname}" \
+		sysctl -wq net.ipv4.conf."${RT2HS_DEVNAME}".rp_filter=0
+
+	ip netns exec "${rtname}" sh -c "echo 1 > /proc/sys/net/vrf/strict_mode"
+}
+
+setup()
+{
+	local i
+
+	# create routers
+	ROUTERS="1 2 3 4"; readonly ROUTERS
+	for i in ${ROUTERS}; do
+		create_router "${i}"
+	done
+
+	# create hosts
+	HOSTS="1 2"; readonly HOSTS
+	for i in ${HOSTS}; do
+		create_host "${i}"
+	done
+
+	# set up the links for connecting routers
+	add_link_rt_pairs 1 "2 3 4"
+	add_link_rt_pairs 2 "3 4"
+	add_link_rt_pairs 3 "4"
+
+	# set up the basic connectivity of routers and routes required for
+	# reachability of SIDs.
+	setup_rt_networking 1 "2 3 4"
+	setup_rt_networking 2 "1 3 4"
+	setup_rt_networking 3 "1 2 4"
+	setup_rt_networking 4 "1 2 3"
+
+	# set up the hosts connected to routers
+	setup_hs 1 1
+	setup_hs 2 2
+
+	# set up default SRv6 Endpoints (i.e. SRv6 End and SRv6 End.DT46)
+	setup_rt_local_sids 1 "2 3 4"
+	setup_rt_local_sids 2 "1 3 4"
+	setup_rt_local_sids 3 "1 2 4"
+	setup_rt_local_sids 4 "1 2 3"
+
+	# set up SRv6 Policies
+
+	# create an IPv6 VPN between hosts hs-1 and hs-2.
+	#
+	# Direction hs-1 -> hs-2
+	# - rt-1 encap (H.Encaps.Red)
+	# - rt-4 SRv6 End behavior (NEXT-C-SID flavor)
+	# - rt-3 SRv6 End behavior (NEXT-C-SID flavor)
+	# - rt-2 SRv6 End.DT46 behavior
+	setup_ipv6_vpn_1sid 1 2 "4 3"
+
+	# Direction hs2 -> hs-1
+	# - rt-2 encap (H.Encaps.Red)
+	# - rt-3 SRv6 End behavior (NEXT-C-SID flavor)
+	# - rt-4 SRv6 End behavior (NEXT-C-SID flavor)
+	# - rt-1 SRv6 End.DT46 behavior
+	setup_ipv6_vpn_1sid 2 1 "3 4"
+
+	# create an IPv4 VPN between hosts hs-1 and hs-2
+	#
+	# Direction hs-1 -> hs-2
+	# - rt-1 encap (H.Encaps.Red)
+	# - rt-3 SRv6 End behavior (NEXT-C-SID flavor)
+	# - rt-2 SRv6 End.DT46 behavior
+	setup_ipv4_vpn_2sids 1 2 "3"
+
+	# Direction hs-2 -> hs-1
+	# - rt-2 encap (H.Encaps.Red)
+	# - rt-3 SRv6 End behavior (NEXT-C-SID flavor)
+	# - rt-1 SRv6 End.DT46 behavior
+	setup_ipv4_vpn_2sids 2 1 "3"
+
+	# testing environment was set up successfully
+	SETUP_ERR=0
+}
+
+check_rt_connectivity()
+{
+	local rtsrc="$1"
+	local rtdst="$2"
+	local prefix
+	local rtsrc_nsname
+
+	rtsrc_nsname="$(get_rtname "${rtsrc}")"
+
+	prefix="$(get_network_prefix "${rtsrc}" "${rtdst}")"
+
+	ip netns exec "${rtsrc_nsname}" ping -c 1 -W "${PING_TIMEOUT_SEC}" \
+		"${prefix}::${rtdst}" >/dev/null 2>&1
+}
+
+check_and_log_rt_connectivity()
+{
+	local rtsrc="$1"
+	local rtdst="$2"
+
+	check_rt_connectivity "${rtsrc}" "${rtdst}"
+	log_test $? 0 "Routers connectivity: rt-${rtsrc} -> rt-${rtdst}"
+}
+
+check_hs_ipv6_connectivity()
+{
+	local hssrc="$1"
+	local hsdst="$2"
+	local hssrc_nsname
+
+	hssrc_nsname="$(get_hsname "${hssrc}")"
+
+	ip netns exec "${hssrc_nsname}" ping -c 1 -W "${PING_TIMEOUT_SEC}" \
+		"${IPv6_HS_NETWORK}::${hsdst}" >/dev/null 2>&1
+}
+
+check_hs_ipv4_connectivity()
+{
+	local hssrc="$1"
+	local hsdst="$2"
+	local hssrc_nsname
+
+	hssrc_nsname="$(get_hsname "${hssrc}")"
+
+	ip netns exec "${hssrc_nsname}" ping -c 1 -W "${PING_TIMEOUT_SEC}" \
+		"${IPv4_HS_NETWORK}.${hsdst}" >/dev/null 2>&1
+}
+
+check_and_log_hs2gw_connectivity()
+{
+	local hssrc="$1"
+
+	check_hs_ipv6_connectivity "${hssrc}" 254
+	log_test $? 0 "IPv6 Hosts connectivity: hs-${hssrc} -> gw"
+
+	check_hs_ipv4_connectivity "${hssrc}" 254
+	log_test $? 0 "IPv4 Hosts connectivity: hs-${hssrc} -> gw"
+}
+
+check_and_log_hs_ipv6_connectivity()
+{
+	local hssrc="$1"
+	local hsdst="$2"
+
+	check_hs_ipv6_connectivity "${hssrc}" "${hsdst}"
+	log_test $? 0 "IPv6 Hosts connectivity: hs-${hssrc} -> hs-${hsdst}"
+}
+
+check_and_log_hs_ipv4_connectivity()
+{
+	local hssrc="$1"
+	local hsdst="$2"
+
+	check_hs_ipv4_connectivity "${hssrc}" "${hsdst}"
+	log_test $? 0 "IPv4 Hosts connectivity: hs-${hssrc} -> hs-${hsdst}"
+}
+
+router_tests()
+{
+	local i
+	local j
+
+	log_section "IPv6 routers connectivity test"
+
+	for i in ${ROUTERS}; do
+		for j in ${ROUTERS}; do
+			if [ "${i}" -eq "${j}" ]; then
+				continue
+			fi
+
+			check_and_log_rt_connectivity "${i}" "${j}"
+		done
+	done
+}
+
+host2gateway_tests()
+{
+	local hs
+
+	log_section "IPv4/IPv6 connectivity test among hosts and gateways"
+
+	for hs in ${HOSTS}; do
+		check_and_log_hs2gw_connectivity "${hs}"
+	done
+}
+
+host_vpn_tests()
+{
+	log_section "SRv6 VPN connectivity test hosts (h1 <-> h2, IPv6)"
+
+	check_and_log_hs_ipv6_connectivity 1 2
+	check_and_log_hs_ipv6_connectivity 2 1
+
+	log_section "SRv6 VPN connectivity test hosts (h1 <-> h2, IPv4)"
+
+	check_and_log_hs_ipv4_connectivity 1 2
+	check_and_log_hs_ipv4_connectivity 2 1
+}
+
+__nextcsid_end_behavior_test()
+{
+	local nsname="$1"
+	local cmd="$2"
+	local blen="$3"
+	local flen="$4"
+	local layout=""
+
+	if [ "${blen}" != "d" ]; then
+		layout="${layout} lblen ${blen}"
+	fi
+
+	if [ "${flen}" != "d" ]; then
+		layout="${layout} nflen ${flen}"
+	fi
+
+	ip -netns "${nsname}" -6 route \
+		"${cmd}" "${CSID_CNTR_PREFIX}" \
+		table "${CSID_CNTR_RT_TABLE}" \
+		encap seg6local action End flavors next-csid ${layout} \
+		dev "${DUMMY_DEVNAME}" &>/dev/null
+
+	return "$?"
+}
+
+rt_x_nextcsid_end_behavior_test()
+{
+	local rt="$1"
+	local blen="$2"
+	local flen="$3"
+	local nsname
+	local ret
+
+	nsname="$(get_rtname "${rt}")"
+
+	__nextcsid_end_behavior_test "${nsname}" "add" "${blen}" "${flen}"
+	ret="$?"
+	__nextcsid_end_behavior_test "${nsname}" "del" "${blen}" "${flen}"
+
+	return "${ret}"
+}
+
+__parse_csid_container_cfg()
+{
+	local cfg="$1"
+	local index="$2"
+	local out
+
+	echo "${cfg}" | cut -d',' -f"${index}"
+}
+
+csid_container_cfg_tests()
+{
+	local valid
+	local blen
+	local flen
+	local cfg
+	local ret
+
+	log_section "C-SID Container config tests (legend: d='kernel default')"
+
+	for cfg in "${CSID_CONTAINER_CFGS[@]}"; do
+		blen="$(__parse_csid_container_cfg "${cfg}" 1)"
+		flen="$(__parse_csid_container_cfg "${cfg}" 2)"
+		valid="$(__parse_csid_container_cfg "${cfg}" 3)"
+
+		rt_x_nextcsid_end_behavior_test \
+			"${CSID_CNTR_RT_ID_TEST}" \
+			"${blen}" \
+			"${flen}"
+		ret="$?"
+
+		if [ "${valid}" == "y" ]; then
+			log_test "${ret}" 0 \
+				"Accept valid C-SID container cfg (lblen=${blen}, nflen=${flen})"
+		else
+			log_test "${ret}" 2 \
+				"Reject invalid C-SID container cfg (lblen=${blen}, nflen=${flen})"
+		fi
+	done
+}
+
+test_iproute2_supp_or_ksft_skip()
+{
+	if ! ip route help 2>&1 | grep -qo "next-csid"; then
+		echo "SKIP: Missing SRv6 NEXT-C-SID flavor support in iproute2"
+		exit "${ksft_skip}"
+	fi
+}
+
+test_dummy_dev_or_ksft_skip()
+{
+        local test_netns
+
+        test_netns="dummy-$(mktemp -u XXXXXXXX)"
+
+        if ! ip netns add "${test_netns}"; then
+                echo "SKIP: Cannot set up netns for testing dummy dev support"
+                exit "${ksft_skip}"
+        fi
+
+        modprobe dummy &>/dev/null || true
+        if ! ip -netns "${test_netns}" link \
+                add "${DUMMY_DEVNAME}" type dummy; then
+                echo "SKIP: dummy dev not supported"
+
+                ip netns del "${test_netns}"
+                exit "${ksft_skip}"
+        fi
+
+        ip netns del "${test_netns}"
+}
+
+test_vrf_or_ksft_skip()
+{
+	modprobe vrf &>/dev/null || true
+	if [ ! -e /proc/sys/net/vrf/strict_mode ]; then
+		echo "SKIP: vrf sysctl does not exist"
+		exit "${ksft_skip}"
+	fi
+}
+
+if [ "$(id -u)" -ne 0 ]; then
+	echo "SKIP: Need root privileges"
+	exit "${ksft_skip}"
+fi
+
+# required programs to carry out this selftest
+test_command_or_ksft_skip ip
+test_command_or_ksft_skip ping
+test_command_or_ksft_skip sysctl
+test_command_or_ksft_skip grep
+test_command_or_ksft_skip cut
+
+test_iproute2_supp_or_ksft_skip
+test_dummy_dev_or_ksft_skip
+test_vrf_or_ksft_skip
+
+set -e
+trap cleanup EXIT
+
+setup
+set +e
+
+csid_container_cfg_tests
+
+router_tests
+host2gateway_tests
+host_vpn_tests
+
+print_log_test_results