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

Andrea Mayer says:

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

In the Segment Routing (SR) architecture 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.

Considering the Segment Routing over IPv6 data plane (SRv6) [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).

In some SRv6 scenarios, the number of segments carried by the SID List may
increase dramatically, reducing the MTU (Maximum Transfer Unit) size and/or
limiting the processing power of legacy hardware devices (due to longer IPv6
headers).

The NEXT-C-SID mechanism [3] extends the SRv6 architecture by providing several
ways to efficiently represent the SID List.
By leveraging the NEXT-C-SID, it is possible to encode several SRv6 segments
within a single 128 bit SID address (also referenced as Compressed SID
Container). In this way, the length of the SID List can be drastically reduced.

The NEXT-C-SID mechanism is built upon the "flavors" framework defined in [2].
This framework is already supported by the Linux SRv6 subsystem and is used to
modify and/or extend a subset of existing behaviors.

In this patchset, we extend the SRv6 End.X behavior in order to support the
NEXT-C-SID mechanism.

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

From the user space perspective, we do not need to change the iproute2 code to
support the NEXT-C-SID flavor for the SRv6 End.X behavior. However, we will
update the man page considering the NEXT-C-SID flavor applied to the SRv6 End.X
behavior in a separate patch.

[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/20230812180926.16689-1-andrea.mayer@uniroma2.itSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv6/seg6_local.c

@@ -109,15 +109,19 @@ struct bpf_lwt_prog {
 #define next_csid_chk_lcnode_fn_bits(flen)		\
 	next_csid_chk_lcblock_bits(flen)
 
+/* flag indicating that flavors are set up for a given End* behavior */
+#define SEG6_F_LOCAL_FLAVORS		SEG6_F_ATTR(SEG6_LOCAL_FLAVORS)
+
 #define SEG6_F_LOCAL_FLV_OP(flvname)	BIT(SEG6_LOCAL_FLV_OP_##flvname)
+#define SEG6_F_LOCAL_FLV_NEXT_CSID	SEG6_F_LOCAL_FLV_OP(NEXT_CSID)
 #define SEG6_F_LOCAL_FLV_PSP		SEG6_F_LOCAL_FLV_OP(PSP)
 
 /* Supported RFC8986 Flavor operations are reported in this bitmask */
 #define SEG6_LOCAL_FLV8986_SUPP_OPS	SEG6_F_LOCAL_FLV_PSP
 
-/* Supported Flavor operations are reported in this bitmask */
-#define SEG6_LOCAL_FLV_SUPP_OPS		(SEG6_F_LOCAL_FLV_OP(NEXT_CSID) | \
+#define SEG6_LOCAL_END_FLV_SUPP_OPS	(SEG6_F_LOCAL_FLV_NEXT_CSID | \
 					 SEG6_LOCAL_FLV8986_SUPP_OPS)
+#define SEG6_LOCAL_END_X_FLV_SUPP_OPS	SEG6_F_LOCAL_FLV_NEXT_CSID
 
 struct seg6_flavors_info {
 	/* Flavor operations */
@@ -411,9 +415,72 @@ static int end_next_csid_core(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 	return input_action_end_finish(skb, slwt);
 }
 
+static int input_action_end_x_finish(struct sk_buff *skb,
+				     struct seg6_local_lwt *slwt)
+{
+	seg6_lookup_nexthop(skb, &slwt->nh6, 0);
+
+	return dst_input(skb);
+}
+
+static int input_action_end_x_core(struct sk_buff *skb,
+				   struct seg6_local_lwt *slwt)
+{
+	struct ipv6_sr_hdr *srh;
+
+	srh = get_and_validate_srh(skb);
+	if (!srh)
+		goto drop;
+
+	advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
+
+	return input_action_end_x_finish(skb, slwt);
+
+drop:
+	kfree_skb(skb);
+	return -EINVAL;
+}
+
+static int end_x_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_x_core(skb, slwt);
+
+	/* update DA */
+	seg6_next_csid_advance_arg(daddr, finfo);
+
+	return input_action_end_x_finish(skb, slwt);
+}
+
 static bool seg6_next_csid_enabled(__u32 fops)
 {
-	return fops & BIT(SEG6_LOCAL_FLV_OP_NEXT_CSID);
+	return fops & SEG6_F_LOCAL_FLV_NEXT_CSID;
+}
+
+/* Processing of SRv6 End, End.X, and End.T behaviors can be extended through
+ * the flavors framework. These behaviors must report the subset of (flavor)
+ * operations they currently implement. In this way, if a user specifies a
+ * flavor combination that is not supported by a given End* behavior, the
+ * kernel refuses to instantiate the tunnel reporting the error.
+ */
+static int seg6_flv_supp_ops_by_action(int action, __u32 *fops)
+{
+	switch (action) {
+	case SEG6_LOCAL_ACTION_END:
+		*fops = SEG6_LOCAL_END_FLV_SUPP_OPS;
+		break;
+	case SEG6_LOCAL_ACTION_END_X:
+		*fops = SEG6_LOCAL_END_X_FLV_SUPP_OPS;
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return 0;
 }
 
 /* We describe the packet state in relation to the absence/presence of the SRH
@@ -746,21 +813,14 @@ static int input_action_end(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 /* regular endpoint, and forward to specified nexthop */
 static int input_action_end_x(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 {
-	struct ipv6_sr_hdr *srh;
-
-	srh = get_and_validate_srh(skb);
-	if (!srh)
-		goto drop;
-
-	advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
-
-	seg6_lookup_nexthop(skb, &slwt->nh6, 0);
+	const struct seg6_flavors_info *finfo = &slwt->flv_info;
+	__u32 fops = finfo->flv_ops;
 
-	return dst_input(skb);
+	/* check for the presence of NEXT-C-SID since it applies first */
+	if (seg6_next_csid_enabled(fops))
+		return end_x_next_csid_core(skb, slwt);
 
-drop:
-	kfree_skb(skb);
-	return -EINVAL;
+	return input_action_end_x_core(skb, slwt);
 }
 
 static int input_action_end_t(struct sk_buff *skb, struct seg6_local_lwt *slwt)
@@ -1404,13 +1464,14 @@ static struct seg6_action_desc seg6_action_table[] = {
 		.action		= SEG6_LOCAL_ACTION_END,
 		.attrs		= 0,
 		.optattrs	= SEG6_F_LOCAL_COUNTERS |
-				  SEG6_F_ATTR(SEG6_LOCAL_FLAVORS),
+				  SEG6_F_LOCAL_FLAVORS,
 		.input		= input_action_end,
 	},
 	{
 		.action		= SEG6_LOCAL_ACTION_END_X,
 		.attrs		= SEG6_F_ATTR(SEG6_LOCAL_NH6),
-		.optattrs	= SEG6_F_LOCAL_COUNTERS,
+		.optattrs	= SEG6_F_LOCAL_COUNTERS |
+				  SEG6_F_LOCAL_FLAVORS,
 		.input		= input_action_end_x,
 	},
 	{
@@ -2070,7 +2131,8 @@ static int parse_nla_flavors(struct nlattr **attrs, struct seg6_local_lwt *slwt,
 {
 	struct seg6_flavors_info *finfo = &slwt->flv_info;
 	struct nlattr *tb[SEG6_LOCAL_FLV_MAX + 1];
-	unsigned long fops;
+	int action = slwt->action;
+	__u32 fops, supp_fops;
 	int rc;
 
 	rc = nla_parse_nested_deprecated(tb, SEG6_LOCAL_FLV_MAX,
@@ -2086,7 +2148,8 @@ static int parse_nla_flavors(struct nlattr **attrs, struct seg6_local_lwt *slwt,
 		return -EINVAL;
 
 	fops = nla_get_u32(tb[SEG6_LOCAL_FLV_OPERATION]);
-	if (fops & ~SEG6_LOCAL_FLV_SUPP_OPS) {
+	rc = seg6_flv_supp_ops_by_action(action, &supp_fops);
+	if (rc < 0 || (fops & ~supp_fops)) {
 		NL_SET_ERR_MSG(extack, "Unsupported Flavor operation(s)");
 		return -EOPNOTSUPP;
 	}
@@ -2618,6 +2681,11 @@ int __init seg6_local_init(void)
 	 */
 	BUILD_BUG_ON(SEG6_LOCAL_MAX + 1 > BITS_PER_TYPE(unsigned long));
 
+	/* Check whether the number of defined flavors exceeds the maximum
+	 * allowed value.
+	 */
+	BUILD_BUG_ON(SEG6_LOCAL_FLV_OP_MAX + 1 > BITS_PER_TYPE(__u32));
+
 	/* If the default NEXT-C-SID Locator-Block/Node Function lengths (in
 	 * bits) have been changed with invalid values, kernel build stops
 	 * here.

tools/testing/selftests/net/Makefile

@@ -40,6 +40,7 @@ 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 += srv6_end_x_next_csid_l3vpn_test.sh
 TEST_PROGS += srv6_end_flavors_test.sh
 TEST_PROGS += vrf_strict_mode_test.sh
 TEST_PROGS += arp_ndisc_evict_nocarrier.sh

tools/testing/selftests/net/srv6_end_x_next_csid_l3vpn_test.sh

+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# author: Andrea Mayer <andrea.mayer@uniroma2.it>
+# author: Paolo Lungaroni <paolo.lungaroni@uniroma2.it>
+#
+# This script is designed for testing the support of NEXT-C-SID flavor for SRv6
+# End.X 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 of
+# 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.X behavior [1] (Endpoint with L3 cross connect) is a
+#       variant of SRv6 End behavior. It advances the active SID in the SID
+#       List carried by the SRH and forwards the packet to an L3 adjacency;
+#
+#  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.X 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.X
+#       behavior will apply the End.X 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.X 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 IPv6 addresses of hs-1 and hs-2, for
+# the double SID test case, we use their IPv4 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:0:0300:0200: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. 0300, 0200, etc).
+#
+# As the packet reaches the router rt-3, the enabled NEXT-C-SID SRv6 End.X
+# behavior (associated with fcbb:0:0300::/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-3 enabled NEXT-C-SID SRv6 End.X behavior |
+# +-----------------------------------------------------------------+
+# |                            +---------- Argument                 |
+# |                     vvvvvvvvvv                                  |
+# | IPv6 DA fcbb:0:0300:0200:d46::                                  |
+# |                ^^^^    <-- shifting                             |
+# |                  |                                              |
+# |          Locator-Node Function                                  |
+# +-----------------------------------------------------------------+
+# | After applying the rt-3 enabled NEXT-C-SID SRv6 End.X behavior  |
+# +-----------------------------------------------------------------+
+# |                          +---------- Argument                   |
+# |                    vvvvvv                                       |
+# | IPv6 DA fcbb:0:0200:d46::                                       |
+# |                ^^^^                                             |
+# |                  |                                              |
+# |          Locator-Node Function                                  |
+# +-----------------------------------------------------------------+
+#
+# After having applied the enabled NEXT-C-SID SRv6 End.X behavior, the packet
+# is sent to rt-4 node using the L3 adjacency address fcf0:0:3:4::4.
+#
+# The node rt-4 performs a plain IPv6 forward to the rt-2 router according to
+# its Local SID table and using the IPv6 DA fcbb:0:0200:d46:: .
+#
+# 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.X behavior.
+#
+# +-----------------------------------------------------------------+
+# | Before applying the rt-3 enabled NEXT-C-SID SRv6 End.X 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.X 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.X behavior operates as the
+# traditional End.X behavior: it updates the IPv6 DA by copying the next
+# available SID in the SID List carried by the SRH. Next, the packet is
+# forwarded to the rt-4 node using the L3 adjacency fcf0:3:4::4 previously
+# configured for this behavior.
+#
+# The node rt-4 performs a plain IPv6 forward to the rt-2 router according to
+# its Local SID table and using the IPv6 DA fcff:2::d46.
+#
+# Once the packet is received by rt-2, the router decapsulates the inner IPv4
+# 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:0:0400:0100:d46::
+#  ii) IPv4 DA=10.0.0.1, SID List=fcbb:0:0300::,fcff:1::d46
+#
+# ### i) single SID
+#
+# The node hs-2 sends an IPv6 packet directed to node hs-1. The router rt-2 is
+# directly connected to hs-2 and receives the packet. Rt-2 applies the
+# H.Encap.Red behavior with policy i) described above. Since there is only one
+# SID, the SRH header is omitted and the policy is inserted directly into the DA
+# of IPv6 packet.
+#
+# The packet reaches the router rt-4 and the enabled NEXT-C-SID SRv6 End.X
+# 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. The Argument is *NOT* zero and the C-SID in the IPv6 DA is
+# advanced. At this point, the current IPv6 DA is fcbb:0:0100:d46:: .
+# The enabled NEXT-C-SID SRv6 End.X behavior is configured with the L3 adjacency
+# fcf0:0:1:4::1, used to route traffic to the rt-1 node.
+#
+# The router rt-1 is configured for decapsulating the inner packet. It applies
+# the SRv6 End.DT46 behavior on the received packet. Decapsulation does not
+# require the presence of the SRH. At the end of the decap operation, the packet
+# is sent to the host hs-1.
+#
+# ### ii) double SID
+#
+# The router rt-2 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:1::d46. Hence, the packet sent by hs-2 to hs-1 is encapsulated in an
+# outer IPv6 header plus the SRH.
+#
+# As the packet reaches the node rt-3, the enabled NEXT-C-SID SRv6 End.X
+# behavior bound to the SID fcbb:0:0300::/48 is triggered.
+# 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-X behavior operates as the
+# traditional End.X 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
+# forwarded to the rt-4 node using the L3 adjacency (fcf0:3:4::4) previously
+# configured for this behavior.
+#
+# The node rt-4 performs a plain IPv6 forward to the rt-1 router according to
+# its Local SID table, considering the IPv6 DA fcff:1::d46.
+#
+# Once the packet is received by rt-1, the router decapsulates the inner IPv4
+# packet using the SRv6 End.DT46 behavior (associated with the SID fcff:1::d46)
+# and sends it to the host hs-1.
+
+# 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}"
+
+	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
+}
+
+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
+}
+
+# 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}"
+}
+
+set_end_x_nextcsid()
+{
+	local rt="$1"
+	local adj="$2"
+
+	nsname="$(get_rtname "${rt}")"
+	net_prefix="$(get_network_prefix "${rt}" "${adj}")"
+	lcnode_func_prefix="$(build_lcnode_func_prefix "${rt}")"
+
+	# enabled NEXT-C-SID SRv6 End.X behavior (note that "dev" is the dummy
+	# dum0 device chosen for the sake of simplicity).
+	ip -netns "${nsname}" -6 route \
+		replace "${lcnode_func_prefix}" \
+		table "${LOCALSID_TABLE_ID}" \
+		encap seg6local action End.X nh6 "${net_prefix}::${adj}" \
+		flavors next-csid lblen "${LCBLOCK_BLEN}" \
+		nflen "${LCNODEFUNC_BLEN}" dev "${DUMMY_DEVNAME}"
+}
+
+set_underlay_sids_reachability()
+{
+	local rt="$1"
+	local rt_neighs="$2"
+
+	nsname="$(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 "${nsname}" -6 route \
+			replace "${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 \
+			replace "${lcnode_func_prefix}" \
+			table "${LOCALSID_TABLE_ID}" \
+			via "${net_prefix}::${neigh}" dev "${devname}"
+	done
+}
+
+# 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 "${rt}")"
+
+        set_underlay_sids_reachability "${rt}" "${rt_neighs}"
+
+	# all SIDs for VPNs start with a common locator. Routes and SRv6
+	# Endpoint behavior instaces are grouped together in the 'localsid'
+	# table.
+	ip -netns "${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.X 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-3 SRv6 End.X behavior adj rt-4 (NEXT-C-SID flavor)
+	# - rt-4 Plain IPv6 Forwarding to rt-2
+	# - rt-2 SRv6 End.DT46 behavior
+	setup_ipv6_vpn_1sid 1 2 "3"
+
+	# Direction hs2 -> hs-1
+	# - rt-2 encap (H.Encaps.Red)
+	# - rt-4 SRv6 End.X behavior adj rt-1 (NEXT-C-SID flavor)
+	# - rt-1 SRv6 End.DT46 behavior
+	setup_ipv6_vpn_1sid 2 1 "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.X behavior adj rt-4 (NEXT-C-SID flavor)
+	# - rt-4 Plain IPv6 Forwarding to rt-2
+	# - 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.X behavior adj rt-4 (NEXT-C-SID flavor)
+	# - rt-4 Plain IPv6 Forwarding to rt-1
+	# - rt-1 SRv6 End.DT46 behavior
+	setup_ipv4_vpn_2sids 2 1 "3"
+
+	# Setup the adjacencies in the SRv6 aware routers
+	# - rt-3 SRv6 End.X adjacency with rt-4
+	# - rt-4 SRv6 End.X adjacency with rt-1
+        set_end_x_nextcsid 3 4
+        set_end_x_nextcsid 4 1
+
+	# 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_x_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.X nh6 :: \
+		flavors next-csid ${layout} \
+		dev "${DUMMY_DEVNAME}" &>/dev/null
+
+	return "$?"
+}
+
+rt_x_nextcsid_end_x_behavior_test()
+{
+	local rt="$1"
+	local blen="$2"
+	local flen="$3"
+	local nsname
+	local ret
+
+	nsname="$(get_rtname "${rt}")"
+
+	__nextcsid_end_x_behavior_test "${nsname}" "add" "${blen}" "${flen}"
+	ret="$?"
+	__nextcsid_end_x_behavior_test "${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_x_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