Merge branch 'seg6-add-psp-flavor-support-for-srv6-end-behavior'

Andrea Mayer says:

====================
seg6: add PSP flavor support for SRv6 End behavior

Segment Routing for IPv6 (SRv6 in short) [1] is the instantiation of the
Segment Routing (SR) [2] architecture on the IPv6 dataplane.
In SRv6, the segment identifiers (SID) are IPv6 addresses and the segment list
(SID List) is carried in the Segment Routing Header (SRH). A segment may be
bound to a specific packet processing operation called "behavior". The RFC8986
[3] defines and standardizes the most common/relevant behaviors for network
operators, e.g., End, End.X and End.T and so on.

The RFC8986 also introduces the "flavors" framework aiming to modify or extend
the capabilities of SRv6 End, End.X and End.T behaviors. Specifically, these
behaviors support the following flavors (either individually or in
combinations):
 - Penultimate Segment Pop (PSP);
 - Ultimate Segment Pop (USP);
 - Ultimate Segment Decapsulation (USD).

Such flavors enable an End/End.X/End.T behavior to pop the SRH on the
penultimate/ultimate SR endpoint node listed in the SID List or to perform a
full decapsulation.

Currently, the Linux kernel supports a large subset of behaviors described in
RFC8986, including the End, End.X and End.T. However, PSP, USP and USD flavors
have not yet been implemented.

In this patchset, we extend the SRv6 subsystem to implement the PSP flavor in
the SRv6 End behavior. To accomplish this task, we leverage the flavor
framework previously introduced by another patchset required for supporting the
efficient representation of the SID List through the NEXT-C-SID mechanism [4].

In details, the patchset is made of:
 - patch 1/3: seg6: factor out End lookup nexthop processing to a dedicated
              function
 - patch 2/3: seg6: add PSP flavor support for SRv6 End behavior
 - patch 3/3: selftests: seg6: add selftest for PSP flavor in SRv6 End
              behavior

From the user space perspective, we do not need to change the iproute2 code to
support the PSP flavor. However, we provide the man page for the PSP flavor in
a separate patch.

Comments, improvements and suggestions are always appreciated.

[1] - RFC8754: https://datatracker.ietf.org/doc/html/rfc8754
[2] - RFC8402: https://datatracker.ietf.org/doc/html/rfc8402
[3] - RFC8986: https://datatracker.ietf.org/doc/html/rfc8986
[4] - https://datatracker.ietf.org/doc/html/draft-ietf-spring-srv6-srh-compression
====================

Link: https://lore.kernel.org/r/20230215134659.7613-1-andrea.mayer@uniroma2.it
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

3 files changed, 1213 insertions, 9 deletions

diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c
index 487f8e98deaa..dd433cc265c8 100644
--- a/net/ipv6/seg6_local.c
+++ b/net/ipv6/seg6_local.c
@@ -109,8 +109,15 @@ struct bpf_lwt_prog {
 #define next_csid_chk_lcnode_fn_bits(flen)		\
 	next_csid_chk_lcblock_bits(flen)
 
+#define SEG6_F_LOCAL_FLV_OP(flvname)	BIT(SEG6_LOCAL_FLV_OP_##flvname)
+#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	(BIT(SEG6_LOCAL_FLV_OP_NEXT_CSID))
+#define SEG6_LOCAL_FLV_SUPP_OPS		(SEG6_F_LOCAL_FLV_OP(NEXT_CSID) | \
+					 SEG6_LOCAL_FLV8986_SUPP_OPS)
 
 struct seg6_flavors_info {
 	/* Flavor operations */
@@ -364,6 +371,14 @@ static void seg6_next_csid_advance_arg(struct in6_addr *addr,
 	memset(&addr->s6_addr[16 - fnc_octects], 0x00, fnc_octects);
 }
 
+static int input_action_end_finish(struct sk_buff *skb,
+				   struct seg6_local_lwt *slwt)
+{
+	seg6_lookup_nexthop(skb, NULL, 0);
+
+	return dst_input(skb);
+}
+
 static int input_action_end_core(struct sk_buff *skb,
 				 struct seg6_local_lwt *slwt)
 {
@@ -375,9 +390,7 @@ static int input_action_end_core(struct sk_buff *skb,
 
 	advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
 
-	seg6_lookup_nexthop(skb, NULL, 0);
-
-	return dst_input(skb);
+	return input_action_end_finish(skb, slwt);
 
 drop:
 	kfree_skb(skb);
@@ -395,9 +408,7 @@ static int end_next_csid_core(struct sk_buff *skb, struct seg6_local_lwt *slwt)
 	/* update DA */
 	seg6_next_csid_advance_arg(daddr, finfo);
 
-	seg6_lookup_nexthop(skb, NULL, 0);
-
-	return dst_input(skb);
+	return input_action_end_finish(skb, slwt);
 }
 
 static bool seg6_next_csid_enabled(__u32 fops)
@@ -405,15 +416,331 @@ static bool seg6_next_csid_enabled(__u32 fops)
 	return fops & BIT(SEG6_LOCAL_FLV_OP_NEXT_CSID);
 }
 
+/* We describe the packet state in relation to the absence/presence of the SRH
+ * and the Segment Left (SL) field.
+ * For our purposes, it is not necessary to record the exact value of the SL
+ * when the SID List consists of two or more segments.
+ */
+enum seg6_local_pktinfo {
+	/* the order really matters! */
+	SEG6_LOCAL_PKTINFO_NOHDR	= 0,
+	SEG6_LOCAL_PKTINFO_SL_ZERO,
+	SEG6_LOCAL_PKTINFO_SL_ONE,
+	SEG6_LOCAL_PKTINFO_SL_MORE,
+	__SEG6_LOCAL_PKTINFO_MAX,
+};
+
+#define SEG6_LOCAL_PKTINFO_MAX (__SEG6_LOCAL_PKTINFO_MAX - 1)
+
+static enum seg6_local_pktinfo seg6_get_srh_pktinfo(struct ipv6_sr_hdr *srh)
+{
+	__u8 sgl;
+
+	if (!srh)
+		return SEG6_LOCAL_PKTINFO_NOHDR;
+
+	sgl = srh->segments_left;
+	if (sgl < 2)
+		return SEG6_LOCAL_PKTINFO_SL_ZERO + sgl;
+
+	return SEG6_LOCAL_PKTINFO_SL_MORE;
+}
+
+enum seg6_local_flv_action {
+	SEG6_LOCAL_FLV_ACT_UNSPEC	= 0,
+	SEG6_LOCAL_FLV_ACT_END,
+	SEG6_LOCAL_FLV_ACT_PSP,
+	SEG6_LOCAL_FLV_ACT_USP,
+	SEG6_LOCAL_FLV_ACT_USD,
+	__SEG6_LOCAL_FLV_ACT_MAX
+};
+
+#define SEG6_LOCAL_FLV_ACT_MAX (__SEG6_LOCAL_FLV_ACT_MAX - 1)
+
+/* The action table for RFC8986 flavors (see the flv8986_act_tbl below)
+ * contains the actions (i.e. processing operations) to be applied on packets
+ * when flavors are configured for an End* behavior.
+ * By combining the pkinfo data and from the flavors mask, the macro
+ * computes the index used to access the elements (actions) stored in the
+ * action table. The index is structured as follows:
+ *
+ *                     index
+ *       _______________/\________________
+ *      /                                 \
+ *      +----------------+----------------+
+ *      |        pf      |      afm       |
+ *      +----------------+----------------+
+ *        ph-1 ... p1 p0   fk-1 ... f1 f0
+ *     MSB                               LSB
+ *
+ * where:
+ *  - 'afm' (adjusted flavor mask) is the mask containing a combination of the
+ *     RFC8986 flavors currently supported. 'afm' corresponds to the @fm
+ *     argument of the macro whose value is righ-shifted by 1 bit. By doing so,
+ *     we discard the SEG6_LOCAL_FLV_OP_UNSPEC flag (bit 0 in @fm) which is
+ *     never used here;
+ *  - 'pf' encodes the packet info (pktinfo) regarding the presence/absence of
+ *    the SRH, SL = 0, etc. 'pf' is set with the value of @pf provided as
+ *    argument to the macro.
+ */
+#define flv8986_act_tbl_idx(pf, fm)					\
+	((((pf) << bits_per(SEG6_LOCAL_FLV8986_SUPP_OPS)) |		\
+	  ((fm) & SEG6_LOCAL_FLV8986_SUPP_OPS)) >> SEG6_LOCAL_FLV_OP_PSP)
+
+/* We compute the size of the action table by considering the RFC8986 flavors
+ * actually supported by the kernel. In this way, the size is automatically
+ * adjusted when new flavors are supported.
+ */
+#define FLV8986_ACT_TBL_SIZE						\
+	roundup_pow_of_two(flv8986_act_tbl_idx(SEG6_LOCAL_PKTINFO_MAX,	\
+					       SEG6_LOCAL_FLV8986_SUPP_OPS))
+
+/* tbl_cfg(act, pf, fm) macro is used to easily configure the action
+ * table; it accepts 3 arguments:
+ *     i) @act, the suffix from SEG6_LOCAL_FLV_ACT_{act} representing
+ *        the action that should be applied on the packet;
+ *    ii) @pf, the suffix from SEG6_LOCAL_PKTINFO_{pf} reporting the packet
+ *        info about the lack/presence of SRH, SRH with SL = 0, etc;
+ *   iii) @fm, the mask of flavors.
+ */
+#define tbl_cfg(act, pf, fm)						\
+	[flv8986_act_tbl_idx(SEG6_LOCAL_PKTINFO_##pf,			\
+			     (fm))] = SEG6_LOCAL_FLV_ACT_##act
+
+/* shorthand for improving readability */
+#define F_PSP	SEG6_F_LOCAL_FLV_PSP
+
+/* The table contains, for each combination of the pktinfo data and
+ * flavors, the action that should be taken on a packet (e.g.
+ * "standard" Endpoint processing, Penultimate Segment Pop, etc).
+ *
+ * By default, table entries not explicitly configured are initialized with the
+ * SEG6_LOCAL_FLV_ACT_UNSPEC action, which generally has the effect of
+ * discarding the processed packet.
+ */
+static const u8 flv8986_act_tbl[FLV8986_ACT_TBL_SIZE] = {
+	/* PSP variant for packet where SRH with SL = 1 */
+	tbl_cfg(PSP, SL_ONE, F_PSP),
+	/* End for packet where the SRH with SL > 1*/
+	tbl_cfg(END, SL_MORE, F_PSP),
+};
+
+#undef F_PSP
+#undef tbl_cfg
+
+/* For each flavor defined in RFC8986 (or a combination of them) an action is
+ * performed on the packet. The specific action depends on:
+ *  - info extracted from the packet (i.e. pktinfo data) regarding the
+ *    lack/presence of the SRH, and if the SRH is available, on the value of
+ *    Segment Left field;
+ *  - the mask of flavors configured for the specific SRv6 End* behavior.
+ *
+ * The function combines both the pkinfo and the flavors mask to evaluate the
+ * corresponding action to be taken on the packet.
+ */
+static enum seg6_local_flv_action
+seg6_local_flv8986_act_lookup(enum seg6_local_pktinfo pinfo, __u32 flvmask)
+{
+	unsigned long index;
+
+	/* check if the provided mask of flavors is supported */
+	if (unlikely(flvmask & ~SEG6_LOCAL_FLV8986_SUPP_OPS))
+		return SEG6_LOCAL_FLV_ACT_UNSPEC;
+
+	index = flv8986_act_tbl_idx(pinfo, flvmask);
+	if (unlikely(index >= FLV8986_ACT_TBL_SIZE))
+		return SEG6_LOCAL_FLV_ACT_UNSPEC;
+
+	return flv8986_act_tbl[index];
+}
+
+/* skb->data must be aligned with skb->network_header */
+static bool seg6_pop_srh(struct sk_buff *skb, int srhoff)
+{
+	struct ipv6_sr_hdr *srh;
+	struct ipv6hdr *iph;
+	__u8 srh_nexthdr;
+	int thoff = -1;
+	int srhlen;
+	int nhlen;
+
+	if (unlikely(srhoff < sizeof(*iph) ||
+		     !pskb_may_pull(skb, srhoff + sizeof(*srh))))
+		return false;
+
+	srh = (struct ipv6_sr_hdr *)(skb->data + srhoff);
+	srhlen = ipv6_optlen(srh);
+
+	/* we are about to mangle the pkt, let's check if we can write on it */
+	if (unlikely(skb_ensure_writable(skb, srhoff + srhlen)))
+		return false;
+
+	/* skb_ensure_writable() may change skb pointers; evaluate srh again */
+	srh = (struct ipv6_sr_hdr *)(skb->data + srhoff);
+	srh_nexthdr = srh->nexthdr;
+
+	if (unlikely(!skb_transport_header_was_set(skb)))
+		goto pull;
+
+	nhlen = skb_network_header_len(skb);
+	/* we have to deal with the transport header: it could be set before
+	 * the SRH, after the SRH, or within it (which is considered wrong,
+	 * however).
+	 */
+	if (likely(nhlen <= srhoff))
+		thoff = nhlen;
+	else if (nhlen >= srhoff + srhlen)
+		/* transport_header is set after the SRH */
+		thoff = nhlen - srhlen;
+	else
+		/* transport_header falls inside the SRH; hence, we can't
+		 * restore the transport_header pointer properly after
+		 * SRH removing operation.
+		 */
+		return false;
+pull:
+	/* we need to pop the SRH:
+	 *  1) first of all, we pull out everything from IPv6 header up to SRH
+	 *     (included) evaluating also the rcsum;
+	 *  2) we overwrite (and then remove) the SRH by properly moving the
+	 *     IPv6 along with any extension header that precedes the SRH;
+	 *  3) At the end, we push back the pulled headers (except for SRH,
+	 *     obviously).
+	 */
+	skb_pull_rcsum(skb, srhoff + srhlen);
+	memmove(skb_network_header(skb) + srhlen, skb_network_header(skb),
+		srhoff);
+	skb_push(skb, srhoff);
+
+	skb_reset_network_header(skb);
+	skb_mac_header_rebuild(skb);
+	if (likely(thoff >= 0))
+		skb_set_transport_header(skb, thoff);
+
+	iph = ipv6_hdr(skb);
+	if (iph->nexthdr == NEXTHDR_ROUTING) {
+		iph->nexthdr = srh_nexthdr;
+	} else {
+		/* we must look for the extension header (EXTH, for short) that
+		 * immediately precedes the SRH we have just removed.
+		 * Then, we update the value of the EXTH nexthdr with the one
+		 * contained in the SRH nexthdr.
+		 */
+		unsigned int off = sizeof(*iph);
+		struct ipv6_opt_hdr *hp, _hdr;
+		__u8 nexthdr = iph->nexthdr;
+
+		for (;;) {
+			if (unlikely(!ipv6_ext_hdr(nexthdr) ||
+				     nexthdr == NEXTHDR_NONE))
+				return false;
+
+			hp = skb_header_pointer(skb, off, sizeof(_hdr), &_hdr);
+			if (unlikely(!hp))
+				return false;
+
+			if (hp->nexthdr == NEXTHDR_ROUTING) {
+				hp->nexthdr = srh_nexthdr;
+				break;
+			}
+
+			switch (nexthdr) {
+			case NEXTHDR_FRAGMENT:
+				fallthrough;
+			case NEXTHDR_AUTH:
+				/* we expect SRH before FRAG and AUTH */
+				return false;
+			default:
+				off += ipv6_optlen(hp);
+				break;
+			}
+
+			nexthdr = hp->nexthdr;
+		}
+	}
+
+	iph->payload_len = htons(skb->len - sizeof(struct ipv6hdr));
+
+	skb_postpush_rcsum(skb, iph, srhoff);
+
+	return true;
+}
+
+/* process the packet on the basis of the RFC8986 flavors set for the given
+ * SRv6 End behavior instance.
+ */
+static int end_flv8986_core(struct sk_buff *skb, struct seg6_local_lwt *slwt)
+{
+	const struct seg6_flavors_info *finfo = &slwt->flv_info;
+	enum seg6_local_flv_action action;
+	enum seg6_local_pktinfo pinfo;
+	struct ipv6_sr_hdr *srh;
+	__u32 flvmask;
+	int srhoff;
+
+	srh = seg6_get_srh(skb, 0);
+	srhoff = srh ? ((unsigned char *)srh - skb->data) : 0;
+	pinfo = seg6_get_srh_pktinfo(srh);
+#ifdef CONFIG_IPV6_SEG6_HMAC
+	if (srh && !seg6_hmac_validate_skb(skb))
+		goto drop;
+#endif
+	flvmask = finfo->flv_ops;
+	if (unlikely(flvmask & ~SEG6_LOCAL_FLV8986_SUPP_OPS)) {
+		pr_warn_once("seg6local: invalid RFC8986 flavors\n");
+		goto drop;
+	}
+
+	/* retrieve the action triggered by the combination of pktinfo data and
+	 * the flavors mask.
+	 */
+	action = seg6_local_flv8986_act_lookup(pinfo, flvmask);
+	switch (action) {
+	case SEG6_LOCAL_FLV_ACT_END:
+		/* process the packet as the "standard" End behavior */
+		advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
+		break;
+	case SEG6_LOCAL_FLV_ACT_PSP:
+		advance_nextseg(srh, &ipv6_hdr(skb)->daddr);
+
+		if (unlikely(!seg6_pop_srh(skb, srhoff)))
+			goto drop;
+		break;
+	case SEG6_LOCAL_FLV_ACT_UNSPEC:
+		fallthrough;
+	default:
+		/* by default, we drop the packet since we could not find a
+		 * suitable action.
+		 */
+		goto drop;
+	}
+
+	return input_action_end_finish(skb, slwt);
+
+drop:
+	kfree_skb(skb);
+	return -EINVAL;
+}
+
 /* 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;
+	__u32 fops = finfo->flv_ops;
 
-	if (seg6_next_csid_enabled(finfo->flv_ops))
+	if (!fops)
+		return input_action_end_core(skb, slwt);
+
+	/* check for the presence of NEXT-C-SID since it applies first */
+	if (seg6_next_csid_enabled(fops))
 		return end_next_csid_core(skb, slwt);
 
-	return input_action_end_core(skb, slwt);
+	/* the specific processing function to be performed on the packet
+	 * depends on the combination of flavors defined in RFC8986 and some
+	 * information extracted from the packet, e.g. presence/absence of SRH,
+	 * Segment Left = 0, etc.
+	 */
+	return end_flv8986_core(skb, slwt);
 }
 
 /* regular endpoint, and forward to specified nexthop */
@@ -2300,6 +2627,13 @@ int __init seg6_local_init(void)
 	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));
 
+	/* To be memory efficient, we use 'u8' to represent the different
+	 * actions related to RFC8986 flavors. If the kernel build stops here,
+	 * it means that it is not possible to correctly encode these actions
+	 * with the data type chosen for the action table.
+	 */
+	BUILD_BUG_ON(SEG6_LOCAL_FLV_ACT_MAX > (typeof(flv8986_act_tbl[0]))~0U);
+
 	return lwtunnel_encap_add_ops(&seg6_local_ops,
 				      LWTUNNEL_ENCAP_SEG6_LOCAL);
 }
diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index 3364c548a23b..6cd8993454d7 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -38,6 +38,7 @@ 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_flavors_test.sh
 TEST_PROGS += vrf_strict_mode_test.sh
 TEST_PROGS += arp_ndisc_evict_nocarrier.sh
 TEST_PROGS += ndisc_unsolicited_na_test.sh
diff --git a/tools/testing/selftests/net/srv6_end_flavors_test.sh b/tools/testing/selftests/net/srv6_end_flavors_test.sh
new file mode 100755
index 000000000000..50563443a4ad
--- /dev/null
+++ b/tools/testing/selftests/net/srv6_end_flavors_test.sh
@@ -0,0 +1,869 @@
+#!/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 to test the support for "flavors" in the SRv6 End
+# behavior.
+#
+# Flavors defined in RFC8986 [1] represent additional operations that can modify
+# or extend the existing SRv6 End, End.X and End.T behaviors. For the sake of
+# convenience, we report the list of flavors described in [1] hereafter:
+#   - Penultimate Segment Pop (PSP);
+#   - Ultimate Segment Pop (USP);
+#   - Ultimate Segment Decapsulation (USD).
+#
+# The End, End.X, and End.T behaviors can support these flavors either
+# individually or in combinations.
+# Currently in this selftest we consider only the PSP flavor for the SRv6 End
+# behavior. However, it is possible to extend the script as soon as other
+# flavors will be supported in the kernel.
+#
+# The purpose of the PSP flavor consists in instructing the penultimate node
+# listed in the SRv6 policy to remove (i.e. pop) the outermost SRH from the IPv6
+# header.
+# A PSP enabled SRv6 End behavior instance processes the SRH by:
+#  - decrementing the Segment Left (SL) value from 1 to 0;
+#  - copying the last SID from the SID List into the IPv6 Destination Address
+#    (DA);
+#  - removing the SRH from the extension headers following the IPv6 header.
+#
+# Once the SRH is removed, the IPv6 packet is forwarded to the destination using
+# the IPv6 DA updated during the PSP operation (i.e. the IPv6 DA corresponding
+# to the last SID carried by the removed SRH).
+#
+# Although the PSP flavor can be set for any SRv6 End behavior instance on any
+# SR node, it will be active only on such behaviors bound to a penultimate SID
+# for a given SRv6 policy.
+#                                                SL=2 SL=1 SL=0
+#                                                  |    |    |
+# For example, given the SRv6 policy (SID List := <X,   Y,   Z>):
+#  - a PSP enabled SRv6 End behavior bound to SID Y will apply the PSP operation
+#    as Segment Left (SL) is 1, corresponding to the Penultimate Segment of the
+#    SID List;
+#  - a PSP enabled SRv6 End behavior bound to SID X will *NOT* apply the PSP
+#    operation as the Segment Left is 2. This behavior instance will apply the
+#    "standard" End packet processing, ignoring the configured PSP flavor at
+#    all.
+#
+# [1] RFC8986: https://datatracker.ietf.org/doc/html/rfc8986
+#
+# Network topology
+# ================
+#
+# The network topology used in this selftest is depicted hereafter, composed by
+# two hosts (hs-1, hs-2) and four routers (rt-1, rt-2, rt-3, rt-4).
+# Hosts hs-1 and hs-2 are connected to routers rt-1 and rt-2, respectively,
+# allowing them to communicate with each other.
+# Traffic exchanged between hs-1 and hs-2 can follow different network paths.
+# The network operator, through specific SRv6 Policies can steer traffic to one
+# path rather than another. In this selftest this is implemented as follows:
+#
+#   i) The SRv6 H.Insert behavior applies SRv6 Policies on traffic received by
+#      connected hosts. It pushes the Segment Routing Header (SRH) after the
+#      IPv6 header. The SRH contains the SID List (i.e. SRv6 Policy) needed for
+#      steering traffic across the segments/waypoints specified in that list;
+#
+#  ii) The SRv6 End behavior advances the active SID in the SID List carried by
+#      the SRH;
+#
+# iii) The PSP enabled SRv6 End behavior is used to remove the SRH when such
+#      behavior is configured on a node bound to the Penultimate Segment carried
+#      by the SID List.
+#
+#                cafe::1                      cafe::2
+#              +--------+                   +--------+
+#              |        |                   |        |
+#              |  hs-1  |                   |  hs-2  |
+#              |        |                   |        |
+#              +---+----+                   +--- +---+
+#     cafe::/64    |                             |      cafe::/64
+#                  |                             |
+#              +---+----+                   +----+---+
+#              |        |  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 IPv6 operator network.
+#
+#
+# Local SID table
+# ===============
+#
+# Each SRv6 router is configured with a Local SID table in which SIDs are
+# stored. Considering the given SRv6 router rt-x, at least two SIDs are
+# configured in the Local SID table:
+#
+#   Local SID table for SRv6 router rt-x
+#   +---------------------------------------------------------------------+
+#   |fcff:x::e is associated with the SRv6 End behavior                   |
+#   |fcff:x::ef1 is associated with the SRv6 End behavior with PSP flavor |
+#   +---------------------------------------------------------------------+
+#
+# The fcff::/16 prefix is reserved by the operator for the SIDs. Reachability of
+# SIDs is ensured by proper configuration of the IPv6 operator's network and
+# SRv6 routers.
+#
+#
+# SRv6 Policies
+# =============
+#
+# An SRv6 ingress router applies different SRv6 Policies to the traffic received
+# from connected hosts on the basis of the destination addresses.
+# In case of SRv6 H.Insert behavior, the SRv6 Policy enforcement consists of
+# pushing the SRH (carrying a given SID List) after the existing IPv6 header.
+# Note that in the inserting mode, there is no encapsulation at all.
+#
+#   Before applying an SRv6 Policy using the SRv6 H.Insert behavior
+#   +------+---------+
+#   | IPv6 | Payload |
+#   +------+---------+
+#
+#   After applying an SRv6 Policy using the SRv6 H.Insert behavior
+#   +------+-----+---------+
+#   | IPv6 | SRH | Payload |
+#   +------+-----+---------+
+#
+# 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 following SRv6 Policy:
+#
+#   i.a) IPv6 traffic, SID List=fcff:3::e,fcff:4::ef1,fcff:2::ef1,cafe::2
+#
+# Router rt-1 is configured to enforce the Policy (i.a) through the SRv6
+# H.Insert behavior which pushes the SRH after the existing IPv6 header. This
+# Policy steers the traffic from hs-1 across rt-3, rt-4, rt-2 and finally to the
+# destination hs-2.
+#
+# As the packet reaches the router rt-3, the SRv6 End behavior bound to SID
+# fcff:3::e is triggered. The behavior updates the Segment Left (from SL=3 to
+# SL=2) in the SRH, the IPv6 DA with fcff:4::ef1 and forwards the packet to the
+# next router on the path, i.e. rt-4.
+#
+# When router rt-4 receives the packet, the PSP enabled SRv6 End behavior bound
+# to SID fcff:4::ef1 is executed. Since the SL=2, the PSP operation is *NOT*
+# kicked in and the behavior applies the default End processing: the Segment
+# Left is decreased (from SL=2 to SL=1), the IPv6 DA is updated with the SID
+# fcff:2::ef1 and the packet is forwarded to router rt-2.
+#
+# The PSP enabled SRv6 End behavior on rt-2 is associated with SID fcff:2::ef1
+# and is executed as the packet is received. Because SL=1, the behavior applies
+# the PSP processing on the packet as follows: i) SL is decreased, i.e. from
+# SL=1 to SL=0; ii) last SID (cafe::2) is copied into the IPv6 DA; iii) the
+# outermost SRH is removed from the extension headers following the IPv6 header.
+# Once the PSP processing is completed, the packet is forwarded to the host hs-2
+# (destination).
+#
+# Traffic from hs-2 to hs-1
+# -------------------------
+#
+# Packets generated from hs-2 and directed to hs-1 are handled by rt-2 which
+# applies the following SRv6 Policy:
+#
+#   i.b) IPv6 traffic, SID List=fcff:1::ef1,cafe::1
+#
+# Router rt-2 is configured to enforce the Policy (i.b) through the SRv6
+# H.Insert behavior which pushes the SRH after the existing IPv6 header. This
+# Policy steers the traffic from hs-2 across rt-1 and finally to the
+# destination hs-1
+#
+#
+# When the router rt-1 receives the packet, the PSP enabled SRv6 End behavior
+# associated with the SID fcff:1::ef1 is triggered. Since the SL=1,
+# the PSP operation takes place: i) the SL is decremented; ii) the IPv6 DA is
+# set with the last SID; iii) the SRH is removed from the extension headers
+# after the IPv6 header. At this point, the packet with IPv6 DA=cafe::1 is sent
+# to the destination, i.e. hs-1.
+
+# Kselftest framework requirement - SKIP code is 4.
+readonly ksft_skip=4
+
+readonly RDMSUFF="$(mktemp -u XXXXXXXX)"
+readonly DUMMY_DEVNAME="dum0"
+readonly RT2HS_DEVNAME="veth1"
+readonly LOCALSID_TABLE_ID=90
+readonly IPv6_RT_NETWORK=fcf0:0
+readonly IPv6_HS_NETWORK=cafe
+readonly IPv6_TESTS_ADDR=2001:db8::1
+readonly LOCATOR_SERVICE=fcff
+readonly END_FUNC=000e
+readonly END_PSP_FUNC=0ef1
+
+PING_TIMEOUT_SEC=4
+PAUSE_ON_FAIL=${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}"
+}
+
+# Given the description of a router <id:op> as an input, the function returns
+# the <id> token which represents the ID of the router.
+# i.e. input: "12:psp"
+#      output: "12"
+__get_srv6_rtcfg_id()
+{
+	local element="$1"
+
+	echo "${element}" | cut -d':' -f1
+}
+
+# Given the description of a router <id:op> as an input, the function returns
+# the <op> token which represents the operation (e.g. End behavior with or
+# withouth flavors) configured for the node.
+
+# Note that when the operation represents an End behavior with a list of
+# flavors, the output is the ordered version of that list.
+# i.e. input: "5:usp,psp,usd"
+#      output: "psp,usd,usp"
+__get_srv6_rtcfg_op()
+{
+	local element="$1"
+
+	# return the lexicographically ordered flavors
+	echo "${element}" | cut -d':' -f2 | sed 's/,/\n/g' | sort | \
+		xargs | sed 's/ /,/g'
+}
+
+# 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 "${nsname}" link set lo up
+
+	ip -netns "${nsname}" link add ${DUMMY_DEVNAME} type dummy
+	ip -netns "${nsname}" link set ${DUMMY_DEVNAME} up
+
+	ip netns exec "${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
+}
+
+# Setup local SIDs for an SRv6 router
+setup_rt_local_sids()
+{
+	local rt="$1"
+	local rt_neighs="$2"
+	local net_prefix
+	local devname
+	local nsname
+	local neigh
+
+	nsname="$(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 "${nsname}" -6 route \
+			add "${LOCATOR_SERVICE}:${neigh}::/32" \
+			table "${LOCALSID_TABLE_ID}" \
+			via "${net_prefix}::${neigh}" dev "${devname}"
+	done
+
+	# Local End behavior (note that "dev" is a dummy interface chosen for
+	# the sake of simplicity).
+	ip -netns "${nsname}" -6 route \
+		add "${LOCATOR_SERVICE}:${rt}::${END_FUNC}" \
+		table "${LOCALSID_TABLE_ID}" \
+		encap seg6local action End dev "${DUMMY_DEVNAME}"
+
+
+	# all SIDs start with a common locator. Routes and SRv6 Endpoint
+	# behavior instaces are grouped together in the 'localsid' table.
+	ip -netns "${nsname}" -6 rule \
+		add to "${LOCATOR_SERVICE}::/16" \
+		lookup "${LOCALSID_TABLE_ID}" prio 999
+
+	# set default routes to unreachable
+	ip -netns "${nsname}" -6 route \
+		add unreachable default metric 4278198272 \
+		dev "${DUMMY_DEVNAME}"
+}
+
+# This helper function builds and installs the SID List (i.e. SRv6 Policy)
+# to be applied on incoming packets at the ingress node. Moreover, it
+# configures the SRv6 nodes specified in the SID List to process the traffic
+# according to the operations required by the Policy itself.
+# args:
+#  $1 - destination host (i.e. cafe::x host)
+#  $2 - SRv6 router configured for enforcing the SRv6 Policy
+#  $3 - compact way to represent a list of SRv6 routers with their operations
+#       (i.e. behaviors) that each of them needs to perform. Every <nodeid:op>
+#       element constructs a SID that is associated with the behavior <op> on
+#       the <nodeid> node. The list of such elements forms an SRv6 Policy.
+__setup_rt_policy()
+{
+	local dst="$1"
+	local encap_rt="$2"
+	local policy_rts="$3"
+	local behavior_cfg
+	local in_nsname
+	local rt_nsname
+	local policy=''
+	local function
+	local fullsid
+	local op_type
+	local node
+	local n
+
+	in_nsname="$(get_rtname "${encap_rt}")"
+
+	for n in ${policy_rts}; do
+		node="$(__get_srv6_rtcfg_id "${n}")"
+		op_type="$(__get_srv6_rtcfg_op "${n}")"
+		rt_nsname="$(get_rtname "${node}")"
+
+		case "${op_type}" in
+		"noflv")
+			policy="${policy}${LOCATOR_SERVICE}:${node}::${END_FUNC},"
+			function="${END_FUNC}"
+			behavior_cfg="End"
+			;;
+
+		"psp")
+			policy="${policy}${LOCATOR_SERVICE}:${node}::${END_PSP_FUNC},"
+			function="${END_PSP_FUNC}"
+			behavior_cfg="End flavors psp"
+			;;
+
+		*)
+			break
+			;;
+		esac
+
+		fullsid="${LOCATOR_SERVICE}:${node}::${function}"
+
+		# add SRv6 Endpoint behavior to the selected router
+		if ! ip -netns "${rt_nsname}" -6 route get "${fullsid}" \
+			&>/dev/null; then
+			ip -netns "${rt_nsname}" -6 route \
+				add "${fullsid}" \
+				table "${LOCALSID_TABLE_ID}" \
+				encap seg6local action ${behavior_cfg} \
+				dev "${DUMMY_DEVNAME}"
+		fi
+	done
+
+	# we need to remove the trailing comma to avoid inserting an empty
+	# address (::0) in the SID List.
+	policy="${policy%,}"
+
+	# add SRv6 policy to incoming traffic sent by connected hosts
+	ip -netns "${in_nsname}" -6 route \
+		add "${IPv6_HS_NETWORK}::${dst}" \
+		encap seg6 mode inline segs "${policy}" \
+		dev "${DUMMY_DEVNAME}"
+
+	ip -netns "${in_nsname}" -6 neigh \
+		add proxy "${IPv6_HS_NETWORK}::${dst}" \
+		dev "${RT2HS_DEVNAME}"
+}
+
+# see __setup_rt_policy
+setup_rt_policy_ipv6()
+{
+	__setup_rt_policy "$1" "$2" "$3"
+}
+
+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}" link set veth0 up
+	ip -netns "${hsname}" link set lo up
+
+	ip -netns "${rtname}" addr \
+		add "${IPv6_HS_NETWORK}::254/64" dev "${RT2HS_DEVNAME}" nodad
+
+	ip -netns "${rtname}" link set "${RT2HS_DEVNAME}" up
+
+	ip netns exec "${rtname}" \
+		sysctl -wq net.ipv6.conf."${RT2HS_DEVNAME}".proxy_ndp=1
+}
+
+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 behavior)
+	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 a connection between hosts hs-1 and hs-2.
+	# The path between hs-1 and hs-2 traverses SRv6 aware routers.
+	# For each direction two path are chosen:
+	#
+	# Direction hs-1 -> hs-2 (PSP flavor)
+	#  - rt-1 (SRv6 H.Insert policy)
+	#  - rt-3 (SRv6 End behavior)
+	#  - rt-4 (SRv6 End flavor PSP with SL>1, acting as End behavior)
+	#  - rt-2 (SRv6 End flavor PSP with SL=1)
+	#
+	# Direction hs-2 -> hs-1 (PSP flavor)
+	#  - rt-2 (SRv6 H.Insert policy)
+	#  - rt-1 (SRv6 End flavor PSP with SL=1)
+	setup_rt_policy_ipv6 2 1 "3:noflv 4:psp 2:psp"
+	setup_rt_policy_ipv6 1 2 "1:psp"
+
+	# 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_and_log_hs2gw_connectivity()
+{
+	local hssrc="$1"
+
+	check_hs_ipv6_connectivity "${hssrc}" 254
+	log_test $? 0 "IPv6 Hosts connectivity: hs-${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_connectivity()
+{
+	local hssrc="$1"
+	local hsdst="$2"
+
+	check_and_log_hs_ipv6_connectivity "${hssrc}" "${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 "IPv6 connectivity test among hosts and gateways"
+
+	for hs in ${HOSTS}; do
+		check_and_log_hs2gw_connectivity "${hs}"
+	done
+}
+
+host_srv6_end_flv_psp_tests()
+{
+	log_section "SRv6 connectivity test hosts (h1 <-> h2, PSP flavor)"
+
+	check_and_log_hs_connectivity 1 2
+	check_and_log_hs_connectivity 2 1
+}
+
+test_iproute2_supp_or_ksft_skip()
+{
+	local flavor="$1"
+
+	if ! ip route help 2>&1 | grep -qo "${flavor}"; then
+		echo "SKIP: Missing SRv6 ${flavor} flavor support in iproute2"
+		exit "${ksft_skip}"
+	fi
+}
+
+test_kernel_supp_or_ksft_skip()
+{
+	local flavor="$1"
+	local test_netns
+
+	test_netns="kflv-$(mktemp -u XXXXXXXX)"
+
+	if ! ip netns add "${test_netns}"; then
+		echo "SKIP: Cannot set up netns to test kernel support for flavors"
+		exit "${ksft_skip}"
+	fi
+
+	if ! ip -netns "${test_netns}" link \
+		add "${DUMMY_DEVNAME}" type dummy; then
+		echo "SKIP: Cannot set up dummy dev to test kernel support for flavors"
+
+		ip netns del "${test_netns}"
+		exit "${ksft_skip}"
+	fi
+
+	if ! ip -netns "${test_netns}" link \
+		set "${DUMMY_DEVNAME}" up; then
+		echo "SKIP: Cannot activate dummy dev to test kernel support for flavors"
+
+		ip netns del "${test_netns}"
+		exit "${ksft_skip}"
+	fi
+
+	if ! ip -netns "${test_netns}" -6 route \
+		add "${IPv6_TESTS_ADDR}" encap seg6local \
+		action End flavors "${flavor}" dev "${DUMMY_DEVNAME}"; then
+		echo "SKIP: ${flavor} flavor not supported in kernel"
+
+		ip netns del "${test_netns}"
+		exit "${ksft_skip}"
+	fi
+
+	ip netns del "${test_netns}"
+}
+
+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}"
+}
+
+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_command_or_ksft_skip sed
+test_command_or_ksft_skip sort
+test_command_or_ksft_skip xargs
+
+test_dummy_dev_or_ksft_skip
+test_iproute2_supp_or_ksft_skip psp
+test_kernel_supp_or_ksft_skip psp
+
+set -e
+trap cleanup EXIT
+
+setup
+set +e
+
+router_tests
+host2gateway_tests
+host_srv6_end_flv_psp_tests
+
+print_log_test_results