selftests: add selftest for the SRv6 End.DX4 behavior with netfilter

this selftest is designed for evaluating the SRv6 End.DX4 behavior
used with netfilter(rpfilter), in this example, for implementing
IPv4 L3 VPN use cases.
Signed-off-by: Jianguo Wu <wujianguo@chinatelecom.cn>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

tools/testing/selftests/net/Makefile

@@ -43,6 +43,7 @@ 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 += srv6_end_dx4_netfilter_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/config

@@ -101,3 +101,4 @@ CONFIG_NETFILTER_XT_MATCH_POLICY=m
 CONFIG_CRYPTO_ARIA=y
 CONFIG_XFRM_INTERFACE=m
 CONFIG_XFRM_USER=m
+CONFIG_IP_NF_MATCH_RPFILTER=m

tools/testing/selftests/net/srv6_end_dx4_netfilter_test.sh

+#!/bin/bash
+# SPDX-License-Identifier: GPL-2.0
+#
+# author: Jianguo Wu <wujianguo@chinatelecom.cn>
+#
+# Mostly copied from tools/testing/selftests/net/srv6_end_dt4_l3vpn_test.sh.
+#
+# This script is designed for testing the support of netfilter hooks for
+# SRv6 End.DX4 behavior.
+#
+# Hereafter a network diagram is shown, where one tenants (named 100) offer
+# IPv4 L3 VPN services allowing hosts to communicate with each other across
+# an IPv6 network.
+#
+# Routers rt-1 and rt-2 implement IPv4 L3 VPN services leveraging the SRv6
+# architecture. The key components for such VPNs are: a) SRv6 Encap behavior,
+# b) SRv6 End.DX4 behavior.
+#
+# To explain how an IPv4 L3 VPN based on SRv6 works, let us briefly consider an
+# example where, within the same domain of tenant 100, the host hs-1 pings
+# the host hs-2.
+#
+# First of all, L2 reachability of the host hs-2 is taken into account by
+# the router rt-1 which acts as an arp proxy.
+#
+# When the host hs-1 sends an IPv4 packet destined to hs-2, the router rt-1
+# receives the packet on the internal veth-t100 interface, rt-1 contains the
+# SRv6 Encap route for encapsulating the IPv4 packet in a IPv6 plus the Segment
+# Routing Header (SRH) packet. This packet is sent through the (IPv6) core
+# network up to the router rt-2 that receives it on veth0 interface.
+#
+# The rt-2 router uses the 'localsid' routing table to process incoming
+# IPv6+SRH packets which belong to the VPN of the tenant 100. For each of these
+# packets, the SRv6 End.DX4 behavior removes the outer IPv6+SRH headers and
+# routs the packet to the specified nexthop. Afterwards, the packet is sent to
+# the host hs-2 through the veth-t100 interface.
+#
+# The ping response follows the same processing but this time the role of rt-1
+# and rt-2 are swapped.
+#
+# And when net.netfilter.nf_hooks_lwtunnel is set to 1 in rt-1 or rt-2, and a
+# rpfilter iptables rule is added, SRv6 packets will go through netfilter PREROUTING
+# hooks.
+#
+#
+# +-------------------+                                   +-------------------+
+# |                   |                                   |                   |
+# |    hs-1 netns     |                                   |     hs-2 netns    |
+# |                   |                                   |                   |
+# |  +-------------+  |                                   |  +-------------+  |
+# |  |    veth0    |  |                                   |  |    veth0    |  |
+# |  | 10.0.0.1/24 |  |                                   |  | 10.0.0.2/24 |  |
+# |  +-------------+  |                                   |  +-------------+  |
+# |        .          |                                   |         .         |
+# +-------------------+                                   +-------------------+
+#          .                                                        .
+#          .                                                        .
+#          .                                                        .
+# +-----------------------------------+   +-----------------------------------+
+# |        .                          |   |                         .         |
+# | +---------------+                 |   |                 +---------------- |
+# | |   veth-t100   |                 |   |                 |   veth-t100   | |
+# | | 10.0.0.11/24  |    +----------+ |   | +----------+    | 10.0.0.22/24  | |
+# | +-------+-------+   |   route   | |   | |   route  |    +-------+-------- |
+# |                     |   table   | |   | |   table  |                      |
+# |                      +----------+ |   | +----------+                      |
+# |                  +--------------+ |   | +--------------+                  |
+# |                 |      veth0    | |   | |   veth0       |                 |
+# |                 | 2001:11::1/64 |.|...|.| 2001:11::2/64 |                 |
+# |                  +--------------+ |   | +--------------+                  |
+# |                                   |   |                                   |
+# |                        rt-1 netns |   | rt-2 netns                        |
+# |                                   |   |                                   |
+# +-----------------------------------+   +-----------------------------------+
+#
+# ~~~~~~~~~~~~~~~~~~~~~~~~~
+# | Network configuration |
+# ~~~~~~~~~~~~~~~~~~~~~~~~~
+#
+# rt-1: localsid table
+# +----------------------------------------------------------------+
+# |SID              |Action                                        |
+# +----------------------------------------------------------------+
+# |fc00:21:100::6004|apply SRv6 End.DX4 nh4 10.0.0.1 dev veth-t100 |
+# +----------------------------------------------------------------+
+#
+# rt-1: route table
+# +---------------------------------------------------+
+# |host       |Action                                 |
+# +---------------------------------------------------+
+# |10.0.0.2   |apply seg6 encap segs fc00:12:100::6004|
+# +---------------------------------------------------+
+# |10.0.0.0/24|forward to dev veth_t100               |
+# +---------------------------------------------------+
+#
+#
+# rt-2: localsid table
+# +---------------------------------------------------------------+
+# |SID              |Action                                       |
+# +---------------------------------------------------------------+
+# |fc00:12:100::6004|apply SRv6 End.DX4 nh4 10.0.0.2 dev veth-t100|
+# +---------------------------------------------------------------+
+#
+# rt-2: route table
+# +---------------------------------------------------+
+# |host       |Action                                 |
+# +---------------------------------------------------+
+# |10.0.0.1   |apply seg6 encap segs fc00:21:100::6004|
+# +---------------------------------------------------+
+# |10.0.0.0/24|forward to dev veth_t100               |
+# +---------------------------------------------------+
+#
+
+# Kselftest framework requirement - SKIP code is 4.
+ksft_skip=4
+
+readonly IPv6_RT_NETWORK=2001:11
+readonly IPv4_HS_NETWORK=10.0.0
+readonly SID_LOCATOR=fc00
+
+PING_TIMEOUT_SEC=4
+
+ret=0
+
+PAUSE_ON_FAIL=${PAUSE_ON_FAIL:=no}
+
+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
+			[ "$a" = "q" ] && exit 1
+		fi
+	fi
+}
+
+print_log_test_results()
+{
+	if [ "$TESTS" != "none" ]; then
+		printf "\nTests passed: %3d\n" ${nsuccess}
+		printf "Tests failed: %3d\n"   ${nfail}
+	fi
+}
+
+log_section()
+{
+	echo
+	echo "################################################################################"
+	echo "TEST SECTION: $*"
+	echo "################################################################################"
+}
+
+cleanup()
+{
+	ip link del veth-rt-1 2>/dev/null || true
+	ip link del veth-rt-2 2>/dev/null || true
+
+	# destroy routers rt-* and hosts hs-*
+	for ns in $(ip netns show | grep -E 'rt-*|hs-*'); do
+		ip netns del ${ns} || true
+	done
+}
+
+# Setup the basic networking for the routers
+setup_rt_networking()
+{
+	local rt=$1
+	local nsname=rt-${rt}
+
+	ip netns add ${nsname}
+
+	ip netns exec ${nsname} sysctl -wq net.ipv6.conf.all.accept_dad=0
+	ip netns exec ${nsname} sysctl -wq net.ipv6.conf.default.accept_dad=0
+
+	ip link set veth-rt-${rt} netns ${nsname}
+	ip -netns ${nsname} link set veth-rt-${rt} name veth0
+
+	ip -netns ${nsname} addr add ${IPv6_RT_NETWORK}::${rt}/64 dev veth0 nodad
+	ip -netns ${nsname} link set veth0 up
+	ip -netns ${nsname} link set lo up
+
+	ip netns exec ${nsname} sysctl -wq net.ipv4.ip_forward=1
+	ip netns exec ${nsname} sysctl -wq net.ipv6.conf.all.forwarding=1
+}
+
+setup_rt_netfilter()
+{
+	local rt=$1
+	local nsname=rt-${rt}
+
+	ip netns exec ${nsname} sysctl -wq net.netfilter.nf_hooks_lwtunnel=1
+	ip netns exec ${nsname} iptables -t raw -A PREROUTING -m rpfilter --invert -j DROP
+}
+
+setup_hs()
+{
+	local hs=$1
+	local rt=$2
+	local tid=$3
+	local hsname=hs-${hs}
+	local rtname=rt-${rt}
+	local rtveth=veth-t${tid}
+
+	# set the networking for the host
+	ip netns add ${hsname}
+
+	ip -netns ${hsname} link add veth0 type veth peer name ${rtveth}
+	ip -netns ${hsname} link set ${rtveth} netns ${rtname}
+	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
+
+	ip -netns ${rtname} addr add ${IPv4_HS_NETWORK}.${rt}${hs}/24 dev ${rtveth}
+	ip -netns ${rtname} link set ${rtveth} up
+
+	ip netns exec ${rtname} sysctl -wq net.ipv4.conf.${rtveth}.proxy_arp=1
+}
+
+setup_vpn_config()
+{
+	local hssrc=$1
+	local rtsrc=$2
+	local hsdst=$3
+	local rtdst=$4
+	local tid=$5
+
+	local hssrc_name=hs-t${tid}-${hssrc}
+	local hsdst_name=hs-t${tid}-${hsdst}
+	local rtsrc_name=rt-${rtsrc}
+	local rtdst_name=rt-${rtdst}
+	local vpn_sid=${SID_LOCATOR}:${hssrc}${hsdst}:${tid}::6004
+
+	# set the encap route for encapsulating packets which arrive from the
+	# host hssrc and destined to the access router rtsrc.
+	ip -netns ${rtsrc_name} -4 route add ${IPv4_HS_NETWORK}.${hsdst}/32 \
+		encap seg6 mode encap segs ${vpn_sid} dev veth0
+	ip -netns ${rtsrc_name} -6 route add ${vpn_sid}/128 \
+		via 2001:11::${rtdst} dev veth0
+
+	# set the decap route for decapsulating packets which arrive from
+	# the rtdst router and destined to the hsdst host.
+	ip -netns ${rtdst_name} -6 route add ${vpn_sid}/128 \
+		encap seg6local action End.DX4 nh4 ${IPv4_HS_NETWORK}.${hsdst} dev veth-t${tid}
+}
+
+setup()
+{
+	ip link add veth-rt-1 type veth peer name veth-rt-2
+	# setup the networking for router rt-1 and router rt-2
+	setup_rt_networking 1
+	setup_rt_networking 2
+
+	# setup two hosts for the tenant 100.
+	#  - host hs-1 is directly connected to the router rt-1;
+	#  - host hs-2 is directly connected to the router rt-2.
+	setup_hs 1 1 100
+	setup_hs 2 2 100
+
+	# setup the IPv4 L3 VPN which connects the host hs-1 and host hs-2.
+	setup_vpn_config 1 1 2 2 100  #args: src_host src_router dst_host dst_router tenant
+	setup_vpn_config 2 2 1 1 100
+}
+
+check_hs_connectivity()
+{
+	local hssrc=$1
+	local hsdst=$2
+	local tid=$3
+
+	ip netns exec hs-${hssrc} ping -c 1 -W ${PING_TIMEOUT_SEC} \
+		${IPv4_HS_NETWORK}.${hsdst} >/dev/null 2>&1
+}
+
+check_and_log_hs_connectivity()
+{
+	local hssrc=$1
+	local hsdst=$2
+	local tid=$3
+
+	check_hs_connectivity ${hssrc} ${hsdst} ${tid}
+	log_test $? 0 "Hosts connectivity: hs-${hssrc} -> hs-${hsdst} (tenant ${tid})"
+}
+
+host_tests()
+{
+	log_section "SRv6 VPN connectivity test among hosts in the same tenant"
+
+	check_and_log_hs_connectivity 1 2 100
+	check_and_log_hs_connectivity 2 1 100
+}
+
+router_netfilter_tests()
+{
+	log_section "SRv6 VPN connectivity test with netfilter enabled in routers"
+	setup_rt_netfilter 1
+	setup_rt_netfilter 2
+
+	check_and_log_hs_connectivity 1 2 100
+	check_and_log_hs_connectivity 2 1 100
+}
+
+if [ "$(id -u)" -ne 0 ];then
+	echo "SKIP: Need root privileges"
+	exit $ksft_skip
+fi
+
+if [ ! -x "$(command -v ip)" ]; then
+	echo "SKIP: Could not run test without ip tool"
+	exit $ksft_skip
+fi
+
+cleanup &>/dev/null
+
+setup
+
+host_tests
+router_netfilter_tests
+
+print_log_test_results
+
+cleanup &>/dev/null
+
+exit ${ret}