Re: [PATCH net-next 5/5] selftests: seg6: add tests for PSP with a consumed SRH

[Hangbin Liu]

On Sun, Oct 11, 2026 at 09:23:10PM +0200, Andrea Mayer wrote:
> Extend srv6_end_flavors_test.sh with tests for the SRv6 End behavior
> with the PSP flavor, alone and together with NEXT-C-SID, on packets that
> carry a consumed SRH in front of the SRH to process.
> 
> Each test sends a ping along an existing SRv6 Policy, and a router on
> the path inserts an extra SRH in front of the Policy's SRH. An End
> behavior on another router consumes the extra SRH, and the router
> connected to the host must then remove only the Policy's SRH. A test
> passes if the ping succeeds.
> 
> These tests set seg6_enabled to 1 on the hosts, which must accept the
> extra SRH, and set it back to 0 at the end. PSP itself is checked
> by the other PSP tests, which run with seg6_enabled set to 0.
> 
> Signed-off-by: Andrea Mayer <andrea.mayer@xxxxxxxxxxx>
> ---
>  .../selftests/net/srv6_end_flavors_test.sh    | 144 +++++++++++++++++-
>  1 file changed, 142 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/net/srv6_end_flavors_test.sh b/tools/testing/selftests/net/srv6_end_flavors_test.sh
> index baa1b09a1aab..b5dbf53a7f23 100755
> --- a/tools/testing/selftests/net/srv6_end_flavors_test.sh
> +++ b/tools/testing/selftests/net/srv6_end_flavors_test.sh
> @@ -22,8 +22,7 @@
>  # 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.
> +# listed in the SRv6 policy to remove (i.e. pop) the 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
> @@ -258,6 +257,60 @@
>  # the hosts). The loopback address of a host is reached only through the
>  # router connected to that host: the ping succeeds only if the SRH is removed
>  # by that router.
> +#
> +# Traffic with a consumed SRH
> +# ---------------------------
> +#
> +# A packet can carry more than one SRH. The SRv6 End behavior skips an SRH with
> +# SL=0 and processes the next header [1].
> +#
> +# The traffic of this section reuses the Policies (i.a), (i.b), (i.c) and (i.d).
> +# A router on the path inserts an extra SRH in front of the Policy's SRH, and
> +# another router then consumes the extra SRH.
> +#
> +# The Policy (i.a) has SID List=fcff:3::e,fcff:4::ef1,fcff:2::ef1,cafe::2. A
> +# packet from hs-1 to hs-2 goes as follows:
> +#
> +#  - rt-1 applies the Policy and sends the packet to rt-3:
> +#      IPv6 DA=fcff:3::e | Policy's SRH, SL=3 | Payload
> +#
> +#  - rt-3 (End) processes the Policy's SRH and sends the packet to rt-4:
> +#      IPv6 DA=fcff:4::ef1 | Policy's SRH, SL=2 | Payload
> +#
> +#  - rt-4 (End with PSP and SL>1, acting as End) processes the Policy's SRH.
> +#    The new DA is fcff:2::ef1:
> +#      IPv6 DA=fcff:2::ef1 | Policy's SRH, SL=1 | Payload
> +#    On rt-4, the route added by the test for fcff:2::ef1 then inserts the
> +#    extra SRH, with SID List=fcff:3::e,fcff:2::ef1, and the packet goes back to
> +#    rt-3:
> +#      IPv6 DA=fcff:3::e | extra SRH, SL=1 | Policy's SRH, SL=1 | Payload
> +#
> +#  - rt-3 (End) consumes the extra SRH and sets the DA back to fcff:2::ef1:
> +#      IPv6 DA=fcff:2::ef1 | extra SRH, SL=0 | Policy's SRH, SL=1 | Payload
> +#
> +#  - rt-2 (End with PSP) skips the extra SRH, processes the Policy's SRH and
> +#    removes it:
> +#      IPv6 DA=cafe::2 | extra SRH, SL=0 | Payload
> +#
> +# The extra SRH reaches hs-2, which skips it as its SL is 0. The other
> +# Policies work in the same way:
> +#
> +#   (i.b) hs-2 -> hs-1: on the packets with DA=fcff:1::ef1, rt-2 inserts the
> +#         extra SRH with SID List=fcff:3::e,fcff:1::ef1, and rt-3 consumes it.
> +#   (i.c) hs-1 -> hs-2: on the packets with DA=fcbb:0:02a1::, rt-4 inserts the
> +#         extra SRH with SID List=fcff:3::e,fcbb:0:02a1::, and rt-3 consumes it.
> +#   (i.d) hs-2 -> hs-1: on the packets with DA=fcbb:0:01a1::, rt-3 inserts the
> +#         extra SRH with SID List=fcff:4::e,fcbb:0:01a1::, and rt-4 consumes it.
> +#
> +# The Policy (i.b) has no router between rt-2 and rt-1. For this reason, rt-2
> +# applies the Policy, inserts the extra SRH and sends the packet to rt-3:
> +#      IPv6 DA=fcff:3::e | extra SRH, SL=1 | Policy's SRH, SL=1 | Payload
> +# rt-3 consumes the extra SRH, and rt-1 removes the Policy's SRH.
> +#
> +# The hosts need seg6_enabled set to 1 to accept the extra SRH, and it is set
> +# back to 0 at the end. These tests only check that the ping succeeds: PSP
> +# itself is checked by the PSP flavor and NEXT-C-SID,PSP tests, which run with
> +# seg6_enabled set to 0.
>  
>  # shellcheck source=lib.sh
>  source lib.sh
> @@ -967,6 +1020,92 @@ host_srv6_end_flv_next_csid_psp_tests()
>  	check_and_log_hs_lo_addr_connectivity 2 1 "${END_CSID_PSP_FUNC}"
>  }
>  
> +# On a router, add a route for a SID with seg6 encap in inline mode. The packets
> +# that the router forwards to that SID get an extra SRH with the End SID of the
> +# router that consumes it.
> +# args:
> +#  $1 - router on which the route is added
> +#  $2 - SID of the route
> +#  $3 - router with the SRv6 End behavior that consumes the extra SRH
> +setup_rt_consumed_srh()
> +{
> +	local rt="$1"
> +	local sid="$2"
> +	local end_rt="$3"
> +	local nsname
> +
> +	nsname="$(get_rtname "${rt}")"
> +
> +	ip -netns "${nsname}" -6 route \
> +		add "${sid}" table "${LOCALSID_TABLE_ID}" \
> +		encap seg6 mode inline \
> +		segs "${LOCATOR_SERVICE}:${end_rt}::${END_FUNC}" \
> +		dev "${DUMMY_DEVNAME}"
> +}
> +
> +cleanup_rt_consumed_srh()
> +{
> +	local rt="$1"
> +	local sid="$2"
> +	local nsname
> +
> +	nsname="$(get_rtname "${rt}")"
> +
> +	ip -netns "${nsname}" -6 route \
> +		del "${sid}" table "${LOCALSID_TABLE_ID}"
> +}
> +
> +set_hs_seg6_enabled()
> +{
> +	local val="$1"
> +	local hsname
> +	local hs
> +
> +	for hs in ${HOSTS}; do
> +		hsname="$(get_hsname "${hs}")"
> +
> +		ip netns exec "${hsname}" \
> +			sysctl -wq net.ipv6.conf.all.seg6_enabled="${val}"
> +		ip netns exec "${hsname}" \
> +			sysctl -wq net.ipv6.conf.veth0.seg6_enabled="${val}"
> +	done
> +}
> +
> +host_srv6_end_flv_consumed_srh_tests()
> +{
> +	local sid
> +
> +	log_section "SRv6 connectivity test hosts (h1 <-> h2, consumed SRH)"
> +
> +	set_hs_seg6_enabled 1
> +
> +	# Policy (i.a): rt-4 inserts the extra SRH consumed by rt-3
> +	sid="${LOCATOR_SERVICE}:2::${END_PSP_FUNC}"
> +	setup_rt_consumed_srh 4 "${sid}" 3
> +	check_and_log_hs_connectivity 1 2
> +	cleanup_rt_consumed_srh 4 "${sid}"
> +
> +	# Policy (i.b): rt-2 inserts the extra SRH consumed by rt-3
> +	sid="${LOCATOR_SERVICE}:1::${END_PSP_FUNC}"
> +	setup_rt_consumed_srh 2 "${sid}" 3
> +	check_and_log_hs_connectivity 2 1
> +	cleanup_rt_consumed_srh 2 "${sid}"
> +
> +	# Policy (i.c): rt-4 inserts the extra SRH consumed by rt-3
> +	sid="$(build_csid_container 2 "${END_CSID_PSP_FUNC}")"
> +	setup_rt_consumed_srh 4 "${sid}" 3
> +	check_and_log_hs_lo_addr_connectivity 1 2 "${END_CSID_PSP_FUNC}"
> +	cleanup_rt_consumed_srh 4 "${sid}"
> +
> +	# Policy (i.d): rt-3 inserts the extra SRH consumed by rt-4
> +	sid="$(build_csid_container 1 "${END_CSID_PSP_FUNC}")"
> +	setup_rt_consumed_srh 3 "${sid}" 4
> +	check_and_log_hs_lo_addr_connectivity 2 1 "${END_CSID_PSP_FUNC}"
> +	cleanup_rt_consumed_srh 3 "${sid}"
> +
> +	set_hs_seg6_enabled 0
> +}
> +
>  test_iproute2_supp_or_ksft_skip()
>  {
>  	local flavor="$1"
> @@ -1071,5 +1210,6 @@ router_tests
>  host2gateway_tests
>  host_srv6_end_flv_psp_tests
>  host_srv6_end_flv_next_csid_psp_tests
> +host_srv6_end_flv_consumed_srh_tests
>  
>  print_log_test_results
> -- 
> 2.43.0
> 

Tested-by: Hangbin Liu <liuhangbin@xxxxxxxxxx>
Reviewed-by: Hangbin Liu <liuhangbin@xxxxxxxxxx>

Thanks
Hangbin