Re: [PATCH net-next v8] net: ipv4: Cache pmtu for all packet paths if multipath enabled

[Ido Schimmel <idosch@idosch.org>]

On Wed, Nov 06, 2024 at 01:30:07PM +0000, Vladimir Vdovin wrote:
> +test_pmtu_ipv4_mp_exceptions() {
> +	setup namespaces routing multipath || return $ksft_skip
> +
> +	trace "${ns_a}"  veth_A-R1    "${ns_r1}" veth_R1-A \
> +	      "${ns_r1}" veth_R1-B    "${ns_b}"  veth_B-R1 \
> +	      "${ns_a}"  veth_A-R2    "${ns_r2}" veth_R2-A \
> +	      "${ns_r2}" veth_R2-B    "${ns_b}"  veth_B-R2
> +
> +	# Set up initial MTU values
> +	mtu "${ns_a}"  veth_A-R1 2000
> +	mtu "${ns_r1}" veth_R1-A 2000
> +	mtu "${ns_r1}" veth_R1-B 1500
> +	mtu "${ns_b}"  veth_B-R1 1500
> +
> +	mtu "${ns_a}"  veth_A-R2 2000
> +	mtu "${ns_r2}" veth_R2-A 2000
> +	mtu "${ns_r2}" veth_R2-B 1500
> +	mtu "${ns_b}"  veth_B-R2 1500
> +
> +	fail=0
> +
> +	# Ping and expect two nexthop exceptions for two routes in nh group
> +	run_cmd ${ns_a} ping -q -M want -i 0.1 -c 1 -s 1800 "${host4_b_addr}"
> +
> +	# Do route lookup before checking cached exceptions.
> +	# The following commands are needed for dst entries to be cached
> +	# in both paths exceptions and therefore dumped to user space
> +	# Check that exceptions have been created with the correct PMTU
> +	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" "${host4_b_addr}" oif veth_A-R1)"
> +	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" "${host4_b_addr}" oif veth_A-R2)"

This overrides the first PMTU

> +
> +	check_pmtu_value "1500" "${pmtu}" "exceeding MTU (veth_A-R2)" || return 1
> +	check_pmtu_value "1500" "${pmtu}" "exceeding MTU (veth_A-R1)" || return 1
> +
> +	return ${fail}

And "fail" does not seem to be used anymore.

Can you squash the following diff to v9?

diff --git a/tools/testing/selftests/net/pmtu.sh b/tools/testing/selftests/net/pmtu.sh
index 9e34b54d9c15..1b4d4c598d66 100755
--- a/tools/testing/selftests/net/pmtu.sh
+++ b/tools/testing/selftests/net/pmtu.sh
@@ -2396,22 +2396,14 @@ test_pmtu_ipv4_mp_exceptions() {
 	mtu "${ns_r2}" veth_R2-B 1500
 	mtu "${ns_b}"  veth_B-R2 1500
 
-	fail=0
-
 	# Ping and expect two nexthop exceptions for two routes in nh group
 	run_cmd ${ns_a} ping -q -M want -i 0.1 -c 1 -s 1800 "${host4_b_addr}"
 
-	# Do route lookup before checking cached exceptions.
-	# The following commands are needed for dst entries to be cached
-	# in both paths exceptions and therefore dumped to user space
 	# Check that exceptions have been created with the correct PMTU
 	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" "${host4_b_addr}" oif veth_A-R1)"
+	check_pmtu_value "1500" "${pmtu}" "exceeding MTU (veth_A-R1)" || return 1
 	pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" "${host4_b_addr}" oif veth_A-R2)"
-
 	check_pmtu_value "1500" "${pmtu}" "exceeding MTU (veth_A-R2)" || return 1
-	check_pmtu_value "1500" "${pmtu}" "exceeding MTU (veth_A-R1)" || return 1
-
-	return ${fail}
 }
 
 usage() {