selftests: udpgso: Pull up network setup into shell script

udpgso regression test configures routing and device MTU directly through
uAPI (Netlink, ioctl) to do its job. While there is nothing wrong with it,
it takes more effort than doing it from shell.

Looking forward, we would like to extend the udpgso regression tests to
cover the EIO corner case [1], once it gets addressed. That will require a
dummy device and device feature manipulation to set it up. Which means more
Netlink code.

So, in preparation, pull out network configuration into the shell script
part of the test, so it is easily extendable in the future.

Also, because it now easy to setup routing, add a second local IPv6
address. Because the second address is not managed by the kernel, we can
"replace" the corresponding local route with a reduced-MTU one. This
unblocks the disabled "ipv6 connected" test case. Add a similar setup for
IPv4 for symmetry.

[1] https://lore.kernel.org/netdev/87jzqsld6q.fsf@cloudflare.com/

Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/r/20240207-jakub-krn-635-v3-1-3dfa3da8a7d3@cloudflare.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 39 insertions, 10 deletions

diff --git a/tools/testing/selftests/net/udpgso.sh b/tools/testing/selftests/net/udpgso.sh
index fec24f584fe9..6c63178086b0 100755
--- a/tools/testing/selftests/net/udpgso.sh
+++ b/tools/testing/selftests/net/udpgso.sh
@@ -3,27 +3,56 @@
 #
 # Run a series of udpgso regression tests
 
+set -o errexit
+set -o nounset
+
+setup_loopback() {
+	ip addr add dev lo 10.0.0.1/32
+	ip addr add dev lo fd00::1/128 nodad noprefixroute
+}
+
+test_dev_mtu() {
+	setup_loopback
+	# Reduce loopback MTU
+	ip link set dev lo mtu 1500
+}
+
+test_route_mtu() {
+	setup_loopback
+	# Remove default local routes
+	ip route del local 10.0.0.1/32 table local dev lo
+	ip route del local fd00::1/128 table local dev lo
+	# Install local routes with reduced MTU
+	ip route add local 10.0.0.1/32 table local dev lo mtu 1500
+	ip route add local fd00::1/128 table local dev lo mtu 1500
+}
+
+if [ "$#" -gt 0 ]; then
+	"$1"
+	shift 2 # pop "test_*" arg and "--" delimiter
+	exec "$@"
+fi
+
 echo "ipv4 cmsg"
-./in_netns.sh ./udpgso -4 -C
+./in_netns.sh "$0" test_dev_mtu -- ./udpgso -4 -C
 
 echo "ipv4 setsockopt"
-./in_netns.sh ./udpgso -4 -C -s
+./in_netns.sh "$0" test_dev_mtu -- ./udpgso -4 -C -s
 
 echo "ipv6 cmsg"
-./in_netns.sh ./udpgso -6 -C
+./in_netns.sh "$0" test_dev_mtu -- ./udpgso -6 -C
 
 echo "ipv6 setsockopt"
-./in_netns.sh ./udpgso -6 -C -s
+./in_netns.sh "$0" test_dev_mtu -- ./udpgso -6 -C -s
 
 echo "ipv4 connected"
-./in_netns.sh ./udpgso -4 -c
+./in_netns.sh "$0" test_route_mtu -- ./udpgso -4 -c
 
-# blocked on 2nd loopback address
-# echo "ipv6 connected"
-# ./in_netns.sh ./udpgso -6 -c
+echo "ipv6 connected"
+./in_netns.sh "$0" test_route_mtu -- ./udpgso -6 -c
 
 echo "ipv4 msg_more"
-./in_netns.sh ./udpgso -4 -C -m
+./in_netns.sh "$0" test_dev_mtu -- ./udpgso -4 -C -m
 
 echo "ipv6 msg_more"
-./in_netns.sh ./udpgso -6 -C -m
+./in_netns.sh "$0" test_dev_mtu -- ./udpgso -6 -C -m