selftests: net: test vxlan pmtu exceptions with tcp

TCP might get stuck if a nonlinear skb exceeds the path MTU,
icmp error contains an incorrect icmp checksum in that case.

Extend the existing test for vxlan to also send at least 1MB worth of
data via TCP in addition to the existing 'large icmp packet adds
route exception'.

On my test VM this fails due to 0-size output file without
"tunnels: fix kasan splat when generating ipv4 pmtu error".

Signed-off-by: Florian Westphal <fw@strlen.de>
Link: https://lore.kernel.org/r/20230803152653.29535-3-fw@strlen.de
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/tools/testing/selftests/net/pmtu.sh b/tools/testing/selftests/net/pmtu.sh
index dfe3d287f01d24cdb9a1b538ff900e11b06e7d18..f838dd370f6af3ef252f0f77bf11e72aa80bed84 100755 (executable)
--- a/tools/testing/selftests/net/pmtu.sh
+++ b/tools/testing/selftests/net/pmtu.sh
@@ -361,6 +361,7 @@ err_buf=
 tcpdump_pids=
 nettest_pids=
 socat_pids=
+tmpoutfile=
 
 err() {
        err_buf="${err_buf}${1}
@@ -951,6 +952,7 @@ cleanup() {
        ip link del veth_A-R1                   2>/dev/null
        ovs-vsctl --if-exists del-port vxlan_a  2>/dev/null
        ovs-vsctl --if-exists del-br ovs_br0    2>/dev/null
+       rm -f "$tmpoutfile"
 }
 
 mtu() {
@@ -1328,6 +1330,39 @@ test_pmtu_ipvX_over_bridged_vxlanY_or_geneveY_exception() {
        check_pmtu_value ${exp_mtu} "${pmtu}" "exceeding link layer MTU on bridged ${type} interface"
        pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" ${dst})"
        check_pmtu_value ${exp_mtu} "${pmtu}" "exceeding link layer MTU on locally bridged ${type} interface"
+
+       tmpoutfile=$(mktemp)
+
+       # Flush Exceptions, retry with TCP
+       run_cmd ${ns_a} ip route flush cached ${dst}
+       run_cmd ${ns_b} ip route flush cached ${dst}
+       run_cmd ${ns_c} ip route flush cached ${dst}
+
+       for target in "${ns_a}" "${ns_c}" ; do
+               if [ ${family} -eq 4 ]; then
+                       TCPDST=TCP:${dst}:50000
+               else
+                       TCPDST="TCP:[${dst}]:50000"
+               fi
+               ${ns_b} socat -T 3 -u -6 TCP-LISTEN:50000 STDOUT > $tmpoutfile &
+
+               sleep 1
+
+               dd if=/dev/zero of=/dev/stdout status=none bs=1M count=1 | ${target} socat -T 3 -u STDIN $TCPDST,connect-timeout=3
+
+               size=$(du -sb $tmpoutfile)
+               size=${size%%/tmp/*}
+
+               [ $size -ne 1048576 ] && err "File size $size mismatches exepcted value in locally bridged vxlan test" && return 1
+       done
+
+       rm -f "$tmpoutfile"
+
+       # Check that exceptions were created
+       pmtu="$(route_get_dst_pmtu_from_exception "${ns_c}" ${dst})"
+       check_pmtu_value ${exp_mtu} "${pmtu}" "tcp: exceeding link layer MTU on bridged ${type} interface"
+       pmtu="$(route_get_dst_pmtu_from_exception "${ns_a}" ${dst})"
+       check_pmtu_value ${exp_mtu} "${pmtu}" "tcp exceeding link layer MTU on locally bridged ${type} interface"
 }
 
 test_pmtu_ipv4_br_vxlan4_exception() {