selftests: pmtu: add explicit tests for PMTU exceptions cleanup [Linux 5.0]

selftests: pmtu: add explicit tests for PMTU exceptions cleanup [Linux 5.0]

This Linux kernel change "selftests: pmtu: add explicit tests for PMTU exceptions cleanup" is included in the Linux 5.0 release. This change is authored by Paolo Abeni <pabeni [at] redhat.com> on Mon Feb 25 16:08:37 2019 +0100. The commit for this change in Linux stable tree is b3cc4f8 (patch).

selftests: pmtu: add explicit tests for PMTU exceptions cleanup

Add a couple of new tests, explicitly checking that the kernel
timely releases PMTU exceptions on related device removal.
This is mostly a regression test vs the issue fixed by
commit f5b51fe804ec ("ipv6: route: purge exception on removal")

Only 2 new test cases have been added, instead of extending all
the existing ones, because the reproducer requires executing
several commands and would slow down too much the tests otherwise.

v2 -> v3:
 - more cleanup, still from Stefano

v1 -> v2:
 - several script cleanups, as suggested by Stefano

Signed-off-by: Paolo Abeni <[email protected]>
Reviewed-by: David Ahern <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

There are 68 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 tools/testing/selftests/net/pmtu.sh | 68 ++++++++++++++++++++++++++++++++++++-
 1 file changed, 67 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/pmtu.sh b/tools/testing/selftests/net/pmtu.sh
index 89aec2f..912b2dc 100755
--- a/tools/testing/selftests/net/pmtu.sh
+++ b/tools/testing/selftests/net/pmtu.sh
@@ -103,6 +103,15 @@
 #  and check that configured MTU is used on link creation and changes, and
 #  that MTU is properly calculated instead when MTU is not configured from
 #  userspace
+#
+# - cleanup_ipv4_exception
+#  Similar to pmtu_ipv4_vxlan4_exception, but explicitly generate PMTU
+#  exceptions on multiple CPUs and check that the veth device tear-down
+#  happens in a timely manner
+#
+# - cleanup_ipv6_exception
+#  Same as above, but use IPv6 transport from A to B
+

 # Kselftest framework requirement - SKIP code is 4.
 ksft_skip=4
@@ -135,7 +144,9 @@ tests="
    pmtu_vti6_default_mtu       vti6: default MTU assignment
    pmtu_vti4_link_add_mtu      vti4: MTU setting on link creation
    pmtu_vti6_link_add_mtu      vti6: MTU setting on link creation
-   pmtu_vti6_link_change_mtu   vti6: MTU changes on link changes"
+   pmtu_vti6_link_change_mtu   vti6: MTU changes on link changes
+   cleanup_ipv4_exception      ipv4: cleanup of cached exceptions
+   cleanup_ipv6_exception      ipv6: cleanup of cached exceptions"

 NS_A="ns-$(mktemp -u XXXXXX)"
 NS_B="ns-$(mktemp -u XXXXXX)"
@@ -1006,6 +1017,61 @@ test_pmtu_vti6_link_change_mtu() {
    return ${fail}
 }

+check_command() {
+   cmd=${1}
+
+   if ! which ${cmd} > /dev/null 2>&1; then
+       err "  missing required command: '${cmd}'"
+       return 1
+   fi
+   return 0
+}
+
+test_cleanup_vxlanX_exception() {
+   outer="${1}"
+   encap="vxlan"
+   ll_mtu=4000
+
+   check_command taskset || return 2
+   cpu_list=$(grep -m 2 processor /proc/cpuinfo | cut -d ' ' -f 2)
+
+   setup namespaces routing ${encap}${outer} || return 2
+   trace "${ns_a}" ${encap}_a   "${ns_b}"  ${encap}_b \
+         "${ns_a}" veth_A-R1    "${ns_r1}" veth_R1-A \
+         "${ns_b}" veth_B-R1    "${ns_r1}" veth_R1-B
+
+   # Create route exception by exceeding link layer MTU
+   mtu "${ns_a}"  veth_A-R1 $((${ll_mtu} + 1000))
+   mtu "${ns_r1}" veth_R1-A $((${ll_mtu} + 1000))
+   mtu "${ns_b}"  veth_B-R1 ${ll_mtu}
+   mtu "${ns_r1}" veth_R1-B ${ll_mtu}
+
+   mtu "${ns_a}" ${encap}_a $((${ll_mtu} + 1000))
+   mtu "${ns_b}" ${encap}_b $((${ll_mtu} + 1000))
+
+   # Fill exception cache for multiple CPUs (2)
+   # we can always use inner IPv4 for that
+   for cpu in ${cpu_list}; do
+       taskset --cpu-list ${cpu} ${ns_a} ping -q -M want -i 0.1 -w 1 -s $((${ll_mtu} + 500)) ${tunnel4_b_addr} > /dev/null
+   done
+
+   ${ns_a} ip link del dev veth_A-R1 &
+   iplink_pid=$!
+   sleep 1
+   if [ "$(cat /proc/${iplink_pid}/cmdline 2>/dev/null | tr -d '\0')" = "iplinkdeldevveth_A-R1" ]; then
+       err "  can't delete veth device in a timely manner, PMTU dst likely leaked"
+       return 1
+   fi
+}
+
+test_cleanup_ipv6_exception() {
+   test_cleanup_vxlanX_exception 6
+}
+
+test_cleanup_ipv4_exception() {
+   test_cleanup_vxlanX_exception 4
+}
+
 usage() {
    echo
    echo "$0 [OPTIONS] [TEST]..."

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