selftests: pmtu: Add optional traffic captures for single tests

If --trace is passed as an option and tcpdump is available,
capture traffic for all relevant interfaces to per-test pcap
files named <test>_<interface>.pcap.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/tools/testing/selftests/net/pmtu.sh b/tools/testing/selftests/net/pmtu.sh
index 8278a24..a369d61 100755 (executable)
--- a/tools/testing/selftests/net/pmtu.sh
+++ b/tools/testing/selftests/net/pmtu.sh
@@ -142,6 +142,7 @@ dummy6_mask="64"
 
 cleanup_done=1
 err_buf=
+tcpdump_pids=
 
 err() {
        err_buf="${err_buf}${1}
@@ -284,7 +285,24 @@ setup() {
        done
 }
 
+trace() {
+       [ $tracing -eq 0 ] && return
+
+       for arg do
+               [ "${ns_cmd}" = "" ] && ns_cmd="${arg}" && continue
+               ${ns_cmd} tcpdump -s 0 -i "${arg}" -w "${name}_${arg}.pcap" 2> /dev/null &
+               tcpdump_pids="${tcpdump_pids} $!"
+               ns_cmd=
+       done
+       sleep 1
+}
+
 cleanup() {
+       for pid in ${tcpdump_pids}; do
+               kill ${pid}
+       done
+       tcpdump_pids=
+
        [ ${cleanup_done} -eq 1 ] && return
        for n in ${NS_A} ${NS_B} ${NS_R1} ${NS_R2}; do
                ip netns del ${n} 2> /dev/null
@@ -357,6 +375,10 @@ test_pmtu_ipvX() {
        family=${1}
 
        setup namespaces routing || return 2
+       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
 
        if [ ${family} -eq 4 ]; then
                ping=ping
@@ -445,6 +467,8 @@ test_pmtu_ipv6_exception() {
 
 test_pmtu_vti4_exception() {
        setup namespaces veth vti4 xfrm4 || return 2
+       trace "${ns_a}" veth_a    "${ns_b}" veth_b \
+             "${ns_a}" vti4_a    "${ns_b}" vti4_b
 
        veth_mtu=1500
        vti_mtu=$((veth_mtu - 20))
@@ -473,6 +497,8 @@ test_pmtu_vti4_exception() {
 
 test_pmtu_vti6_exception() {
        setup namespaces veth vti6 xfrm6 || return 2
+       trace "${ns_a}" veth_a    "${ns_b}" veth_b \
+             "${ns_a}" vti6_a    "${ns_b}" vti6_b
        fail=0
 
        # Create route exception by exceeding link layer MTU
@@ -643,29 +669,49 @@ test_pmtu_vti6_link_change_mtu() {
 
 usage() {
        echo
-       echo "$0 [TEST]..."
+       echo "$0 [OPTIONS] [TEST]..."
        echo "If no TEST argument is given, all tests will be run."
        echo
+       echo "Options"
+       echo "  --trace: capture traffic to TEST_INTERFACE.pcap"
+       echo
        echo "Available tests${tests}"
        exit 1
 }
 
+exitcode=0
+desc=0
+IFS="  
+"
+
+tracing=0
 for arg do
-       # Check first that all requested tests are available before running any
-       command -v > /dev/null "test_${arg}" || { echo "=== Test ${arg} not found"; usage; }
+       if [ "${arg}" != "${arg#--*}" ]; then
+               opt="${arg#--}"
+               if [ "${opt}" = "trace" ]; then
+                       if which tcpdump > /dev/null 2>&1; then
+                               tracing=1
+                       else
+                               echo "=== tcpdump not available, tracing disabled"
+                       fi
+               else
+                       usage
+               fi
+       else
+               # Check first that all requested tests are available before
+               # running any
+               command -v > /dev/null "test_${arg}" || { echo "=== Test ${arg} not found"; usage; }
+       fi
 done
 
 trap cleanup EXIT
 
-exitcode=0
-desc=0
-IFS="  
-"
 for t in ${tests}; do
        [ $desc -eq 0 ] && name="${t}" && desc=1 && continue || desc=0
 
        run_this=1
        for arg do
+               [ "${arg}" != "${arg#--*}" ] && continue
                [ "${arg}" = "${name}" ] && run_this=1 && break
                run_this=0
        done