[ovs-dev,branch-23.09,1/2] tests: Add helper for tcpdump.

The way how tcpdump was called in tests was inconsistent,
a lot fo the tests didn't even wait for the tcpdump to properly
start, some of them didn't redirect the stderr which could cause
leak into the test stderr and fail the test.

To prevent that add macro that starts tcpdump and properly
waits for the "listening" state, at the same time redirects
the stderr into separate file.

Signed-off-by: Ales Musil <amusil@redhat.com>
Signed-off-by: Dumitru Ceara <dceara@redhat.com>
(cherry picked from commit e8ac18104df0bbd6579d8c62fd4282939631b878)
---
 tests/system-common-macros.at |  29 ++--
 tests/system-ovn-kmod.at      |  26 +--
 tests/system-ovn.at           | 312 ++++++++++++++--------------------
 3 files changed, 154 insertions(+), 213 deletions(-)

Thanks Ales, I pushed this and patch 2 to branch-23.09.

On 3/20/24 06:16, Ales Musil wrote:
> The way how tcpdump was called in tests was inconsistent,
> a lot fo the tests didn't even wait for the tcpdump to properly
> start, some of them didn't redirect the stderr which could cause
> leak into the test stderr and fail the test.
> 
> To prevent that add macro that starts tcpdump and properly
> waits for the "listening" state, at the same time redirects
> the stderr into separate file.
> 
> Signed-off-by: Ales Musil <amusil@redhat.com>
> Signed-off-by: Dumitru Ceara <dceara@redhat.com>
> (cherry picked from commit e8ac18104df0bbd6579d8c62fd4282939631b878)
> ---
>   tests/system-common-macros.at |  29 ++--
>   tests/system-ovn-kmod.at      |  26 +--
>   tests/system-ovn.at           | 312 ++++++++++++++--------------------
>   3 files changed, 154 insertions(+), 213 deletions(-)
> 
> diff --git a/tests/system-common-macros.at b/tests/system-common-macros.at
> index 8fe93cbdb..683f15fe3 100644
> --- a/tests/system-common-macros.at
> +++ b/tests/system-common-macros.at
> @@ -271,6 +271,18 @@ m4_define([OVS_START_L7],
>      ]
>   )
>   
> +# NETNS_START_TCPDUMP([namespace], [params], [name])
> +#
> +# Helper to properly start tcpdump and wait for the startup.
> +# The tcpdump output is available in <name>.tcpdump file.
> +m4_define([NETNS_START_TCPDUMP],
> +    [
> +     NETNS_DAEMONIZE([$1], [tcpdump -l $2 >$3.tcpdump 2>$3.stderr], [$3.pid])
> +     OVS_WAIT_UNTIL([grep -q "listening" $3.stderr])
> +    ]
> +)
> +
> +
>   # OVS_CHECK_VXLAN()
>   #
>   # Do basic check for vxlan functionality, skip the test if it's not there.
> @@ -437,8 +449,7 @@ chown root:dhcpd /var/lib/dhcp /var/lib/dhcp/dhcpd6.leases
>   chmod 775 /var/lib/dhcp
>   chmod 664 /var/lib/dhcp/dhcpd6.leases
>   
> -NS_CHECK_EXEC([server], [tcpdump -nni s1 > pkt.pcap &])
> -
> +NETNS_START_TCPDUMP([server], [-nni s1], [server])
>   NETNS_DAEMONIZE([server], [dhcpd -6 -f s1 > dhcpd.log 2>&1], [dhcpd.pid])
>   ovn-nbctl --wait=hv sync
>   
> @@ -456,17 +467,17 @@ prefix=$(ovn-nbctl list logical_router_port rp-public | awk -F/ '/ipv6_prefix/{p
>   ovn-nbctl list logical_router_port rp-public > /tmp/rp-public
>   
>   # Wait for 2 renew on each port.
> -NS_CHECK_EXEC([server], [tcpdump -c 4 -nni s1 ip6[[48:1]]=0x05 and ip6[[113:4]]=0x${prefix} > renew.pcap &])
> +NETNS_START_TCPDUMP([server], [-c 4 -nni s1 ip6[[48:1]]=0x05 and ip6[[113:4]]=0x${prefix}], [renew])
>   # Reply message with Status OK
> -NS_CHECK_EXEC([server], [tcpdump -c 4 -nni s1 ip6[[48:1]]=0x07 and ip6[[81:4]]=0x${prefix} > reply.pcap &])
> +NETNS_START_TCPDUMP([server], [-c 4 -nni s1 ip6[[48:1]]=0x07 and ip6[[81:4]]=0x${prefix}], [reply])
>   
>   OVS_WAIT_UNTIL([
> -    total_pkts=$(cat renew.pcap | wc -l)
> +    total_pkts=$(cat renew.tcpdump | wc -l)
>       test "${total_pkts}" = "4"
>   ])
>   
>   OVS_WAIT_UNTIL([
> -    total_pkts=$(cat reply.pcap | wc -l)
> +    total_pkts=$(cat reply.tcpdump | wc -l)
>       test "${total_pkts}" = "4"
>   ])
>   
> @@ -474,7 +485,7 @@ ovn-nbctl set logical_router_port rp-public options:prefix=false
>   ovn-nbctl set logical_router_port rp-sw0 options:prefix=false
>   ovn-nbctl --wait=hv set logical_router_port rp-sw1 options:prefix=true
>   sleep_sb
> -NS_CHECK_EXEC([server], [tcpdump -c 2 -nni s1 ip6[[48:1]]=0x05 and ip6[[113:4]]=0x${prefix} > renew.pcap &])
> +NETNS_START_TCPDUMP([server], [-c 2 -nni s1 ip6[[48:1]]=0x05 and ip6[[113:4]]=0x${prefix}], [renew2])
>   
>   # Sleep enough to have solicit and renew being sent, then wait for 2 renew.
>   # The reply to the request will usually be received as sb is sleeping.
> @@ -482,12 +493,10 @@ NS_CHECK_EXEC([server], [tcpdump -c 2 -nni s1 ip6[[48:1]]=0x05 and ip6[[113:4]]=
>   sleep 10
>   wake_up_sb
>   OVS_WAIT_UNTIL([
> -    total_pkts=$(cat renew.pcap | wc -l)
> +    total_pkts=$(cat renew2.tcpdump | wc -l)
>       test "${total_pkts}" = "2"
>   ])
>   
> -kill $(pidof tcpdump)
> -
>   ovn-nbctl set logical_router_port rp-sw0 options:prefix=false
>   ovn-nbctl clear logical_router_port rp-sw0 ipv6_prefix
>   OVS_WAIT_WHILE([test "$(ovn-nbctl get logical_router_port rp-sw0 ipv6_prefix | cut -c3-16)" = "[2001:1db8:3333]"])
> diff --git a/tests/system-ovn-kmod.at b/tests/system-ovn-kmod.at
> index 3a533d5e6..254a4b0a0 100644
> --- a/tests/system-ovn-kmod.at
> +++ b/tests/system-ovn-kmod.at
> @@ -664,14 +664,11 @@ ovn-nbctl --wait=hv sync
>   NETNS_DAEMONIZE([server], [nc -l -u 172.16.1.2 4242 > /dev/null], [server.pid])
>   
>   # Collect ICMP packets on client side
> -NETNS_DAEMONIZE([client], [tcpdump -l -U -i client -vnne \
> -icmp > client.pcap 2>client_err], [tcpdump0.pid])
> -OVS_WAIT_UNTIL([grep "listening" client_err])
> +NETNS_START_TCPDUMP([client], [-U -i client -vnne icmp], [tcpdump-client])
>   
>   # Collect UDP packets on server side
> -NETNS_DAEMONIZE([server], [tcpdump -l -U -i server -vnne \
> -'udp and ip[[6:2]] > 0 and not ip[[6]] = 64' > server.pcap 2>server_err], [tcpdump1.pid])
> -OVS_WAIT_UNTIL([grep "listening" server_err])
> +NETNS_START_TCPDUMP([server], [-U -i server -vnne \
> +'udp and ip[[6:2]] > 0 and not ip[[6]] = 64'], [tcpdump-server])
>   
>   check ip netns exec client python3 << EOF
>   import os
> @@ -679,7 +676,7 @@ import socket
>   import sys
>   import time
>   
> -FILE="client.pcap"
> +FILE="tcpdump-client.tcpdump"
>   
>   
>   def contains_string(file, str):
> @@ -707,8 +704,7 @@ else:
>       sys.exit(1)
>   EOF
>   
> -OVS_WAIT_UNTIL([test "$(cat server.pcap | wc -l)" = "4"])
> -
> +OVS_WAIT_UNTIL([test "$(cat tcpdump-server.tcpdump | wc -l)" = "4"])
>   
>   OVS_APP_EXIT_AND_WAIT([ovn-controller])
>   
> @@ -997,14 +993,10 @@ while True:
>   NETNS_DAEMONIZE([server], [$PYTHON3 ./server.py > server.log], [server.pid])
>   
>   dnl Collect packets on server side.
> -NETNS_DAEMONIZE([server], [tcpdump -l -U -i server -vnne \
> -          'ip and (icmp or udp)' > server.tcpdump 2>server_err], [tcpdump0.pid])
> -OVS_WAIT_UNTIL([grep "listening" server_err])
> +NETNS_START_TCPDUMP([server], [-U -i server -vnne 'ip and (icmp or udp)'], [tcpdump-server])
>   
>   dnl Collect packets on client side.
> -NETNS_DAEMONIZE([client], [tcpdump -l -U -i client -vnne \
> -          'ip and (icmp or udp)' > client.tcpdump 2>client_err], [tcpdump1.pid])
> -OVS_WAIT_UNTIL([grep "listening" client_err])
> +NETNS_START_TCPDUMP([client], [-U -i client -vnne 'ip and (icmp or udp)'], [tcpdump-client])
>   
>   dnl Send two packets to the server with a short interval.
>   dnl First packet should generate 'needs frag', the second should result in
> @@ -1022,8 +1014,8 @@ time.sleep(5)
>   NS_CHECK_EXEC([client], [$PYTHON3 ./client.py])
>   
>   dnl Expecting 2 outgoing packets and 2 fragments back - 8 lines total.
> -OVS_WAIT_UNTIL([test "$(cat client.tcpdump | wc -l)" = "8"])
> -AT_CHECK([test $(grep -c "need to frag (mtu 800)" server.tcpdump) -eq 1])
> +OVS_WAIT_UNTIL([test "$(cat tcpdump-client.tcpdump | wc -l)" = "8"])
> +AT_CHECK([test $(grep -c "need to frag (mtu 800)" tcpdump-server.tcpdump) -eq 1])
>   
>   ovn-appctl -t ovn-controller vlog/set info
>   
> diff --git a/tests/system-ovn.at b/tests/system-ovn.at
> index 213483176..605bb0569 100644
> --- a/tests/system-ovn.at
> +++ b/tests/system-ovn.at
> @@ -1602,12 +1602,11 @@ OVS_WAIT_UNTIL([
>   ovn-nbctl --reject lb-add lb3 30.0.0.10:80 ""
>   ovn-nbctl ls-lb-add foo lb3
>   # Filter reset segments
> -NS_CHECK_EXEC([foo1], [tcpdump -l -c 1 -neei foo1 ip[[33:1]]=0x14 > rst.pcap 2>tcpdump_err &])
> -OVS_WAIT_UNTIL([grep "listening" tcpdump_err])
> +NETNS_START_TCPDUMP([foo1], [-c 1 -neei foo1 ip[[33:1]]=0x14], [rst])
>   NS_CHECK_EXEC([foo1], [wget -q 30.0.0.10],[4])
>   
>   OVS_WAIT_UNTIL([
> -    n_reset=$(cat rst.pcap | wc -l)
> +    n_reset=$(cat rst.tcpdump | wc -l)
>       test "${n_reset}" = "1"
>   ])
>   
> @@ -3564,8 +3563,7 @@ icmp,orig=(src=192.168.2.2,dst=172.16.1.2,id=<cleared>,type=8,code=0),reply=(src
>   ])
>   
>   # Try to ping external network
> -NS_CHECK_EXEC([ext-net], [tcpdump -l -n -c 3 -i ext-veth dst 172.16.1.3 and icmp > ext-net.pcap 2>tcpdump_err &])
> -OVS_WAIT_UNTIL([grep "listening" tcpdump_err])
> +NETNS_START_TCPDUMP([ext-net], [-n -c 3 -i ext-veth dst 172.16.1.3 and icmp], [ext-net])
>   AT_CHECK([ovn-nbctl lr-nat-del R1 snat])
>   NS_CHECK_EXEC([foo1], [ping -q -c 3 -i 0.3 -w 2 10.0.0.1 | FORMAT_PING], \
>   [0], [dnl
> @@ -3573,7 +3571,7 @@ NS_CHECK_EXEC([foo1], [ping -q -c 3 -i 0.3 -w 2 10.0.0.1 | FORMAT_PING], \
>   ])
>   
>   OVS_WAIT_UNTIL([
> -    total_pkts=$(cat ext-net.pcap | wc -l)
> +    total_pkts=$(cat ext-net.tcpdump | wc -l)
>       test "${total_pkts}" = "3"
>   ])
>   
> @@ -4316,19 +4314,19 @@ ovn-nbctl set Logical_Switch sw2 \
>       other_config:mcast_ip6_src="2000::fe"
>   
>   # Check that v4 queries are generated.
> -NS_CHECK_EXEC([sw2-p1], [tcpdump -n -c 2 -i sw2-p1 igmp > sw2-p1-v4.pcap &])
> +NETNS_START_TCPDUMP([sw2-p1], [-n -c 2 -i sw2-p1 igmp], [sw2-p1-v4])
>   
>   OVS_WAIT_UNTIL([
> -    total_queries=`grep "igmp query" -c sw2-p1-v4.pcap`
> +    total_queries=`grep "igmp query" -c sw2-p1-v4.tcpdump`
>       test "${total_queries}" = "2"
>   ])
>   
>   # Check that v6 queries are generated (ip6 next header == Hop-By-Hop and
>   # icmpv6 type == MLD Query).
> -NS_CHECK_EXEC([sw2-p1], [tcpdump -n -c 2 -i sw2-p1 ip6[[6]]==0 and ip6[[48]]==0x82 > sw2-p1-v6.pcap &])
> +NETNS_START_TCPDUMP([sw2-p1], [-n -c 2 -i sw2-p1 ip6[[6]]==0 and ip6[[48]]==0x82], [sw2-p1-v6])
>   
>   OVS_WAIT_UNTIL([
> -    total_queries=`grep "multicast listener query" -c sw2-p1-v6.pcap`
> +    total_queries=`grep "multicast listener query" -c sw2-p1-v6.tcpdump`
>       test "${total_queries}" = "2"
>   ])
>   
> @@ -4546,13 +4544,13 @@ service_monitor protocol=udp | sed '/^$/d' | grep offline | wc -l`])
>   pid_file=$(cat l7_pid_file)
>   NS_CHECK_EXEC([sw1-p1], [kill $(cat $pid_file)])
>   
> -NS_CHECK_EXEC([sw0-p2], [tcpdump -c 1 -neei sw0-p2 ip[[33:1]]=0x14 > rst.pcap &])
> +NETNS_START_TCPDUMP([sw0-p2], [-c 1 -neei sw0-p2 ip[[33:1]]=0x14], [rst])
>   OVS_WAIT_UNTIL([test 2 = `ovn-sbctl --bare --columns status find \
>   service_monitor protocol=tcp | sed '/^$/d' | grep offline | wc -l`])
>   NS_CHECK_EXEC([sw0-p2], [wget 10.0.0.10 -v -o wget$i.log],[4])
>   
>   OVS_WAIT_UNTIL([
> -    n_reset=$(cat rst.pcap | wc -l)
> +    n_reset=$(cat rst.tcpdump | wc -l)
>       test "${n_reset}" = "1"
>   ])
>   
> @@ -4818,8 +4816,7 @@ NS_CHECK_EXEC([lsp], [nc 88.88.88.90 4041 -z], [0], [ignore], [ignore])
>   
>   # Capture IPv4 UDP hairpinned packets.
>   filter="dst 42.42.42.1 and dst port 2021 and udp"
> -NS_CHECK_EXEC([lsp], [tcpdump -l -nn -c 3 -i lsp ${filter} > lsp.pcap 2>tcpdump_err &])
> -OVS_WAIT_UNTIL([grep "listening" tcpdump_err])
> +NETNS_START_TCPDUMP([lsp], [-nn -c 3 -i lsp ${filter}], [lsp])
>   
>   # Generate IPv4 UDP hairpin traffic.
>   NS_CHECK_EXEC([lsp], [echo a | nc -u 88.88.88.88 4040], [ignore], [ignore], [ignore])
> @@ -4828,7 +4825,7 @@ NS_CHECK_EXEC([lsp], [echo a | nc -u 88.88.88.90 2021], [ignore], [ignore], [ign
>   
>   # Check hairpin traffic.
>   OVS_WAIT_UNTIL([
> -    total_pkts=$(cat lsp.pcap | wc -l)
> +    total_pkts=$(cat lsp.tcpdump | wc -l)
>       test "${total_pkts}" = "3"
>   ])
>   
> @@ -4916,8 +4913,7 @@ NS_CHECK_EXEC([lsp], [nc 8800::0090 4041 -z], [0], [ignore], [ignore])
>   
>   # Capture IPv6 UDP hairpinned packets.
>   filter="dst 4200::1 and dst port 2021 and udp"
> -NS_CHECK_EXEC([lsp], [tcpdump -l -nn -c 3 -i lsp $filter > lsp.pcap 2>tcpdump_err &])
> -OVS_WAIT_UNTIL([grep "listening" tcpdump_err])
> +NETNS_START_TCPDUMP([lsp], [-nn -c 3 -i lsp $filter], [lsp])
>   
>   # Generate IPv6 UDP hairpin traffic.
>   NS_CHECK_EXEC([lsp], [echo a | nc -u 8800::0088 4040], [ignore], [ignore], [ignore])
> @@ -4926,7 +4922,7 @@ NS_CHECK_EXEC([lsp], [echo a | nc -u 8800::0090 2021], [ignore], [ignore], [igno
>   
>   # Check hairpin traffic.
>   OVS_WAIT_UNTIL([
> -    total_pkts=$(cat lsp.pcap | wc -l)
> +    total_pkts=$(cat lsp.tcpdump | wc -l)
>       test "${total_pkts}" = "3"
>   ])
>   
> @@ -5040,10 +5036,7 @@ ADD_VETH(sw1-p1-rej, sw1-p1-rej, br-int, "20.0.0.3/24", "40:54:00:00:00:03", \
>            "20.0.0.1")
>   
>   # Capture packets in sw0-p1-rej.
> -NS_CHECK_EXEC([sw0-p1-rej], [tcpdump -l -nn -i sw0-p1-rej tcp > sw0-p1-rej-ip4.pcap 2> err &], [0])
> -
> -#Wait for tcpdump to get started before generating first packets
> -OVS_WAIT_UNTIL([test 1 = $(cat err | grep -c listening)])
> +NETNS_START_TCPDUMP([sw0-p1-rej], [-nn -i sw0-p1-rej tcp], [sw0-p1-rej-ip4])
>   
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p1-rej nc -vz 10.0.0.4 80 2>&1 | grep -i 'connection refused'
> @@ -5061,17 +5054,12 @@ grep controller | grep tp_dst=84 -c)
>   ])
>   
>   OVS_WAIT_UNTIL([
> -    total=`cat sw0-p1-rej-ip4.pcap |  grep "10\.0\.0\.3" | wc -l`
> +    total=`cat sw0-p1-rej-ip4.tcpdump |  grep "10\.0\.0\.3" | wc -l`
>       echo "total = $total"
>       test "${total}" = "4"
>   ])
>   
> -kill $(pidof tcpdump)
> -
> -NS_CHECK_EXEC([sw0-p2-rej], [tcpdump -l -nn -i sw0-p2-rej tcp port 80 > sw0-p2-rej-ip6.pcap 2> err &], [0])
> -
> -#Wait for tcpdump to get started before generating first packets
> -OVS_WAIT_UNTIL([test 1 = $(cat err | grep -c listening)])
> +NETNS_START_TCPDUMP([sw0-p2-rej], [-nn -i sw0-p2-rej tcp port 80], [sw0-p2-rej-ip6])
>   
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p2-rej nc -vz6 aef0::3 80 2>&1 | grep -i 'connection refused'
> @@ -5079,7 +5067,7 @@ OVS_WAIT_UNTIL([
>   
>   
>   OVS_WAIT_UNTIL([
> -    total=`cat sw0-p2-rej-ip6.pcap |  grep "aef0::3\.80" |wc -l`
> +    total=`cat sw0-p2-rej-ip6.tcpdump |  grep "aef0::3\.80" |wc -l`
>       echo "total = $total"
>       test "${total}" = "2"
>   ])
> @@ -5091,61 +5079,57 @@ OVS_WAIT_UNTIL([
>       ip netns exec sw1-p1-rej nc -vz 10.0.0.4 84 2>&1 | grep -i 'connection refused'
>   ])
>   
> -kill $(pidof tcpdump)
> -
>   
>   # Now test for IPv4 UDP.
> -NS_CHECK_EXEC([sw0-p1-rej], [tcpdump -l -nn -i sw0-p1-rej udp port 90 > sw0-p1-rej-udp.pcap 2> err &], [0])
> -NS_CHECK_EXEC([sw0-p1-rej], [tcpdump -l -nn -i sw0-p1-rej icmp > sw0-p1-rej-icmp.pcap 2> err &], [0])
> +NETNS_START_TCPDUMP([sw0-p1-rej], [-nn -i sw0-p1-rej udp port 90], [sw0-p1-rej-udp])
> +NETNS_START_TCPDUMP([sw0-p1-rej], [-nn -i sw0-p1-rej icmp], [sw0-p1-rej-icmp])
>   
>   printf '.%.0s' {1..100} > foo
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p1-rej nc -u 10.0.0.4 90 < foo
> -    c=$(cat sw0-p1-rej-icmp.pcap | grep \
> +    c=$(cat sw0-p1-rej-icmp.tcpdump | grep \
>   "10.0.0.4 > 10.0.0.3: ICMP 10.0.0.4 udp port 90 unreachable" | uniq | wc -l)
>       test $c -ge 1
>   ])
>   
>   kill $(pidof tcpdump)
> -rm -f *.pcap
> +rm -f *.tcpdump
>   
> -NS_CHECK_EXEC([sw0-p1-rej], [tcpdump -l -nn -i sw0-p1-rej udp port 94 > sw0-p1-rej-udp.pcap 2> err &], [0])
> -NS_CHECK_EXEC([sw0-p1-rej], [tcpdump -l -nn -i sw0-p1-rej icmp > sw0-p1-rej-icmp.pcap 2> err &], [0])
> +NETNS_START_TCPDUMP([sw0-p1-rej], [-nn -i sw0-p1-rej udp port 94], [sw0-p1-rej-udp])
> +NETNS_START_TCPDUMP([sw0-p1-rej], [-nn -i sw0-p1-rej icmp], [sw0-p1-rej-icmp])
>   
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p1-rej nc -u 10.0.0.4 94 < foo
> -    c=$(cat sw0-p1-rej-icmp.pcap | grep \
> +    c=$(cat sw0-p1-rej-icmp.tcpdump | grep \
>   "10.0.0.4 > 10.0.0.3: ICMP 10.0.0.4 udp port 94 unreachable" | uniq | wc -l)
>       test $c -ge 1
>   ])
> -kill $(pidof tcpdump)
>   
>   # Now test for IPv6 UDP.
> -NS_CHECK_EXEC([sw0-p2-rej], [tcpdump -l -nn -i sw0-p2-rej udp port 90 > sw0-p2-rej-ip6-udp.pcap 2> err &], [0])
> -NS_CHECK_EXEC([sw0-p2-rej], [tcpdump -l -nn -i sw0-p2-rej icmp6 > sw0-p2-rej-icmp6.pcap 2> err &], [0])
> +NETNS_START_TCPDUMP([sw0-p2-rej], [-nn -i sw0-p2-rej udp port 90], [sw0-p2-rej-ip6-udp])
> +NETNS_START_TCPDUMP([sw0-p2-rej], [-nn -i sw0-p2-rej icmp6], [sw0-p2-rej-icmp6])
>   
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p2-rej nc -u -6 aef0::3 90 < foo
> -    c=$(cat sw0-p2-rej-icmp6.pcap | grep \
> +    c=$(cat sw0-p2-rej-icmp6.tcpdump | grep \
>   "IP6 aef0::3 > aef0::4: ICMP6, destination unreachable, unreachable port, \
>   aef0::3 udp port 90" | uniq | wc -l)
>       test $c -ge 1
>   ])
>   
>   kill $(pidof tcpdump)
> -rm -f *.pcap
> +rm -f *.tcpdump
>   
> -NS_CHECK_EXEC([sw0-p2-rej], [tcpdump -l -nn -i sw0-p2-rej udp port 94 > sw0-p2-rej-ip6-udp.pcap 2> err &], [0])
> -NS_CHECK_EXEC([sw0-p2-rej], [tcpdump -l -nn -i sw0-p2-rej icmp6 > sw0-p2-rej-icmp6.pcap 2> err &], [0])
> +NETNS_START_TCPDUMP([sw0-p2-rej], [-nn -i sw0-p2-rej udp port 94], [sw0-p2-rej-ip6-udp])
> +NETNS_START_TCPDUMP([sw0-p2-rej], [-nn -i sw0-p2-rej icmp6], [sw0-p2-rej-icmp6])
>   
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p2-rej nc -u -6 aef0::3 94 < foo
> -    c=$(cat sw0-p2-rej-icmp6.pcap | grep \
> +    c=$(cat sw0-p2-rej-icmp6.tcpdump | grep \
>   "IP6 aef0::3 > aef0::4: ICMP6, destination unreachable, unreachable port, \
>   aef0::3 udp port 94" | uniq | wc -l)
>       test $c -ge 1
>   ])
> -kill $(pidof tcpdump)
>   
>   # Delete all the ACLs of pg0 and add the ACL with a generic match with reject action.
>   ovn-nbctl pg-del pg0
> @@ -5160,31 +5144,30 @@ OVS_WAIT_UNTIL([
>       ip netns exec sw0-p2-rej nc -vz6 aef0::3 80 2>&1 | grep -i 'connection refused'
>   ])
>   
> -rm -f *.pcap
> +rm -f *.tcpdump
>   
> -NS_CHECK_EXEC([sw0-p1-rej], [tcpdump -l -nn -i sw0-p1-rej icmp > sw0-p1-rej-icmp.pcap 2> err &], [0])
> +NETNS_START_TCPDUMP([sw0-p1-rej], [-nn -i sw0-p1-rej icmp], [sw0-p1-rej-icmp])
>   
>   printf '.%.0s' {1..100} > foo
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p1-rej nc -u 10.0.0.4 90 < foo
> -    c=$(cat sw0-p1-rej-icmp.pcap | grep \
> +    c=$(cat sw0-p1-rej-icmp.tcpdump | grep \
>   "10.0.0.4 > 10.0.0.3: ICMP 10.0.0.4 udp port 90 unreachable" | uniq | wc -l)
>       test $c -ge 1
>   ])
>   
>   kill $(pidof tcpdump)
> -rm -f *.pcap
> +rm -f *.tcpdump
>   # Now test for IPv6 UDP.
> -NS_CHECK_EXEC([sw0-p2-rej], [tcpdump -l -nn -i sw0-p2-rej icmp6 > sw0-p2-rej-icmp6.pcap 2> err &], [0])
> +NETNS_START_TCPDUMP([sw0-p2-rej], [-nn -i sw0-p2-rej icmp6], [sw0-p2-rej-icmp6])
>   
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p2-rej nc -u -6 aef0::3 90 < foo
> -    c=$(cat sw0-p2-rej-icmp6.pcap | grep \
> +    c=$(cat sw0-p2-rej-icmp6.tcpdump | grep \
>   "IP6 aef0::3 > aef0::4: ICMP6, destination unreachable, unreachable port, \
>   aef0::3 udp port 90" | uniq | wc -l)
>       test $c -ge 1
>   ])
> -kill $(pidof tcpdump)
>   
>   OVS_APP_EXIT_AND_WAIT([ovn-controller])
>   
> @@ -5287,10 +5270,7 @@ ADD_VETH(sw1-p1-rej, sw1-p1-rej, br-int, "20.0.0.3/24", "40:54:00:00:00:03", \
>            "20.0.0.1")
>   
>   # Capture packets in sw0-p1-rej.
> -NS_CHECK_EXEC([sw0-p1-rej], [tcpdump -l -nn -i sw0-p1-rej tcp > sw0-p1-rej-ip4.pcap 2> err &], [0])
> -
> -#Wait for tcpdump to get started before generating first packets
> -OVS_WAIT_UNTIL([test 1 = $(cat err | grep -c listening)])
> +NETNS_START_TCPDUMP([sw0-p1-rej], [-nn -i sw0-p1-rej tcp], [sw0-p1-rej-ip4])
>   
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p1-rej nc -vz 10.0.0.4 80 2>&1 | grep -i 'connection refused'
> @@ -5308,17 +5288,12 @@ grep controller | grep tp_dst=84 -c)
>   ])
>   
>   OVS_WAIT_UNTIL([
> -    total=`cat sw0-p1-rej-ip4.pcap |  grep "10\.0\.0\.4" | wc -l`
> +    total=`cat sw0-p1-rej-ip4.tcpdump |  grep "10\.0\.0\.4" | wc -l`
>       echo "total = $total"
>       test "${total}" = "4"
>   ])
>   
> -kill $(pidof tcpdump)
> -
> -NS_CHECK_EXEC([sw0-p2-rej], [tcpdump -l -nn -i sw0-p2-rej tcp port 80 > sw0-p2-rej-ip6.pcap 2> err &], [0])
> -
> -#Wait for tcpdump to get started before generating first packets
> -OVS_WAIT_UNTIL([test 1 = $(cat err | grep -c listening)])
> +NETNS_START_TCPDUMP([sw0-p2-rej], [-nn -i sw0-p2-rej tcp port 80], [sw0-p2-rej-ip6])
>   
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p2-rej nc -vz6 aef0::3 80 2>&1 | grep -i 'connection refused'
> @@ -5326,7 +5301,7 @@ OVS_WAIT_UNTIL([
>   
>   
>   OVS_WAIT_UNTIL([
> -    total=`cat sw0-p2-rej-ip6.pcap | grep "aef0::3\.80" | wc -l`
> +    total=`cat sw0-p2-rej-ip6.tcpdump | grep "aef0::3\.80" | wc -l`
>       echo "total = $total"
>       test "${total}" = "2"
>   ])
> @@ -5342,53 +5317,51 @@ OVS_WAIT_UNTIL([
>   ])
>   
>   # Now test for IPv4 UDP.
> -NS_CHECK_EXEC([sw0-p1-rej], [tcpdump -l -nn -i sw0-p1-rej udp port 90 > sw0-p1-rej-udp.pcap 2> err &], [0])
> -NS_CHECK_EXEC([sw0-p1-rej], [tcpdump -l -nn -i sw0-p1-rej icmp > sw0-p1-rej-icmp.pcap 2> err &], [0])
> +NETNS_START_TCPDUMP([sw0-p1-rej], [-nn -i sw0-p1-rej udp port 90], [sw0-p1-rej-udp])
> +NETNS_START_TCPDUMP([sw0-p1-rej], [-nn -i sw0-p1-rej icmp], [sw0-p1-rej-icmp])
>   
>   printf '.%.0s' {1..100} > foo
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p1-rej nc -u 10.0.0.4 90 < foo
> -    c=$(cat sw0-p1-rej-icmp.pcap | grep \
> +    c=$(cat sw0-p1-rej-icmp.tcpdump | grep \
>   "10.0.0.4 > 10.0.0.3: ICMP 10.0.0.4 udp port 90 unreachable" | uniq | wc -l)
>       test $c -ge 1
>   ])
>   
>   kill $(pidof tcpdump)
> -rm -f *.pcap
> +rm -f *.tcpdump
>   
> -NS_CHECK_EXEC([sw0-p1-rej], [tcpdump -l -nn -i sw0-p1-rej udp port 94 > sw0-p1-rej-udp.pcap 2> err &], [0])
> -NS_CHECK_EXEC([sw0-p1-rej], [tcpdump -l -nn -i sw0-p1-rej icmp > sw0-p1-rej-icmp.pcap 2> err &], [0])
> +NETNS_START_TCPDUMP([sw0-p1-rej], [-nn -i sw0-p1-rej udp port 94], [sw0-p1-rej-udp])
> +NETNS_START_TCPDUMP([sw0-p1-rej], [-nn -i sw0-p1-rej icmp], [sw0-p1-rej-icmp])
>   
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p1-rej nc -u 10.0.0.4 94 < foo
> -    c=$(cat sw0-p1-rej-icmp.pcap | grep \
> +    c=$(cat sw0-p1-rej-icmp.tcpdump | grep \
>   "10.0.0.4 > 10.0.0.3: ICMP 10.0.0.4 udp port 94 unreachable" | uniq | wc -l)
>       test $c -ge 1
>   ])
>   
> -kill $(pidof tcpdump)
> -
>   # Now test for IPv6 UDP.
> -NS_CHECK_EXEC([sw0-p2-rej], [tcpdump -l -nn -i sw0-p2-rej udp port 90 > sw0-p2-rej-ip6-udp.pcap 2> err &], [0])
> -NS_CHECK_EXEC([sw0-p2-rej], [tcpdump -l -nn -i sw0-p2-rej icmp6 > sw0-p2-rej-icmp6.pcap 2> err &], [0])
> +NETNS_START_TCPDUMP([sw0-p2-rej], [-nn -i sw0-p2-rej udp port 90], [sw0-p2-rej-ip6-udp])
> +NETNS_START_TCPDUMP([sw0-p2-rej], [-nn -i sw0-p2-rej icmp6], [sw0-p2-rej-icmp6])
>   
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p2-rej nc -u -6 aef0::3 90 < foo
> -    c=$(cat sw0-p2-rej-icmp6.pcap | grep \
> +    c=$(cat sw0-p2-rej-icmp6.tcpdump | grep \
>   "IP6 aef0::3 > aef0::4: ICMP6, destination unreachable, unreachable port, \
>   aef0::3 udp port 90" | uniq | wc -l)
>       test $c -ge 1
>   ])
>   
>   kill $(pidof tcpdump)
> -rm -f *.pcap
> +rm -f *.tcpdump
>   
> -NS_CHECK_EXEC([sw0-p2-rej], [tcpdump -l -nn -i sw0-p2-rej udp port 94 > sw0-p2-rej-ip6-udp.pcap 2> err &], [0])
> -NS_CHECK_EXEC([sw0-p2-rej], [tcpdump -l -nn -i sw0-p2-rej icmp6 > sw0-p2-rej-icmp6.pcap 2> err &], [0])
> +NETNS_START_TCPDUMP([sw0-p2-rej], [-nn -i sw0-p2-rej udp port 94], [sw0-p2-rej-ip6-udp])
> +NETNS_START_TCPDUMP([sw0-p2-rej], [-nn -i sw0-p2-rej icmp6], [sw0-p2-rej-icmp6])
>   
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p2-rej nc -u -6 aef0::3 94 < foo
> -    c=$(cat sw0-p2-rej-icmp6.pcap | grep \
> +    c=$(cat sw0-p2-rej-icmp6.tcpdump | grep \
>   "IP6 aef0::3 > aef0::4: ICMP6, destination unreachable, unreachable port, \
>   aef0::3 udp port 94" | uniq | wc -l)
>       test $c -ge 1
> @@ -5408,33 +5381,31 @@ OVS_WAIT_UNTIL([
>   ])
>   
>   kill $(pidof tcpdump)
> -rm -f *.pcap
> +rm -f *.tcpdump
>   
> -NS_CHECK_EXEC([sw0-p1-rej], [tcpdump -l -nn -i sw0-p1-rej icmp > sw0-p1-rej-icmp.pcap 2> err &], [0])
> +NETNS_START_TCPDUMP([sw0-p1-rej], [-nn -i sw0-p1-rej icmp], [sw0-p1-rej-icmp])
>   
>   printf '.%.0s' {1..100} > foo
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p1-rej nc -u 10.0.0.4 90 < foo
> -    c=$(cat sw0-p1-rej-icmp.pcap | grep \
> +    c=$(cat sw0-p1-rej-icmp.tcpdump | grep \
>   "10.0.0.4 > 10.0.0.3: ICMP 10.0.0.4 udp port 90 unreachable" | uniq | wc -l)
>       test $c -ge 1
>   ])
>   
>   kill $(pidof tcpdump)
> -rm -f *.pcap
> +rm -f *.tcpdump
>   # Now test for IPv6 UDP.
> -NS_CHECK_EXEC([sw0-p2-rej], [tcpdump -l -nn -i sw0-p2-rej icmp6 > sw0-p2-rej-icmp6.pcap 2> err &], [0])
> +NETNS_START_TCPDUMP([sw0-p2-rej], [-nn -i sw0-p2-rej icmp6], [sw0-p2-rej-icmp6])
>   
>   OVS_WAIT_UNTIL([
>       ip netns exec sw0-p2-rej nc -u -6 aef0::3 90 < foo
> -    c=$(cat sw0-p2-rej-icmp6.pcap | grep \
> +    c=$(cat sw0-p2-rej-icmp6.tcpdump | grep \
>   "IP6 aef0::3 > aef0::4: ICMP6, destination unreachable, unreachable port, \
>   aef0::3 udp port 90" | uniq | wc -l)
>       test $c -ge 1
>   ])
>   
> -kill $(pidof tcpdump)
> -
>   OVS_APP_EXIT_AND_WAIT([ovn-controller])
>   
>   as ovn-sb
> @@ -6858,10 +6829,10 @@ OVS_WAIT_UNTIL([ovn-sbctl dump-flows R1 | grep 'match=(ip4.dst == 100.0.0.0/8)'
>   check ovn-nbctl clear logical_router_static_route $route_uuid bfd
>   wait_column "admin_down" nb:bfd status logical_port=rp-public
>   OVS_WAIT_UNTIL([ip netns exec server bfdd-control status | grep -qi state=Down])
> -NS_CHECK_EXEC([server], [tcpdump -nni s1 udp port 3784 -Q in > bfd.pcap &])
> +NETNS_START_TCPDUMP([server], [-nni s1 udp port 3784 -Q in], [bfd])
>   sleep 5
>   kill $(pidof tcpdump)
> -AT_CHECK([grep -qi bfd bfd.pcap],[1])
> +AT_CHECK([grep -qi bfd bfd.tcpdump],[1])
>   
>   # restart the connection
>   check ovn-nbctl set logical_router_static_route $route_uuid bfd=$uuid
> @@ -6887,10 +6858,10 @@ OVS_WAIT_UNTIL([test "$(ovn-sbctl dump-flows R1 | grep 'match=(ip4.dst == 100.0.
>   # remove bfd entry
>   ovn-nbctl destroy bfd $uuid
>   check_row_count bfd 0
> -NS_CHECK_EXEC([server], [tcpdump -nni s1 udp port 3784 -Q in > bfd.pcap &])
> +NETNS_START_TCPDUMP([server], [-nni s1 udp port 3784 -Q in], [bfd])
>   sleep 5
>   kill $(pidof tcpdump)
> -AT_CHECK([grep -qi bfd bfd.pcap],[1])
> +AT_CHECK([grep -qi bfd bfd.tcpdump],[1])
>   
>   uuid_v6=$(ovn-nbctl create bfd logical_port=rp-public dst_ip=\"1000::b\")
>   check ovn-nbctl lr-route-add R1 2000::/64 1000::b
> @@ -7351,7 +7322,7 @@ check ovn-nbctl lsp-add public public1 \
>           -- lsp-set-type public1 localnet \
>           -- lsp-set-options public1 network_name=phynet
>   
> -NS_EXEC([sw01], [tcpdump -l -n -i sw01 icmp -Q in > reject.pcap &])
> +NETNS_START_TCPDUMP([sw01], [-n -i sw01 icmp -Q in], [reject])
>   check ovn-nbctl meter-add acl-meter drop 1 pktps 0
>   check ovn-nbctl copp-add copp0 reject acl-meter
>   check ovn-nbctl ls-copp-add copp0 sw0
> @@ -7368,14 +7339,14 @@ EOF
>   
>   # 1pps
>   OVS_WAIT_UNTIL([
> -    n_reject=$(grep unreachable reject.pcap | wc -l)
> +    n_reject=$(grep unreachable reject.tcpdump | wc -l)
>       test "${n_reject}" = "1"
>   ])
>   kill $(pidof tcpdump)
> -rm -f reject.pcap
> +rm -f reject.tcpdump
>   
>   # Let's update the meter
> -NS_EXEC([sw01], [tcpdump -l -n -i sw01 icmp -Q in > reject.pcap &])
> +NETNS_START_TCPDUMP([sw01], [-n -i sw01 icmp -Q in], [reject])
>   check ovn-nbctl --may-exist --wait=hv meter-add acl-meter drop 10 pktps 0
>   ip netns exec sw01 scapy -H <<-EOF
>   p = IP(src="192.168.1.2", dst="192.168.1.1") / UDP(dport = 12345) / Raw(b"X"*64)
> @@ -7384,14 +7355,14 @@ EOF
>   
>   # 10pps
>   OVS_WAIT_UNTIL([
> -    n_reject=$(grep unreachable reject.pcap | wc -l)
> +    n_reject=$(grep unreachable reject.tcpdump | wc -l)
>       test "${n_reject}" = "10"
>   ])
>   
>   kill $(pidof tcpdump)
> -rm -f reject.pcap
> +rm -f reject.tcpdump
>   
> -NS_EXEC([sw01], [tcpdump -l -n -i sw01 icmp -Q in > reject.pcap &])
> +NETNS_START_TCPDUMP([sw01], [-n -i sw01 icmp -Q in], [reject])
>   check ovn-nbctl --wait=hv copp-del copp0 reject
>   
>   ip netns exec sw01 scapy -H <<-EOF
> @@ -7400,12 +7371,11 @@ send (p, iface='sw01', loop = 0, verbose = 0, count = 20)
>   EOF
>   
>   OVS_WAIT_UNTIL([
> -    n_reject=$(grep unreachable reject.pcap | wc -l)
> +    n_reject=$(grep unreachable reject.tcpdump | wc -l)
>       test "${n_reject}" = "20"
>   ])
> -kill $(pidof tcpdump)
>   
> -NS_EXEC([server], [tcpdump -l -n -i s1 arp[[24:4]]=0xac100164 > arp.pcap &])
> +NETNS_START_TCPDUMP([server], [-n -i s1 arp[[24:4]]=0xac100164], [arp])
>   check ovn-nbctl meter-add arp-meter drop 1 pktps 0
>   check ovn-nbctl copp-add copp1 arp-resolve arp-meter
>   check ovn-nbctl --wait=hv lr-copp-add copp1 R1
> @@ -7420,10 +7390,9 @@ EOF
>   
>   # 1pps
>   OVS_WAIT_UNTIL([
> -    n_arp=$(grep ARP arp.pcap | wc -l)
> +    n_arp=$(grep ARP arp.tcpdump | wc -l)
>       test "${n_arp}" = "1"
>   ])
> -kill $(pidof tcpdump)
>   
>   check ovn-nbctl meter-add icmp-meter drop 1 pktps 0
>   check ovn-nbctl copp-add copp2 icmp4-error icmp-meter
> @@ -7432,7 +7401,7 @@ AT_CHECK([ovn-nbctl copp-list copp2 |grep icmp4-error], [0], [dnl
>   icmp4-error: icmp-meter
>   ])
>   
> -NS_EXEC([sw01], [tcpdump -l -n -i sw01 icmp > icmp.pcap &])
> +NETNS_START_TCPDUMP([sw01], [-n -i sw01 icmp], [icmp])
>   ip netns exec sw01 scapy -H <<-EOF
>   p = IP(src="192.168.1.2", dst="172.16.1.100", ttl=1) / TCP(dport = 8080, flags="S") / Raw(b"X"*64)
>   send (p, iface='sw01', loop = 0, verbose = 0, count = 100)
> @@ -7440,10 +7409,9 @@ EOF
>   
>   # 1pps
>   OVS_WAIT_UNTIL([
> -    n_icmp=$(grep ICMP icmp.pcap | wc -l)
> +    n_icmp=$(grep ICMP icmp.tcpdump | wc -l)
>       test "${n_icmp}" = "1"
>   ])
> -kill $(pidof tcpdump)
>   
>   check ovn-nbctl meter-add bfd-meter drop 1 pktps 0
>   check ovn-nbctl copp-add copp3 bfd bfd-meter
> @@ -7454,7 +7422,7 @@ bfd: bfd-meter
>   
>   check ovn-nbctl --wait=hv --bfd lr-route-add R1 240.0.0.0/8 172.16.1.50 rp-public
>   printf "%08x" $(ovn-sbctl get bfd . disc) > /tmp/disc
> -NS_EXEC([server], [tcpdump -l -nn -i s1 udp port 3784 and ip[[29]]==0x90 -Q in > bfd.pcap &])
> +NETNS_START_TCPDUMP([server], [-nn -i s1 udp port 3784 and ip[[29]]==0x90 -Q in], [bfd])
>   ip netns exec server scapy -H <<-EOF
>   import binascii
>   f = open("/tmp/disc", "r")
> @@ -7469,10 +7437,9 @@ rm /tmp/disc
>   
>   # 1pps
>   OVS_WAIT_UNTIL([
> -    n_bfd=$(grep 3784 bfd.pcap | wc -l)
> +    n_bfd=$(grep 3784 bfd.tcpdump | wc -l)
>       test "${n_bfd}" = "1"
>   ])
> -kill $(pidof tcpdump)
>   
>   check ovn-nbctl set nb_global . options:svc_monitor_mac="33:33:33:33:33:33"
>   check ovn-nbctl meter-add svc-meter drop 1 pktps 0
> @@ -8788,7 +8755,7 @@ ADD_NAMESPACES(vm2)
>   ADD_VETH(vm2, vm2, br-int, "42.42.42.2/24", "00:00:00:00:00:02")
>   
>   ADD_NAMESPACES(vm3)
> -NETNS_DAEMONIZE([vm3], [tcpdump -n -i any -nnleX > vm3.pcap 2>/dev/null], [tcpdump3.pid])
> +NETNS_START_TCPDUMP([vm3], [-n -i any -nnleX], [vm3])
>   
>   ADD_VETH(vm3, vm3, br-int, "42.42.42.3/24", "00:00:00:00:00:03", \
>            "42.42.42.5")
> @@ -8803,11 +8770,11 @@ wait_igmp_flows_installed 228.0.0.1
>   NS_CHECK_EXEC([vm1], [ping -q -c 3 -i 0.3 -w 2 228.0.0.1], [ignore], [ignore])
>   
>   OVS_WAIT_UNTIL([
> -    requests=`grep "ICMP echo request" -c vm3.pcap`
> +    requests=`grep "ICMP echo request" -c vm3.tcpdump`
>       test "${requests}" -ge "3"
>   ])
>   
> -NETNS_DAEMONIZE([vm2], [tcpdump -n -i any -nnleX > vm2.pcap 2>/dev/null], [tcpdump2.pid])
> +NETNS_START_TCPDUMP([vm2], [-n -i any -nnleX], [vm2])
>   
>   for i in `seq 1 40`;do
>       NS_CHECK_EXEC([vm2], [ip addr add 228.1.$i.1 dev vm2 autojoin &], [0])
> @@ -8826,7 +8793,7 @@ ovn-sbctl list multicast_group
>   NS_CHECK_EXEC([vm1], [ping -q -c 3 -i 0.3 -w 2 228.1.1.1], [ignore], [ignore])
>   
>   OVS_WAIT_UNTIL([
> -    requests=`grep "ICMP echo request" -c vm2.pcap`
> +    requests=`grep "ICMP echo request" -c vm2.tcpdump`
>       test "${requests}" -ge "3"
>   ])
>   
> @@ -9004,16 +8971,13 @@ test_related_traffic() {
>   
>       check ovs-appctl dpctl/flush-conntrack
>   
> -    NETNS_DAEMONIZE([client], [tcpdump -l -U -i client -w client.pcap 2>client_err], [tcpdump0.pid])
> -    NETNS_DAEMONIZE([server], [tcpdump -l -U -i server -w server.pcap 2>server_err], [tcpdump1.pid])
> +    NETNS_START_TCPDUMP([client], [-U -i client -w client.pcap], [tcpdump0])
> +    NETNS_START_TCPDUMP([server], [-U -i server -w server.pcap], [tcpdump1])
>   
>       # Setup a dummy UDP listeners so we don't get "port unreachable".
>       NETNS_DAEMONIZE([client], [nc -l -u 1], [nc0.pid])
>       NETNS_DAEMONIZE([server], [nc -l -u 2], [nc1.pid])
>   
> -    OVS_WAIT_UNTIL([grep "listening" client_err])
> -    OVS_WAIT_UNTIL([grep "listening" server_err])
> -
>       # Send UDP client -> server
>       check ovs-ofctl packet-out br-int "in_port=ovs-client,packet=$client_udp,actions=resubmit(,0)"
>   
> @@ -9232,10 +9196,9 @@ name: 'vport4' value: '999'
>   # Start IPv4 TCP server on vm1.
>   NETNS_DAEMONIZE([vm1], [nc -k -l 42.42.42.2 4242], [nc-vm1.pid])
>   
> -NETNS_DAEMONIZE([vm1],
> -    [tcpdump -n -i vm1 -nnleX -c6 udp and dst 42.42.42.2 and dst port 4343 > vm1.pcap 2> vm1.pcap.stderr],
> -    [tcpdump1.pid])
> -OVS_WAIT_UNTIL([grep "listening" vm1.pcap.stderr])
> +NETNS_START_TCPDUMP([vm1],
> +    [-n -i vm1 -nnleX -c6 udp and dst 42.42.42.2 and dst port 4343],
> +    [vm1])
>   
>   # Make sure connecting to the VIP works (hairpin, via ls and via lr).
>   NS_CHECK_EXEC([vm1], [nc 66.66.66.66 666 -z], [0], [ignore], [ignore])
> @@ -9255,7 +9218,7 @@ NS_CHECK_EXEC([vm2], [echo a | nc -u 66.66.66.66 999], [ignore], [ignore], [igno
>   NS_CHECK_EXEC([vm3], [echo a | nc -u 66.66.66.66 999], [ignore], [ignore], [ignore])
>   
>   OVS_WAIT_UNTIL([
> -    requests=`grep "UDP" -c vm1.pcap`
> +    requests=`grep "UDP" -c vm1.tcpdump`
>       test "${requests}" -ge "6"
>   ])
>   
> @@ -9384,10 +9347,9 @@ name: 'vport4' value: '999'
>   # Start IPv6 TCP server on vm1.
>   NETNS_DAEMONIZE([vm1], [nc -k -l 4242::2 4242], [nc-vm1.pid])
>   
> -NETNS_DAEMONIZE([vm1],
> -    [tcpdump -n -i vm1 -nnleX -c6 udp and dst 4242::2 and dst port 4343 > vm1.pcap 2> vm1.pcap.stderr],
> -    [tcpdump1.pid])
> -OVS_WAIT_UNTIL([grep "listening" vm1.pcap.stderr])
> +NETNS_START_TCPDUMP([vm1],
> +    [-n -i vm1 -nnleX -c6 udp and dst 4242::2 and dst port 4343],
> +    [vm1])
>   
>   # Make sure connecting to the VIP works (hairpin, via ls and via lr).
>   NS_CHECK_EXEC([vm1], [nc 6666::1 666 -z], [0], [ignore], [ignore])
> @@ -9407,7 +9369,7 @@ NS_CHECK_EXEC([vm2], [echo a | nc -u 6666::1 999], [ignore], [ignore], [ignore])
>   NS_CHECK_EXEC([vm3], [echo a | nc -u 6666::1 999], [ignore], [ignore], [ignore])
>   
>   OVS_WAIT_UNTIL([
> -    requests=`grep "UDP" -c vm1.pcap`
> +    requests=`grep "UDP" -c vm1.tcpdump`
>       test "${requests}" -ge "6"
>   ])
>   
> @@ -9465,10 +9427,10 @@ ADD_NAMESPACES(remote1)
>   ADD_VETH(remote1, remote1, br-ext, "172.16.1.4/24", "f0:00:00:01:02:06", \
>            "172.16.1.1")
>   
> -NETNS_DAEMONIZE([remote], [tcpdump -c 3 -nneei remote -Q in src 192.168.1.2 and dst 172.16.1.2 and icmp > icmp.pcap], [tcpdump0.pid])
> -NETNS_DAEMONIZE([remote], [tcpdump -c 1 -nneei remote -Q in arp and arp[[24:4]]==0xac100102 > arp.pcap], [tcpdump1.pid])
> -NETNS_DAEMONIZE([remote1], [tcpdump -c 3 -nneei remote1 -Q in src 172.16.1.3 and dst 172.16.1.4 and icmp > icmp1.pcap 2>/dev/null], [tcpdump2.pid])
> -NETNS_DAEMONIZE([remote1], [tcpdump -c 1 -nneei remote1 -Q in arp and arp[[24:4]]==0xac100104 > arp1.pcap 2>/dev/null], [tcpdump3.pid])
> +NETNS_START_TCPDUMP([remote], [-c 3 -nneei remote -Q in src 192.168.1.2 and dst 172.16.1.2 and icmp], [icmp])
> +NETNS_START_TCPDUMP([remote], [-c 1 -nneei remote -Q in arp and arp[[24:4]]==0xac100102], [arp])
> +NETNS_START_TCPDUMP([remote1], [-c 3 -nneei remote1 -Q in src 172.16.1.3 and dst 172.16.1.4 and icmp], [icmp1])
> +NETNS_START_TCPDUMP([remote1], [-c 1 -nneei remote1 -Q in arp and arp[[24:4]]==0xac100104], [arp1])
>   
>   check ovn-nbctl lr-add R1 -- set Logical_Router R1 options:chassis=hv1
>   check ovn-nbctl ls-add sw0
> @@ -9515,12 +9477,12 @@ NS_CHECK_EXEC([sw01], [ping -q -c 3 -i 0.3 -w 2 172.16.1.2 | FORMAT_PING], \
>   ])
>   
>   OVS_WAIT_UNTIL([
> -        total_arp_pkts=$(cat arp.pcap | wc -l)
> +        total_arp_pkts=$(cat arp.tcpdump | wc -l)
>           test "${total_arp_pkts}" = "1"
>   ])
>   
>   OVS_WAIT_UNTIL([
> -        total_icmp_pkts=$(cat icmp.pcap | wc -l)
> +        total_icmp_pkts=$(cat icmp.tcpdump | wc -l)
>           test "${total_icmp_pkts}" = "3"
>   ])
>   
> @@ -9530,12 +9492,12 @@ NS_CHECK_EXEC([sw11], [ping -q -c 3 -i 0.3 -w 2 172.16.1.4 | FORMAT_PING], \
>   ])
>   
>   OVS_WAIT_UNTIL([
> -        total_arp1_pkts=$(cat arp1.pcap | wc -l)
> +        total_arp1_pkts=$(cat arp1.tcpdump | wc -l)
>           test "${total_arp1_pkts}" = "1"
>   ])
>   
>   OVS_WAIT_UNTIL([
> -        total_icmp1_pkts=$(cat icmp1.pcap | wc -l)
> +        total_icmp1_pkts=$(cat icmp1.tcpdump | wc -l)
>           test "${total_icmp1_pkts}" = "3"
>   ])
>   
> @@ -10713,8 +10675,7 @@ check ovn-nbctl lsp-add bar bar1 \
>   # wait for ovn-controller to catch up.
>   check ovn-nbctl --wait=hv sync
>   
> -NETNS_DAEMONIZE([foo1], [tcpdump -l -nn -e -i foo1 'ether dst 0a:58:a9:fe:01:01 and icmp' > foo1-icmp.pcap 2>foo1-tcpdump.stderr], [foo1-icmp-tcpdump.pid])
> -OVS_WAIT_UNTIL([grep "listening" foo1-tcpdump.stderr])
> +NETNS_START_TCPDUMP([foo1], [-nn -e -i foo1 'ether dst 0a:58:a9:fe:01:01 and icmp'], [foo1-icmp])
>   
>   # 'foo1' should be able to ping 'bar1'
>   NS_CHECK_EXEC([foo1], [ping -q -c 3 -i 0.3 -w 2 192.168.2.2 | FORMAT_PING], \
> @@ -10722,12 +10683,11 @@ NS_CHECK_EXEC([foo1], [ping -q -c 3 -i 0.3 -w 2 192.168.2.2 | FORMAT_PING], \
>   3 packets transmitted, 3 received, 0% packet loss, time 0ms
>   ])
>   OVS_WAIT_UNTIL([
> -    total_pkts=$(cat foo1-icmp.pcap| wc -l)
> +    total_pkts=$(cat foo1-icmp.tcpdump| wc -l)
>       test "${total_pkts}" = "3"
>   ])
>   
> -NETNS_DAEMONIZE([foo2], [tcpdump -l -nn -e -i foo2 'ether dst 0a:58:a9:fe:01:01 and icmp' > foo2-icmp.pcap 2>foo2-tcpdump.stderr], [foo2-icmp-tcpdump.pid])
> -OVS_WAIT_UNTIL([grep "listening" foo2-tcpdump.stderr])
> +NETNS_START_TCPDUMP([foo2], [-nn -e -i foo2 'ether dst 0a:58:a9:fe:01:01 and icmp'], [foo2-icmp])
>   
>   # 'foo2' should be able to ping 'bar1'
>   NS_CHECK_EXEC([foo2], [ping -q -c 3 -i 0.3 -w 2 192.168.2.2 | FORMAT_PING], \
> @@ -10735,12 +10695,11 @@ NS_CHECK_EXEC([foo2], [ping -q -c 3 -i 0.3 -w 2 192.168.2.2 | FORMAT_PING], \
>   3 packets transmitted, 3 received, 0% packet loss, time 0ms
>   ])
>   OVS_WAIT_UNTIL([
> -    total_pkts=$(cat foo2-icmp.pcap| wc -l)
> +    total_pkts=$(cat foo2-icmp.tcpdump| wc -l)
>       test "${total_pkts}" = "3"
>   ])
>   
> -NETNS_DAEMONIZE([foo3], [tcpdump -l -nn -e -i foo3 'ether dst 0a:58:a9:fe:01:01 and icmp' > foo3-icmp.pcap 2>foo3-tcpdump.stderr], [foo3-icmp-tcpdump.pid])
> -OVS_WAIT_UNTIL([grep "listening" foo3-tcpdump.stderr])
> +NETNS_START_TCPDUMP([foo3], [-nn -e -i foo3 'ether dst 0a:58:a9:fe:01:01 and icmp'], [foo3-icmp])
>   
>   # 'foo3' should be able to ping 'bar1'
>   NS_CHECK_EXEC([foo3], [ping -q -c 3 -i 0.3 -w 2 192.168.2.2 | FORMAT_PING], \
> @@ -10748,12 +10707,11 @@ NS_CHECK_EXEC([foo3], [ping -q -c 3 -i 0.3 -w 2 192.168.2.2 | FORMAT_PING], \
>   3 packets transmitted, 3 received, 0% packet loss, time 0ms
>   ])
>   OVS_WAIT_UNTIL([
> -    total_pkts=$(cat foo3-icmp.pcap| wc -l)
> +    total_pkts=$(cat foo3-icmp.tcpdump| wc -l)
>       test "${total_pkts}" = "3"
>   ])
>   
> -NETNS_DAEMONIZE([ext1], [tcpdump -l -nn -e -i ext1 'ether dst 0a:58:a9:fe:01:01 and icmp' > ext1-icmp.pcap 2>ext1-tcpdump.stderr], [ext1-icmp-tcpdump.pid])
> -OVS_WAIT_UNTIL([grep "listening" ext1-tcpdump.stderr])
> +NETNS_START_TCPDUMP([ext1], [-nn -e -i ext1 'ether dst 0a:58:a9:fe:01:01 and icmp'], [ext1-icmp])
>   
>   # 'ext1' should be able to ping 'bar1'
>   NS_CHECK_EXEC([ext1], [ping -q -c 3 -i 0.3 -w 2 192.168.2.2 | FORMAT_PING], \
> @@ -10761,7 +10719,7 @@ NS_CHECK_EXEC([ext1], [ping -q -c 3 -i 0.3 -w 2 192.168.2.2 | FORMAT_PING], \
>   3 packets transmitted, 3 received, 0% packet loss, time 0ms
>   ])
>   OVS_WAIT_UNTIL([
> -    total_pkts=$(cat ext1-icmp.pcap| wc -l)
> +    total_pkts=$(cat ext1-icmp.tcpdump| wc -l)
>       test "${total_pkts}" = "3"
>   ])
>   
> @@ -10857,8 +10815,7 @@ check ovn-nbctl --wait=hv sync
>   # Force ipv6 nd neighbour solicitation
>   NS_EXEC([foo1], [ping6 -c 1 fd12::2])
>   
> -NETNS_DAEMONIZE([foo1], [tcpdump -vvvv -ttt -l -nn -e -i foo1 'ether dst 0a:58:a9:fe:01:01 and icmp6' > foo1-icmp6.pcap 2> foo1-tcpdump.stderr], [foo1-icmp6-tcpdump.pid])
> -OVS_WAIT_UNTIL([grep "listening" foo1-tcpdump.stderr])
> +NETNS_START_TCPDUMP([foo1], [-vvvv -ttt -nn -e -i foo1 'ether dst 0a:58:a9:fe:01:01 and icmp6'], [foo1-icmp6])
>   
>   # 'foo1' should be able to ping 'bar1'
>   NS_CHECK_EXEC([foo1], [ping6 -q -c 3 -i 0.3 -w 2 fd12::2 | FORMAT_PING], \
> @@ -10866,15 +10823,14 @@ NS_CHECK_EXEC([foo1], [ping6 -q -c 3 -i 0.3 -w 2 fd12::2 | FORMAT_PING], \
>   3 packets transmitted, 3 received, 0% packet loss, time 0ms
>   ])
>   OVS_WAIT_UNTIL([
> -    total_pkts=$(cat foo1-icmp6.pcap| grep "echo request" | wc -l)
> +    total_pkts=$(cat foo1-icmp6.tcpdump| grep "echo request" | wc -l)
>       test "${total_pkts}" = "3"
>   ])
>   
>   # Force ipv6 nd neighbour solicitation
>   NS_EXEC([foo2], [ping6 -c 1 fd12::2])
>   
> -NETNS_DAEMONIZE([foo2], [tcpdump -vvvv -ttt -l -nn -e -i foo2 'ether dst 0a:58:a9:fe:01:01 and icmp6' > foo2-icmp6.pcap 2> foo2-tcpdump.stderr], [foo2-icmp6-tcpdump.pid])
> -OVS_WAIT_UNTIL([grep "listening" foo2-tcpdump.stderr])
> +NETNS_START_TCPDUMP([foo2], [-vvvv -ttt -nn -e -i foo2 'ether dst 0a:58:a9:fe:01:01 and icmp6'], [foo2-icmp6])
>   
>   # 'foo2' should be able to ping 'bar1'
>   NS_CHECK_EXEC([foo2], [ping6 -q -c 3 -i 0.3 -w 2 fd12::2 | FORMAT_PING], \
> @@ -10882,15 +10838,14 @@ NS_CHECK_EXEC([foo2], [ping6 -q -c 3 -i 0.3 -w 2 fd12::2 | FORMAT_PING], \
>   3 packets transmitted, 3 received, 0% packet loss, time 0ms
>   ])
>   OVS_WAIT_UNTIL([
> -    total_pkts=$(cat foo2-icmp6.pcap| grep "echo request" | wc -l)
> +    total_pkts=$(cat foo2-icmp6.tcpdump| grep "echo request" | wc -l)
>       test "${total_pkts}" = "3"
>   ])
>   
>   # Force ipv6 nd neighbour solicitation
>   NS_EXEC([foo3], [ping6 -c 1 fd12::2])
>   
> -NETNS_DAEMONIZE([foo3], [tcpdump -vvvv -ttt -l -nn -e -i foo3 'ether dst 0a:58:a9:fe:01:01 and icmp6' > foo3-icmp6.pcap 2> foo3-tcpdump.stderr], [foo3-icmp6-tcpdump.pid])
> -OVS_WAIT_UNTIL([grep "listening" foo3-tcpdump.stderr])
> +NETNS_START_TCPDUMP([foo3], [-vvvv -ttt -nn -e -i foo3 'ether dst 0a:58:a9:fe:01:01 and icmp6'], [foo3-icmp6])
>   
>   # 'foo3' should be able to ping 'bar1'
>   NS_CHECK_EXEC([foo3], [ping6 -q -c 3 -i 0.3 -w 2 fd12::2 | FORMAT_PING], \
> @@ -10898,7 +10853,7 @@ NS_CHECK_EXEC([foo3], [ping6 -q -c 3 -i 0.3 -w 2 fd12::2 | FORMAT_PING], \
>   3 packets transmitted, 3 received, 0% packet loss, time 0ms
>   ])
>   OVS_WAIT_UNTIL([
> -    total_pkts=$(cat foo3-icmp6.pcap| grep "echo request" | wc -l)
> +    total_pkts=$(cat foo3-icmp6.tcpdump| grep "echo request" | wc -l)
>       test "${total_pkts}" = "3"
>   ])
>   
> @@ -11318,27 +11273,23 @@ AT_CHECK([ip addr add 172.16.0.101/24 dev br-mirror])
>   AT_CHECK([ip addr add 2003::a/64 dev br-mirror nodad])
>   AT_CHECK([ip link set dev br-mirror up])
>   
> -NS_CHECK_EXEC([mirror], [tcpdump -l -c 3 -neei mirror proto GRE > gre_mirror4.pcap 2>gre_mirror4_error &])
> -OVS_WAIT_UNTIL([grep "listening" gre_mirror4_error])
> +NETNS_START_TCPDUMP([mirror], [-c 3 -neei mirror proto GRE], [gre_mirror4])
>   
>   NS_CHECK_EXEC([foo1], [ping -q -c 3 -i 0.3 -w 2 192.168.2.2 | FORMAT_PING], \
>   [0], [dnl
>   3 packets transmitted, 3 received, 0% packet loss, time 0ms
>   ])
>   OVS_WAIT_UNTIL([
> -    n_packets=$(grep "GRE" -c gre_mirror4.pcap)
> +    n_packets=$(grep "GRE" -c gre_mirror4.tcpdump)
>       test "${n_packets}" = "3"
>   ])
>   
> -killall tcpdump
> -
>   ovn-nbctl mirror-del mirror0
>   ovn-nbctl mirror-add mirror1 gre 2 to-lport 2003::b
>   
>   ovn-nbctl --wait=hv lsp-attach-mirror bar1 mirror1
>   
> -NS_CHECK_EXEC([mirror], [tcpdump -l -c 3 -neei mirror proto GRE > gre_mirror6.pcap 2>gre_mirror6_error &])
> -OVS_WAIT_UNTIL([grep "listening" gre_mirror6_error])
> +NETNS_START_TCPDUMP([mirror], [-c 3 -neei mirror proto GRE], [gre_mirror6])
>   
>   NS_CHECK_EXEC([foo1], [ping6 -q -c 3 -i 0.3 -w 2 2002::2 | FORMAT_PING], \
>   [0], [dnl
> @@ -11346,53 +11297,44 @@ NS_CHECK_EXEC([foo1], [ping6 -q -c 3 -i 0.3 -w 2 2002::2 | FORMAT_PING], \
>   ])
>   
>   OVS_WAIT_UNTIL([
> -    n_packets=$(grep "GRE" -c gre_mirror6.pcap)
> +    n_packets=$(grep "GRE" -c gre_mirror6.tcpdump)
>       test "${n_packets}" = "3"
>   ])
>   
> -killall tcpdump
> -
>   ovn-nbctl mirror-del mirror1
>   ovn-nbctl mirror-add mirror2 erspan 3 to-lport 172.16.0.100
>   ovn-nbctl --wait=hv lsp-attach-mirror bar1 mirror2
>   
> -NS_CHECK_EXEC([mirror], [tcpdump -l -c 3 -neei mirror ip[[22:2]]=0x88be > erspan_mirror4.pcap 2>erspan_mirror4_error &])
> -OVS_WAIT_UNTIL([grep "listening" erspan_mirror4_error])
> +NETNS_START_TCPDUMP([mirror], [-c 3 -neei mirror ip[[22:2]]=0x88be], [erspan_mirror4])
>   
>   NS_CHECK_EXEC([foo1], [ping -q -c 3 -i 0.3 -w 2 192.168.2.2 | FORMAT_PING], \
>   [0], [dnl
>   3 packets transmitted, 3 received, 0% packet loss, time 0ms
>   ])
>   OVS_WAIT_UNTIL([
> -    n_packets=$(grep "gre-proto-0x88be" -c erspan_mirror4.pcap)
> +    n_packets=$(grep "gre-proto-0x88be" -c erspan_mirror4.tcpdump)
>       test "${n_packets}" = "3"
>   ])
>   
> -killall tcpdump
> -
>   ovn-nbctl mirror-del mirror2
>   ovn-nbctl mirror-add mirror3 erspan 4 to-lport 2003::b
>   ovn-nbctl --wait=hv lsp-attach-mirror bar1 mirror3
>   
> -NS_CHECK_EXEC([mirror], [tcpdump -l -c 3 -neei mirror ip6[[42:2]]=0x88be > erspan_mirror6.pcap 2>erspan_mirror6_error &])
> -OVS_WAIT_UNTIL([grep "listening" erspan_mirror6_error])
> +NETNS_START_TCPDUMP([mirror], [-c 3 -neei mirror ip6[[42:2]]=0x88be], [erspan_mirror6])
>   
>   NS_CHECK_EXEC([foo1], [ping6 -q -c 3 -i 0.3 -w 2 2002::2 | FORMAT_PING], \
>   [0], [dnl
>   3 packets transmitted, 3 received, 0% packet loss, time 0ms
>   ])
>   OVS_WAIT_UNTIL([
> -    n_packets=$(grep "gre-proto-0x88be" -c erspan_mirror6.pcap)
> +    n_packets=$(grep "gre-proto-0x88be" -c erspan_mirror6.tcpdump)
>       test "${n_packets}" = "3"
>   ])
>   
> -killall tcpdump
> -
>   uuid=$(fetch_column nb:mirror _uuid name="mirror3")
>   ovn-nbctl --wait=hv set mirror $uuid type=gre
>   
> -NS_CHECK_EXEC([mirror], [tcpdump -c 3 -l -neei mirror proto GRE > gre_mirror6.pcap 2>gre_mirror6_error &])
> -OVS_WAIT_UNTIL([grep "listening" gre_mirror6_error])
> +NETNS_START_TCPDUMP([mirror], [-c 3 -neei mirror proto GRE], [gre2_mirror6])
>   
>   NS_CHECK_EXEC([foo1], [ping6 -q -c 3 -i 0.3 -w 2 2002::2 | FORMAT_PING], \
>   [0], [dnl
> @@ -11400,12 +11342,10 @@ NS_CHECK_EXEC([foo1], [ping6 -q -c 3 -i 0.3 -w 2 2002::2 | FORMAT_PING], \
>   ])
>   
>   OVS_WAIT_UNTIL([
> -    n_packets=$(grep "GRE" -c gre_mirror6.pcap)
> +    n_packets=$(grep "GRE" -c gre2_mirror6.tcpdump)
>       test "${n_packets}" = "3"
>   ])
>   
> -killall tcpdump
> -
>   OVS_APP_EXIT_AND_WAIT([ovn-controller])
>   
>   as ovn-sb