In the TCP throughput tests, we adjust the guest's MTU in order to test various packet sizes. Some of those are below 1280 which causes IPv6 to be deconfigured on the guest interface. When we increase it above 1280 again, IPv6 is re-enabled and we get an address in the right prefix with NDP, but we don't get exactly the expected address back - that's only communicated with --config-net or DHCPv6. With changes to how we handle NAT this can cause some of the IPv6 tests to fail, because they don't use the address that passt/pasta expects, and the guest doesn't initiate any traffic which allows us to learn what the new address is. Work around this by re-invoking dhclient -6 between adjusting the MTU and running IPv6 test cases. Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au> --- test/perf/passt_tcp | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/test/perf/passt_tcp b/test/perf/passt_tcp index 695479f3..635998e1 100644 --- a/test/perf/passt_tcp +++ b/test/perf/passt_tcp @@ -112,6 +112,10 @@ bw __BW__ 7.0 8.0 iperf3k ns +# Reducing MTU below 1280 deconfigures IPv6, get our address back +guest dhclient -6 -x +guest dhclient -6 __IFNAME__ + tl TCP RR latency over IPv4: guest to host lat - lat - -- 2.46.0