Re: [PATCH mptcp-net] selftests: mptcp: enable syncookie only in absence of reorders

[Paolo Abeni <pabeni@redhat.com>]

On Thu, 2021-06-03 at 13:29 +0200, Florian Westphal wrote:
> Paolo Abeni <pabeni@redhat.com> wrote:
> > Syncookie validation may fail for OoO packets, causing spurious
> > resets and self-tests failures, so let's force syncookie only
> > for tests iteration with no OoO.
> > 
> > Fixes: fed61c4b584c ("selftests: mptcp: make 2nd net namespace use tcp syn cookies unconditionally")
> > Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/198
> > Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> > ---
> >  tools/testing/selftests/net/mptcp/mptcp_connect.sh | 10 +++++++---
> >  1 file changed, 7 insertions(+), 3 deletions(-)
> > 
> > diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.sh b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
> > index 69351c3eb68c..9e53334c9512 100755
> > --- a/tools/testing/selftests/net/mptcp/mptcp_connect.sh
> > +++ b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
> > @@ -202,9 +202,6 @@ ip -net "$ns4" link set ns4eth3 up
> >  ip -net "$ns4" route add default via 10.0.3.2
> >  ip -net "$ns4" route add default via dead:beef:3::2
> >  
> > -# use TCP syn cookies, even if no flooding was detected.
> > -ip netns exec "$ns2" sysctl -q net.ipv4.tcp_syncookies=2
> > -
> >  if $checksum; then
> >  	for i in "$ns1" "$ns2" "$ns3" "$ns4";do
> >  		ip netns exec $i sysctl -q net.mptcp.checksum_enabled=1
> > @@ -748,6 +745,13 @@ for sender in $ns1 $ns2 $ns3 $ns4;do
> >  		exit $ret
> >  	fi
> >  
> > +	# force TCP syn cookies only if there is no reorder
> > +	if [ $sender = $ns1 ]; then
> > +		ip netns exec "$ns2" sysctl -q net.ipv4.tcp_syncookies=2
> 
> I wasn't clear to me at first glance what $sender = $ns1 had to
> do with reordering.
> 
> Maybe:
> 
> # ns1<->ns2 is not subject to reordering/tc delays.  Use it to test
> # mptcp syncookie support.

Yep, that does not hurt ;) Will add in v2, thanks!

/P
>