Re: [PATCH v3 4/4] fwd: Direct inbound spliced forwards to the guest's external address

[David Gibson <david@gibson.dropbear.id.au>]

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On Wed, Oct 16, 2024 at 05:26:48PM +0200, Stefano Brivio wrote:
[snip]
> Adding 2-second delays as we have them for NDP doesn't look that bad:

> $ grep --exclude-dir=demo -rn "dhclient -6" pasta/dhcp:37:ns
> /sbin/dhclient -6 --no-pid __IFNAME__ passt_in_ns/dhcp:54:guest
> /sbin/dhclient -6 __IFNAME__ passt/dhcp:51:guest /sbin/dhclient -6
> __IFNAME__ perf/passt_tcp:117:guest dhclient -6 -x
> perf/passt_tcp:118:guest dhclient -6 __IFNAME__
> two_guests/basic:40:guest1 /sbin/dhclient -6 __IFNAME1__
> two_guests/basic:41:guest2 /sbin/dhclient -6 __IFNAME2__

> given that we don't need it on dhclient -x, tests would take about
> 12 seconds longer.

> Or we could switch to the arp off / nodad / arp on approach for
> everything, including SLAAC:

> $ grep --exclude-dir=demo --exclude-dir=mbuto --exclude-dir=distro
> --exclude-dir=memory -rn "sleep[ $(printf '\t')].*2"
> pasta/ndp:21:sleep 2 passt_in_ns/icmp:29:ns ip addr add 2001:db8::1
> dev __IFNAME_NS__ && sleep 2 # DAD passt/ndp:19:guest ip link set
> dev __IFNAME__ up && sleep 2 two_guests/basic:39:sleep 2

> and save slightly less than 8 seconds. If you ask me, I would have a
> slight preference for the nodad approach.

Much as I don't like making the tests slower, I don't think the nodad
approach is a good idea.  It's fine if we think of the NDP/DHCP only
as setting things up for the transfer tests.  But they also serve the
purpose of testing the NDP and DHCP paths themselves.  For that
purpose we should perform a full "normal" configuration, including
DAD.  [e.g. if we really did manage to break our NS responses so that
we totally broke DAD, we'd want our tests to catch that].

I have a draft implementation of explicitly waiting for DAD to
complete both for SLAAC and for DHCPv6, patches coming shortly.

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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