From: David Gibson <david@gibson.dropbear.id.au>
To: passt-dev@passt.top
Subject: Re: [PATCH 17/18] tests: Correct determination of host interface name in tests
Date: Wed, 20 Jul 2022 12:47:57 +1000 [thread overview]
Message-ID: <Ytds3SUyiIHm8x7o@yekko> (raw)
In-Reply-To: <20220719210552.45329b70@elisabeth>
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On Tue, Jul 19, 2022 at 09:05:52PM +0200, Stefano Brivio wrote:
> On Tue, 19 Jul 2022 16:20:45 +1000
> David Gibson <david(a)gibson.dropbear.id.au> wrote:
>
> > On Fri, Jul 15, 2022 at 03:21:40PM +1000, David Gibson wrote:
> > > By default, passt itself attaches to the first host interface with a
> > > default route. However, when determining the host interface name the tests
> > > implicitly select the *last* host interface: they use a jq expression which
> > > will list all interfaces with default routes, but the way output detection
> > > works in the scripts, it will only pick up the last line.
> > >
> > > If there are multiple interfaces with default routes on the host, and they
> > > each have a different address, this can cause spurious test
> > > failures.
> >
> > It seems this change is not enough to always fix the tests when there
> > are multiple default routes. I'm still sometimes getting failures,
> > now because passt itself doesn't seem to be picking the interface
> > with the first default route.
> >
> > I'm wondering if this is because ip(8) is sorting the output, not just
> > presenting it in the same order that the underlying netlink interface
> > does.
>
> I don't see that happening at least in my environment (and I also can't
> see any code that would sort it, that pretty much comes from
> rtnl_dump_filter_l() in lib/libnetlink.c).
>
> The netlink "filter", though, is slightly different. For IPv4:
>
> $ strace -e sendto ip route show >/dev/null
> sendto(3, [{{len=36, type=RTM_GETROUTE, flags=NLM_F_REQUEST|NLM_F_DUMP, seq=1658257027, pid=0}, {rtm_family=AF_INET, rtm_dst_len=0, rtm_src_len=0, rtm_tos=0, rtm_table=RT_TABLE_UNSPEC, rtm_protocol=RTPROT_UNSPEC, rtm_scope=RT_SCOPE_UNIVERSE, rtm_type=RTN_UNSPEC, rtm_flags=0}, {{nla_len=8, nla_type=RTA_TABLE}, RT_TABLE_MAIN}}, {len=0, type=0 /* NLMSG_??? */, flags=0, seq=0, pid=0}], 156, 0, NULL, 0) = 156
>
> $ strace -e sendto ./passt -f
> sendto(5, {{len=28, type=RTM_GETROUTE, flags=NLM_F_REQUEST|NLM_F_DUMP, seq=0, pid=0}, {rtm_family=AF_INET, rtm_dst_len=0, rtm_src_len=0, rtm_tos=0, rtm_table=RT_TABLE_MAIN, rtm_protocol=RTPROT_UNSPEC, rtm_scope=RT_SCOPE_UNIVERSE, rtm_type=RTN_UNICAST, rtm_flags=0}}, 28, 0, NULL, 0) = 28
> [...]
>
> and, while I don't think the FIB trie is actually descended in a
> different way, we might still have a slightly different result from the
> kernel (if I recall correctly, I didn't check right now).
>
> But letting that aside for a moment: if you have two default routes, I
> suppose they have different metrics. If not, what's the intended usage?
Yes, there are two different metrics. I was thinking after I sent
this that we should sort by metric.
> If yes, we should probably implement a sorting logic in passt, so that
> the route with the lowest metric is picked, and then adjust the jq
> expression to also pick that one.
Agreed. I'll see if I can implement this. Up to you whether you drop
this patch or I just do another update on top of it.
--
David Gibson | 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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next prev parent reply other threads:[~2022-07-20 2:47 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-15 5:21 [PATCH 00/18] Test fixes, batch 5 David Gibson
2022-07-15 5:21 ` [PATCH 01/18] tests: Remove no longer needed /usr/bin/bash link David Gibson
2022-07-15 5:21 ` [PATCH 02/18] tests: Let Fedora find dhclient-script in /usr/sbin David Gibson
2022-07-15 5:21 ` [PATCH 03/18] tests: Add rudimentary debugging to dhclient-script David Gibson
2022-07-15 5:21 ` [PATCH 04/18] tests: Add some extra dhclient support directories to mbuto.img David Gibson
2022-07-15 5:21 ` [PATCH 05/18] tests: More robust parsing of resolv.conf for DHCP tests David Gibson
2022-07-15 5:21 ` [PATCH 06/18] tests: Handle the case of a nameserver on host localhost David Gibson
2022-07-15 5:21 ` [PATCH 07/18] tests: Correctly handle domain search list in dhclient-script David Gibson
2022-07-15 5:21 ` [PATCH 08/18] tests: Fix detection of empty 'hout' responses in passt{,_in_ns} tests David Gibson
2022-07-15 5:21 ` [PATCH 09/18] tests: Fix creation of test file in udp passt tests David Gibson
2022-07-15 5:21 ` [PATCH 10/18] valgrind needs futex David Gibson
2022-07-15 5:21 ` [PATCH 11/18] tests: Use socat instead of netcat David Gibson
2022-07-15 5:21 ` [PATCH 12/18] tests: Remove unnecessary ^D in passt_in_ns teardown David Gibson
2022-07-15 5:21 ` [PATCH 13/18] tests: Remove unnecessary truncation of temporary files in udp tests David Gibson
2022-07-15 5:21 ` [PATCH 14/18] tests: Use dhclient --no-pid for namespaces in two_guests tests David Gibson
2022-07-15 5:21 ` [PATCH 15/18] tests: Clean up better after iperf tests David Gibson
2022-07-15 5:21 ` [PATCH 16/18] tests: No need to retrieve host ifname in ndp/pasta David Gibson
2022-07-15 5:21 ` [PATCH 17/18] tests: Correct determination of host interface name in tests David Gibson
2022-07-19 6:20 ` David Gibson
2022-07-19 19:05 ` Stefano Brivio
2022-07-20 2:47 ` David Gibson [this message]
2022-07-20 7:24 ` David Gibson
2022-07-20 8:23 ` Stefano Brivio
2022-07-20 10:33 ` David Gibson
2022-07-15 5:21 ` [PATCH 18/18] demo: Use git protocol downloads David Gibson
2022-07-21 12:13 ` [PATCH 00/18] Test fixes, batch 5 Stefano Brivio
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