Re: [PATCH 17/18] tests: Correct determination of host interface name in tests

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

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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.

> Signed-off-by: David Gibson <david(a)gibson.dropbear.id.au>
> ---
>  test/dhcp/passt       | 2 +-
>  test/two_guests/basic | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/test/dhcp/passt b/test/dhcp/passt
> index 3d2e939..f45227a 100644
> --- a/test/dhcp/passt
> +++ b/test/dhcp/passt
> @@ -16,7 +16,7 @@ htools	ip jq sed tr head
>  
>  test	Interface name
>  gout	IFNAME ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
> -hout	HOST_IFNAME ip -j -4 route show|jq -rM '.[] | select(.dst == "default").dev'
> +hout	HOST_IFNAME ip -j -4 route show|jq -rM '[.[] | select(.dst == "default").dev] | .[0]'
>  check	[ -n "__IFNAME__" ]
>  
>  test	DHCP: address
> diff --git a/test/two_guests/basic b/test/two_guests/basic
> index cf0b975..f7c016d 100644
> --- a/test/two_guests/basic
> +++ b/test/two_guests/basic
> @@ -18,7 +18,7 @@ htools	ip jq md5sum cut
>  test	Interface names
>  g1out	IFNAME1 ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
>  g2out	IFNAME2 ip -j link show | jq -rM '.[] | select(.link_type == "ether").ifname'
> -hout	HOST_IFNAME ip -j -4 route show|jq -rM '.[] | select(.dst == "default").dev'
> +hout	HOST_IFNAME ip -j -4 route show|jq -rM '[.[] | select(.dst == "default").dev] | .[0]'
>  check	[ -n "__IFNAME1__" ]
>  check	[ -n "__IFNAME2__" ]
>  

-- 
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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