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

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

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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.

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__" ]
 
-- 
@@ -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__" ]
 
-- 
2.36.1