[OSSTEST PATCH 3/3] ts-xen-install: nodhcp: Make idempotent

[Ian Jackson <ian.jackson@eu.citrix.com>]

If run more than once, this function would erroneously determine that
xenbr0 was the primary physical interface name and try to enroll it
into the bridge (also named xenbr0).

Instead, spot the "bridge_ports" line and use it to extract the
physical interface name.  Eliminate from consideration any interfaces
matching xenbr\d+.

Signed-off-by: Ian Jackson <Ian.Jackson@eu.citrix.com>
---
 ts-xen-install |   17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/ts-xen-install b/ts-xen-install
index c59fdd3..4215ed3 100755
--- a/ts-xen-install
+++ b/ts-xen-install
@@ -217,6 +217,7 @@ sub nodhcp () {
 	if (!defined $physif) {
 	    # preread /etc/network/interfaces to figure out the interface
 	    my %candidates;
+	    my @bridges;
 	    while (<EI>) {
 		if (
 		    m{^ \s* (  auto \s+ (\S+)               ) \s* $}x ||
@@ -225,10 +226,24 @@ sub nodhcp () {
 		    ) {
 		    push @{ $candidates{$2} }, $1;
 		}
+		if (
+			(
+			 (m{^ \s* iface \s+ (xenbr\w*) \s+ inet \s+ }x
+			      ? ((push @bridges, $1), 1) : 0)
+			 ...
+			 !m{^ [ \t] }x
+			)
+		    &&
+			m{^ \s+ bridge_ports \s+ (\S+) \s }x
+		    ) {
+		    push @{ $candidates{$1} }, "$bridges[$#bridges] $_";
+		}
 	    }
 	    EI->error and die $!;
 	    delete $candidates{'lo'};
-	    die Dumper(\%candidates)." -- cannot determine default interface"
+	    delete $candidates{$_} foreach @bridges;
+	    die Dumper(\%candidates, \@bridges).
+		" -- cannot determine default interface"
 		unless (scalar keys %candidates) == 1;
 	    ($physif,) = keys %candidates;
 	    seek EI,0,0 or die $!;
-- 
1.7.10.4