[PATCH iproute2 v3 4/4] testsuite: remove gre kmods if the test loads them

[Luca Boccassi <bluca@debian.org>]

The tunnel test leaves behind link devices created by the GRE kernel
modules:

$ ip -br link
...
gre0@NONE    DOWN 0.0.0.0 <NOARP>
gretap0@NONE DOWN 00:00:00:00:00:00 <BROADCAST,MULTICAST>
erspan0@NONE DOWN 00:00:00:00:00:00 <BROADCAST,MULTICAST>
ip6tnl0@NONE DOWN :: <NOARP>
ip6gre0@NONE DOWN 00:00:00:00:

$ lsmod | grep gre
ip6_gre      40960  0
ip6_tunnel   40960  1 ip6_gre
ip_gre       32768  0
ip_tunnel    24576  1 ip_gre
gre          16384  2 ip6_gre,ip_gre

Check beforehand if the gre kernel module is loaded, and if not unload
them all at the end of the test. This should avoid causing problems if
a user is already using GRE for other purposes.

Signed-off-by: Luca Boccassi <bluca@debian.org>
Reviewed-by: Petr Vorel <pvorel@suse.cz>
---
v2: applied suggestions from Petr to simplify the modules parsing/unloading
v3: ditto, added reviewed-by tag

 testsuite/tests/ip/tunnel/add_tunnel.t | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/testsuite/tests/ip/tunnel/add_tunnel.t b/testsuite/tests/ip/tunnel/add_tunnel.t
index 3f5a9d3c..65db431c 100755
--- a/testsuite/tests/ip/tunnel/add_tunnel.t
+++ b/testsuite/tests/ip/tunnel/add_tunnel.t
@@ -3,6 +3,16 @@
 . lib/generic.sh
 
 TUNNEL_NAME="tunnel_test_ip"
+KMODS="ip6_gre ip6_tunnel ip_gre ip_tunnel gre"
+
+# unload kernel modules to remove dummy interfaces only if they were not in use beforehand
+kmods_remove=
+# note that checkbashism reports command -v, but dash supports it and it's POSIX 2008 compliant
+if command -v lsmod >/dev/null 2>&1 && command -v rmmod >/dev/null 2>&1; then
+    for i in $KMODS; do
+        lsmod | grep -q "^$i" || kmods_remove="$kmods_remove $i";
+    done
+fi
 
 ts_log "[Testing add/del tunnels]"
 
@@ -12,3 +22,6 @@ ts_ip "$0" "Del GRE tunnel over IPv4" tunnel del $TUNNEL_NAME
 ts_ip "$0" "Add GRE tunnel over IPv6" tunnel add name $TUNNEL_NAME mode ip6gre local dead:beef::1 remote dead:beef::2
 ts_ip "$0" "Del GRE tunnel over IPv6" tunnel del $TUNNEL_NAME
 
+for mod in $kmods_remove; do
+    sudo rmmod "$mod"
+done
-- 
2.19.2