Fixing network detection when using multipath route

lib/ohai/plugins/linux/network.rb

@@ -578,6 +578,8 @@ def parse_ip_addr_inet6_line(cint, iface, line)
 
   # returns the macaddress for interface from a hash of interfaces (iface elsewhere in this file)
   def get_mac_for_interface(interfaces, interface)
+    return "00:00:00:00:00:00" if interfaces[interface][:flags].include?("LOOPBACK")
+
     interfaces[interface][:addresses].find { |k, v| v["family"] == "lladdr" }.first unless interfaces[interface][:addresses].nil? || interfaces[interface][:flags].include?("NOARP")
   end
 

spec/unit/plugins/linux/network_spec.rb

@@ -1260,6 +1260,48 @@
         end
       end
 
+      describe "when there're multipath default routes with a loopback src" do
+        let(:linux_ip_route) do
+          <<~EOM
+            default nhid 18 proto bgp src 10.116.201.76 metric 20 \\ nexthop via 10.117.201.1 dev eth0 weight 1 \\ nexthop via 10.117.202.1 dev eth1 weight 1
+          EOM
+        end
+
+        let(:linux_ip_addr) do
+          <<~EOM
+            1: lo: <LOOPBACK,UP,LOWER_UP> mtu 16436 qdisc noqueue state UNKNOWN
+                link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
+                inet 127.0.0.1/8 scope host lo
+                inet 10.116.201.76/32 scope global lo
+                inet6 ::1/128 scope host
+                   valid_lft forever preferred_lft forever
+            2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP qlen 1000
+                link/ether 12:31:3d:02:be:a2 brd ff:ff:ff:ff:ff:ff
+                inet 10.117.201.76/24 brd 10.117.201.255 scope global eth0
+                inet6 fe80::1031:3dff:fe02:bea2/64 scope link
+                   valid_lft forever preferred_lft forever
+               inet6 2001:44b8:4160:8f00:a00:27ff:fe13:eacd/64 scope global dynamic
+                   valid_lft 6128sec preferred_lft 2526sec
+            3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP
+                link/ether 00:aa:bb:cc:dd:ee brd ff:ff:ff:ff:ff:ff
+                inet 10.117.202.76/24 brd 10.117.202.255 scope global eth1
+                inet6 fe80::2e0:81ff:fe2b:48e7/64 scope link
+                inet6 1111:2222:3333:4444::2/64 scope global
+                   valid_lft forever preferred_lft forever
+                inet6 1111:2222:3333:4444::3/64 scope global
+                   valid_lft forever preferred_lft forever
+          EOM
+        end
+
+        before do
+          plugin.run
+        end
+
+        it "finds the default interface" do
+          expect(plugin["network"]["default_interface"]).to eq("lo")
+        end
+      end
+
       describe "when there's a source field in a local route entry but it isnt in the default route" do
         let(:linux_ip_route) do
           <<~EOM