prefer route that explicitly define a device

in theory I don't this should occur in real life, as I'm pretty sure
/usr/sbin/ip should always print the dev routes above non dev routes if
the metric is the same, but it is a good case to cover in code.

also removed the default metric 10 gateway route as it was
spurious/irrelevant to the test.

Signed-off-by: Matt Phillips <mphillips81@bloomberg.net>

2 files changed, 25 insertions, 4 deletions

diff --git a/lib/ohai/plugins/linux/network.rb b/lib/ohai/plugins/linux/network.rb
index cbecae86..eb83843c 100644
--- a/lib/ohai/plugins/linux/network.rb
+++ b/lib/ohai/plugins/linux/network.rb
@@ -103,16 +103,20 @@ Ohai.plugin(:Network) do
         next
       end
       route_endings.each do |route_ending|
+        route_entry = Mash.new(destination: route_dest,
+                               family: family[:name])
         route_int = nil
         if route_ending =~ /\bdev\s+([^\s]+)\b/
           route_int = $1
         end
         # does any known interface own the src address?
+        # we try to infer the interface/device from its address if it isn't specified
         # we want to override the interface set via nexthop but only if possible
         if line =~ /\bsrc\s+([^\s]+)\b/ && (!route_int || line.include?("nexthop"))
           # only clobber previously set route_int if we find a match
           if (match = iface.select { |name, intf| intf.fetch("addresses", {}).any? { |addr, _| addr == $1 } }.keys.first)
             route_int = match
+            route_entry[:inferred] = true
           end
         end
 
@@ -127,8 +131,6 @@ Ohai.plugin(:Network) do
           next
         end
 
-        route_entry = Mash.new(destination: route_dest,
-                               family: family[:name])
         %w{via scope metric proto src}.each do |k|
           # http://rubular.com/r/pwTNp65VFf
           route_entry[k] = $1 if route_ending =~ /\b#{k}\s+([^\s]+)/
@@ -656,10 +658,12 @@ Ohai.plugin(:Network) do
       # sorting the selected routes:
       # - getting default routes first
       # - then sort by metric
+      # - then sort by if the device was inferred or not (preferring explicit to inferred)
       # - then by prefixlen
       [
        r[:destination] == "default" ? 0 : 1,
        r[:metric].nil? ? 0 : r[:metric].to_i,
+       r[:inferred] ? 1 : 0,
        # for some reason IPAddress doesn't accept "::/0", it doesn't like prefix==0
        # just a quick workaround: use 0 if IPAddress fails
        begin
diff --git a/spec/unit/plugins/linux/network_spec.rb b/spec/unit/plugins/linux/network_spec.rb
index 0bb20597..f3928322 100644
--- a/spec/unit/plugins/linux/network_spec.rb
+++ b/spec/unit/plugins/linux/network_spec.rb
@@ -1339,7 +1339,6 @@ describe Ohai::System, "Linux Network Plugin" do
         let(:linux_ip_route) do
           <<~EOM
             default proto bird src 172.16.19.39 metric 10 \\      nexthop via 10.1.81.1 dev eth0 weight 20
-            default via 10.116.201.1 dev eth0 metric 10 src 10.116.201.1
             10.116.201.0/24 dev eth0  proto kernel  src 10.116.201.76
             192.168.0.0/24 dev eth0  proto kernel  src 192.168.0.2
             default via 10.116.201.254 dev eth0 metric 20 src 10.116.201.74
@@ -1353,6 +1352,7 @@ describe Ohai::System, "Linux Network Plugin" do
         end
       end
 
+      # note: default via 10.116.201.1 discarded because src not on eth0
       describe "when there's a source field in a local route entry but no dev with a higher priority default route" do
         let(:linux_ip_route) do
           <<~EOM
@@ -1365,7 +1365,24 @@ describe Ohai::System, "Linux Network Plugin" do
         end
         let(:linux_ip_route_inet6) { "" }
 
-        it "maps the no-dev route and sets ipaddress" do
+        it "maps the dev route and sets ipaddress" do
+          plugin.run
+          expect(plugin["ipaddress"]).to eq("10.116.201.74")
+        end
+      end
+
+      describe "when there's a source field in a local route entry but no dev, but a dev route with the same metric" do
+        let(:linux_ip_route) do
+          <<~EOM
+            default proto bird src 172.16.19.39 metric 10 \\      nexthop via 10.1.81.1 dev eth0 weight 20
+            default via 10.116.201.254 dev eth0 metric 10 src 10.116.201.74
+            10.116.201.0/24 dev eth0  proto kernel  src 10.116.201.76
+            192.168.0.0/24 dev eth0  proto kernel  src 192.168.0.2
+          EOM
+        end
+        let(:linux_ip_route_inet6) { "" }
+
+        it "maps the dev route and sets ipaddress" do
           plugin.run
           expect(plugin["ipaddress"]).to eq("10.116.201.74")
         end