networking/linux: map src only default routes accordingly

in certain configurations a default route can be set via src only / not
dev, but should still be accounted for in terms of calculating the
'favored' default route / what is chosen as ipaddress for a given node.

This change augments the previously added changes to account for nexthop
multipath routing; but only in scenarios src address is set but only in
scenarios src address is set.

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

2 files changed, 48 insertions, 1 deletions

diff --git a/lib/ohai/plugins/linux/network.rb b/lib/ohai/plugins/linux/network.rb
index 4a5ddb3c..cbecae86 100644
--- a/lib/ohai/plugins/linux/network.rb
+++ b/lib/ohai/plugins/linux/network.rb
@@ -103,9 +103,20 @@ Ohai.plugin(:Network) do
         next
       end
       route_endings.each do |route_ending|
+        route_int = nil
         if route_ending =~ /\bdev\s+([^\s]+)\b/
           route_int = $1
-        else
+        end
+        # does any known interface own the src address?
+        # 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
+          end
+        end
+
+        unless route_int
           logger.trace("Plugin Network: Skipping route entry without a device: '#{line}'")
           next
         end
diff --git a/spec/unit/plugins/linux/network_spec.rb b/spec/unit/plugins/linux/network_spec.rb
index 48f84ffc..0bb20597 100644
--- a/spec/unit/plugins/linux/network_spec.rb
+++ b/spec/unit/plugins/linux/network_spec.rb
@@ -1335,6 +1335,42 @@ describe Ohai::System, "Linux Network Plugin" do
         end
       end
 
+      describe "when there's a source field in a local route entry but no dev" 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
+          EOM
+        end
+        let(:linux_ip_route_inet6) { "" }
+
+        it "maps the no-dev route and sets ipaddress" do
+          plugin.run
+          expect(plugin["ipaddress"]).to eq("172.16.19.39")
+        end
+      end
+
+      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
+            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 5 src 10.116.201.74
+          EOM
+        end
+        let(:linux_ip_route_inet6) { "" }
+
+        it "maps the no-dev route and sets ipaddress" do
+          plugin.run
+          expect(plugin["ipaddress"]).to eq("10.116.201.74")
+        end
+      end
+
       describe "with a link level default route" do
         let(:linux_ip_route) do
           <<~EOM