Merge pull request #1741 from mattp-/main

networking/linux: map src only default routes accordingly

2 files changed, 86 insertions, 3 deletions

diff --git a/lib/ohai/plugins/linux/network.rb b/lib/ohai/plugins/linux/network.rb
index 4a5ddb3c..eb83843c 100644
--- a/lib/ohai/plugins/linux/network.rb
+++ b/lib/ohai/plugins/linux/network.rb
@@ -103,9 +103,24 @@ 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
-        else
+        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
+
+        unless route_int
           logger.trace("Plugin Network: Skipping route entry without a device: '#{line}'")
           next
         end
@@ -116,8 +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]+)/
@@ -645,10 +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 48f84ffc..810fc37f 100644
--- a/spec/unit/plugins/linux/network_spec.rb
+++ b/spec/unit/plugins/linux/network_spec.rb
@@ -477,6 +477,7 @@ describe Ohai::System, "Linux Network Plugin" do
   end
 
   before do
+    allow(File).to receive(:exist?).and_call_original
     allow(plugin).to receive(:collect_os).and_return(:linux)
 
     allow(plugin).to receive(:shell_out).with("ip addr").and_return(mock_shell_out(0, linux_ip_addr, ""))
@@ -1335,6 +1336,73 @@ describe Ohai::System, "Linux Network Plugin" do
         end
       end
 
+      # notes:
+      # route 172.16.19.39 is the addr of tun0 ; see :linux_ifconfig at top of file
+      # route 10.116.201.0/24 is discarded because it is not a default route
+      # route 192.168.0.0/24 is discarded because src 192.168.0.2 does not match eth0 ("Skipping route entry whose src does not match the interface IP")
+      # route 172.16.19.39 is chosen over 10.116.201.254 because its metric is lower (10 < 20)
+      describe "when there's a source field in a local route entry but no dev in the 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 10.116.201.254 dev eth0 metric 20 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 no-dev route and sets ipaddress" do
+          plugin.run
+          expect(plugin["ipaddress"]).to eq("172.16.19.39")
+        end
+      end
+
+      # notes:
+      # route 172.16.19.39 is the addr of tun0 ; see :linux_ifconfig at top of file
+      # route 10.116.201.0/24 is discarded because it is not a default route
+      # route 192.168.0.0/24 is discarded because src 192.168.0.2 does not match eth0 ("Skipping route entry whose src does not match the interface IP")
+      # route 10.116.201.254 is chosen over 172.16.19.39 and 10.116.201.1 because its metric is lower (5 < 10, 10)
+      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 via 10.116.201.254 dev eth0 metric 5 src 10.116.201.74
+            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
+          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
+      end
+
+      # notes:
+      # route 172.16.19.39 is the addr of tun0 ; see :linux_ifconfig at top of file
+      # route 10.116.201.0/24 is discarded because it is not a default route
+      # route 192.168.0.0/24 is discarded because src 192.168.0.2 does not match eth0 ("Skipping route entry whose src does not match the interface IP")
+      # route 10.116.201.254 is chosen over 172.16.19.39 because routes with an explict device are preferred over ones that are inferred when metrics are equal
+      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
+      end
+
       describe "with a link level default route" do
         let(:linux_ip_route) do
           <<~EOM