guests/linux: Place ethernet devices at start of device list

plugins/guests/linux/cap/network_interfaces.rb

@@ -2,6 +2,11 @@ module VagrantPlugins
   module GuestLinux
     module Cap
       class NetworkInterfaces
+        # Valid ethernet device prefix values.
+        # eth - classic prefix
+        # en  - predictable interface names prefix
+        POSSIBLE_ETHERNET_PREFIXES = ["eth".freeze, "en".freeze].freeze
+
         @@logger = Log4r::Logger.new("vagrant::guest::linux::network_interfaces")
 
         # Get network interfaces as a list. The result will be something like:
@@ -15,10 +20,16 @@ def self.network_interfaces(machine, path = "/sbin/ip")
             s << data if type == :stdout
           end
           ifaces = s.split("\n")
+          eth_prefix = nil
           @@logger.debug("Unsorted list: #{ifaces.inspect}")
           # Break out integers from strings and sort the arrays to provide
           # a natural sort for the interface names
           ifaces = ifaces.map do |iface|
+            if eth_prefix.nil?
+              eth_prefix = POSSIBLE_ETHERNET_PREFIXES.detect do |prefix|
+                iface.start_with?(prefix)
+              end
+            end
             iface.scan(/(.+?)(\d+)/).flatten.map do |iface_part|
               if iface_part.to_i.to_s == iface_part
                 iface_part.to_i
@@ -28,6 +39,13 @@ def self.network_interfaces(machine, path = "/sbin/ip")
             end
           end.sort.map(&:join)
           @@logger.debug("Sorted list: #{ifaces.inspect}")
+          # Extract ethernet devices and place at start of list
+          if eth_prefix
+            eth_start = ifaces.index{|iface| iface.start_with?(eth_prefix) }
+            eth_end = ifaces.rindex{|iface| iface.start_with?(eth_prefix) }
+            ifaces.unshift(*ifaces.slice!(eth_start, eth_end - 1))
+            @@logger.debug("Ethernet preferred sorted list: #{ifaces.inspect}")
+          end
           ifaces
         end
       end

test/unit/plugins/guests/linux/cap/network_interfaces_test.rb

@@ -44,5 +44,17 @@
       result = cap.network_interfaces(machine)
       expect(result).to eq(["enp0s3", "enp0s5", "enp0s8", "enp0s10", "enp1s3"])
     end
+
+    it "sorts ethernet devices discovered with classic naming first in list" do
+      expect(comm).to receive(:sudo).and_yield(:stdout, "eth1\neth2\ndocker0\nbridge0\neth0")
+      result = cap.network_interfaces(machine)
+      expect(result).to eq(["eth0", "eth1", "eth2", "bridge0", "docker0"])
+    end
+
+    it "sorts ethernet devices discovered with predictable network interfaces naming first in list" do
+      expect(comm).to receive(:sudo).and_yield(:stdout, "enp0s8\ndocker0\nenp0s3\nbridge0\nenp0s5")
+      result = cap.network_interfaces(machine)
+      expect(result).to eq(["enp0s3", "enp0s5", "enp0s8", "bridge0", "docker0"])
+    end
   end
 end