v2v: Add s_mapping_explanation field to source NIC.

Instead of storing the original network name (s_vnet_orig) in the
source NIC struct and then trying to guess what happened much later
when we're writing target metadata, get our newly created Networks
abstract data type to store the precise mapping explanation.

v2v/create_libvirt_xml.ml

@@ -243,7 +243,7 @@ let create_libvirt_xml ?pool source target_buses guestcaps
       | Virtio_net -> "virtio" | E1000 -> "e1000" | RTL8139 -> "rtl8139" in
     List.map (
       fun { s_mac = mac; s_vnet_type = vnet_type;
-            s_vnet = vnet; s_vnet_orig = vnet_orig } ->
+            s_vnet = vnet; s_mapping_explanation = explanation } ->
         let vnet_type_str =
           match vnet_type with
           | Bridge -> "bridge" | Network -> "network" in
@@ -254,11 +254,9 @@ let create_libvirt_xml ?pool source target_buses guestcaps
             e "model" [ "type", net_model ] [];
           ] in
           let children =
-            if vnet_orig <> vnet then
-              Comment (sprintf "%s mapped from \"%s\" to \"%s\""
-                         vnet_type_str vnet_orig vnet) :: children
-            else
-              children in
+            match explanation with
+            | Some explanation -> Comment explanation :: children
+            | None -> children in
           e "interface" [ "type", vnet_type_str ] children in
 
         (match mac with

v2v/create_ovf.ml

@@ -916,7 +916,7 @@ and add_networks nics guestcaps ovf_flavour ovf =
   (* Iterate over the NICs, adding them to the OVF document. *)
   List.iteri (
     fun i { s_mac = mac; s_vnet_type = vnet_type;
-            s_vnet = vnet; s_vnet_orig = vnet_orig } ->
+            s_vnet = vnet; s_mapping_explanation = explanation } ->
       let dev = sprintf "eth%d" i in
 
       let model =
@@ -929,10 +929,10 @@ and add_networks nics guestcaps ovf_flavour ovf =
         bus dev;
         "1" *) in
 
-      if vnet_orig <> vnet then (
-        let c =
-          Comment (sprintf "mapped from \"%s\" to \"%s\"" vnet_orig vnet) in
-        append_child c network_section
+      (match explanation with
+       | None -> ()
+       | Some explanation ->
+          append_child (Comment explanation) network_section
       );
 
       let network = e "Network" ["ovf:name", vnet] [] in

v2v/input_disk.ml

@@ -72,8 +72,9 @@ class input_disk input_format disk = object
     let network = {
       s_mac = None;
       s_nic_model = None;
-      s_vnet = "default"; s_vnet_orig = "default";
-      s_vnet_type = Network
+      s_vnet = "default";
+      s_vnet_type = Network;
+      s_mapping_explanation = None
     } in
 
     let source = {

v2v/input_vmx.ml

@@ -372,8 +372,9 @@ and find_nics vmx =
              | Some _ | None -> Network in
            Some (port,
                  { s_mac = mac; s_nic_model = model;
-                   s_vnet = vnet; s_vnet_orig = vnet;
-                   s_vnet_type = vnet_type })
+                   s_vnet = vnet;
+                   s_vnet_type = vnet_type;
+                   s_mapping_explanation = None })
         | _ -> None
     ) nics in
   let nics = List.filter_map identity nics in

v2v/networks.ml

@@ -18,6 +18,8 @@
 
 (* Network, bridge mapping. *)
 
+open Printf
+
 open Tools_utils
 open Common_gettext.Gettext
 
@@ -40,20 +42,42 @@ let map t nic =
   | Network ->
      (try
         let vnet = StringMap.find nic.s_vnet t.network_map in
-        { nic with s_vnet = vnet }
+        { nic with
+          s_vnet = vnet;
+          s_mapping_explanation =
+            Some (sprintf "network mapped from %S to %S"
+                          nic.s_vnet vnet)
+        }
       with Not_found ->
            match t.default_network with
            | None -> nic (* no mapping done *)
-           | Some default_network -> { nic with s_vnet = default_network }
+           | Some default_network ->
+              { nic with
+                s_vnet = default_network;
+                s_mapping_explanation =
+                  Some (sprintf "network mapped from %S to default %S"
+                                nic.s_vnet default_network)
+              }
      )
   | Bridge ->
      (try
         let vnet = StringMap.find nic.s_vnet t.bridge_map in
-        { nic with s_vnet = vnet }
+        { nic with
+          s_vnet = vnet;
+          s_mapping_explanation =
+            Some (sprintf "bridge mapped from %S to %S"
+                          nic.s_vnet vnet)
+        }
       with Not_found ->
            match t.default_bridge with
            | None -> nic (* no mapping done *)
-           | Some default_bridge -> { nic with s_vnet = default_bridge }
+           | Some default_bridge ->
+              { nic with
+                s_vnet = default_bridge;
+                s_mapping_explanation =
+                  Some (sprintf "bridge mapped from %S to default %S"
+                                nic.s_vnet default_bridge)
+              }
      )
 
 let create () = {

v2v/networks.mli

@@ -45,4 +45,7 @@ val add_default_bridge : t -> string -> unit
 
 val map : t -> Types.source_nic -> Types.source_nic
 (** Apply the mapping to the source NIC, returning the updated
-    NIC with possibly modified [s_vnet] field. *)
+    NIC with possibly modified [s_vnet] field.
+
+    [s_mapping_explanation] is set in the output with an
+    informational message about what was done. *)

v2v/parse_libvirt_xml.ml

@@ -445,8 +445,8 @@ let parse_libvirt_xml ?conn xml =
              s_mac = mac;
              s_nic_model = model;
              s_vnet = vnet;
-             s_vnet_orig = vnet;
-             s_vnet_type = vnet_type
+             s_vnet_type = vnet_type;
+             s_mapping_explanation = None
            } in
            List.push_front nic nics
          in

v2v/parse_ovf_from_ova.ml

@@ -238,8 +238,8 @@ and parse_nics xpathctx =
       s_mac = mac;
       s_nic_model = nic_model;
       s_vnet = vnet;
-      s_vnet_orig = vnet;
       s_vnet_type = vnet_type;
+      s_mapping_explanation = None
     } in
     List.push_front nic nics
   done;

v2v/test-v2v-networks-and-bridges-expected.xml

@@ -3,7 +3,7 @@
       <source bridge='bridge1'/>
     </interface>
     <interface type='bridge'>
-      <!-- bridge mapped from "bob" to "bridge2" -->
+      <!-- bridge mapped from "bob" to default "bridge2" -->
       <source bridge='bridge2'/>
       <mac address='52:54:00:01:02:03'/>
     </interface>
@@ -23,12 +23,12 @@
       <mac address='52:54:00:01:02:06'/>
     </interface>
     <interface type='network'>
-      <!-- network mapped from "george" to "network4" -->
+      <!-- network mapped from "george" to default "network4" -->
       <source network='network4'/>
       <mac address='52:54:00:01:02:07'/>
     </interface>
     <interface type='network'>
-      <!-- network mapped from "ringo" to "network4" -->
+      <!-- network mapped from "ringo" to default "network4" -->
       <source network='network4'/>
       <mac address='52:54:00:01:02:08'/>
     </interface>

v2v/types.ml

@@ -71,8 +71,8 @@ and source_nic = {
   s_mac : string option;
   s_nic_model : s_nic_model option;
   s_vnet : string;
-  s_vnet_orig : string;
   s_vnet_type : vnet_type;
+  s_mapping_explanation : string option;
 }
 and s_nic_model = Source_other_nic of string |
                   Source_rtl8139 | Source_e1000 | Source_virtio_net

v2v/types.mli

@@ -130,8 +130,11 @@ and source_nic = {
   s_mac : string option;                (** MAC address. *)
   s_nic_model : s_nic_model option;     (** Network adapter model. *)
   s_vnet : string;                      (** Source network name. *)
-  s_vnet_orig : string;                 (** Original network (if we map it). *)
   s_vnet_type : vnet_type;              (** Source network type. *)
+  s_mapping_explanation : string option;
+  (** If the NIC or network was mapped, this contains an English
+      explanation of the change which can be written to the target
+      hypervisor metadata for informational purposes. *)
 }
 (** Network adapter models. *)
 and s_nic_model = Source_other_nic of string |