CP-47046 optimise rule emitter for xenopsd PVS Proxy setup

Emit port-oriented rules for IPv4 and IPv6 only when needed.

The complication is that a single PVS server can have multiple addresses
each of which can be IPv4 or IPv6. So we need both kind of rules if
addresses as mixed but can emit only one kind if addresses are of one
kind.

Signed-off-by: Christian Lindig <[email protected]>

ocaml/xenopsd/pvs/pvs_proxy_setup.ml

@@ -85,6 +85,20 @@ let is_ipv6 str =
   | Unix.PF_UNIX ->
       error "unexpected address format: %s" str
 
+let ( let+ ) x f = Result.map f x
+
+let is_ipv4 str =
+  let+ res = is_ipv6 str in
+  not res
+
+(** List.exits but with [p] returning a [Result.t] *)
+let rec exists p = function
+  | [] ->
+      ok false
+  | x :: xs ->
+      let* res = p x in
+      if res then ok true else exists p xs
+
 (** open [path] to be consumed by [f] for scanning with Scanf *)
 let scanning path f =
   let io = Scanf.Scanning.open_in path in
@@ -313,6 +327,8 @@ let add debug dev vif priv hotplug =
   let add_pvs_server bridge n =
     D.debug "%s: bridge=%s server=%d" __FUNCTION__ bridge n ;
     let* ip_addrs = pvs_server_addrs ~n priv in
+    let* has_ipv6 = exists is_ipv6 ip_addrs in
+    let* has_ipv4 = exists is_ipv4 ip_addrs in
     let* port_lo, port_hi = pvs_server_ports ~n priv in
     let* () =
       (* flows per server address *)
@@ -393,34 +409,43 @@ let add debug dev vif priv hotplug =
         ok ()
     | Device.VIF ->
         let* () =
-          seq port_lo port_hi @@ fun port ->
-          (* flows per port *)
-          iter (* over flows below *)
-            (OVS.add_flow ~debug bridge)
-            [
-              [
-                p "cookie=%Ld" id
-              ; p "table=%d" Const.port_table
-              ; p "priority=%d" Const.rule_prio
-              ; p "%s=%d" Const.client_lsb id_lsb
-              ; p "%s=%d" Const.client_msb id_msb
-              ; "udp"
-              ; p "tp_dst=%d" port
-              ; p "actions=resubmit(,%d)" Const.action_table
-              ]
-            ; [
-                p "cookie=%Ld" id
-              ; p "table=%d" Const.port_table
-              ; p "priority=%d" Const.rule_prio
-              ; p "%s=%d" Const.client_lsb id_lsb
-              ; p "%s=%d" Const.client_msb id_msb
-              ; "udp6"
-              ; p "tp_dst=%d" port
-              ; p "actions=resubmit(,%d)" Const.action_table
-              ]
-            ]
+          seq port_lo port_hi (fun port ->
+              (* flows per port *)
+              let* () =
+                if has_ipv4 then
+                  OVS.add_flow ~debug bridge
+                    [
+                      p "cookie=%Ld" id
+                    ; p "table=%d" Const.port_table
+                    ; p "priority=%d" Const.rule_prio
+                    ; p "%s=%d" Const.client_lsb id_lsb
+                    ; p "%s=%d" Const.client_msb id_msb
+                    ; "udp"
+                    ; p "tp_dst=%d" port
+                    ; p "actions=resubmit(,%d)" Const.action_table
+                    ]
+                else
+                  ok ()
+              in
+              let* () =
+                if has_ipv6 then
+                  OVS.add_flow ~debug bridge
+                    [
+                      p "cookie=%Ld" id
+                    ; p "table=%d" Const.port_table
+                    ; p "priority=%d" Const.rule_prio
+                    ; p "%s=%d" Const.client_lsb id_lsb
+                    ; p "%s=%d" Const.client_msb id_msb
+                    ; "udp6"
+                    ; p "tp_dst=%d" port
+                    ; p "actions=resubmit(,%d)" Const.action_table
+                    ]
+                else
+                  ok ()
+              in
+              ok ()
+          )
         in
-
         iter (* over flows below *)
           (OVS.add_flow ~debug bridge)
           [