[SAIP4] Break routing.p4 into routing_lookup and routing_resolution. …

…Move routing_resolution to after ACL ingress stage. (sonic-net#611)



Co-authored-by: smolkaj <[email protected]>
Co-authored-by: kheradmandG <[email protected]>
Co-authored-by: kishanps <[email protected]>

sai_p4/fixed/metadata.p4

@@ -273,6 +273,15 @@ struct local_metadata_t {
   bool nexthop_id_valid;
   // Nexthop id, only valid if `nexthop_id_valid` is true.
   nexthop_id_t nexthop_id_value;
+
+  // Determines if packet was dropped in ACL ingress/egress stage. If true, the
+  // actual call to mark_to_drop (that affects standard_metadata) takes place at
+  // the end of the respective pipeline.
+  // This is done this way because we want to call mark_to_drop after
+  // determining the target_egress_port through the value assigned to
+  // standard_metadata.egress_spec (which happens in routing_resolution *after*
+  // ACL ingress) for punted packets.
+  bool acl_drop;
 }
 
 #endif  // SAI_METADATA_P4_

sai_p4/fixed/parser.p4

@@ -36,6 +36,11 @@ parser packet_parser(packet_in packet, out headers_t headers,
     local_metadata.ingress_port = (port_id_t)standard_metadata.ingress_port;
     local_metadata.route_metadata = 0;
     local_metadata.bypass_ingress = false;
+    local_metadata.wcmp_group_id_valid = false;
+    local_metadata.wcmp_group_id_value = 0;
+    local_metadata.nexthop_id_valid = false;
+    local_metadata.nexthop_id_value = 0;
+    local_metadata.acl_drop = false;
 
   transition select(standard_metadata.ingress_port) {
       SAI_P4_CPU_PORT: parse_packet_out_header;

sai_p4/instantiations/google/acl_common_actions.p4

@@ -11,8 +11,15 @@
 // more information.
 @id(ACL_DROP_ACTION_ID)
 @sai_action(SAI_PACKET_ACTION_DROP)
-action acl_drop(inout standard_metadata_t standard_metadata) {
-  mark_to_drop(standard_metadata);
+action acl_drop(inout local_metadata_t local_metadata) {
+  // It is necessary (and enough) to set acl_drop metadata at this point. The
+  // actual call to mark_to_drop (that affects standard_metadata) happens at the
+  // end of the current pipeline.
+  // This is done this way because we want to call mark_to_drop after
+  // determining the target_egress_port through the value assigned to
+  // standard_metadata.egress_spec (which happens in routing_resolution *after*
+  // ACL ingress) for punted packets.
+  local_metadata.acl_drop = true;
 }
 
 #endif  // SAI_ACL_COMMON_ACTIONS_P4_

sai_p4/instantiations/google/acl_egress.p4

@@ -90,7 +90,7 @@ control acl_egress(in headers_t headers,
 #endif
     }
     actions = {
-      @proto_id(1) acl_drop(standard_metadata);
+      @proto_id(1) acl_drop(local_metadata);
 #if defined(SAI_INSTANTIATION_TOR) 
       @proto_id(2) acl_egress_forward();
 #endif
@@ -139,7 +139,7 @@ control acl_egress(in headers_t headers,
           @sai_field(SAI_ACL_TABLE_ATTR_FIELD_OUT_PORT);
     }
     actions = {
-      @proto_id(1) acl_drop(standard_metadata);
+      @proto_id(1) acl_drop(local_metadata);
       @defaultonly NoAction;
     }
     const default_action = NoAction;
@@ -167,6 +167,10 @@ control acl_egress(in headers_t headers,
       acl_egress_table.apply();
       acl_egress_dhcp_to_host_table.apply();
 #endif
+    // Act on ACL drop metadata.
+      if (local_metadata.acl_drop) {
+        mark_to_drop(standard_metadata);
+      }
     }
   }
 }  // control ACL_EGRESS

sai_p4/instantiations/google/acl_ingress.p4

@@ -78,7 +78,9 @@ control acl_ingress(in headers_t headers,
 #endif
   action acl_trap(@sai_action_param(QOS_QUEUE) @id(1) qos_queue_t qos_queue) {
     acl_copy(qos_queue);
-    mark_to_drop(standard_metadata);
+    // TODO: Use `acl_drop(local_metadata)` instead when supported
+    // in P4-Symbolic.
+    local_metadata.acl_drop = true;
   }
 
   // Forward the packet normally (i.e., perform no action). This is useful as
@@ -184,7 +186,9 @@ control acl_ingress(in headers_t headers,
   @sai_action(SAI_PACKET_ACTION_DENY)
   action acl_deny() {
     cancel_copy = true;
-    mark_to_drop(standard_metadata);
+    // TODO: Use `acl_drop(local_metadata)` instead when supported
+    // in P4-Symbolic.
+    local_metadata.acl_drop = true;
   }
 
   @p4runtime_role(P4RUNTIME_ROLE_SDN_CONTROLLER)
@@ -295,7 +299,7 @@ control acl_ingress(in headers_t headers,
       @proto_id(2) acl_trap();
       @proto_id(3) acl_forward();
       @proto_id(4) acl_mirror();
-      @proto_id(5) acl_drop(standard_metadata);
+      @proto_id(5) acl_drop(local_metadata);
       @defaultonly NoAction;
     }
     const default_action = NoAction;
@@ -378,7 +382,7 @@ control acl_ingress(in headers_t headers,
       @proto_id(1) set_qos_queue_and_cancel_copy_above_rate_limit();
       @proto_id(2) set_cpu_queue_and_deny_above_rate_limit();
       @proto_id(3) acl_forward();
-      @proto_id(4) acl_drop(standard_metadata);
+      @proto_id(4) acl_drop(local_metadata);
       @proto_id(5) set_cpu_queue();
       @proto_id(6)
         set_cpu_and_multicast_queues_and_deny_above_rate_limit();
@@ -585,7 +589,7 @@ control acl_ingress(in headers_t headers,
     }
     actions = {
       @proto_id(1) acl_forward();
-      @proto_id(2) acl_drop(standard_metadata);
+      @proto_id(2) acl_drop(local_metadata);
       @proto_id(3) acl_deny();
       @defaultonly NoAction;
     }
@@ -607,12 +611,6 @@ control acl_ingress(in headers_t headers,
       ip_protocol = headers.ipv6.next_header;
     }
 
-    // If a packet gets punted, this adds relevant metadata to it. Must happen
-    // here, rather than below, since `standard_metadata` can change based on
-    // actions taken in the various tables.
-    local_metadata.packet_in_target_egress_port = standard_metadata.egress_spec;
-    local_metadata.packet_in_ingress_port = standard_metadata.ingress_port;
-
 #if defined(SAI_INSTANTIATION_MIDDLEBLOCK)
     acl_ingress_table.apply();
     acl_ingress_security_table.apply();

sai_p4/instantiations/google/fabric_border_router.p4

@@ -40,11 +40,12 @@ control ingress(inout headers_t headers,
       tunnel_termination_decap.apply(headers, local_metadata);
       admit_google_system_mac.apply(headers, local_metadata);
       l3_admit.apply(headers, local_metadata, standard_metadata);
-      routing.apply(headers, local_metadata, standard_metadata);
-      drop_martians.apply(headers, local_metadata, standard_metadata);
+      routing_lookup.apply(headers, local_metadata, standard_metadata);
       acl_ingress.apply(headers, local_metadata, standard_metadata);
+      routing_resolution.apply(headers, local_metadata, standard_metadata);
       mirror_session_lookup.apply(headers, local_metadata, standard_metadata);
       ingress_cloning.apply(headers, local_metadata, standard_metadata);
+      drop_martians.apply(headers, local_metadata, standard_metadata);
     }
   }
 }  // control ingress