[SDFAB-187] Add UpfProgrammable interface in ONOS core

Change-Id: Icef23a14015bb0ebe33ebe57eadecaaadc8eebd3
diff --git a/core/api/src/main/java/org/onosproject/net/behaviour/upf/UpfInterface.java b/core/api/src/main/java/org/onosproject/net/behaviour/upf/UpfInterface.java
new file mode 100644
index 0000000..3fee11a
--- /dev/null
+++ b/core/api/src/main/java/org/onosproject/net/behaviour/upf/UpfInterface.java
@@ -0,0 +1,246 @@
+/*
+ * Copyright 2021-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.onosproject.net.behaviour.upf;
+
+import org.onlab.packet.Ip4Address;
+import org.onlab.packet.Ip4Prefix;
+
+import java.util.Objects;
+
+import static com.google.common.base.Preconditions.checkNotNull;
+
+/**
+ * A UPF device interface, such as a S1U or UE IP address pool.
+ */
+public final class UpfInterface {
+    private final Ip4Prefix prefix;
+    private final Type type;
+
+    private UpfInterface(Ip4Prefix prefix, Type type) {
+        this.prefix = prefix;
+        this.type = type;
+    }
+
+    public static Builder builder() {
+        return new Builder();
+    }
+
+    @Override
+    public String toString() {
+        String typeStr;
+        if (type.equals(Type.ACCESS)) {
+            typeStr = "Access";
+        } else if (type.equals(Type.CORE)) {
+            typeStr = "Core";
+        } else if (type.equals(Type.DBUF)) {
+            typeStr = "Dbuf-Receiver";
+        } else {
+            typeStr = "UNKNOWN";
+        }
+        return String.format("Interface{%s, %s}", typeStr, prefix);
+    }
+
+    @Override
+    public boolean equals(Object obj) {
+        if (obj == this) {
+            return true;
+        }
+        if (obj == null) {
+            return false;
+        }
+        if (getClass() != obj.getClass()) {
+            return false;
+        }
+        UpfInterface that = (UpfInterface) obj;
+        return (this.type.equals(that.type) &&
+                this.prefix.equals(that.prefix));
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(prefix, type);
+    }
+
+    /**
+     * Create a core-facing UPF Interface from the given address, which will be treated as a /32 prefix.
+     *
+     * @param address the address of the new core-facing interface
+     * @return a new UPF interface
+     */
+    public static UpfInterface createS1uFrom(Ip4Address address) {
+        return builder().setAccess().setPrefix(Ip4Prefix.valueOf(address, 32)).build();
+    }
+
+    /**
+     * Create a core-facing UPF Interface from the given IP prefix.
+     *
+     * @param prefix the prefix of the new core-facing interface
+     * @return a new UPF interface
+     */
+    public static UpfInterface createUePoolFrom(Ip4Prefix prefix) {
+        return builder().setCore().setPrefix(prefix).build();
+    }
+
+    /**
+     * Create a dbuf-receiving UPF interface from the given IP address.
+     *
+     * @param address the address of the dbuf-receiving interface
+     * @return a new UPF interface
+     */
+    public static UpfInterface createDbufReceiverFrom(Ip4Address address) {
+        return UpfInterface.builder().setDbufReceiver().setAddress(address).build();
+    }
+
+    /**
+     * Get the IP prefix of this interface.
+     *
+     * @return the interface prefix
+     */
+    public Ip4Prefix prefix() {
+        return prefix;
+    }
+
+    /**
+     * Check if this UPF interface is for packets traveling from UEs.
+     * This will be true for S1U interface table entries.
+     *
+     * @return true if interface receives from access
+     */
+    public boolean isAccess() {
+        return type == Type.ACCESS;
+    }
+
+    /**
+     * Check if this UPF interface is for packets traveling towards UEs.
+     * This will be true for UE IP address pool table entries.
+     *
+     * @return true if interface receives from core
+     */
+    public boolean isCore() {
+        return type == Type.CORE;
+    }
+
+
+    /**
+     * Check if this UPF interface is for receiving buffered packets as they are released from the dbuf
+     * buffering device.
+     *
+     * @return true if interface receives from dbuf
+     */
+    public boolean isDbufReceiver() {
+        return type == Type.DBUF;
+    }
+
+    /**
+     * Get the IPv4 prefix of this UPF interface.
+     *
+     * @return the interface prefix
+     */
+    public Ip4Prefix getPrefix() {
+        return this.prefix;
+    }
+
+    public enum Type {
+        /**
+         * Unknown UPF interface type.
+         */
+        UNKNOWN,
+
+        /**
+         * Interface that receives GTP encapsulated packets.
+         * This is the type of the S1U interface.
+         */
+        ACCESS,
+
+        /**
+         * Interface that receives unencapsulated packets from the core of the network.
+         * This is the type of UE IP address pool interfaces.
+         */
+        CORE,
+
+        /**
+         * Interface that receives buffered packets as they are drained from a dbuf device.
+         */
+        DBUF
+    }
+
+    public static class Builder {
+        private Ip4Prefix prefix;
+        private Type type;
+
+        public Builder() {
+            type = Type.UNKNOWN;
+        }
+
+        /**
+         * Set the IPv4 prefix of this interface.
+         *
+         * @param prefix the interface prefix
+         * @return this builder object
+         */
+        public Builder setPrefix(Ip4Prefix prefix) {
+            this.prefix = prefix;
+            return this;
+        }
+
+        /**
+         * Set the IPv4 prefix of this interface, by turning the given address into a /32 prefix.
+         *
+         * @param address the interface address that will become a /32 prefix
+         * @return this builder object
+         */
+        public Builder setAddress(Ip4Address address) {
+            this.prefix = Ip4Prefix.valueOf(address, 32);
+            return this;
+        }
+
+        /**
+         * Make this an access-facing interface.
+         *
+         * @return this builder object
+         */
+        public Builder setAccess() {
+            this.type = Type.ACCESS;
+            return this;
+        }
+
+        /**
+         * Make this a core-facing interface.
+         *
+         * @return this builder object
+         */
+        public Builder setCore() {
+            this.type = Type.CORE;
+            return this;
+        }
+
+        /**
+         * Make this a dbuf-facing interface.
+         *
+         * @return this builder object
+         */
+        public Builder setDbufReceiver() {
+            this.type = Type.DBUF;
+            return this;
+        }
+
+        public UpfInterface build() {
+            checkNotNull(prefix);
+            return new UpfInterface(prefix, type);
+        }
+    }
+}