Add new ConnKey abstraction.

src/ConnKey.h

@@ -0,0 +1,89 @@
+// See the file "COPYING" in the main distribution directory for copyright.
+
+#pragma once
+
+#include <memory>
+
+#include "zeek/IntrusivePtr.h"
+#include "zeek/session/Key.h"
+
+namespace zeek {
+
+class Packet;
+
+class RecordVal;
+using RecordValPtr = zeek::IntrusivePtr<RecordVal>;
+
+/**
+ * Abstract ConnKey, for any type of connection.
+ */
+class ConnKey {
+public:
+    virtual ~ConnKey() = default;
+
+    /**
+     * Initialization of this key with the current packet.
+     *
+     * @param pkt The packet that's currently being processed.
+     */
+    void Init(const Packet& pkt) { DoInit(pkt); }
+
+    /**
+     * When Zeek renders a connection into a script-layer record, it calls this
+     * method to populate custom conn_id fields unique to this ConnKey, such as
+     * VLAN fields. This only needs to populate in fields in addition to Zeek's
+     * five-tuple (i.e., complete the record, not populate all of it).
+     *
+     * The default implementation does nothing.
+     *
+     * @param conn_id The conn_id record to populate.
+     */
+    void PopulateConnIdVal(RecordVal& conn_id) { DoPopulateConnIdVal(conn_id); };
+
+    /**
+     * Return a non-owning session::detail::Key instance for connection lookups.
+     *
+     * Callers that need more than just a view of the key should copy the data.
+     * Callers are not supposed to hold on to the returned Key for longer than
+     * the ConnKey instance exists.
+     *
+     * @return A zeek::session::detail::Key
+     */
+    zeek::session::detail::Key SessionKey() const { return DoSessionKey(); }
+
+protected:
+    /**
+     * Hook method for ConnKey::Init.
+     *
+     * Note that a given ConnKey instance may be re-used for different
+     * packets if it wasn't consumed to create a new connection. Therefore,
+     * implementers of this method are required to always set all fields
+     * that will affect the SessionKey result within DoInit anew.
+     *
+     * This a bit of an optimization done in the packet path that's shining
+     * through here. Rather than introducing a dedicated Reset method,
+     * implementers are asked to reset the key at initialization time
+     * which they most likely would do anyhow.
+     *
+     * @param pkt The packet that's currently being processed.
+     */
+    virtual void DoInit(const Packet& pkt) {};
+
+    /**
+     * Hook method for ConnKey::PopulateConnIdVal.
+     *
+     * The default implementation does nothing.
+     */
+    virtual void DoPopulateConnIdVal(RecordVal& conn_id) {}
+
+    /**
+     * Hook method for implementing ConnKey::SessionKey.
+     *
+     * @return A zeek::session::detail::Key
+     */
+    virtual session::detail::Key DoSessionKey() const = 0;
+};
+
+using ConnKeyPtr = std::unique_ptr<ConnKey>;
+
+} // namespace zeek