Added "junk" response to filter protocol

include/protocol/protocol.hpp

@@ -35,10 +35,11 @@ namespace protocol {
         void absorb(const std::string& input);
         void send(const token::list_t& tokens);
 
+        // TODO: Move these methods to a separate session_t class!
         void send_result(const session_key_t& session_key, token::list_t tokens);
         void proceed(const session_key_t& session_key);
+        void junk(const session_key_t& session_key);
         void fail(const session_key_t& session_key);
-
         void submit_message(const session_key_t& session_key, const std::vector<std::string>& header, const std::vector<std::string>& body);
 
     protected:

src/protocol/protocol.cpp

@@ -8,9 +8,8 @@
 using namespace std;
 using namespace util;
 
-    //config|smtpd-version|6.6.1
-    //config|smtp-session-timeout|300
-    //config|subsystem|smtp-in
+// OpenSMTPD filter protocol documentation:
+// https://man7.org/linux/man-pages/man7/smtpd-filters.7.html
 
 const bool debug = true;
 
@@ -24,10 +23,10 @@ namespace protocol {
                 }
             }
         }
+        max_pattern_length = length;
         debug && cerr << "Maximum handler pattern length is " << length << endl;
 
         this->handlers = handlers;
-        max_pattern_length = length;
     }
 
     void protocol_t::send(const token::list_t& tokens) {
@@ -59,6 +58,10 @@ namespace protocol {
         send_result(session_key, {"proceed"});
     }
 
+    void protocol_t::junk(const session_key_t& session_key) {
+        send_result(session_key, {"junk"});
+    }
+
     void protocol_t::fail(const session_key_t& session_key) {
         send_result(session_key, {"disconnect", "451 Aborted"});
     }