Add support for smtpd filter protocol <v0.5

include/protocol/protocol.hpp

@@ -48,6 +48,7 @@ namespace protocol {
     private:
         handler_map_t handlers;
         size_t max_pattern_length;
+        std::string version;
 
         void send_data_line(const session_key_t& session_key, const std::string& data_line);
     };

src/protocol/protocol.cpp

@@ -38,6 +38,10 @@ namespace protocol {
         auto pattern = token::pattern_t(tokens, false);
         debug && cerr << "Received pattern " << pattern << endl;
 
+        if(tokens.size() >= 2 && tokens.at(0) == "filter") {
+            version = tokens.at(1);
+        }
+
         auto element = handlers.find(pattern);
         if(element == handlers.end()) {
             debug && cerr << "Unknown pattern " << pattern << endl;
@@ -47,7 +51,12 @@ namespace protocol {
     }
 
     void protocol_t::send_result(const session_key_t& session_key, token::list_t tokens) {
-        token::list_t result{"filter-result", session_key.session, session_key.token};
+        token::list_t result{"filter-result"};
+        if(version < "0.5") {
+            result.insert(result.end(), {session_key.token, session_key.session});
+        } else {
+            result.insert(result.end(), {session_key.session, session_key.token});
+        }
         for(auto& token : tokens) {
             result.push_back(token);
         }