# 
# patch "ChangeLog"
#  from [746912cbb100ebc57364b0e9c8d3785cb3cc5f7d]
#    to [c472ec862675aabab5b00c7a463564a22747966c]
# 
# patch "netcmd.cc"
#  from [75a0d51313f112ec54f83d29eca1d1077d2547bb]
#    to [38e6b3a85549ed7c7e5f109623d9ea1b802fc340]
# 
# patch "netcmd.hh"
#  from [8bea78d5e3429c65cc158c90450a7473528ceb07]
#    to [87007edfa58287e177df2f3246b28eaa5c5f6146]
# 
# patch "netsync.cc"
#  from [5a4a894840cdd806535dd34121a150ea8d7a0870]
#    to [f29b8cf04f7f4ef176165d31cd446c359233007a]
# 
========================================================================
--- ChangeLog	746912cbb100ebc57364b0e9c8d3785cb3cc5f7d
+++ ChangeLog	c472ec862675aabab5b00c7a463564a22747966c
@@ -1,3 +1,12 @@
+2005-09-16  Timothy Brownawell  <address@hidden>
+
+	* netcmd.{cc,hh}, netsync.cc: new netcmd types: usher_cmd and
+	usher_reply_cmd. They are not included in the HMAC, and do not
+	occur during normal communication. Purpose: running multiple servers
+	from the same port. This allows a special server to ask for the
+	client's include pattern, and then forward the connection to a real
+	monotone server.
+
 2005-09-15  Timothy Brownawell  <address@hidden>
 
 	* app_state.{cc,hh}: restrictions now understand --exclude
========================================================================
--- netcmd.cc	75a0d51313f112ec54f83d29eca1d1077d2547bb
+++ netcmd.cc	38e6b3a85549ed7c7e5f109623d9ea1b802fc340
@@ -62,7 +62,8 @@
     cmd_code == other.cmd_code &&
     payload == other.payload;
 }
-  
+
+// note: usher_reply_cmd does not get included in the hmac.
 void 
 netcmd::write(string & out, chained_hmac & hmac) const
 {
@@ -71,11 +72,15 @@
   out += static_cast<char>(cmd_code);
   insert_variable_length_string(payload, out);
 
-  string digest = hmac.process(out, oldlen);
-  I(hmac.hmac_length == constants::netsync_hmac_value_length_in_bytes);
-  out.append(digest);
+  if (cmd_code != usher_reply_cmd)
+    {
+      string digest = hmac.process(out, oldlen);
+      I(hmac.hmac_length == constants::netsync_hmac_value_length_in_bytes);
+      out.append(digest);
+    }
 }
 
+// note: usher_cmd does not get included in the hmac.
 bool 
 netcmd::read(string_queue & inbuf, chained_hmac & hmac)
 {
@@ -107,6 +112,7 @@
     case static_cast<u8>(data_cmd):
     case static_cast<u8>(delta_cmd):
     case static_cast<u8>(nonexistant_cmd):
+    case static_cast<u8>(usher_cmd):
       cmd_code = static_cast<netcmd_code>(cmd_byte);
       break;
     default:
@@ -124,21 +130,30 @@
     throw bad_decode(F("oversized payload of '%d' bytes") % payload_len);
   
   // there might not be enough data yet in the input buffer
-  if (inbuf.size() < pos + payload_len + constants::netsync_hmac_value_length_in_bytes)
+  unsigned int minsize;
+  if (cmd_code == usher_cmd)
+    minsize = pos + payload_len;
+  else
+    minsize = pos + payload_len + constants::netsync_hmac_value_length_in_bytes;
+  if (inbuf.size() < minsize)
     {
       return false;
     }
 
   // grab it before the data gets munged
   I(hmac.hmac_length == constants::netsync_hmac_value_length_in_bytes);
-  string digest = hmac.process(inbuf, 0, pos + payload_len);
+  string digest;
+  if (cmd_code != usher_cmd)
+    digest = hmac.process(inbuf, 0, pos + payload_len);
 
   payload = extract_substring(inbuf, pos, payload_len, "netcmd payload");
 
   // they might have given us bogus data
-  string cmd_digest = extract_substring(inbuf, pos, 
-      constants::netsync_hmac_value_length_in_bytes,
-                                        "netcmd HMAC");
+  string cmd_digest;
+  if (cmd_code != usher_cmd)
+    cmd_digest = extract_substring(inbuf, pos, 
+        constants::netsync_hmac_value_length_in_bytes,
+                                          "netcmd HMAC");
   inbuf.pop_front(pos);
   if (cmd_digest != digest)
     throw bad_decode(F("bad HMAC checksum (got %s, wanted %s)\n"
@@ -544,7 +559,25 @@
   payload += item();
 }
 
+void 
+netcmd::read_usher_cmd(utf8 & greeting) const
+{
+  size_t pos = 0;
+  std::string str;
+  extract_variable_length_string(payload, str, pos, "error netcmd, message");
+  greeting = utf8(str);
+  assert_end_of_buffer(payload, pos, "error netcmd payload");
+}
 
+void 
+netcmd::write_usher_reply_cmd(utf8 const & pattern)
+{
+  cmd_code = usher_reply_cmd;
+  payload.clear();
+  insert_variable_length_string(pattern(), payload);
+}
+
+
 #ifdef BUILD_UNIT_TESTS
 
 #include "unit_tests.hh"
========================================================================
--- netcmd.hh	8bea78d5e3429c65cc158c90450a7473528ceb07
+++ netcmd.hh	87007edfa58287e177df2f3246b28eaa5c5f6146
@@ -44,7 +44,16 @@
     send_delta_cmd = 9,
     data_cmd = 10,
     delta_cmd = 11,
-    nonexistant_cmd = 12
+    nonexistant_cmd = 12,
+
+    // usher commands
+    // usher_cmd is sent by a server farm (or anyone else who wants to serve
+    // from multiple databases over the same port), and the reply (containing
+    // the client's include pattern) is used to choose a server to forward the
+    // connection to.
+    // usher_cmd is never sent by the monotone server itself.
+    usher_cmd = 100,
+    usher_reply_cmd = 101
   }
 netcmd_code;
 
@@ -158,6 +167,9 @@
   void write_nonexistant_cmd(netcmd_item_type type,
                              id const & item);
 
+  void read_usher_cmd(utf8 & greeting) const;
+  void write_usher_reply_cmd(utf8 const & pattern);
+
 };
 
 #endif // __NETCMD_HH__
========================================================================
--- netsync.cc	5a4a894840cdd806535dd34121a150ea8d7a0870
+++ netsync.cc	f29b8cf04f7f4ef176165d31cd446c359233007a
@@ -442,6 +442,7 @@
                          delta const & del);
   bool process_nonexistant_cmd(netcmd_item_type type,
                                id const & item);
+  bool process_usher_cmd(utf8 const & msg);
 
   bool merkle_node_exists(netcmd_item_type type,
                           size_t level,
@@ -2976,6 +2977,23 @@
 }
 
 bool
+session::process_usher_cmd(utf8 const & msg)
+{
+  if (greeting().size())
+    {
+      if (greeting()[0] == '!')
+        P(F("Received warning from usher: %s") % greeting().substr(1));
+      else
+        L(F("Received greeting from usher: %s") % greeting().substr(1));
+    }
+  netcmd cmdout;
+  cmdout.write_usher_reply_cmd(our_include_pattern);
+  write_netcmd_and_try_flush(cmdout);
+  L(F("Sent reply."));
+  return true;
+}
+
+bool
 session::merkle_node_exists(netcmd_item_type type,
                             size_t level,
                             prefix const & pref)
@@ -3193,6 +3211,16 @@
         return process_nonexistant_cmd(type, item);
       }
       break;
+    case usher_cmd:
+      {
+        utf8 greeting;
+        cmd.read_usher_cmd(greeting);
+        return process_usher_cmd(greeting);
+      }
+      break;
+    case usher_reply_cmd:
+      return false;// should not happen
+      break;
     }
   return false;
 }