NGC handshake protocol change

src/Network/Tox/Application/GroupChatsPackets.lhs

@@ -78,6 +78,7 @@ Handshake packet payloads are structured as follows:
   \texttt{32}           & Public Session Key \\
   \texttt{32}           & Public Signature Key \\
   \texttt{1}            & Request Type \\
+  \texttt{1}            & Join Type \\
   variable              & 1 Packed TCP Relay \\
 \end{tabular}
 \hline
@@ -109,6 +110,18 @@ peer info exchange, the receiving peer must respond with a
 \textbf{\verb'PEER_INFO_RESPONSE'} packet followed immediately by a
 \textbf{\verb'PEER_INFO_REQUEST'} packet.
 
+The \textbf{\verb'Join Type'} indicates whether the initiator of a handshake
+is joining via the public DHT or a private friend invite. This field is ignored
+in handshake response packets. It is defined as an enumerator beginning at zero
+as follows:
+
+\begin{tabular}{l|l}
+  Type                        & ID \\
+  \hline
+  \textbf{\verb'PUBLIC'}      & 0x00 \\
+  \textbf{\verb'PRIVATE'}     & 0x01 \\
+\end{tabular}
+
 The packed TCP relay contains a TCP relay that the sender may be
 connected through by the receiver.