Support multihomed servers

network.cpp

@@ -84,7 +84,7 @@ void Connection::setup( void )
   }
 }
 
-Connection::Connection() /* server */
+Connection::Connection( const char *desired_ip ) /* server */
   : sock( -1 ),
     remote_addr(),
     server( true ),
@@ -103,11 +103,26 @@ Connection::Connection() /* server */
 {
   setup();
 
-  /* Bind to free local port.
+  /* Attempt to bind free local port, with
+     address client used to connect to us.
+
      This usage does not seem to be endorsed by POSIX. */
+
   struct sockaddr_in local_addr;
   local_addr.sin_family = AF_INET;
   local_addr.sin_port = htons( 0 );
+  if ( desired_ip
+       && inet_aton( desired_ip, &local_addr.sin_addr )
+       && (bind( sock, (sockaddr *)&local_addr, sizeof( local_addr ) ) == 0) ) {
+    return;
+  }
+
+  if ( desired_ip ) {
+    fprintf( stderr, "Could not bind to desired local address %s.\n", desired_ip );
+  }
+
+  /* Could not bind to that IP (maybe we are behind NAT).
+     Try again with any IP. */
   local_addr.sin_addr.s_addr = INADDR_ANY;
   if ( bind( sock, (sockaddr *)&local_addr, sizeof( local_addr ) ) < 0 ) {
     throw NetworkException( "bind", errno );

network.hpp

@@ -85,8 +85,8 @@ namespace Network {
     void update_MTU( void );
 
   public:
-    Connection();
+    Connection( const char *desired_ip ); /* server */
-    Connection( const char *key_str, const char *ip, int port );
+    Connection( const char *key_str, const char *ip, int port ); /* client */
     
     void send( string s );
     string recv( void );

networktransport.cpp

@@ -9,8 +9,9 @@ using namespace Network;
 using namespace std;
 
 template <class MyState, class RemoteState>
-Transport<MyState, RemoteState>::Transport( MyState &initial_state, RemoteState &initial_remote )
+Transport<MyState, RemoteState>::Transport( MyState &initial_state, RemoteState &initial_remote,
-  : connection(),
+					    const char *desired_ip )
+  : connection( desired_ip ),
     sender( &connection, initial_state ),
     received_states( 1, TimestampedState<RemoteState>( timestamp(), 0, initial_remote ) ),
     last_receiver_state( initial_remote ),

networktransport.hpp

@@ -34,7 +34,7 @@ namespace Network {
     bool verbose;
 
   public:
-    Transport( MyState &initial_state, RemoteState &initial_remote );
+    Transport( MyState &initial_state, RemoteState &initial_remote, const char *desired_ip );
     Transport( MyState &initial_state, RemoteState &initial_remote,
 	       const char *key_str, const char *ip, int port );
 

ntester.cpp

@@ -29,7 +29,7 @@ int main( int argc, char *argv[] )
       
       n = new Transport<UserStream, UserStream>( me, remote, key, ip, port );
     } else {
-      n = new Transport<UserStream, UserStream>( me, remote );
+      n = new Transport<UserStream, UserStream>( me, remote, NULL );
     }
   } catch ( CryptoException e ) {
     fprintf( stderr, "Fatal error: %s\n", e.text.c_str() );

stm-server.cpp

@@ -20,12 +20,22 @@
 
 #include "networktransport.cpp"
 
-void serve( int host_fd );
+void serve( int host_fd, const char *desired_ip );
 
 using namespace std;
 
-int main( void )
+int main( int argc, char *argv[] )
 {
+  char *desired_ip = NULL;
+  if ( argc == 1 ) {
+    desired_ip = NULL;
+  } else if ( argc == 2 ) {
+    desired_ip = argv[ 1 ];
+  } else {
+    fprintf( stderr, "Usage: %s [LOCALADDR]\n", argv[ 0 ] );
+    exit( 1 );
+  }
+
   int master;
   struct termios child_termios;
 
@@ -98,7 +108,7 @@ int main( void )
     exit( 0 );
   } else {
     /* parent */
-    serve( master );
+    serve( master, desired_ip );
     if ( close( master ) < 0 ) {
       perror( "close" );
       exit( 1 );
@@ -110,7 +120,7 @@ int main( void )
   return 0;
 }
 
-void serve( int host_fd )
+void serve( int host_fd, const char *desired_ip )
 {
   /* establish fd for shutdown signals */
   sigset_t signal_mask;
@@ -151,7 +161,7 @@ void serve( int host_fd )
 
   /* open network */
   Network::UserStream blank;
-  Network::Transport< Terminal::Complete, Network::UserStream > network( terminal, blank );
+  Network::Transport< Terminal::Complete, Network::UserStream > network( terminal, blank, desired_ip );
 
   network.set_verbose();