From 89da6105aa4c94e563661a0c684d457c5427c54e Mon Sep 17 00:00:00 2001
From: Keith Winstein <keithw@mit.edu>
Date: Mon, 13 Aug 2012 11:19:25 +0300
Subject: [PATCH] When not connected, (1) client hops port numbers (2) server
 stops sending.

---
 src/frontend/mosh-server.cc |  4 ++--
 src/network/network.cc      | 27 +++++++++++++++++++++++++++
 src/network/network.h       |  6 ++++++
 3 files changed, 35 insertions(+), 2 deletions(-)

diff --git a/src/frontend/mosh-server.cc b/src/frontend/mosh-server.cc
index 3e3936d..711bba7 100644
--- a/src/frontend/mosh-server.cc
+++ b/src/frontend/mosh-server.cc
@@ -526,7 +526,7 @@ void serve( int host_fd, Terminal::Complete &terminal, ServerConnection &network
 
       const int timeout_if_no_client = 60000;
       int timeout = min( network.wait_time(), terminal.wait_time( now ) );
-      if ( !network.has_remote_addr() ) {
+      if ( !network.get_remote_state_num() ) {
         timeout = min( timeout, timeout_if_no_client );
       }
 
@@ -696,7 +696,7 @@ void serve( int host_fd, Terminal::Complete &terminal, ServerConnection &network
 	}
       }
 
-      if ( !network.has_remote_addr()
+      if ( !network.get_remote_state_num()
            && time_since_remote_state >= uint64_t( timeout_if_no_client ) ) {
         fprintf( stderr, "No connection within %d seconds.\n",
                  timeout_if_no_client / 1000 );
diff --git a/src/network/network.cc b/src/network/network.cc
index 2e9db55..a5cc510 100644
--- a/src/network/network.cc
+++ b/src/network/network.cc
@@ -107,6 +107,20 @@ Packet Connection::new_packet( string &s_payload )
   return p;
 }
 
+void Connection::reset( void )
+{
+  if ( server ) {
+    has_remote_addr = false;
+  } else { /* client */
+    if ( close( sock ) < 0 ) {
+      throw NetworkException( "close", errno );
+    }
+
+    setup();
+    last_association = timestamp();
+  }
+}
+
 void Connection::setup( void )
 {
   /* create socket */
@@ -144,6 +158,8 @@ Connection::Connection( const char *desired_ip, const char *desired_port ) /* se
     saved_timestamp( -1 ),
     saved_timestamp_received_at( 0 ),
     expected_receiver_seq( 0 ),
+    last_heard( -1 ),
+    last_association( -1 ),
     RTT_hit( false ),
     SRTT( 1000 ),
     RTTVAR( 500 ),
@@ -253,6 +269,8 @@ Connection::Connection( const char *key_str, const char *ip, int port ) /* clien
     saved_timestamp( -1 ),
     saved_timestamp_received_at( 0 ),
     expected_receiver_seq( 0 ),
+    last_heard( -1 ),
+    last_association( -1 ),
     RTT_hit( false ),
     SRTT( 1000 ),
     RTTVAR( 500 ),
@@ -272,6 +290,7 @@ Connection::Connection( const char *key_str, const char *ip, int port ) /* clien
   }
 
   has_remote_addr = true;
+  last_association = timestamp();
 }
 
 void Connection::send( string s )
@@ -294,6 +313,13 @@ void Connection::send( string s )
     have_send_exception = true;
     send_exception = NetworkException( "sendto", errno );
   }
+
+  /* association timeout */
+  uint64_t now = timestamp();
+  if ( ( now - last_association > ASSOCIATION_TIMEOUT )
+       && ( now - last_heard > ASSOCIATION_TIMEOUT ) ) {
+    reset();
+  }
 }
 
 string Connection::recv( void )
@@ -351,6 +377,7 @@ string Connection::recv( void )
 
     /* auto-adjust to remote host */
     has_remote_addr = true;
+    last_heard = last_association = timestamp();
 
     if ( server ) { /* only client can roam */
       if ( (remote_addr.sin_addr.s_addr != packet_remote_addr.sin_addr.s_addr)
diff --git a/src/network/network.h b/src/network/network.h
index 5219f27..cc6a450 100644
--- a/src/network/network.h
+++ b/src/network/network.h
@@ -91,6 +91,8 @@ namespace Network {
     static const int PORT_RANGE_LOW  = 60001;
     static const int PORT_RANGE_HIGH = 60999;
 
+    static const unsigned int ASSOCIATION_TIMEOUT = 20000; /* ms */
+
     static bool try_bind( int socket, uint32_t addr, int port );
 
     int sock;
@@ -112,6 +114,8 @@ namespace Network {
     uint64_t saved_timestamp_received_at;
     uint64_t expected_receiver_seq;
 
+    uint64_t last_heard, last_association;
+
     bool RTT_hit;
     double SRTT;
     double RTTVAR;
@@ -123,6 +127,8 @@ namespace Network {
 
     Packet new_packet( string &s_payload );
 
+    void reset( void );
+
   public:
     Connection( const char *desired_ip, const char *desired_port ); /* server */
     Connection( const char *key_str, const char *ip, int port ); /* client */