Allow manual re-resolving of server hostname

Author: eminence

scripts/mosh.pl

@@ -69,6 +69,7 @@ BEGIN
 my $overwrite = 0;
 
 my $bind_ip = undef;
+my $host = undef;
 
 my $use_remote_ip = 'proxy';
 
@@ -245,6 +246,7 @@ sub predict_check {
   }
   $userhost = shift;
   @command = @ARGV;
+  (my $user, $host) = $userhost =~ /^((?:.*@)?)(.*)$/;
   if ( not defined $bind_ip or $bind_ip =~ m{^ssh$}i ) {
     if ( not defined $localhost ) {
       push @bind_arguments, '-s';
@@ -334,7 +336,7 @@ sub predict_check {
 my $ip;
 if ( $use_remote_ip eq 'local' ) {
   # "parse" the host from what the user gave us
-  my ($user, $host) = $userhost =~ /^((?:.*@)?)(.*)$/;
+  (my $user, $host) = $userhost =~ /^((?:.*@)?)(.*)$/;
   # get list of addresses
   my @res = resolvename( $host, 22, $family );
   # Use only the first address as the Mosh IP
@@ -462,7 +464,7 @@ sub predict_check {
   $ENV{ 'MOSH_KEY' } = $key;
   $ENV{ 'MOSH_PREDICTION_DISPLAY' } = $predict;
   $ENV{ 'MOSH_NO_TERM_INIT' } = '1' if !$term_init;
-  exec {$client} ("$client", "-# @cmdline |", $ip, $port);
+  exec {$client} ("$client", "-# @cmdline |", "-n", "$host", $ip, $port);
 }
 
 sub shell_quote { join ' ', map {(my $a = $_) =~ s/'/'\\''/g; "'$a'"} @_ }

src/frontend/mosh-client.cc

@@ -85,7 +85,7 @@ static void print_usage( FILE* file, const char* argv0 )
 {
   print_version( file );
   fprintf( file,
-           "\nUsage: %s [-# 'ARGS'] IP PORT\n"
+           "\nUsage: %s [-# 'ARGS'] [-n hostname] IP PORT\n"
            "       %s -c\n",
            argv0,
            argv0 );
@@ -126,8 +126,10 @@ int main( int argc, char* argv[] )
     }
   }
 
+  char *hostname = NULL;
+
   int opt;
-  while ( ( opt = getopt( argc, argv, "#:cv" ) ) != -1 ) {
+  while ( ( opt = getopt( argc, argv, "#:cvn:" ) ) != -1 ) {
     switch ( opt ) {
       case '#':
         // Ignore the original arguments to mosh wrapper
@@ -139,6 +141,9 @@ int main( int argc, char* argv[] )
       case 'v':
         verbose++;
         break;
+      case 'n':
+        hostname = optarg;
+        break;
       default:
         print_usage( stderr, argv[0] );
         exit( 1 );
@@ -190,7 +195,7 @@ int main( int argc, char* argv[] )
 
   bool success = false;
   try {
-    STMClient client( ip, desired_port, key.c_str(), predict_mode, verbose, predict_overwrite );
+    STMClient client( hostname, ip, desired_port, key.c_str(), predict_mode, verbose, predict_overwrite );
     client.init();
 
     try {

src/frontend/stmclient.cc

@@ -45,6 +45,8 @@
 #include <sys/ioctl.h>
 #include <sys/types.h>
 #include <unistd.h>
+#include <netdb.h>
+#include <sys/socket.h>
 
 #if HAVE_PTY_H
 #include <pty.h>
@@ -193,7 +195,7 @@ void STMClient::init( void )
     tmp = std::string( escape_key_name_buf );
     std::wstring escape_key_name = std::wstring( tmp.begin(), tmp.end() );
     escape_key_help
-      = L"Commands: Ctrl-Z suspends, \".\" quits, " + escape_pass_name + L" gives literal " + escape_key_name;
+      = L"Commands: Ctrl-Z suspends, \".\" quits, \"r\" forces a re-resolve, " + escape_pass_name + L" gives literal " + escape_key_name;
     overlays.get_notification_engine().set_escape_key_string( tmp );
   }
   wchar_t tmp[128];
@@ -367,6 +369,41 @@ bool STMClient::process_user_input( int fd )
         kill( 0, SIGSTOP );
 
         resume();
+      } else if ( the_byte == 'r' || the_byte == 'R' ) {
+        if ( !hostname.empty() ) {
+          overlays.get_notification_engine().set_notification_string( std::wstring( L"Re-resolving..." ), true );
+          output_new_frame();
+          struct addrinfo hints, *res;
+          memset( &hints, 0, sizeof( hints ) );
+          hints.ai_family = AF_UNSPEC;
+          hints.ai_socktype = SOCK_DGRAM;
+          int err = getaddrinfo( hostname.c_str(), port.c_str(), &hints, &res );
+          if ( err == 0 ) {
+            struct addrinfo *p;
+            struct addrinfo *match = NULL;
+            int current_family = net.get_remote_addr().sa.sa_family;
+
+            for ( p = res; p != NULL; p = p->ai_next ) {
+              if ( p->ai_family == current_family ) {
+                match = p;
+                break;
+              }
+            }
+
+            if ( match ) {
+              net.set_remote_addr( match->ai_addr, match->ai_addrlen );
+            } else {
+              net.set_remote_addr( res->ai_addr, res->ai_addrlen );
+            }
+
+            freeaddrinfo( res );
+            overlays.get_notification_engine().set_notification_string( std::wstring( L"Re-resolved hostname." ), false );
+          } else {
+            std::string msg = "DNS failure: ";
+            msg += gai_strerror( err );
+            overlays.get_notification_engine().set_notification_string( std::wstring( msg.begin(), msg.end() ), false );
+          }
+        }
       } else if ( ( the_byte == escape_pass_key ) || ( the_byte == escape_pass_key2 ) ) {
         /* Emulation sequence to type escape_key is escape_key +
            escape_pass_key (that is escape key without Ctrl) */

src/frontend/stmclient.h

@@ -47,6 +47,7 @@
 class STMClient
 {
 private:
+  std::string hostname;
   std::string ip;
   std::string port;
   std::string key;
@@ -89,16 +90,18 @@ class STMClient
   void resume( void ); /* restore state after SIGCONT */
 
 public:
-  STMClient( const char* s_ip,
+  STMClient( const char* s_hostname,
+             const char* s_ip,
              const char* s_port,
              const char* s_key,
              const char* predict_mode,
              unsigned int s_verbose,
              const char* predict_overwrite )
-    : ip( s_ip ? s_ip : "" ), port( s_port ? s_port : "" ), key( s_key ? s_key : "" ), escape_key( 0x1E ),
-      escape_pass_key( '^' ), escape_pass_key2( '^' ), escape_requires_lf( false ), escape_key_help( L"?" ),
-      saved_termios(), raw_termios(), window_size(), local_framebuffer( 1, 1 ), new_state( 1, 1 ), overlays(),
-      network(), display( true ) /* use TERM environment var to initialize display */, connecting_notification(),
+    : hostname( s_hostname ? s_hostname : "" ), ip( s_ip ? s_ip : "" ), port( s_port ? s_port : "" ),
+      key( s_key ? s_key : "" ), escape_key( 0x1E ), escape_pass_key( '^' ), escape_pass_key2( '^' ),
+      escape_requires_lf( false ), escape_key_help( L"?" ), saved_termios(), raw_termios(), window_size(),
+      local_framebuffer( 1, 1 ), new_state( 1, 1 ), overlays(), network(),
+      display( true ) /* use TERM environment var to initialize display */, connecting_notification(),
       repaint_requested( false ), lf_entered( false ), quit_sequence_started( false ), clean_shutdown( false ),
       verbose( s_verbose )
   {

src/network/network.cc

@@ -364,6 +364,24 @@ Connection::Connection( const char* key_str, const char* ip, const char* port )
   set_MTU( remote_addr.sa.sa_family );
 }
 
+void Connection::set_remote_addr( const struct sockaddr* addr, socklen_t len )
+{
+  fatal_assert( len <= sizeof( remote_addr ) );
+
+  bool family_changed = ( remote_addr.sa.sa_family != addr->sa_family );
+
+  remote_addr_len = len;
+  memcpy( &remote_addr.sa, addr, remote_addr_len );
+
+  has_remote_addr = true;
+
+  if ( family_changed ) {
+    socks.push_back( Socket( remote_addr.sa.sa_family ) );
+  }
+
+  set_MTU( remote_addr.sa.sa_family );
+}
+
 void Connection::send( const std::string& s )
 {
   if ( !has_remote_addr ) {

src/network/network.h

@@ -233,6 +233,7 @@ class Connection
 
   const Addr& get_remote_addr( void ) const { return remote_addr; }
   socklen_t get_remote_addr_len( void ) const { return remote_addr_len; }
+  void set_remote_addr( const struct sockaddr* addr, socklen_t len );
 
   std::string& get_send_error( void ) { return send_error; }
 

src/network/networktransport.h

@@ -126,6 +126,7 @@ class Transport
 
   const Addr& get_remote_addr( void ) const { return connection.get_remote_addr(); }
   socklen_t get_remote_addr_len( void ) const { return connection.get_remote_addr_len(); }
+  void set_remote_addr( const struct sockaddr* addr, socklen_t len ) { connection.set_remote_addr( addr, len ); }
 
   std::string& get_send_error( void ) { return connection.get_send_error(); }
 };