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Allow manual re-resolving of server hostname #1365

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6 changes: 4 additions & 2 deletions scripts/mosh.pl
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Original file line number Diff line number Diff line change
Expand Up @@ -69,6 +69,7 @@ BEGIN
my $overwrite = 0;

my $bind_ip = undef;
my $host = undef;

my $use_remote_ip = 'proxy';

Expand Down Expand Up @@ -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';
Expand Down Expand Up @@ -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
Expand Down Expand Up @@ -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'"} @_ }
Expand Down
11 changes: 8 additions & 3 deletions src/frontend/mosh-client.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -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 );
Expand Down Expand Up @@ -130,8 +130,10 @@ 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
Expand All @@ -143,6 +145,9 @@ int main( int argc, char* argv[] )
case 'v':
verbose++;
break;
case 'n':
hostname = optarg;
break;
default:
print_usage( stderr, argv[0] );
exit( 1 );
Expand Down Expand Up @@ -194,7 +199,7 @@ 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 {
Expand Down
39 changes: 38 additions & 1 deletion src/frontend/stmclient.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -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>
Expand Down Expand Up @@ -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];
Expand Down Expand Up @@ -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) */
Expand Down
13 changes: 8 additions & 5 deletions src/frontend/stmclient.h
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Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,7 @@
class STMClient
{
private:
std::string hostname;
std::string ip;
std::string port;
std::string key;
Expand Down Expand Up @@ -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 )
{
Expand Down
18 changes: 18 additions & 0 deletions src/network/network.cc
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Expand Up @@ -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 )
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@eminence eminence Dec 20, 2025

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I'm a little skeptical of of this impl (I think I want to unconditionally push a new Socket onto socks), but this does work as written. I'll revisit this later

{
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 ) {
Expand Down
1 change: 1 addition & 0 deletions src/network/network.h
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Expand Up @@ -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; }

Expand Down
1 change: 1 addition & 0 deletions src/network/networktransport.h
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Expand Up @@ -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(); }
};
Expand Down
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