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Reserve the client listen port.

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When TRACY_PORT is not pinned the client probes 8086..8105 at startup.
Reserve the first free port up front and hand the already-bound socket
to the client via SetReservedListenSocket, so the reservation is atomic
and the reported port matches what the client listens on. A pinned
TRACY_PORT is validated like --port, since the client pins to any
nonzero value with no fallback.
This commit is contained in:
Bartosz Taudul
2026-08-30 16:41:44 +02:00
parent 6109ab27b5
commit e87b7c873e
1 changed files with 90 additions and 0 deletions
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90
monitor/src/monitor.cpp
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@@ -1,7 +1,10 @@
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <getopt.h>
#include <sys/ioctl.h>
#include <linux/perf_event.h>
#include <netinet/in.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
@@ -9,6 +12,7 @@
#include <string.h>
#include <sys/mman.h>
#include <sys/ptrace.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/wait.h>
@@ -641,6 +645,76 @@ static int RunForked( int argc, char** argv )
return 0;
}
// Reserve the first free port in the client's 8086..8105 scan range and hand the
// probe socket to the client (SetReservedListenSocket) so the reservation is atomic.
// The probe must mirror the client's bind exactly (ListenSocket::Listen): IPv6
// dual-stack first, IPv4 only if socket() itself fails, SO_REUSEADDR,
// TRACY_ONLY_LOCALHOST narrows to loopback, fd CLOEXEC (no leak into the target).
static bool ProbeClientBind( int port, bool ipv4Only, bool onlyLocalhost, int& fdOut )
{
fdOut = -1;
int s = -1;
int family = AF_INET6;
if( !ipv4Only ) s = socket( AF_INET6, SOCK_STREAM, 0 );
if( s < 0 )
{
family = AF_INET;
s = socket( AF_INET, SOCK_STREAM, 0 );
}
if( s < 0 ) return false;
fcntl( s, F_SETFD, FD_CLOEXEC );
int val = 1;
setsockopt( s, SOL_SOCKET, SO_REUSEADDR, &val, sizeof( val ) );
bool ok = false;
if( family == AF_INET6 )
{
sockaddr_in6 addr = {};
addr.sin6_family = AF_INET6;
if( onlyLocalhost ) addr.sin6_addr = in6addr_loopback;
addr.sin6_port = htons( (uint16_t)port );
ok = bind( s, (sockaddr*)&addr, sizeof( addr ) ) == 0 && listen( s, 4 ) == 0;
}
else
{
sockaddr_in addr = {};
addr.sin_family = AF_INET;
addr.sin_addr.s_addr = onlyLocalhost ? htonl( INADDR_LOOPBACK ) : INADDR_ANY;
addr.sin_port = htons( (uint16_t)port );
ok = bind( s, (sockaddr*)&addr, sizeof( addr ) ) == 0 && listen( s, 4 ) == 0;
}
if( ok )
{
fdOut = s;
}
else
{
close( s );
}
return ok;
}
static void ReservePortIfUnpinned()
{
if( getenv( "TRACY_PORT" ) ) return;
const char* onlyIPv4 = getenv( "TRACY_ONLY_IPV4" );
const char* onlyLocalhost = getenv( "TRACY_ONLY_LOCALHOST" );
const bool ipv4Only = onlyIPv4 && onlyIPv4[0] == '1';
const bool localhost = onlyLocalhost && onlyLocalhost[0] == '1';
for( int i=0; i<20; i++ )
{
const int port = 8086 + i;
int fd = -1;
if( ProbeClientBind( port, ipv4Only, localhost, fd ) )
{
char buf[8];
snprintf( buf, sizeof( buf ), "%d", port );
setenv( "TRACY_PORT", buf, 1 );
tracy::SetReservedListenSocket( fd );
return;
}
}
}
int main( int argc, char** argv )
{
auto progName = argv[0];
@@ -730,6 +804,22 @@ int main( int argc, char** argv )
}
}
// validate a pinned TRACY_PORT like --port: the client pins to any nonzero value
// (single listen, no fallback), so a bad value would report a port never used.
{
const char* portEnv = getenv( "TRACY_PORT" );
if( portEnv )
{
char* end = nullptr;
const long port = strtol( portEnv, &end, 10 );
if( end == portEnv || *end != '\0' || port < 1 || port > 65535 )
{
fprintf( stderr, "Invalid TRACY_PORT '%s' (expected a number in 1..65535); unset it or use --port.\n", portEnv );
return 1;
}
}
}
ReservePortIfUnpinned();
if( wantAttach )
{
if( attachName[0] )