Revision: 4303
http://tigervnc.svn.sourceforge.net/tigervnc/?rev=4303&view=rev
Author: dcommander
Date: 2011-02-21 13:43:44 +0000 (Mon, 21 Feb 2011)
Log Message:
-----------
Using a fixed port range with -via can cause a race condition between multiple
vncviewer instances, whereby one instance calls bind() and finds the port to be
free, then another instance calls bind() and finds the same port to be free,
because the first instance hasn't started the SSH tunnel on it yet. This patch
works around the issue by using ephemeral ports. All known modern O/S's
increment the ephemeral port number by 1 after bind(), so the port is
effectively "reserved" after bind(), and this prevents another vncviewer
instance from trying to reserve the same port.
Modified Paths:
--------------
trunk/common/network/TcpSocket.cxx
Modified: trunk/common/network/TcpSocket.cxx
===================================================================
--- trunk/common/network/TcpSocket.cxx 2011-02-21 13:40:33 UTC (rev 4302)
+++ trunk/common/network/TcpSocket.cxx 2011-02-21 13:43:44 UTC (rev 4303)
@@ -71,7 +71,7 @@
/* Tunnelling support. */
int network::findFreeTcpPort (void)
{
- int sock, port;
+ int sock;
struct sockaddr_in addr;
memset(&addr, 0, sizeof(addr));
addr.sin_family = AF_INET;
@@ -80,15 +80,16 @@
if ((sock = socket (AF_INET, SOCK_STREAM, 0)) < 0)
throw SocketException ("unable to create socket", errorNumber);
- for (port = TUNNEL_PORT_OFFSET + 99; port > TUNNEL_PORT_OFFSET; port--) {
- addr.sin_port = htons ((unsigned short) port);
- if (bind (sock, (struct sockaddr *)&addr, sizeof (addr)) == 0) {
- closesocket (sock);
- return port;
- }
- }
- throw SocketException ("no free port in range", 0);
- return 0;
+ addr.sin_port = 0;
+ if (bind (sock, (struct sockaddr *)&addr, sizeof (addr)) < 0)
+ throw SocketException ("unable to find free port", errorNumber);
+
+ socklen_t n = sizeof(addr);
+ if (getsockname (sock, (struct sockaddr *)&addr, &n) < 0)
+ throw SocketException ("unable to get port number", errorNumber);
+
+ closesocket (sock);
+ return ntohs(addr.sin_port);
}
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