I recently ported an applciation from Solaris to Linux (Red Hat ES 3) and noticed that Linux doesn't allow you to bind to a port if the port is currently in a state of ESTABLISHED.

I run services listening on High ports (e.g. 47510). The problem is I also make outgoing connections, which will grab a random high port as the source port for this connection. Once a connection is establish from a high port, I am unable to bind to that port as a listen port.

On Solaris, I did not have this problem. The only states of a socket port that would prevent me from binding to it were:
LISTEN
CLOSE_WAIT
TIME_WAIT (I could get around this by setting SO_REUSEADDR)

Has anyone seen this, and have any suggestions on how to get around this?


Is there a way to force the local bind to a port, even if that port is being used as the source port for an outgoing connection?

Is there a way to tell the OS to exclude certain high ports from its list of outgoing source ports? (/proc/sys/net/ipv4/ip_local_port_range)

Thanks,
Dave

Strange. When using SO_REUSEADDR I have no such problems. One thing makes me wonder. Are you trying to open the same socket socket first using listen() and connect() ?

The outgoing socket connection with the source "high port" is being created in the normal way with a socket() and connect() call.

The bind to the listen port is being created as follows:
listen_socket = socket(AF_INET, SOCK_STREAM, 0);
setsocketopt(...) // SO_LINGER=0, SO_REUSEADDR=1, SO_KEEPALIVE=1
address.port = 45000;
bind(listen_socket, &address, sizeof(address);

If port 45000 happened to be in use by an outgoing socket connection, the bind fails with errno = 98 (EADDRINUSE) Address already in use.

This behavior only happens on the Linux build. When I run this on Solaris 9, the bind will be successful, even if port 45000 is in a state of ESTABLISHED due to an outgoing connection using that as a source port.