Description of problem:

As of version 1.4.2, Java defaults to using IPv6 sockets.  When a
Java application connects to an IPv4 address, it creates an IPv6
connection to a "IPv4-mapped address" of the form ::ffff:w.x.y.z
(see http://java.sun.com/j2se/1.4.2/docs/guide/net/ipv6_guide/).
If authd receives a query from an IPv4 program on the other end of
such a socket, it only searches /proc/net/tcp.  Since the socket is
not listed there, it reports an error.

authd needs to be changed to also look for IPv4 sockets in
/proc/net/tcp6, using their IPv4-mapped addresses.


Version-Release number of selected component (if applicable):

authd-1.4.3-1


How reproducible:

I have created a very simple client/server program to demonstrate this
problem.  I will attach three files:

  * sockserv.c is the server
  * sockcl.c is a C client
  * SocketClient.java is a Java client

The server listens on port 9999, accepts a single connection, and
prints anything that is typed on the client.  The Java client requires
a single parameter, the name or address of the server (the port is
hardcoded).  Both the server address and the port are hardcoded in the
C client, so you'll probably need to edit it.

I recommend using two separate systems for testing; things can get a
little confusing when running both the server and the Java client on a
single system; you'll need to open port 9999 in the firewall on the
server system to do this.

Once you set everything up and connect with the C client, you'll be
able to see the socket in /proc/net/tcp (or 'netstat --inet') on both
systems, as you would expect.  If you're running authd on the client
system, it will work as expected.  You'll need to use Ctrl-C to exit
the client, at which point the server should also exit.

Now restart the server and connect with the Java client.  Note that
the socket appears in /proc/net/tcp ('netstat --inet') on the server
system.  On the client system, however, the socket shows up only in
/proc/net/tcp6 ('netstat --inet6'), so authd won't find it.

  
Actual results:

See above.


Expected results:

authd should search /proc/net/tcp6, using IPv4-mapped addresses, find
the socket, and return the appropriate user information.


Additional info:

Note that this doesn't just authd-based authentication over the
network.  It also breaks it over the loopback adapter, which is the
only type of socket available to Java applications.  (For example, a
JDBC connection to a PostgreSQL database.)