Date: Mon, 13 Aug 2001 12:51:43 -0400 (EDT) From: Joe Clarke <marcus@marcuscom.com> To: <freebsd-hackers@freebsd.org> Subject: Writing a packet alias translator, need help Message-ID: <20010813124054.F13703-100000@shumai.marcuscom.com>
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I'm trying to write a packet alias translator for a protocol that uses TCP
to setup a UDP streaming session (much like the smedia driver that's
already there). I'm having a problem getting the translated port to mesh
with the actual port. Here's what I've done:
/* msg is a TCP setup packet
struct msg {
u_int32_t ipAddr;
u_int32_t portNumber;
};
*/
null_addr.s_addr = 0;
msg->ipAddr = (u_int32_t)GetAliasAddress(link).s_addr;
my_link = FindUdpTcpOut(pip->ip_src, null_addr,
msg->portNumber, 0, IPPROTO_UDP, 1);
msg->portNumber = (u_int32_t)GetAliasPort(my_link);
What happens is that the IP address gets handled correctly, but not the
port number. The translation occurs in the packet, but it doesn't get
translated to the correct number. For example, the actual port being used
is UDP 16704, but the translation puts 50535 in the packet.
I guess my question is how can I put the correct port number in the TCP
setup packet? How can I then use this port number in the upcoming UDP
stream?
I've never written a NAT translator before, so I'm not sure if
FindUdpTcpOut() does what I think. any help would be appreciated.
Joe Clarke
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