Date: Fri, 19 Apr 2002 14:53:18 -0600 From: Brett Glass <brett@lariat.org> To: chat@freebsd.org Subject: How to control address used by INADDR_ANY? Message-ID: <4.3.2.7.2.20020419144005.0358c610@nospam.lariat.org>
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I'm in the process of creating a router which will sit on an ISP's
internal subnet, which uses unregistered addresses. The router's upstream
interface will have an unregistered address, say, 10.X.Y.Z. Its
downstream interfaces will have registered IPs, so it will look like this:
_A.B.C.1 -> feeds
A.B.C.0/25
10.X.Y.Z /
ISP and Internet ------[Router]\_A.B.D.1 -> feeds A.B.D.0/26
10.X.Y/24 etc.
But here's the rub. When the router communicates with the outside world
on its own behalf (which it has to do; it's going to have some services
running, including a a transparent Web cache), it needs to use one of its
registered addresses as the source address, or the packets won't leave
the ISP's internal network and get to the rest of the Internet.
My first attempt at configuring a FreeBSD machine to be the router didn't
work. When attempting to speak to the Internet at large, it used its
10.X.Y.Z address as the source address on its packets, and of course this
caused them to stop at the ISP's gateway router (which is not doing NAT).
As best I can tell, the trouble is that when a process running on the
router itself opens an outbound socket with INADDR_ANY (which most
networked applications do), it picks 10.X.Y.Z as the source address
instead of A.B.C.1.
What's the easiest way to specify the address to be used as the source
address when an app opens an outbound socket with INADDR_ANY? I'm unclear
about how the system is picking it now (I haven't yet found the place in
the source where this decision is made), but it seems to be picking
10.X.Y.Z, which of course will not work.
Also, if I'm doing an FTP install of FreeBSD on the router (I want to
load 4.5-RELEASE-p3 rather than 4.5-RELEASE, to nuke the zlib, OpenSSH,
and tcp memory leak bugs), how do I configure the interfaces, etc. from
sysinstall so that I can install properly? Any help with this would be
much appreciated.
--Brett Glass
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