At 10:34 PM 12/30/2005, Robert Collins wrote:
At 09:07 PM 12/30/2005, Robert Collins wrote:
I've got a situation where I've got an internal host using a
private ip/domainname. Let's say for the sake of this discussion
the host is privatehost.internal.freebsd.org. privatehost isn't
running a webserver. But I would like machines on the
internal.freebsd.org network to query privatehost as if it was.
When one of these machines queries privatehost I would like
privatehost to forward those requests to my webserver,
www.freebsd.org, so that it can handle the request. In order to
accomplish that I have done the following:
My kernel was compiled with these options:
options IPFIREWALL
options IPFIREWALL_FORWARD
options IPFIREWALL_FORWARD_EXTENDED
"ipfw list" looks like this:
00100 allow ip from any to any via lo0
00110 deny ip from any to 127.0.0.0/8
00120 deny ip from 127.0.0.0/8 to any
10000 fwd 216.136.204.117 tcp from any to me dst-port 80
65000 allow ip from any to any
65535 deny ip from any to any
The problem I am having is that it seems the packets never leave
privatehost. tcpdump shows packets coming in destined for port 80.
"ipfw show" shows that packets are matching my rule, but tcpdump
never shows any packets going out to 216.136.204.117. tcpdump on
216.136.204.117 also shows that no packets are being recieved. I
did a tcpdump on lo0 just for kicks, and that didn't show
anything. It seems as if the packets are just disappearing.
Someone on #freebsdhelp suggested doing a "sysctl -w
net.inet.ip.forwarding=1" but that didn't help the situation. Is
there something minor I'm missing here...or am I totally off in my
understanding of how "ipfw fwd" works?
To quote the ipfw man page:
"The fwd action does not change the contents of the packet at
all. In particular, the destination address remains unmodified, so
packets forwarded to another system will usually be rejected by
that system unless there is a matching rule on that system to capture them."
You probably need to re-think what you are trying to do.
My understanding of this portion of the man page is that the machine
receiving the packet, in this case www.freebsd.org, needs to be
prepared to recive a packet whose destination address is not it's
own. If I am correct in my interpretation then this part of the man
page is irrelivent to my problem. My question is not, why is
www.freebsd.org not receiving the packet. My question is, why is
privatehost.internal.freebsd.org not sending the packet.
What tcpdump rules are you using to look for packets leaving
"privatehost"? Same question for packets arriving at 216.136.204.117?
-Glenn
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