dhcrelay

["Dr. Lars Hanke" <lars@lhanke.de>]

Hi,

google told me that dhcrelay has been discussed quite a couple of times on 
this list. However,I could not find a solution to my problem.

I want to set up a router, which distributes the DHCP configuration service to 
all subnets attached (well currently only one subnet at eth0, 172.16.2.1). 
Reading the dhcrelay man page
#> dhcrelay -i eth0 adept.mgr

should do exactly that. In practice - almost:

dhcrelay gets the request, asks the dhcp server, gets a reply, but never sends 
it to the requesting device:

#> tcpdump -i any port bootpc or port bootps
09:42:09.996479 172.16.1.12.bootpc > 255.255.255.255.bootps: xid:0x960f0000 
flags:0x8000 [|bootp] 
09:42:09.997009 surtur.mgr.bootps > adept.mgr.bootps: (request) xid:0x960f0000 
flags:0x8000 G:172.16.2.1 ether 0:9:5b:68:19:fb [|bootp] (DF) 
09:42:09.997603 adept.mgr.bootps > 172.16.2.1.bootps: (reply) xid:0x960f0000 
flags:0x8000 Y:ymir.mgr S:adept.mgr G:172.16.2.1 ether 0:9:5b:68:19:fb [|
bootp] (DF) 

... but something like the following never appears (line taken from DHCP 
exchange from server installed on router, alternatively):

09:59:38.780364 172.16.2.1.bootps > 255.255.255.255.bootpc: xid:0x960f0000 
flags:0x8000 Y:ymir.mgr S:172.16.2.1 [|bootp] [tos 0x10] 

Therefore, ymir never gets his IP! 

netfilter policies were set to ACCEPT and all tables were flushed (including 
nat and mangle). I can ping all NIC from anywhere, ymir of course only if it 
is configured!

The system is Debian Woody with 2.4.26-grsec Kernel from backports. grsec 
stuff is not activated by gradm.

Any help appreciated,
 - lars.