Forwarding directed broadcasts

[flemingh]

I'm trying to enable a NGX FW-1 box running SPLAT to allow directed broadcasts to be forwarded
I can see the packets arriving on the external interface and a log entry in the firewall logs accepting the traffic but on the internal interface a tcpdump shows that the packet does not get sent out on the broadcast address
I suspect it's a SPLAT thing rather than a FW-1 thing but the method I would expect to use seems to be an invalid option under SPLAT
sysctl -w net.inet.ip.directed-broadcast=1

Or if I was on a Solaris box
ndd -set /dev/ip ip_forward_directed_broadcasts 1

I know that disabling directed broadcast is more the usual requirement to prevent the likes of smurf attacks but the application I have to accomodate has a requirement to have this feature enabled so if anyone has hit this issue before and can point me in the right direction it would be appreciated