LSRR option in IP


dheeraj@chakra.cs.umd.edu
Wed, 4 May 88 10:39:31 EDT


I have been trying to use LSRR option of IP to route a packet through
various machines on the campus. Most machines just drop the packet.
I went into the ip_input code. It seems that ip_forward(ip, ifp)
drops the packet if
        1. ipforwarding is off OR
        2. in_interfaces is <= 1

That means that hosts with only one interface cannot have packets
loose source routed through them. I don't understand why this should
be the case. If some Gateway is trying to route the packet through
this machine, then it make sense to let the Gateway know that it is
inefficient to route the packet this way but if a user is forcing the
packet through this machine then I don't see why should the packet be
dropped.

Actually, if the machine has more than one interfaces and the routing
alogrithm decides to forward the packet through the same interface as
it came on then the packet is not dropped. (Isn't it similar to having
one interface and forwarding the packet through the same one.)

Thanks,
dheeraj sanghi



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