Messages in this thread | | | Subject | Re: Fw: Linux 2.0/2.1/2.2 -- Anyway to avoid different binaries?? | Date | Mon, 08 Feb 1999 20:37:46 -0500 | From | Ted Lemon <> |
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> Linux 2.2 provides a link layer independent interface to packet sockets > (using PF_PACKET, SOCK_DGRAM - see packet.4 in ftp.muc.de:/people/ak/netman*)
> It is probably better to not use LPF currently, because the version in > 2.2.1 is buggy. For DHCP's need user space filtering should be fast > enough anyways (remember that you can bind on a link layer protocol for > packet sockets)
This feature has been present since Linux version 1. The reason we didn't use it from the start is because your statement, "For DHCP's need user space filtering should be fast enough" is hopelessly optimistic. Whether or not user space filtering is fast enough depends on how many packets the machine on which the DHCP server is running receives, not on the usual packet rate the DHCP protocol requires.
If you run just the DHCP server on a machine, on a relatively broadcast-quiet network, then sure, the overhead is limited. If you want to run the DHCP service from a busy NFS server, the kernel's going to copy every single NFS mobygram into user space for the DHCP server to examine. Here, the overhead is somewhat horrifying. It might still work, but nobody could ever claim that it'd be a sensible way to go.
If the lpf implementation is not reliable, this is yet another reason why the old API, which worked just fine, should be reinstated.
_MelloN_
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