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Date: Wed, 20 Aug 1997 16:20:15 -0500
From: Prashant Dongre <pdongre@opentech.stpn.soft.net>
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To: ETX-B-SL Martti Kuparinen <erakupa@kk.etx.ericsson.se>
CC: freebsd-questions@FreeBSD.ORG
Subject: Re: poll() for ethernet devices
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ETX-B-SL Martti Kuparinen wrote:

> Ok, seems like my description was not clear enough... I try to make
> a better story now :-)
>
> > > I am running FreeBSD 2.2.2 on a PPro 200 MHz PC. I have created a
> > > loadable kernel module which will schedule IP-packets on user-defineable
> > > interfaces and priorities.
>
> So I have a router which is able to prioritize outgoing packets
> based on {address, port, protocol}-decision. To achieve this I have
> two different tables in memory:
>
>         addresstable:   { address, port, protocol, priority }
>         interfacetable: list of interfaces which are scheduled
>
> So the user is able to type e.g.
>
>         schconfig attach fxp0 fxp1 fxp2 fxp3
>         schconfig add 192.168.100.200 icmp high
>         schconfig add \* \* \* low
>
>         (schconfig is a user-space control program like ifconfig to
>          modify the scheduler at run-time)
>
> This means that icmp packets (e.g. ping) to 192.168.100.200 have the
> high priority whereas all other packets are low priority traffic. These
> actions take effect on fxp[0-3] interfaces.
>
> I have modified ether_output() to put the packet in to the correct
> position inside the if_snd queue. The position is calculated from
> { address, port, protocol, priority }-information.
>
> In order to do the prioritity queueing one must always read packets
> from interfaces before writing them out. So inside ether_output()
> I want to force the kernel to execute ether_input().
>
> My version work great (checking the priority and the position
> in the queue for every packet) expect that it is always writing
> someting out from ether_output. As a "minor" side effect packets
> are not prioritized :-('So I need to check if there is more packets
> to read from any of the attached interfaces. Of course I have a "timeout"
> mechanism to prevent the system from not writing anything out...
>
> Any ideas how to check for new incoming packets on all interfaces in
> the system?
>
> /Martti

Hi,

Have you checked code in 'if_ethersubr.c' in directory '/usr/src/sys/net'  ????.

Check ether_input() function. Here you can directly read ethernet packets from
all the interfaces attached. But here you need to check for wheather the packet
is IP, ARP (from ether_header) stc. etc. and you may also incorporate routing
mechanism, as you need to schedule incoming packet to the right interface queue.

I think, the trick is, hijacking the packet off the ether interface before it
reaches IP level.

Let me know if this is what you were looking for.

Good luck !!

Prashant.