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SubjectRe: [PATCH] bootp arp corruption fix (was Re: 2.2.0 Bug summary)
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Martin Mares <mj@ucw.cz> writes:
> > My patch to reintroduce 2.0-alike 0.0.0.0 ip address behaviour happens
> > to fix this. The main point is to allow bootpc/bootp setup scripts
> > that work with 2.0 to work with 2.1, and as a side effect it
> > simplifies the ip autoconfiguration via bootp code, fixing this bug.
>
> I've not actually tried it, but after some minutes of gazing at the code
> it seems to me that it it's just a coincidence it fixes this bug. The arp_rcv
> function in net/ipv4/arp.c calls ip_route_input() and replies to the request
> whenever rt_type is RTN_LOCAL. The routing table lookup ends up in
> ip_route_input_slow() and gets accepted by the condition you added, but
> rt_type is set according to res.type which is in this case _uninitialized_.

Argghh. Thanks for spotting this. Yes, I had intended rt_type to be
RTN_LOCAL, in which case the ARP bug remains.

Linus: Please revert the patch.

> As Alexey has already said, handling BOOTP by adding special cases to
> the IP route code is plain wrong and going to produce disastrous effects
> like the `reply to all ARP packets' bug.

I see it as maintaining the 0.0.0.0 special case that used to be there
rather than adding a new one. That bug can still be fixed easily. But
if those with far more experience in these areas than myself see the
trade-off differently, I guess it's time to hack bootpc to use raw IP
sockets instead.

> I've already rewritten the kernel IP autoconfiguration to send and receive
> packets on its own and it already waits in DaveM's queue of networking patches.

Then I look forward to the networking resync.

Dave Wragg

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