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RE: [lwip-devel] Suggestion re ARP
From: |
Mountifield, Tony |
Subject: |
RE: [lwip-devel] Suggestion re ARP |
Date: |
Wed, 28 Apr 2004 16:34:31 +0100 |
Thanks for the info. In fact, I should have searched the sources more
thoroughly before posting, as the option already exists:
#define ETHARP_ALWAYS_INSERT 0 /* update ARP table only for pre-existing
addresses */
#define ETHARP_ALWAYS_INSERT 1 /* update ARP table from all ARP traffic */
To obey the algorithm as quoted below, use 0.
Cheers,
Tony
> -----Original Message-----
> From: Zschocke, Florian [mailto:address@hidden
> Sent: 28 April 2004 12:16
> To: 'lwip-devel'
> Subject: RE: [lwip-devel] Suggestion re ARP
>
>
> Mountifield, Tony wrote on Wednesday, April 28, 2004 12:54 PM:
>
> > My suggestion is to have a #if option to control whether or
> > not LWIP updates its ARP table from 3rd-party requests it sees.
> > Comments?
>
> This is the algorithm as laid out in RFC 826
> (ftp://ftp.rfc-editor.org/in-notes/std/std37.txt):
>
> -----------------------------------------
> ?Do I have the hardware type in ar$hrd?
> Yes: (almost definitely)
> [optionally check the hardware length ar$hln]
> ?Do I speak the protocol in ar$pro?
> Yes:
> [optionally check the protocol length ar$pln]
> Merge_flag := false
> If the pair <protocol type, sender protocol address> is
> already in my translation table, update the sender
> hardware address field of the entry with the new
> information in the packet and set Merge_flag to true.
> ?Am I the target protocol address?
> Yes:
> If Merge_flag is false, add the triplet <protocol type,
> sender protocol address, sender hardware address> to
> the translation table.
> ?Is the opcode ares_op$REQUEST? (NOW look at the opcode!!)
> Yes:
> Swap hardware and protocol fields, putting the local
> hardware and protocol addresses in the sender fields.
> Set the ar$op field to ares_op$REPLY
> Send the packet to the (new) target hardware address on
> the same hardware on which the request was received.
> ------------------------------------------
>
> As you can see, updates for existing entries are done for any
> ARP packet
> received but new entries are only merged into the table when
> addressing the
> host itself.
>
> Florian
>
>
> _______________________________________________
> lwip-devel mailing list
> address@hidden
> http://mail.nongnu.org/mailman/listinfo/lwip-devel
>
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- [lwip-devel] Suggestion re ARP, Mountifield, Tony, 2004/04/28
- RE: [lwip-devel] Suggestion re ARP, Zschocke, Florian, 2004/04/28
- RE: [lwip-devel] Suggestion re ARP,
Mountifield, Tony <=
- RE: [lwip-devel] Suggestion re ARP, Zschocke, Florian, 2004/04/29
- RE: [lwip-devel] Suggestion re ARP, Zschocke, Florian, 2004/04/29