Subject: Re: [magma] Checksum verification for IGMPv1 messages

From: Bill Fenner <[email-masked]>
Date: Thu, 13 Mar 2003 11:47:07 -0800

Glib answer: if it's longer than 8 bytes, then it's not an IGMPv1 message.

  Bill
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From: Pavlin Radoslavov <[email-masked]>
Date: Thu, 13 Mar 2003 12:09:59 -0800

> Glib answer: if it's longer than 8 bytes, then it's not an IGMPv1 message.

By definition, yes, but my question was if, say,
"Version 1 Membership Report" message is received which is suppose
to be IGMPv1 message, but for whatever reason it is longer than 8
bytes. Then, do I just drop that message, do I completely ignore
the extra bytes and compute the checksum only over the first 8
bytes, or do I still use the extra bytes to verify the checksum?

Thanks,
Pavlin

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From: Pavlin Radoslavov <[email-masked]>
Date: Thu, 13 Mar 2003 12:09:59 -0800

Thanks,
Pavlin

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From: Marshall Eubanks <[email-masked]>
Date: Thu, 13 Mar 2003 16:23:26 -0500

I think that IETF protocols generally don't cover responses to
illegal conditions (i.e., it's up to you, but I would drop it or ignore 
the extra bytes, which
probably amounts to the same thing).

> bytes, or do I still use the extra bytes to verify the checksum?
                                  Regards
                                  Marshall Eubanks

T.M. Eubanks
Multicast Technologies, Inc.
Phone : 703-293-9601       Fax     : 703-293-9609
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From: Marshall Eubanks <[email-masked]>
Date: Thu, 13 Mar 2003 16:23:26 -0500

Regards
                                  Marshall Eubanks

T.M. Eubanks

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From: [email-masked]
Date: Thu, 13 Mar 2003 15:40:56 -0800 (PST)

> probably amounts to the same thing).

Well there is the rule of thumb: 'Be liberal in what you accept and
conservative in what you send.', of course that assumes the illegal
condition does not lead to insanity.   

> > bytes, or do I still use the extra bytes to verify the checksum?

if you did choose to be liberal, i'd say to compute the checksum over
the entire packet, just computing the checksum over a partial packet
just seems wrong.  Of course dropping the packet makes alot of sense,
since it'd be easy to assume a speaker sending wrong sized igmpv1
packets was insane.

- rusty

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From: [email-masked]
Date: Thu, 13 Mar 2003 15:40:56 -0800 (PST)

- rusty