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[Python-Dev] Request for comments: [issue22941] IPv4Interface arithmetic changes subnet mask

Eric V. Smith eric at trueblade.com
Sat Mar 14 21:52:27 CET 2015 
On 3/14/2015 7:04 AM, francis wrote:
> Hi,
>> I, too, was thinking /24. I think that overflowing the host portion
>> should raise OverflowError.
>>
> Just curiosity, why not a modulo calculation on the subnet instead
> of raising the error?

Personally, I can't imaging wanting that behavior. I can't say I've ever
needed additional at all with an IP address, but if I did, it would only
be to stay within the host portion. To wrap around seems odd. If you had
a /24 address and added 1000, should that really be the same as adding
232 (= 1000 % 256)? It seems more likely it's an error.

I'm +0 on adding addition with an OverflowError for the host portion,
and -1 on addition with modulo arithmetic.

-- 
Eric.
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