[AFS3-std] Re: Encoding IPvN addresses (was Re: first draft: ubik update proposal)

[Hartmut Reuter]

Derrick Brashear wrote:
> On Tue, Feb 8, 2011 at 11:09 AM, Hartmut Reuter<reuter@rzg.mpg.de>  wrote:
>> Simon Wilkinson wrote:
>>>
>>> On 8 Feb 2011, at 15:20, Derrick Brashear wrote:
>>>
>>>> struct {
>>>> int addrtype;
>>>> int addrlen;
>>>> int addr<>
>>>> } rx_addr;
>>>>
>>>> #define RX_ADDRTYPE_IPV4 1
>>>> #define RX_ADDRTYPE_IPV6 2
>>>
>>> Why not just use an opaque? That way you don't get into any of the
>>> ordering issues that ints bring with them.
>>>
>>> struct {
>>> int addrtype;
>>> opaque addr<>;
>>> } rx_addr;
>>
>> opaque requires xdr_alloc and later xdr_free of the data and in the case of
>> IPv4 the address typically is used as an integer which then would have been
>> first converted from the opaque (including changing host byte order).
>>
>> Therefore I had proposed in my change I8aa46a29:
>> src/fsint/fs_rxosd_common.xg
>> for both address types to use afs_uint32s:
>>
>> union ipadd switch(afs_int32 vsn) {
>> case 4:
>>         afs_uint32 ipv4;
>> case 6:
>>         afs_uint32 ipv6[4];
>> };
>>
>> I also think instead of inventing new constants it's better to use the
>> version numbers 4 and 6 directly.
>>
>> In the case of IPv6 the application easily can fill the contents into the
>> host's struct in6_addr using the u6_addr32 fields while for IPv4 the address
>> can be used directly.
>
> the only problem is we're back to a union with fixed discrimination
> that doesn't allow us to add things later.

But only in the memory, not on the wire.

>
>> If we create such a new struct one could think of also adding the port
>> number and the service number as additional fields.
>
> for things that don't want those, it's extra memory, though.

Could be another case (not 4 or 6)
>


-- 
-----------------------------------------------------------------
Hartmut Reuter                  e-mail 		reuter@rzg.mpg.de
			   	phone 		 +49-89-3299-1328
			   	fax   		 +49-89-3299-1301
RZG (Rechenzentrum Garching)   	web    http://www.rzg.mpg.de/~hwr
Computing Center of the Max-Planck-Gesellschaft (MPG) and the
Institut fuer Plasmaphysik (IPP)
-----------------------------------------------------------------