From: Michael Tuexen > On 18 Jun 2014, at 15:25, Vlad Yasevich <vyasevich@xxxxxxxxx> wrote: > > > On 06/18/2014 09:16 AM, David Laight wrote: > >> From: Michael Tuexen [ > >>> On 18 Jun 2014, at 10:42, David Laight <David.Laight@xxxxxxxxxx> wrote: > >>> > >>>> From: Vlad Yasevich > >>>>> On 06/17/2014 11:36 AM, David Laight wrote: > >>>>>> From: Of Geir Ola Vaagland > >>>>>>> These patches are part of my master thesis project. I have been searching for discrepancies > >>> between > >>>>>>> the socket API specificiation in RFC 6458 and the current Linux SCTP implementation. The > >>> following > >>>>>>> patches are my humble attempts at getting somewhat closer to compliancy. > >>>>>> > >>>>>> I've just been reading RFC 6458 - HTF did it get past the editors and > >>>>>> then published in its current form? > >>>>>> Lots of the structures have implied padding. > >>>> ... > >>>>> I've argued the padding issue, but the editor stance is that it's implementation > >>>>> dependent. > >>>> > >>>> It wouldn't be as bad if the RFC said that the structure contained the > >>>> fields that followed (as is typical of the posix definitions), > >>>> but instead it gives a definition of the structure. > >> > >>> That would have been a possibility, but it was never suggested. > >>> As far as I know, C does not guarantee the memory layout for structs, > >>> except for the sequence of the components. So a compiler might add > >>> some padding at any place. When implementing this, you need to take > >>> care of this (and your job might be simpler, since you might only > >>> work with a specific set of compilers). > >>> In FreeBSD we also added some padding to some structures since they > >>> "evolved" during the lifetime of of the internet draft and we wanted > >>> to preserve some compatibility. > >>> I agree, that one must take care of the implied padding and I will double > >>> check how this is handled in FreeBSD. Not sure... > >> > >> You need to add explicit named pad fields in order to zero them. > >> (since you don't really want a memset()) > >> That is against my reading of the RFC. > >> > >> What does FreeBSD do about the 'sockaddr_storage'? > >> I'd have thought it had the same rules as NetBSD - where (IIRC) it should never > >> be instantiated, but only exists as a pointer type for function parameters. > >> > > > > I don't remember any such rules when sockaddr_storage was defined. Can you > > point to any document stating such rules? > > It is definitely useful as a container object at times. > I agree. The description would be OK for struct sockaddr. I have never instantiated > a variable of that type. The only use (I know of) of struct sockaddr_storage > is as a container object. I remember Christos saying something to that effect on one of the NetBSD lists. But I can't remember exactly when and searching the archives might be hard. He might remember. David -- To unsubscribe from this list: send the line "unsubscribe linux-sctp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
