Re: [PATCH 13/15] SUNRPC: RPC buffer size estimates are too large

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Jan 24, 2007 at 03:41:38PM -0500, Chuck Lever wrote:
> J. Bruce Fields wrote:
> >On Wed, Jan 24, 2007 at 02:20:20PM -0500, Chuck Lever wrote:
> >>+ 	req->rq_callsize = RPC_CALLHDRSIZE + (slack << 1) + proc->p_arglen;
> >>+ 	req->rq_callsize <<= 2;
> >>+ 	req->rq_rcvsize = RPC_REPHDRSIZE + slack + proc->p_replen;
> >>+ 	req->rq_rcvsize <<= 2;
> >
> >What happened to rslack?  The callsize calculation should be using
> >cslack and the rcvsize calculation rslack, I think, right?
> 
> As far as I understood it, cslack is the size of the authentication 
> verifier for that flavor.  Shouldn't that be the same for calls and replies?

No--it can even vary from one call or reply to the next, and we can't
necessarily exactly predict the size of the reply verifier (though we
should be able to give a fairly tight upper bound).  Also the call has a
credential in addition to the verifier, and the credential size also
depends on the security flavor.

> >In the krb5p case there's an extra annoyance: rslack is used to decide
> >where to expect page data to start, so it can only take into account
> >extra space needed at the beginning.  But krb5p has to add padding, for
> >example, to the end of each request.
> 
> That padding has to follow XDR rules, though, correct?

This is padding at a different level--the plaintext usually has to be
padded to the nearest block size (at least 8 bytes) before encryption.

--b.

-------------------------------------------------------------------------
Take Surveys. Earn Cash. Influence the Future of IT
Join SourceForge.net's Techsay panel and you'll get the chance to share your
opinions on IT & business topics through brief surveys - and earn cash
http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV
_______________________________________________
NFS maillist  -  NFS@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/nfs