Re: [libvirt] [PATCH] nwfilter: drop unused flag argument

On 05/11/2011 06:16 PM, Stefan Berger wrote: For a single libvirt binary, there are no issues (the driver code is linked privately, and we are allowed to change the API of anything in libvirt_private.syms without impact to public interfaces). And between libvirt binaries, we have the fortunate situation that the over-the-wire protocol didn't pass a flags argument. Thus, when calling the API, you had this scenario: virNWFilterDefineXML(no flags) -> remote callback(0 flag) -> RPC over-wire format (no flags) -> virNWFilterDefineXML(no flags) -> nwfilter callback (0 flag) Removing the flag argument means that every step along the path has the same number of arguments, all without having to invent or ignore a 0 flag argument, and without any externally visible changes. And when mixing an older server with a newer client, or a newer client with an older server, then the older side will still be passing and ignoring an extra argument internally, with no change in behavior. Meanwhile, the only way to use a flags argument is to introduce a new API; if and when we introduce a new virNWFilterDefineXMLFlags(), we will also introduce a new RPC call that also preserves that flags argument over the wire. Whether we then change the driver.h callback to re-add a flags argument at that time, and share the callback between both APIs, or whether we have two driver.h callbacks, is a choice we can make at that time. Thanks; I've gone ahead and pushed this (I wrote it on top of Matthias' generator whitelist patch, and had worried that it might not rebase well, but thankfully it worked without a hitch). -- Eric Blake eblake(a)redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org