Re: [dpdk-dev] [PATCH v1 6/6] net: fix rte_ether conflicts with libc

[Olivier Matz <olivier.matz@6wind.com>]

Hi Adrien,

On Fri, Dec 22, 2017 at 03:25:27PM +0100, Adrien Mazarguil wrote:
> On Fri, Dec 22, 2017 at 02:34:21PM +0100, Olivier MATZ wrote:
> > On Thu, Dec 21, 2017 at 02:00:06PM +0100, Adrien Mazarguil wrote:

...

> > > +#if defined(__FreeBSD__)
> > > +#define addr_bytes octet
> > > +#else
> > > +#define addr_bytes ether_addr_octet
> > > +#endif
> > > +
> > >  #define ETHER_LOCAL_ADMIN_ADDR 0x02 /**< Locally assigned Eth. address. */
> > >  #define ETHER_GROUP_ADDR       0x01 /**< Multicast or broadcast Eth. address. */
> > 
> > This kind of #define looks a bit dangerous to me: it can trigger
> > strange bugs because it will replace all occurences of addr_bytes
> > after this header is included.
> 
> Understandable, I checked before settling on this macro though, there's no
> other usage of addr_bytes inside DPDK.
> 
> As for applications, there's no way to be completely sure. If we consider
> they have to explicitly include rte_ether.h to get this definition, there
> are chances addr_bytes is exclusively used with MAC addresses.
> 
> This change results in an API change (addr_bytes now documented as a
> reserved macro) but has no ABI impact. I think it's a rather harmless
> workaround pending your next suggestion:
> 
> > Wouldn't it be a good opportunity to think about adding the rte_ prefix
> > to all variables/functions of rte_ether.h?
> 
> That would be ideal, however since almost all definitions in librte_net
> (rte_ip.h, rte_udp.h etc.) also lack this prefix and can still technically
> trigger conflicts with outside definitions (I'm aware work was done to avoid
> that, but it doesn't change the fact they're not in the official DPDK
> namespace), a massive API change would be needed for consistency.
> 
> Such a change is unlikely to be accepted for 18.02 in any case, therefore if
> the proposed workaround is deemed too risky, I offer to remove this patch
> from the series. What do you suggest?

I think the only good long term solution is to have a proper namespace
for all rte_net structures and definitions. If there is no blocking issue
requiring this patch now, we can consider the following:

- 18.02: announce an api change for 18.05
- 18.05:
  - add new net structures and definitions with rte_ prefix
  - mark the old ones as deprecated
  - removes the structures or definitions that conflicts with system headers
- 18.08: remove the old structures and definitions