[dpdk-dev] [dpdk-dev v2 1/2] ethdev: add new tunnel type for ecpri

[Kinsella, Ray]

> -----Original Message-----
> From: Thomas Monjalon <thomas at monjalon.net>
> Sent: Friday 8 January 2021 10:24
> To: Guo, Jia <jia.guo at intel.com>; Zhang, Qi Z <qi.z.zhang at intel.com>;
> Yigit, Ferruh <ferruh.yigit at intel.com>
> Cc: Wu, Jingjing <jingjing.wu at intel.com>; Yang, Qiming
> <qiming.yang at intel.com>; Wang, Haiyue <haiyue.wang at intel.com>;
> dev at dpdk.org; andrew.rybchenko at oktetlabs.ru; orika at nvidia.com;
> getelson at nvidia.com; Dodji Seketeli <dodji at redhat.com>; Kinsella, Ray
> <ray.kinsella at intel.com>
> Subject: Re: [dpdk-dev] [dpdk-dev v2 1/2] ethdev: add new tunnel type
> for ecpri
> 
> 08/01/2021 10:22, Ferruh Yigit:
> > On 1/7/2021 1:33 PM, Thomas Monjalon wrote:
> > > 07/01/2021 13:47, Zhang, Qi Z:
> > >> From: Thomas Monjalon <thomas at monjalon.net>
> > >>> 07/01/2021 10:32, Guo, Jia:
> > >>>> From: Thomas Monjalon <thomas at monjalon.net>
> > >>>>> Sorry, it is a nack.
> > >>>>> BTW, it is probably breaking the ABI because of
> RTE_TUNNEL_TYPE_MAX.
> > >>
> > >> Yes that may break the ABI but fortunately the checking-abi-
> compatibility tool shows negative :) , thanks Ferruh' s guide.
> > >> https://github.com/ferruhy/dpdk/actions/runs/468859673
> > >
> > > That's very strange. An enum value is changed.
> > > Why it is not flagged by libabigail?
> >
> > As long as the enum values not sent to the application and kept
> within
> > the library, changing their values shouldn't be problem.
> 
> But RTE_TUNNEL_TYPE_MAX is part of lib/librte_ethdev/rte_ethdev.h so it
> is exposed to the application.
> I think it is a case of ABI breakage.
> 

Really a lot depends on context, Thomas is right it is hard to predict how these _MAX values are used.

We have seen cases in the past where _MAX enumeration values have been used to size arrays the like - I don't immediately see that issue here. My understanding is that the only consumer of this enumeration is rte_eth_dev_udp_tunnel_port_add and rte_eth_dev_udp_tunnel_port_delete, right? On face value, impact looks negligible. 

I will take a look at why libabigail doesn't complain.