Re: [dpdk-dev] [PATCH v6 2/2] net: introduce IPv4 ihl and version fields

[Thomas Monjalon <thomas@monjalon.net>]

14/10/2021 17:11, Ferruh Yigit:
> On 10/13/2021 6:13 PM, Gregory Etelson wrote:
> >   struct rte_ipv4_hdr {
> > -	uint8_t  version_ihl;		/**< version and header length */
> > +	__extension__
> > +	union {
> > +		uint8_t version_ihl;    /**< version and header length */
> > +		struct {
> > +#if RTE_BYTE_ORDER == RTE_LITTLE_ENDIAN
> > +			uint8_t ihl:4;     /**< header length */
> > +			uint8_t version:4; /**< version */
> > +#elif RTE_BYTE_ORDER == RTE_BIG_ENDIAN
> > +			uint8_t version:4; /**< version */
> > +			uint8_t ihl:4;     /**< header length */
> > +#else
> > +#error "setup endian definition"
> > +#endif
> 
> Do we need the last 'else' part?
> Although it is harmless to have it, other protocol headers for endianness
> check doesn't have this part, so I think better to be consistent.

In lib/eal/include/generic/rte_byteorder.h we already have
#if !defined(RTE_BYTE_ORDER)                                                                         
#error Unknown endianness.
#endif

So indeed we don't need this last else part.