Re: [dpdk-dev] [PATCH] librte_lpm: define tbl entry reversely for big endian

[Xuelin Shi <xuelin.shi@freescale.com>]

Hi Bruce,

Yes, it needs to swap the fields. The bit field is first identified as the uint8_t and then packed.

Thanks,
Shi xuelin

> -----Original Message-----
> From: Bruce Richardson [mailto:bruce.richardson@intel.com]
> Sent: Wednesday, March 04, 2015 18:48
> To: Shi Xuelin-B29237
> Cc: thomas.monjalon@6wind.com; dev@dpdk.org
> Subject: Re: [PATCH] librte_lpm: define tbl entry reversely for big
> endian
> 
> On Wed, Mar 04, 2015 at 02:34:12PM +0800, xuelin.shi@freescale.com wrote:
> > From: Xuelin Shi <xuelin.shi@freescale.com>
> >
> > This module uses type conversion between struct and int.
> > Also truncation and comparison is used with this int.
> > It is not safe for different endian arch.
> >
> > Add ifdef for big endian struct to fix this issue.
> >
> > Signed-off-by: Xuelin Shi <xuelin.shi@freescale.com>
> > ---
> >  lib/librte_lpm/rte_lpm.h | 19 +++++++++++++++++++
> >  1 file changed, 19 insertions(+)
> >
> > diff --git a/lib/librte_lpm/rte_lpm.h b/lib/librte_lpm/rte_lpm.h index
> > 1af150c..08a2859 100644
> > --- a/lib/librte_lpm/rte_lpm.h
> > +++ b/lib/librte_lpm/rte_lpm.h
> > @@ -96,6 +96,7 @@ extern "C" {
> >  /** Bitmask used to indicate successful lookup */
> >  #define RTE_LPM_LOOKUP_SUCCESS          0x0100
> >
> > +#if RTE_BYTE_ORDER == RTE_LITTLE_ENDIAN
> >  /** @internal Tbl24 entry structure. */  struct rte_lpm_tbl24_entry {
> >  	/* Stores Next hop or group index (i.e. gindex)into tbl8. */ @@
> > -117,6 +118,24 @@ struct rte_lpm_tbl8_entry {
> >  	uint8_t valid_group :1; /**< Group validation flag. */
> >  	uint8_t depth       :6; /**< Rule depth. */
> >  };
> > +#else
> > +struct rte_lpm_tbl24_entry {
> > +	uint8_t depth 	    :6;
> > +	uint8_t ext_entry   :1;
> > +	uint8_t valid	    :1;
> 
> Since endianness only refers to the order of bytes within a word, do the
> bitfields within the uint8_t really need to be swapped around too?
> 
> /Bruce

> 
> > +	union {
> > +		uint8_t tbl8_gindex;
> > +		uint8_t next_hop;
> > +	};
> > +};
> > +
> > +struct rte_lpm_tbl8_entry {
> > +	uint8_t depth 	    :6;
> > +	uint8_t valid_group :1;
> > +	uint8_t valid	    :1;
> > +	uint8_t next_hop;
> > +};
> > +#endif
> >
> >  /** @internal Rule structure. */
> >  struct rte_lpm_rule {
> > --
> > 1.9.1
> >