[dpdk-dev] [PATCH 1/1] ip_frag: fix creating ipv6 fragment extension header

[Dumitrescu, Cristian]

> -----Original Message-----
> From: Ananyev, Konstantin
> Sent: Monday, September 7, 2015 2:23 PM
> To: Dumitrescu, Cristian; Azarewicz, PiotrX T; dev at dpdk.org
> Subject: RE: [dpdk-dev] [PATCH 1/1] ip_frag: fix creating ipv6 fragment
> extension header
> 
> 
> 
> > -----Original Message-----
> > From: Dumitrescu, Cristian
> > Sent: Monday, September 07, 2015 12:22 PM
> > To: Ananyev, Konstantin; Azarewicz, PiotrX T; dev at dpdk.org
> > Subject: RE: [dpdk-dev] [PATCH 1/1] ip_frag: fix creating ipv6 fragment
> extension header
> >
> >
> >
> > > -----Original Message-----
> > > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Ananyev,
> > > Konstantin
> > > Sent: Friday, September 4, 2015 6:51 PM
> > > To: Azarewicz, PiotrX T; dev at dpdk.org
> > > Subject: Re: [dpdk-dev] [PATCH 1/1] ip_frag: fix creating ipv6 fragment
> > > extension header
> > >
> > > Hi Piotr,
> > >
> > > > -----Original Message-----
> > > > From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Piotr
> > > > Sent: Wednesday, September 02, 2015 3:13 PM
> > > > To: dev at dpdk.org
> > > > Subject: [dpdk-dev] [PATCH 1/1] ip_frag: fix creating ipv6 fragment
> > > extension header
> > > >
> > > > From: Piotr Azarewicz <piotrx.t.azarewicz at intel.com>
> > > >
> > > > Previous implementation won't work on every environment. The order
> of
> > > > allocation of bit-fields within a unit (high-order to low-order or
> > > > low-order to high-order) is implementation-defined.
> > > > Solution: used bytes instead of bit fields.
> > >
> > > Seems like right thing to do to me.
> > > Though I think we also should replace:
> > > union {
> > >                 struct {
> > >                         uint16_t frag_offset:13; /**< Offset from the start of the
> packet
> > > */
> > >                         uint16_t reserved2:2; /**< Reserved */
> > >                         uint16_t more_frags:1;
> > >                         /**< 1 if more fragments left, 0 if last fragment */
> > >                 };
> > >                 uint16_t frag_data;
> > >                 /**< union of all fragmentation data */
> > >         };
> > >
> > > With just:
> > > uint16_t frag_data;
> > >  and probably provide macros to read/set fragment_offset and
> more_flags
> > > values.
> > > Otherwise people might keep using the wrong layout.
> > > Konstantin
> > >
> >
> > I agree with your proposal, but wouldn't this be an ABI change? To avoid an
> ABI change, we should probably leave the union?
> 
> 
> No I don't think it would - the size of the field will remain the same: uint16_t.
> Also if the bit-field is invalid what for to keep it?
> Konstantin
> 

Excellent then.

> >
> > > >
> > > > Signed-off-by: Piotr Azarewicz <piotrx.t.azarewicz at intel.com>
> > > > ---
> > > >  lib/librte_ip_frag/rte_ipv6_fragmentation.c |    6 ++----
> > > >  1 file changed, 2 insertions(+), 4 deletions(-)
> > > >
> > > > diff --git a/lib/librte_ip_frag/rte_ipv6_fragmentation.c
> > > b/lib/librte_ip_frag/rte_ipv6_fragmentation.c
> > > > index 0e32aa8..7342421 100644
> > > > --- a/lib/librte_ip_frag/rte_ipv6_fragmentation.c
> > > > +++ b/lib/librte_ip_frag/rte_ipv6_fragmentation.c
> > > > @@ -65,10 +65,8 @@ __fill_ipv6hdr_frag(struct ipv6_hdr *dst,
> > > >
> > > >  	fh = (struct ipv6_extension_fragment *) ++dst;
> > > >  	fh->next_header = src->proto;
> > > > -	fh->reserved1   = 0;
> > > > -	fh->frag_offset = rte_cpu_to_be_16(fofs);
> > > > -	fh->reserved2   = 0;
> > > > -	fh->more_frags  = rte_cpu_to_be_16(mf);
> > > > +	fh->reserved1 = 0;
> > > > +	fh->frag_data = rte_cpu_to_be_16((fofs & ~IPV6_HDR_FO_MASK) |
> > > mf);
> > > >  	fh->id = 0;
> > > >  }
> > > >
> > > > --
> > > > 1.7.9.5