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

Dumitrescu, Cristian cristian.dumitrescu at intel.com
Mon Sep 7 13:21:31 CEST 2015



> -----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?

> >
> > 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



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