Re: [dpdk-dev] [PATCH v3 0/3] enhance TX checksum command and csum forwarding engine

[Stephen Hemminger <stephen@networkplumber.org>]

On Tue, 20 Jan 2015 16:18:01 +0100
Thomas Monjalon <thomas.monjalon@6wind.com> wrote:

> 2015-01-20 13:39, Olivier MATZ:
> > On 01/20/2015 02:12 AM, Ananyev, Konstantin wrote:
> > >> So I will fix that in my coming patch series. Just for information,
> > >> I'm pretty sure that having PKT_TX_IPV4 and PKT_TX_IP_CSUM as not
> > >> exclusive flag would not require any change anywhere in the PMDs (even
> > >> in i40e).
> > >
> > > Right now - no.
> > > Though as I said from PMD perspective having them exclusive is a bit preferable.
> > > Again, I don't see any big difference from upper layer code.
> > 
> > Sure, it does not make a big difference in terms of code. But
> > in terms of API, the naming of the flag is coherent to what it is
> > used for. And it's easier to find a simple definition, like:
> > 
> >   * Packet is IPv4. This flag must be set when using any offload feature
> >   * (TSO, L3 or L4 checksum) to tell the NIC that the packet is an IPv4
> >   * packet.
> 
> +1
> It's clearer to set PKT_TX_IPV4 in all offload cases of IPv4 packets,
> and add PKT_TX_IP_CSUM when checksum offload is required.
> 
> Simply simpler ;)
> 

Sure. Although in my experience IP checksum is just as cheap done in
software since the header fits in cache.