[dpdk-dev] [PATCH v10 3/5] net: add a helper for making RARP packet

[Wang, Xiao W]

> -----Original Message-----
> From: Wang, Xiao W
> Sent: Tuesday, January 16, 2018 7:03 PM
> To: 'Olivier Matz' <olivier.matz at 6wind.com>
> Cc: yliu at fridaylinux.org; thomas at monjalon.net; Bie, Tiwei
> <tiwei.bie at intel.com>; dev at dpdk.org; stephen at networkplumber.org;
> maxime.coquelin at redhat.com
> Subject: RE: [dpdk-dev] [PATCH v10 3/5] net: add a helper for making RARP
> packet
> 
> Hi Olivier,
> 
> > -----Original Message-----
> > From: Olivier Matz [mailto:olivier.matz at 6wind.com]
> > Sent: Tuesday, January 16, 2018 6:43 PM
> > To: Wang, Xiao W <xiao.w.wang at intel.com>
> > Cc: yliu at fridaylinux.org; thomas at monjalon.net; Bie, Tiwei
> > <tiwei.bie at intel.com>; dev at dpdk.org; stephen at networkplumber.org;
> > maxime.coquelin at redhat.com
> > Subject: Re: [dpdk-dev] [PATCH v10 3/5] net: add a helper for making RARP
> > packet
> >
> > Hi Xiao,
> >
> > On Tue, Jan 16, 2018 at 09:43:43AM +0000, Wang, Xiao W wrote:
> > > Hi Olivier,
> > > > You can also use rte_pktmbuf_append() to check for the tailroom and
> > > > update data_len/pkt_len:
> > > >
> > > > 	m = rte_pktmbuf_alloc();
> 
> I just realized that if we let this function to allocate mbuf, it may restrict this
> api's applicability.
> E.g. the caller just has a mbuf, without a mempool.
> How do you think?
> 
> > > > 	if (m == NULL)
> > > > 		return NULL;
> > > > 	eth_hdr = rte_pktmbuf_append(m, RARP_PKT_SIZE);
> > >
> > > When data_len is not enough, we need to rte_pktmbuf_append(m,
> > RARP_PKT_SIZE - m->data_len);
> >
> > Sorry, I don't get your point here.
> 
> I mean we just need to extend the data_len by "RARP_PKT_SIZE - m-
> >data_len" when the room is not big enough.

OK, in your sample code, you rte_pktmbuf_alloc() a mbuf, it's reset already, so we just append RARP_PKT_SIZE. I got you~

For the mbuf allocation, we can let this function do allocation and content filling. If the app needs special need, e.g. chained mbuf,
then let the app fill it by itself.

> 
> BRs,
> Xiao