Re: [dpdk-dev] [PATCH] testpmd: modify the mac of csum forwarding

["Zhang, Helin" <helin.zhang@intel.com>]

> -----Original Message-----
> From: Qiu, Michael
> Sent: Friday, August 7, 2015 11:53 AM
> To: Zhang, Helin; dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] testpmd: modify the mac of csum forwarding
> 
> On 2015/8/7 9:06, Zhang, Helin wrote:
> >
> >> -----Original Message-----
> >> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Michael Qiu
> >> Sent: Thursday, August 6, 2015 8:29 PM
> >> To: dev@dpdk.org
> >> Subject: [dpdk-dev] [PATCH] testpmd: modify the mac of csum
> >> forwarding
> >>
> >> For some ethnet-switch like intel RRC, all the packet forwarded out
> >> by DPDK will be dropped in switch side, so the packet generator will never
> receive the packet.
> > Is it because of anti-sproof? E.g. When the hardware found that the
> > dest mac is the port itself, then it will be dropped during TX.
> > You need to tell the root cause, and why we need to modify like this.
> 
> Actually, it is not the hardware from PEP(PCI End Point) side, but the switch side.
> 
> The TX is OK for DPDK and NIC, but in switch, it receives the packet and try to
> forward it, but the dest mac is the same as the NIC which transmit this packet.
> So switch will drop it as "Loopback Suppression Drop" in RRC. This should only
> happen when switch forwarding packets using dest mac.
> 
> 
> >
> >> Signed-off-by: Michael Qiu <michael.qiu@intel.com>
> >> ---
> >>  app/test-pmd/csumonly.c | 4 ++++
> >>  1 file changed, 4 insertions(+)
> >>
> >> diff --git a/app/test-pmd/csumonly.c b/app/test-pmd/csumonly.c index
> >> 1bf3485..bf8af1d 100644
> >> --- a/app/test-pmd/csumonly.c
> >> +++ b/app/test-pmd/csumonly.c
> >> @@ -550,6 +550,10 @@ pkt_burst_checksum_forward(struct fwd_stream
> *fs)
> >>  		 * and inner headers */
> >>
> >>  		eth_hdr = rte_pktmbuf_mtod(m, struct ether_hdr *);
> >> +		ether_addr_copy(&peer_eth_addrs[fs->peer_addr],
> >> +				&eth_hdr->d_addr);
> >> +		ether_addr_copy(&ports[fs->tx_port].eth_addr,
> >> +				&eth_hdr->s_addr);
> > Is it really necessary? Why other NICs do not need this?
> 
> Because other NICs is connect directly to packet generator...., if we using switch
> to connect the generator and the NICs, I think it will need this.
There are 'iofwd' and 'mac' mode in testpmd, and mac forware will modify the dest
mac before transmitting the packet. They are for different cases.
Why not use mac forwarding mode for your testing, and just keep it as is?

Regards,
Helin

> 
> Thanks,
> Michael
> >
> >>  		parse_ethernet(eth_hdr, &info);
> >>  		l3_hdr = (char *)eth_hdr + info.l2_len;
> >>
> >> --
> >> 1.9.3
> >