[dpdk-users] Unable to merge packets using GRO feature

[Wisam Monther]

Hey Jiayu,

Thank you for your reply.
I tried what you said with the csum at fwd mode.
Even so the GRO didn't works fine.

I even tested with a new methodology.
Two machines with two different nic for each.
The methodology that I used to test it is described in the attached file.

What I did from gro side:
"""
testpmd>gro on 1
Testpmd>set fwd csum
Testpmd>start
"""
And the packet with correct dst mac.

Best regards,
Wisam Jaddo
-----Original Message-----
From: Jiayu Hu [mailto:jiayu.hu at intel.com] 
Sent: Monday, August 21, 2017 12:14 PM
To: Wisam Monther
Cc: Thomas Monjalon; users at dpdk.org; Raslan Darawsheh; Shahaf Shuler
Subject: Re: Unable to merge packets using GRO feature

Hi,

On Mon, Aug 21, 2017 at 07:25:23AM +0000, Wisam Monther wrote:
> Hello Guys,
> 
>  
> 
> I hope this finds you well, I’m trying to test the GRO feature. But 
> I’m stuck with this scenario.
> 
> As you know, GRO is only support TCP_IPV4 packet until now.
> 
> So I’m trying to test the basic functionality of the feature, as following:
> 
> Start testpmd:
> 
> “””
> 
> ./x86_64-native-linuxapp-gcc/build/app/test-pmd/testpmd -n 4  -w 
> 00:0a.0  -w
> 00:09.0 --  --burst=64 --mbcache=512 --portmask 0xf -i  --txd=512 
> --rxd=512
> --nb-cores=9  --rxq=2 --txq=2 --txqflags=0
> 
> “””
> 
>  
> 
> Then enable GRO at the two ports:
> 
> “””
> 
> Testpmd>gro on 0
> 
> Testpmd>gro on 1

When use GRO in testpmd, there are following things to notice:

1. In testpmd, GRO is supported by csum forwarding engine. Therefore, please use 'set fwd csum' to switch forwarding engine.

2. By default, csum forwarding engine compulsorily changes ethernet addresses. So please make sure that MAC addresses are correct.

3. When enable GRO for port0, csum forwarding engine will merge packets received from port0. If there are no packets from port1 to port0, you don't need to enable GRO for port1.

4. GRO library doesn't re-calculate checksums for merged packets. If you want merged packets have correct checksum, please select HW IP and HW TCP checksum calculation for the port which the merged packets are transmitted to in csum forwarding engine.
This is because the merged packets are multi-segment mbufs, but csum forwarding engine doesn't support to calculate checksums for multi-segment mbufs in SW. So we need to select HW checksum offloading.

e.g. If data flow is "packets -> port0 -> port1", commands used in testpmd:
	gro on port0
	set fwd csum
	csum set ip hw port1
	csum set tcp hw port1


Besides, you need to make sure that your PMD driver doesn't use vector TX function, since vector function doesn't support checksum offloading.

> 
> “””
> 
>  
> 
> And trying to send TCP_IPV4 fragmented packet “packet with length 1500 
> fragmented to three packets of 500”
> 
> “””
> 
> p=Ether(src=get_if_hwaddr('ens10'), dst= 
> '24:8A:07:88:26:6B')/IP()/TCP()
> 
> p.add_payload('F'*(1500 - len(p)))
> 
> frags=fragment(p,fragsize=500)
> 
> for fragment in frags:
> 
>      sendp(fragment, iface='ens10')
> 
> “””
> 
>  
> 
> But the testpmd forward the packets as it is, “ doesn’t do any merge”
> 
>  
> 
> Tcpdump at the TG side,
> 
> The sending fragmets using ens10:
> 
> #tcpdump –I ens10 –vvven
> 
> 15:45:29.083514 24:8a:07:88:26:5b > 24:8a:07:88:26:6b, ethertype IPv4 
> (0x0800), length 538: (tos 0x0, ttl 64, id 1, offset 0, flags [+], 
> proto Options (0), length 524)
> 
>     127.0.0.1 > 127.0.0.1:  ip-proto-0 504
> 
> 15:45:29.115266 24:8a:07:88:26:5b > 24:8a:07:88:26:6b, ethertype IPv4 
> (0x0800), length 538: (tos 0x0, ttl 64, id 1, offset 504, flags [+], 
> proto Options (0), length 524)
> 
>     127.0.0.1 > 127.0.0.1: ip-proto-0
> 
> 15:45:29.147258 24:8a:07:88:26:5b > 24:8a:07:88:26:6b, ethertype IPv4 
> (0x0800), length 492: (tos 0x0, ttl 64, id 1, offset 1008, flags 
> [none], proto Options (0), length 478)
> 
>     127.0.0.1 > 127.0.0.1: ip-proto-0
> 
>  
> 
> #tcpdump -i ens9 –vvven  /// here will be received the forwarded 
> packets from
> testpmd:
> 
> 15:45:29.083996 24:8a:07:88:26:5b > 24:8a:07:88:26:6b, ethertype IPv4 
> (0x0800), length 538: (tos 0x0, ttl 64, id 1, offset 0, flags [+], 
> proto Options (0), length 524)
> 
>     127.0.0.1 > 127.0.0.1:  ip-proto-0 504
> 
> 15:45:29.115425 24:8a:07:88:26:5b > 24:8a:07:88:26:6b, ethertype IPv4 
> (0x0800), length 538: (tos 0x0, ttl 64, id 1, offset 504, flags [+], 
> proto Options (0), length 524)
> 
>     127.0.0.1 > 127.0.0.1: ip-proto-0
> 
> 15:45:29.147492 24:8a:07:88:26:5b > 24:8a:07:88:26:6b, ethertype IPv4 
> (0x0800), length 492: (tos 0x0, ttl 64, id 1, offset 1008, flags 
> [none], proto Options (0), length 478)
> 
>     127.0.0.1 > 127.0.0.1: ip-proto-0
> 
>  
> 
>  
> 
> Am I doing something wrong?! Or it is a bug.
> 
> è As you see the tcpdump shows the offset of each fragment, and 
> testpmd prints L4_FRAG, so the both are recognizing that this is a fragmented packet.

GRO library merges TSOed/GSOed packets, whose IP IDs and TCP sequences are both consecutive. If input packets have same IP IDs, no packets will be merged.

BTW, you can use iperf to test GRO feature.

Best Regards,
Jiayu

> 
>  
> 
> Best regards,
> 
> Wisam Jaddo
> 
>  
> 
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