Re: [dpdk-users] How to change IP and port in packet header and recalculate checksum

[Murad Kablan <Murad.Kablan@Colorado.EDU>]

I see what you are saying now. I tried your solution and it works.

Thanks a lot!
On Apr 9, 2016 12:41 PM, "Jesper Wramberg" <jesper.wramberg@gmail.com>
wrote:

> Assuming you are working on a standard Intel architecture or alike, the
> constants you write are stored in little endian.
> Network byte order is big endian, so for the UDP port (which is 16 bit
> large) your code would be:
>
> udp_h->src_port = rte_cpu_to_be_16(88);
>
> Unless you actually want the port to be read as 22528 by the receiver ;-)
> Check out the DPDK byte order API for your other constants.
>
> 2016-04-09 17:36 GMT+02:00 Murad Kablan <Murad.Kablan@colorado.edu>:
>
>> Hi Jesper,
>> I'm not running DPDK on the receiving side. Just tcpdump.
>> Can you please be more specific? What and how to convert to network byte
>> order?
>>
>> Thanks
>> On Apr 9, 2016 7:45 AM, "Jesper Wramberg" <jesper.wramberg@gmail.com>
>> wrote:
>>
>>> Hey Murad,
>>>
>>> Are you running DPDK on the receiving end as well ?
>>> In any case, I'm guessing you forgot to convert to network byte order ?
>>> :-)
>>>
>>>
>>>
>>> 2016-04-09 12:34 GMT+02:00 Murad Kablan <Murad.Kablan@colorado.edu>:
>>>
>>>> Hi,
>>>> I'm trying to change the IP and port of packets before sending them out.
>>>> The captured packet in the receiving machines seems to be corrupted as
>>>> the
>>>> port is different than the one I inserted. Am I doing the checksum
>>>> right?
>>>> And do I need to do other HW configurations?
>>>>
>>>> This is my code:
>>>> struct udp_hdr *udp_h;
>>>> struct ipv4_hdr *ipv4_h;
>>>> struct ether_hdr *eth_hdr;
>>>> eth_hdr = rte_pktmbuf_mtod(m, struct ether_hdr *);
>>>> ipv4_h = (struct ipv4_hdr *)(eth_hdr + 1);
>>>> udp_h = (struct udp_hdr *)((unsigned char *)ipv4_h + sizeof(struct
>>>> ipv4_hdr));
>>>>
>>>> ipv4_h->dst_addr  = 6777226 //(gateway-ip 10.77.0.51)
>>>> udp_h->src_port = 88
>>>> ipv4_h->hdr_checksum = 0;
>>>> udp_h->dgram_cksum = 0;
>>>> udp_h->dgram_cksum = rte_ipv4_udptcp_cksum(ipv4_h, udp_h);
>>>> ipv4_h->hdr_checksum = rte_ipv4_cksum(ipv4_h);
>>>> l2fwd_simple_forward(m, 0);
>>>>
>>>> Thanks,
>>>>
>>>> Murad
>>>>
>>>
>>>
>