Re: [PATCH] app/test-pmd: fix L4 checksum with padding data

[Stephen Hemminger <stephen@networkplumber.org>]

On Thu, 2 Nov 2023 19:20:07 +0000
Ferruh Yigit <ferruh.yigit@amd.com> wrote:

> On 8/4/2023 9:28 AM, Kaiwen Deng wrote:
> > IEEE 802 packets may have a minimum size limit. The data fields
> > should be padded when necessary. In some cases, the padding data
> > is not zero. Testpmd does not trim these IP packets to the true
> > length of the frame, so errors will occur when calculating TCP
> > or UDP checksum.
> >   
> 
> Hi Kaiwen,
> 
> I am trying to understand the problem, what is the testcase that has
> checksum error?
> 
> Are the received mbuf data_len & pkt_len wrong? Instead of trying to fix
> the mbuf during forwarding, can we fix where packet generated?

The root cause is that get_udptcp_cksum_mbuf is using m->pkt_len
which maybe larger than the actual data. The real issue is there and
in rte_ip.h checksum code. The correct fix would be to use l3_len instead.

It also looks like test-pmd is not validating the IP header.
Both parse_ipv4() and parse_ipv6() should check if packet was truncated.
Same for both UDP and TCP lengths.