Re: [dpdk-stable] [dpdk-dev] [PATCH v3] net: fix Intel-specific Prepare the outer ipv4 hdr for checksum

[Andrew Rybchenko <andrew.rybchenko@oktetlabs.ru>]

On 7/30/21 2:11 PM, Olivier Matz wrote:
> On Wed, Jul 28, 2021 at 06:46:53PM +0300, Andrew Rybchenko wrote:
>> On 7/7/21 12:40 PM, Mohsin Kazmi wrote:
>>> Preparation the headers for the hardware offload
>>> misses the outer ipv4 checksum offload.
>>> It results in bad checksum computed by hardware NIC.
>>>
>>> This patch fixes the issue by setting the outer ipv4
>>> checksum field to 0.
>>>
>>> Fixes: 4fb7e803eb1a ("ethdev: add Tx preparation")
>>> Cc: stable@dpdk.org
>>>
>>> Signed-off-by: Mohsin Kazmi <mohsin.kazmi14@gmail.com>
>>> Acked-by: Qi Zhang <qi.z.zhang@intel.com>
>>> ---
>>> v3:
>>>      * Update the conditional test with PKT_TX_OUTER_IP_CKSUM.
>>>      * Update the commit title with "Intel-specific".
>>>
>>> v2:
>>>      * Update the commit message with Fixes.
>>>
>>>    lib/net/rte_net.h | 15 +++++++++++++--
>>>    1 file changed, 13 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/lib/net/rte_net.h b/lib/net/rte_net.h
>>> index 434435ffa2..3f4c8c58b9 100644
>>> --- a/lib/net/rte_net.h
>>> +++ b/lib/net/rte_net.h
>>> @@ -125,11 +125,22 @@ rte_net_intel_cksum_flags_prepare(struct rte_mbuf *m, uint64_t ol_flags)
>>>    	 * Mainly it is required to avoid fragmented headers check if
>>>    	 * no offloads are requested.
>>>    	 */
>>> -	if (!(ol_flags & (PKT_TX_IP_CKSUM | PKT_TX_L4_MASK | PKT_TX_TCP_SEG)))
>>> +	if (!(ol_flags & (PKT_TX_IP_CKSUM | PKT_TX_L4_MASK | PKT_TX_TCP_SEG |
>>> +			  PKT_TX_OUTER_IP_CKSUM)))
>>>    		return 0;
>>> -	if (ol_flags & (PKT_TX_OUTER_IPV4 | PKT_TX_OUTER_IPV6))
>>> +	if (ol_flags & (PKT_TX_OUTER_IPV4 | PKT_TX_OUTER_IPV6)) {
>>>    		inner_l3_offset += m->outer_l2_len + m->outer_l3_len;
>>> +		/*
>>> +		 * prepare outer ipv4 header checksum by setting it to 0,
>>> +		 * in order to be computed by hardware NICs.
>>> +		 */
>>> +		if (ol_flags & PKT_TX_OUTER_IP_CKSUM) {
>>> +			ipv4_hdr = rte_pktmbuf_mtod_offset(m,
>>> +					struct rte_ipv4_hdr *, m->outer_l2_len);
>>> +			ipv4_hdr->hdr_checksum = 0;
>>
>> Here we assume that the field is located in the first segment.
>> Unlikely but it still could be false. We must handle it properly.
> 
> This is specified in the API comment, so I think it has to be checked
> by the caller.

If no, what's the point to spoil memory here if stricter check is
done few lines below.

>>> +		}
>>> +	}
>>>    	/*
>>>    	 * Check if headers are fragmented.
>>>
>>