Re: [dpdk-dev] [PATCH] net: do fragmented headers check in non-debug build as well

[Andrew Rybchenko <arybchenko@solarflare.com>]

Hi Olivier,

On 7/13/20 4:35 PM, Olivier Matz wrote:
> Hi Andrew,
>
> On Wed, May 27, 2020 at 03:32:56PM +0100, Andrew Rybchenko wrote:
>> Pseudo-header checksum calculation requires contiguous headers.
>> There is no any formal requirements on data location and mbuf
>> structure which could be used by the application.
>>
>> Make corresponding check to be done in non-debug build as well
>> to avoid bad accesses, incorrect checksum caclculation and to
> typo: caclculation -> calculation

Will fix in v2.

>> return appropriate error from Tx prepare.
>>
>> Make no-offloads check more precise and do it in non-debug build
>> as well to avoid contiguous headers check and Tx prepare failure
>> if it is not actually required.
>>
>> Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
>> ---
>>  lib/librte_net/rte_net.h | 6 +-----
>>  1 file changed, 1 insertion(+), 5 deletions(-)
>>
>> diff --git a/lib/librte_net/rte_net.h b/lib/librte_net/rte_net.h
>> index 1560ecfa46..1edc283a47 100644
>> --- a/lib/librte_net/rte_net.h
>> +++ b/lib/librte_net/rte_net.h
>> @@ -120,20 +120,17 @@ rte_net_intel_cksum_flags_prepare(struct rte_mbuf *m, uint64_t ol_flags)
>>  	struct rte_udp_hdr *udp_hdr;
>>  	uint64_t inner_l3_offset = m->l2_len;
>>  
>> -#ifdef RTE_LIBRTE_ETHDEV_DEBUG
>>  	/*
>>  	 * Does packet set any of available offloads?
>>  	 * Mainly it is required to avoid fragmented headers check if
>>  	 * no offloads are requested.
>>  	 */
>> -	if (!(ol_flags & PKT_TX_OFFLOAD_MASK))
>> +	if (!(ol_flags & (PKT_TX_IP_CKSUM | PKT_TX_L4_MASK)))
>>  		return 0;
> Agree, the packet is modified only if one of these flag is set.
>
>> -#endif
>>  
>>  	if (ol_flags & (PKT_TX_OUTER_IPV4 | PKT_TX_OUTER_IPV6))
>>  		inner_l3_offset += m->outer_l2_len + m->outer_l3_len;
>>  
>> -#ifdef RTE_LIBRTE_ETHDEV_DEBUG
>>  	/*
>>  	 * Check if headers are fragmented.
>>  	 * The check could be less strict depending on which offloads are
>> @@ -142,7 +139,6 @@ rte_net_intel_cksum_flags_prepare(struct rte_mbuf *m, uint64_t ol_flags)
>>  	if (unlikely(rte_pktmbuf_data_len(m) <
>>  		     inner_l3_offset + m->l3_len + m->l4_len))
>>  		return -ENOTSUP;
>> -#endif
> Yes, despite the documentation of thus function says that used headers
> should be in the first data segment of the mbuf, when it is used through
> the ethdev tx_prepare() API there is no such requirement.
>
> So yes, it looks safer to do these checks even if debug is off. They
> will only be done when doing tx offload, so I guess it is ok in terms of
> performance.
>
> Maybe it is worth mentioning commit dfc6b2fd8da3 ("mbuf: remove Intel
> offload checks from generic API") in the commit log?

Yes, I think it could be useful will add a bit of history in v2.

>>  
>>  	if (ol_flags & PKT_TX_IPV4) {
>>  		ipv4_hdr = rte_pktmbuf_mtod_offset(m, struct rte_ipv4_hdr *,
>> -- 
>> 2.17.1
>>
> Acked-by: Olivier Matz <olivier.matz@6wind.com>

Thanks for the review,
Andrew.