Re: [dpdk-dev] [PATCH] ether: check the first segment length on SW VLAN insertion

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 6/25/2020 1:27 PM, Andrew Rybchenko wrote:
> On 5/29/20 8:43 AM, Stephen Hemminger wrote:
>> On Wed, 27 May 2020 15:31:41 +0100
>> Andrew Rybchenko <arybchenko@solarflare.com> wrote:
>>
>>> SW VLAN insertion relies on Ethernet addresses location in contigous
>>> memory (do not split across mbuf segments). There is no any formal
>>> requirements on data location and mbuf structure which guarantee it.
>>> So, check it explicitly to avoid corrupted packets if the condition
>>> is violated. Typically software VLAN insertion is done on Tx prepare
>>> stage and application will get indication that the packet is invalid
>>> and cannot be transmitted.
>>>
>>> Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
>>> ---
>>>  lib/librte_net/rte_ether.h | 4 ++++
>>>  1 file changed, 4 insertions(+)
>>>
>>> diff --git a/lib/librte_net/rte_ether.h b/lib/librte_net/rte_ether.h
>>> index 0ae4e75b6c..d7c076bba8 100644
>>> --- a/lib/librte_net/rte_ether.h
>>> +++ b/lib/librte_net/rte_ether.h
>>> @@ -357,6 +357,10 @@ static inline int rte_vlan_insert(struct rte_mbuf **m)
>>>  	if (!RTE_MBUF_DIRECT(*m) || rte_mbuf_refcnt_read(*m) > 1)
>>>  		return -EINVAL;
>>>  
>>> +	/* Can't insert header if the first segment is too short */
>>> +	if (rte_pktmbuf_data_len(*m) < 2 * RTE_ETHER_ADDR_LEN)
>>> +		return -EINVAL;
>>
>> Looks good, but you could also make it handle the fragment case with:
>>
>> diff --git a/lib/librte_net/rte_ether.h b/lib/librte_net/rte_ether.h
>> index 0ae4e75b6c58..4d0e310a4fac 100644
>> --- a/lib/librte_net/rte_ether.h
>> +++ b/lib/librte_net/rte_ether.h
>> @@ -350,14 +350,18 @@ static inline int rte_vlan_strip(struct rte_mbuf *m)
>>   */
>>  static inline int rte_vlan_insert(struct rte_mbuf **m)
>>  {
>> -	struct rte_ether_hdr *oh, *nh;
>> +	struct rte_ether_hdr *nh, tmp;
>> +	const struct rte_ether_hdr *oh;
>>  	struct rte_vlan_hdr *vh;
>>  
>>  	/* Can't insert header if mbuf is shared */
>>  	if (!RTE_MBUF_DIRECT(*m) || rte_mbuf_refcnt_read(*m) > 1)
>>  		return -EINVAL;
>>  
>> -	oh = rte_pktmbuf_mtod(*m, struct rte_ether_hdr *);
>> +	oh = rte_pktmbuf_read(*m, 0, sizeof(*oh), &tmp);
>> +	if (unlikely(oh == NULL))
>> +		return -EINVAL;
>> +
>>  	nh = (struct rte_ether_hdr *)
>>  		rte_pktmbuf_prepend(*m, sizeof(struct rte_vlan_hdr));
>>  	if (nh == NULL)
>>
> 
> It is more complicated since memmove() below should be
> rewritten  in a similar way as rte_pktmbuf_read(), but
> write. I'm not sure it worse the effort.
> 

Reviewed-by: Ferruh Yigit <ferruh.yigit@intel.com>

Applied to dpdk-next-net/main, thanks.