[dpdk-dev] [PATCH] net: introduce IPv4 ihl and version fields

[Min Hu (Connor)]

Hi, Morten and all,
	I have a questions which has bothering me for a long time.
	What's the difference between API and ABI？
	Why does this patch does not breake ABI， but break API(maybe)?
	
	Hope for your reply, thanks.

在 2021/5/27 23:56, Morten Brørup 写道:
>> From: dev [mailto:dev-bounces at dpdk.org] On Behalf Of Gregory Etelson
>> Sent: Thursday, 27 May 2021 17.29
> and version fields
>>
>> RTE IPv4 header definition combines the `version' and `ihl'  fields
>> into a single structure member.
>> This patch introduces dedicated structure members for both `version'
>> and `ihl' IPv4 fields. Separated header fields definitions allow to
>> create simplified code to match on the IHL value in a flow rule.
>> The original `version_ihl' structure member is kept for backward
>> compatibility.
>>
>> Signed-off-by: Gregory Etelson <getelson at nvidia.com>
>> ---
>>   app/test/test_flow_classify.c |  8 ++++----
>>   lib/net/rte_ip.h              | 16 +++++++++++++++-
>>   2 files changed, 19 insertions(+), 5 deletions(-)
>>
>> diff --git a/app/test/test_flow_classify.c
>> b/app/test/test_flow_classify.c
>> index 951606f248..4f64be5357 100644
>> --- a/app/test/test_flow_classify.c
>> +++ b/app/test/test_flow_classify.c
>> @@ -95,7 +95,7 @@ static struct rte_acl_field_def
>> ipv4_defs[NUM_FIELDS_IPV4] = {
>>    *  dst mask 255.255.255.00 / udp src is 32 dst is 33 / end"
>>    */
>>   static struct rte_flow_item_ipv4 ipv4_udp_spec_1 = {
>> -	{ 0, 0, 0, 0, 0, 0, IPPROTO_UDP, 0,
>> +	{ { .version_ihl = 0}, 0, 0, 0, 0, 0, IPPROTO_UDP, 0,
>>   	  RTE_IPV4(2, 2, 2, 3), RTE_IPV4(2, 2, 2, 7)}
>>   };
>>   static const struct rte_flow_item_ipv4 ipv4_mask_24 = {
>> @@ -131,7 +131,7 @@ static struct rte_flow_item  end_item = {
>> RTE_FLOW_ITEM_TYPE_END,
>>    *  dst mask 255.255.255.00 / tcp src is 16 dst is 17 / end"
>>    */
>>   static struct rte_flow_item_ipv4 ipv4_tcp_spec_1 = {
>> -	{ 0, 0, 0, 0, 0, 0, IPPROTO_TCP, 0,
>> +	{ { .version_ihl = 0}, 0, 0, 0, 0, 0, IPPROTO_TCP, 0,
>>   	  RTE_IPV4(1, 2, 3, 4), RTE_IPV4(5, 6, 7, 8)}
>>   };
>>
>> @@ -150,8 +150,8 @@ static struct rte_flow_item  tcp_item_1 = {
>> RTE_FLOW_ITEM_TYPE_TCP,
>>    *  dst mask 255.255.255.00 / sctp src is 16 dst is 17/ end"
>>    */
>>   static struct rte_flow_item_ipv4 ipv4_sctp_spec_1 = {
>> -	{ 0, 0, 0, 0, 0, 0, IPPROTO_SCTP, 0, RTE_IPV4(11, 12, 13, 14),
>> -	RTE_IPV4(15, 16, 17, 18)}
>> +	{ { .version_ihl = 0}, 0, 0, 0, 0, 0, IPPROTO_SCTP, 0,
>> +	RTE_IPV4(11, 12, 13, 14), RTE_IPV4(15, 16, 17, 18)}
>>   };
>>
>>   static struct rte_flow_item_sctp sctp_spec_1 = {
>> diff --git a/lib/net/rte_ip.h b/lib/net/rte_ip.h
>> index 4b728969c1..684bb028b2 100644
>> --- a/lib/net/rte_ip.h
>> +++ b/lib/net/rte_ip.h
>> @@ -38,7 +38,21 @@ extern "C" {
>>    * IPv4 Header
>>    */
>>   struct rte_ipv4_hdr {
>> -	uint8_t  version_ihl;		/**< version and header length */
>> +	__extension__
>> +	union {
>> +		uint8_t version_ihl;    /**< version and header length */
>> +		struct {
>> +#if RTE_BYTE_ORDER == RTE_LITTLE_ENDIAN
>> +			uint8_t ihl:4;
>> +			uint8_t version:4;
>> +#elif RTE_BYTE_ORDER == RTE_BIG_ENDIAN
>> +			uint8_t version:4;
>> +			uint8_t ihl:4;
>> +#else
>> +#error "setup endian definition"
>> +#endif
>> +		};
>> +	};
>>   	uint8_t  type_of_service;	/**< type of service */
>>   	rte_be16_t total_length;	/**< length of packet */
>>   	rte_be16_t packet_id;		/**< packet ID */
>> --
>> 2.31.1
>>
> 
> This does not break the ABI, but it could be discussed if it breaks the API due to the required structure initialization changes shown in test_flow_classify.c. I think this patch is an improvement, and that such structure modifications should be generally accepted, so:
> 
> Acked-by: Morten Brørup <mb at smartsharesystems.com>
> 
> .
>