Re: [dpdk-dev] [PATCH 05/18] mbuf: add function to get packet type from data

["Liang, Cunming" <cunming.liang@intel.com>]

Hi Olivier,

On 7/5/2016 11:41 PM, Olivier Matz wrote:
> Introduce the function rte_pktmbuf_get_ptype() that parses a
> mbuf and returns its packet type. For now, the following packet
> types are parsed:
>     L2: Ether
>     L3: IPv4, IPv6
>     L4: TCP, UDP, SCTP
>
> The goal here is to provide a reference implementation for packet type
> parsing. This function will be used by testpmd in next commits, allowing
> to compare its result with the value given by the hardware.
>
> This function will also be useful when implementing Rx offload support
> in virtio pmd. Indeed, the virtio protocol gives the csum start and
> offset, but it does not give the L4 protocol nor it tells if the
> checksum is relevant for inner or outer. This information has to be
> known to properly set the ol_flags in mbuf.
>
> Signed-off-by: Didier Pallard <didier.pallard@6wind.com>
> Signed-off-by: Jean Dao <jean.dao@6wind.com>
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> ---
>   doc/guides/rel_notes/release_16_11.rst |   5 +
>   lib/librte_mbuf/Makefile               |   5 +-
>   lib/librte_mbuf/rte_mbuf_ptype.c       | 234 +++++++++++++++++++++++++++++++++
>   lib/librte_mbuf/rte_mbuf_ptype.h       |  43 ++++++
>   lib/librte_mbuf/rte_mbuf_version.map   |   1 +
>   5 files changed, 286 insertions(+), 2 deletions(-)
>   create mode 100644 lib/librte_mbuf/rte_mbuf_ptype.c
>
> [...]
> +
> +/* parse mbuf data to get packet type */
> +uint32_t rte_pktmbuf_get_ptype(const struct rte_mbuf *m,
> +	struct rte_mbuf_hdr_lens *hdr_lens)
> +{
> +	struct rte_mbuf_hdr_lens local_hdr_lens;
> +	const struct ether_hdr *eh;
> +	struct ether_hdr eh_copy;
> +	uint32_t pkt_type = RTE_PTYPE_L2_ETHER;
> +	uint32_t off = 0;
> +	uint16_t proto;
> +
> +	if (hdr_lens == NULL)
> +		hdr_lens = &local_hdr_lens;
> +
> +	eh = rte_pktmbuf_read(m, off, sizeof(*eh), &eh_copy);
> +	if (unlikely(eh == NULL))
> +		return 0;
> +	proto = eh->ether_type;
> +	off = sizeof(*eh);
> +	hdr_lens->l2_len = off;
> +
> +	if (proto == rte_cpu_to_be_16(ETHER_TYPE_IPv4)) {
> +		const struct ipv4_hdr *ip4h;
> +		struct ipv4_hdr ip4h_copy;
> +
> +		ip4h = rte_pktmbuf_read(m, off, sizeof(*ip4h), &ip4h_copy);
> +		if (unlikely(ip4h == NULL))
> +			return pkt_type;
> +
> +		pkt_type |= ptype_l3_ip(ip4h->version_ihl);
> +		hdr_lens->l3_len = ip4_hlen(ip4h);
> +		off += hdr_lens->l3_len;
> +		if (ip4h->fragment_offset &
> +				rte_cpu_to_be_16(IPV4_HDR_OFFSET_MASK |
> +					IPV4_HDR_MF_FLAG)) {
> +			pkt_type |= RTE_PTYPE_L4_FRAG;
> +			hdr_lens->l4_len = 0;
> +			return pkt_type;
> +		}
> +		proto = ip4h->next_proto_id;
> +		pkt_type |= ptype_l4(proto);
> +	} else if (proto == rte_cpu_to_be_16(ETHER_TYPE_IPv6)) {
> +		const struct ipv6_hdr *ip6h;
> +		struct ipv6_hdr ip6h_copy;
> +		int frag = 0;
> +
> +		ip6h = rte_pktmbuf_read(m, off, sizeof(*ip6h), &ip6h_copy);
> +		if (unlikely(ip6h == NULL))
> +			return pkt_type;
> +
> +		proto = ip6h->proto;
> +		hdr_lens->l3_len = sizeof(*ip6h);
> +		off += hdr_lens->l3_len;
> +		pkt_type |= ptype_l3_ip6(proto);
> +		if ((pkt_type & RTE_PTYPE_L3_MASK) == RTE_PTYPE_L3_IPV6_EXT) {
> +			proto = skip_ip6_ext(proto, m, &off, &frag);
> +			hdr_lens->l3_len = off - hdr_lens->l2_len;
> +		}
> +		if (proto == 0)
> +			return pkt_type;
> +		if (frag) {
> +			pkt_type |= RTE_PTYPE_L4_FRAG;
> +			hdr_lens->l4_len = 0;
> +			return pkt_type;
> +		}
> +		pkt_type |= ptype_l4(proto);
> +	}
> +
> +	if ((pkt_type & RTE_PTYPE_L4_MASK) == RTE_PTYPE_L4_UDP) {
> +		hdr_lens->l4_len = sizeof(struct udp_hdr);
> +	} else if ((pkt_type & RTE_PTYPE_L4_MASK) == RTE_PTYPE_L4_TCP) {
> +		const struct tcp_hdr *th;
> +		struct tcp_hdr th_copy;
> +
> +		th = rte_pktmbuf_read(m, off, sizeof(*th), &th_copy);
> +		if (unlikely(th == NULL))
> +			return pkt_type & (RTE_PTYPE_L2_MASK |
> +				RTE_PTYPE_L3_MASK);
> +		hdr_lens->l4_len = (th->data_off & 0xf0) >> 2;
> +	} else if ((pkt_type & RTE_PTYPE_L4_MASK) == RTE_PTYPE_L4_SCTP) {
> +		hdr_lens->l4_len = sizeof(struct sctp_hdr);
> +	} else {
> +		hdr_lens->l4_len = 0;
> +	}
> +
> +	return pkt_type;
> +}
> diff --git a/lib/librte_mbuf/rte_mbuf_ptype.h b/lib/librte_mbuf/rte_mbuf_ptype.h
> index 4a34678..f468520 100644
> --- a/lib/librte_mbuf/rte_mbuf_ptype.h
> +++ b/lib/librte_mbuf/rte_mbuf_ptype.h
> @@ -545,6 +545,49 @@ extern "C" {
>   		RTE_PTYPE_INNER_L3_MASK |				\
>   		RTE_PTYPE_INNER_L4_MASK))
>   
> +struct rte_mbuf;
> +
> +/**
> + * Structure containing header lengths associated to a packet.
> + */
> +struct rte_mbuf_hdr_lens {
> +	uint8_t l2_len;
> +	uint8_t l3_len;
> +	uint8_t l4_len;
> +	uint8_t tunnel_len;
> +	uint8_t inner_l2_len;
> +	uint8_t inner_l3_len;
> +	uint8_t inner_l4_len;
> +};
[LC] The header parsing graph usually is not unique. The definition 
maybe nice for the basic IP and L4 tunnel.
However it can't scale out to other cases, e.g. qinq, mac-in-mac, mpls 
l2/l3 tunnel.
The parsing logic of "rte_pktmbuf_get_ptype()" and the definition of 
"struct rte_mbuf_hdr_lens" consist a pair for one specific parser scheme.
In this case, the fixed function is to support below.

+ * Supported packet types are:
+ *   L2: Ether
+ *   L3: IPv4, IPv6
+ *   L4: TCP, UDP, SCTP

Of course, it can add more packet type detection logic in future. But 
the more support, the higher the cost.

One of the alternative way is to allow registering parser pair. APP 
decides to choose the predefined scheme(by DPDK LIB), or to self-define 
the parsing logic.
In this way, the scheme can do some assumption for the specific case and 
ignore some useless graph detection.
In addition, besides the SW parser, the HW parser(identified by 
packet_type in mbuf) can be turn on/off by leveraging the same manner.

Thanks.
> +
> +/**
> + * Parse an Ethernet packet to get its packet type.
> + *
> + * This function parses the network headers in mbuf data and return its
> + * packet type.
> + *
> + * If it is provided by the user, it also fills a rte_mbuf_hdr_lens
> + * structure that contains the lengths of the parsed network
> + * headers. Each length field is valid only if the associated packet
> + * type is set. For instance, hdr_lens->l2_len is valid only if
> + * (retval & RTE_PTYPE_L2_MASK) != RTE_PTYPE_UNKNOWN.
> + *
> + * Supported packet types are:
> + *   L2: Ether
> + *   L3: IPv4, IPv6
> + *   L4: TCP, UDP, SCTP
> + *
> + * @param m
> + *   The packet mbuf to be parsed.
> + * @param hdr_lens
> + *   A pointer to a structure where the header lengths will be returned,
> + *   or NULL.
> + * @return
> + *   The packet type of the packet.
> + */
> +uint32_t rte_pktmbuf_get_ptype(const struct rte_mbuf *m,
> +	struct rte_mbuf_hdr_lens *hdr_lens);
> +
>   #ifdef __cplusplus
>   }
>   #endif
> diff --git a/lib/librte_mbuf/rte_mbuf_version.map b/lib/librte_mbuf/rte_mbuf_version.map
> index 79e4dd8..416af8e 100644
> --- a/lib/librte_mbuf/rte_mbuf_version.map
> +++ b/lib/librte_mbuf/rte_mbuf_version.map
> @@ -23,5 +23,6 @@ DPDK_16.11 {
>   	global:
>   
>   	__rte_pktmbuf_read;
> +	rte_pktmbuf_get_ptype;
>   
>   } DPDK_2.1;