Re: [dpdk-dev] [PATCH 1/3] mbuf:add two TX offload flags and change three fields

[Olivier MATZ <olivier.matz@6wind.com>]

Hi Jijiang,

Please see some comments below.

On 11/27/2014 09:18 AM, Jijiang Liu wrote:
> In place of removing the PKT_TX_VXLAN_CKSUM, we introduce 2 new flags: PKT_TX_OUT_IP_CKSUM, PKT_TX_UDP_TUNNEL_PKT, and a new field: l4_tun_len.
> Replace the inner_l2_len and the inner_l3_len field with the outer_l2_len and outer_l3_len field.
>
> PKT_TX_OUT_IP_CKSUM: is not used for non-tunnelling packet;hardware outer checksum for tunnelling packet.
> PKT_TX_UDP_TUNNEL_PKT: is used to tell PMD that the transmit packet is a UDP tunneling packet.
> l4_tun_len: for VXLAN packet, it should be udp header length plus VXLAN header length.
>
> Signed-off-by: Jijiang Liu <jijiang.liu@intel.com>
> ---
>   lib/librte_mbuf/rte_mbuf.c |    2 +-
>   lib/librte_mbuf/rte_mbuf.h |   23 ++++++++++++++---------
>   2 files changed, 15 insertions(+), 10 deletions(-)
>
> diff --git a/lib/librte_mbuf/rte_mbuf.c b/lib/librte_mbuf/rte_mbuf.c
> index 87c2963..e89c310 100644
> --- a/lib/librte_mbuf/rte_mbuf.c
> +++ b/lib/librte_mbuf/rte_mbuf.c
> @@ -240,7 +240,7 @@ const char *rte_get_tx_ol_flag_name(uint64_t mask)
>   	case PKT_TX_SCTP_CKSUM: return "PKT_TX_SCTP_CKSUM";
>   	case PKT_TX_UDP_CKSUM: return "PKT_TX_UDP_CKSUM";
>   	case PKT_TX_IEEE1588_TMST: return "PKT_TX_IEEE1588_TMST";
> -	case PKT_TX_VXLAN_CKSUM: return "PKT_TX_VXLAN_CKSUM";
> +	case PKT_TX_UDP_TUNNEL_PKT: return "PKT_TX_UDP_TUNNEL_PKT";
>   	case PKT_TX_TCP_SEG: return "PKT_TX_TCP_SEG";
>   	default: return NULL;

As I said as a reply to the cover letter, I suggest to use
PKT_TX_OUT_UDP_CKSUM instead of PKT_TX_UDP_TUNNEL_PKT.

Also, the PKT_TX_OUT_IP_CKSUM case is missing here.

> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index 367fc56..48cd8e1 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -99,10 +99,9 @@ extern "C" {
>   #define PKT_RX_TUNNEL_IPV6_HDR (1ULL << 12) /**< RX tunnel packet with IPv6 header. */
>   #define PKT_RX_FDIR_ID       (1ULL << 13) /**< FD id reported if FDIR match. */
>   #define PKT_RX_FDIR_FLX      (1ULL << 14) /**< Flexible bytes reported if FDIR match. */
> -/* add new RX flags here */
>

We should probably not remove this line.


>   /* add new TX flags here */
> -#define PKT_TX_VXLAN_CKSUM   (1ULL << 50) /**< TX checksum of VXLAN computed by NIC */
> +#define PKT_TX_UDP_TUNNEL_PKT (1ULL << 50) /**< TX packet is an UDP tunneling packet */
>   #define PKT_TX_IEEE1588_TMST (1ULL << 51) /**< TX IEEE1588 packet to timestamp. */
>
>   /**
> @@ -125,13 +124,20 @@ extern "C" {
>   #define PKT_TX_IP_CKSUM      (1ULL << 54) /**< IP cksum of TX pkt. computed by NIC. */
>   #define PKT_TX_IPV4_CSUM     PKT_TX_IP_CKSUM /**< Alias of PKT_TX_IP_CKSUM. */
>
> +#define PKT_TX_VLAN_PKT      (1ULL << 55) /**< TX packet is a 802.1q VLAN packet. */
> +
>   /** Tell the NIC it's an IPv4 packet. Required for L4 checksum offload or TSO. */
> -#define PKT_TX_IPV4          PKT_RX_IPV4_HDR
> +#define PKT_TX_IPV4          (1ULL << 56)
>
>   /** Tell the NIC it's an IPv6 packet. Required for L4 checksum offload or TSO. */
> -#define PKT_TX_IPV6          PKT_RX_IPV6_HDR
> +#define PKT_TX_IPV6          (1ULL << 57)

The description in comment does not match the description in the cover
letter.

Also, I think replacing PKT_RX_IPV[46]_HDR by the value may go in
another commit.


> -#define PKT_TX_VLAN_PKT      (1ULL << 55) /**< TX packet is a 802.1q VLAN packet. */
> +/** Outer IP cksum of TX pkt. computed by NIC for tunneling packet */
> +#define PKT_TX_OUTER_IP_CKSUM   (1ULL << 58)
> +#define PKT_TX_OUTER_IPV4_CSUM  PKT_TX_OUTER_IP_CKSUM /**< Alias of PKT_TX_OUTER_IP_CKSUM. */

Why do we need an alias?

By the way, I think the alias of PKT_TX_IP_CKSUM is also uneeded and
can be removed. But it's not the topic of your series.

Also, the name PKT_TX_OUTER_IP_CKSUM does not match the name in the
cover letter and commit logs.


> +
> +/** Tell the NIC it's an outer IPv6 packet for tunneling packet.*/
> +#define PKT_TX_OUTER_IPV6    (1ULL << 59)
>

This flag is not in the cover letter or commit log. What is its purpose?


>   /**
>    * TCP segmentation offload. To enable this offload feature for a
> @@ -266,10 +272,9 @@ struct rte_mbuf {
>   			uint64_t tso_segsz:16; /**< TCP TSO segment size */
>
>   			/* fields for TX offloading of tunnels */
> -			uint64_t inner_l3_len:9; /**< inner L3 (IP) Hdr Length. */
> -			uint64_t inner_l2_len:7; /**< inner L2 (MAC) Hdr Length. */
> -
> -			/* uint64_t unused:8; */
> +			uint64_t outer_l3_len:9; /**< outer L3 (IP) Hdr Length. */
> +			uint64_t outer_l2_len:7; /**< outer L2 (MAC) Hdr Length. */
> +			uint64_t l4_tun_len:8; /**< L4 tunnelling header length */
>   		};
>   	};
>   } __rte_cache_aligned;
>

About l4_tun_len, I have another comment I forgot to add in the cover
letter. Can we remove it and include its length in outer_l2_len
instead? For instance, replace:

      mb->l2_len =  eth_hdr_in;
      mb->l3_len = ipv4_hdr_in;
      mb->outer_l2_len = eth_hdr_out;
      mb->outer_l3_len = ipv4_hdr_out;
      mb->l4tun_len = vxlan_hdr;
      mb->ol_flags |= PKT_TX_OUT_IP_CKSUM  | PKT_TX_UDP_TUNNEL |
        PKT_TX_IP_CKSUM |  PKT_TX_TCP_CKSUM;

by:

      mb->l2_len =  eth_hdr_in;
      mb->l3_len = ipv4_hdr_in;
      mb->outer_l2_len = eth_hdr_out + vxlan_hdr;
      mb->outer_l3_len = ipv4_hdr_out;
      mb->ol_flags |= PKT_TX_OUT_IP_CKSUM  | PKT_TX_UDP_TUNNEL |
        PKT_TX_IP_CKSUM |  PKT_TX_TCP_CKSUM;

I think it won't bother the driver, and it's coherent with case B.2 of
your cover letter.

Regards,
Olivier