Re: [dpdk-dev] [PATCH 07/12] mbuf: generic support for TCP segmentation offload

["Ananyev, Konstantin" <konstantin.ananyev@intel.com>]

> -----Original Message-----
> From: Olivier Matz [mailto:olivier.matz@6wind.com]
> Sent: Monday, November 10, 2014 3:59 PM
> To: dev@dpdk.org
> Cc: olivier.matz@6wind.com; Walukiewicz, Miroslaw; Liu, Jijiang; Liu, Yong; jigsaw@gmail.com; Richardson, Bruce; Ananyev, Konstantin
> Subject: [PATCH 07/12] mbuf: generic support for TCP segmentation offload
> 
> Some of the NICs supported by DPDK have a possibility to accelerate TCP
> traffic by using segmentation offload. The application prepares a packet
> with valid TCP header with size up to 64K and deleguates the
> segmentation to the NIC.
> 
> Implement the generic part of TCP segmentation offload in rte_mbuf. It
> introduces 2 new fields in rte_mbuf: l4_len (length of L4 header in bytes)
> and tso_segsz (MSS of packets).
> 
> To delegate the TCP segmentation to the hardware, the user has to:
> 
> - set the PKT_TX_TCP_SEG flag in mbuf->ol_flags (this flag implies
>   PKT_TX_TCP_CKSUM)
> - set PKT_TX_IP_CKSUM if it's IPv4, and set the IP checksum to 0 in
>   the packet
> - fill the mbuf offload information: l2_len, l3_len, l4_len, tso_segsz
> - calculate the pseudo header checksum and set it in the TCP header,
>   as required when doing hardware TCP checksum offload
> 
> The API is inspired from ixgbe hardware (the next commit adds the
> support for ixgbe), but it seems generic enough to be used for other
> hw/drivers in the future.
> 
> This commit also reworks the way l2_len and l3_len are used in igb
> and ixgbe drivers as the l2_l3_len is not available anymore in mbuf.
> 
> Signed-off-by: Mirek Walukiewicz <miroslaw.walukiewicz@intel.com>
> Signed-off-by: Olivier Matz <olivier.matz@6wind.com>
> ---
>  app/test-pmd/testpmd.c            |  3 ++-
>  examples/ipv4_multicast/main.c    |  3 ++-
>  lib/librte_mbuf/rte_mbuf.h        | 44 +++++++++++++++++++++++----------------
>  lib/librte_pmd_e1000/igb_rxtx.c   | 11 +++++++++-
>  lib/librte_pmd_ixgbe/ixgbe_rxtx.c | 11 +++++++++-
>  5 files changed, 50 insertions(+), 22 deletions(-)
> 
> diff --git a/app/test-pmd/testpmd.c b/app/test-pmd/testpmd.c
> index 12adafa..a831e31 100644
> --- a/app/test-pmd/testpmd.c
> +++ b/app/test-pmd/testpmd.c
> @@ -408,7 +408,8 @@ testpmd_mbuf_ctor(struct rte_mempool *mp,
>  	mb->ol_flags     = 0;
>  	mb->data_off     = RTE_PKTMBUF_HEADROOM;
>  	mb->nb_segs      = 1;
> -	mb->l2_l3_len       = 0;
> +	mb->l2_len       = 0;
> +	mb->l3_len       = 0;
>  	mb->vlan_tci     = 0;
>  	mb->hash.rss     = 0;
>  }
> diff --git a/examples/ipv4_multicast/main.c b/examples/ipv4_multicast/main.c
> index de5e6be..a31d43d 100644
> --- a/examples/ipv4_multicast/main.c
> +++ b/examples/ipv4_multicast/main.c
> @@ -302,7 +302,8 @@ mcast_out_pkt(struct rte_mbuf *pkt, int use_clone)
>  	/* copy metadata from source packet*/
>  	hdr->port = pkt->port;
>  	hdr->vlan_tci = pkt->vlan_tci;
> -	hdr->l2_l3_len = pkt->l2_l3_len;
> +	hdr->l2_len = pkt->l2_len;
> +	hdr->l3_len = pkt->l3_len;
>  	hdr->hash = pkt->hash;
> 
>  	hdr->ol_flags = pkt->ol_flags;
> diff --git a/lib/librte_mbuf/rte_mbuf.h b/lib/librte_mbuf/rte_mbuf.h
> index bcd8996..f76b768 100644
> --- a/lib/librte_mbuf/rte_mbuf.h
> +++ b/lib/librte_mbuf/rte_mbuf.h
> @@ -126,6 +126,19 @@ extern "C" {
> 
>  #define PKT_TX_VXLAN_CKSUM   (1ULL << 50) /**< TX checksum of VXLAN computed by NIC */
> 
> +/**
> + * TCP segmentation offload. To enable this offload feature for a
> + * packet to be transmitted on hardware supporting TSO:
> + *  - set the PKT_TX_TCP_SEG flag in mbuf->ol_flags (this flag implies
> + *    PKT_TX_TCP_CKSUM)
> + *  - if it's IPv4, set the PKT_TX_IP_CKSUM flag and write the IP checksum
> + *    to 0 in the packet
> + *  - fill the mbuf offload information: l2_len, l3_len, l4_len, tso_segsz
> + *  - calculate the pseudo header checksum and set it in the TCP header,
> + *    as required when doing hardware TCP checksum offload
> + */
> +#define PKT_TX_TCP_SEG       (1ULL << 49)
> +
>  /* Use final bit of flags to indicate a control mbuf */
>  #define CTRL_MBUF_FLAG       (1ULL << 63) /**< Mbuf contains control data */
> 
> @@ -185,6 +198,7 @@ static inline const char *rte_get_tx_ol_flag_name(uint64_t mask)
>  	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_TCP_SEG: return "PKT_TX_TCP_SEG";
>  	default: return NULL;
>  	}
>  }
> @@ -264,22 +278,18 @@ struct rte_mbuf {
> 
>  	/* fields to support TX offloads */
>  	union {
> -		uint16_t l2_l3_len; /**< combined l2/l3 lengths as single var */
> +		uint64_t tx_offload;       /**< combined for easy fetch */
>  		struct {
> -			uint16_t l3_len:9;      /**< L3 (IP) Header Length. */
> -			uint16_t l2_len:7;      /**< L2 (MAC) Header Length. */
> -		};
> -	};
> +			uint64_t l2_len:7; /**< L2 (MAC) Header Length. */
> +			uint64_t l3_len:9; /**< L3 (IP) Header Length. */
> +			uint64_t l4_len:8; /**< L4 (TCP/UDP) Header Length. */
> +			uint64_t tso_segsz:16; /**< TCP TSO segment size */
> 
> -	/* fields for TX offloading of tunnels */
> -	union {
> -		uint16_t inner_l2_l3_len;
> -		/**< combined inner l2/l3 lengths as single var */
> -		struct {
> -			uint16_t inner_l3_len:9;
> -			/**< inner L3 (IP) Header Length. */
> -			uint16_t inner_l2_len:7;
> -			/**< inner L2 (MAC) Header Length. */
> +			/* fields for TX offloading of tunnels */
> +			uint16_t inner_l3_len:9; /**< inner L3 (IP) Hdr Length. */
> +			uint16_t inner_l2_len:7; /**< inner L2 (MAC) Hdr Length. */
> +

Shouldn't these 2 fields be bit fields of uint64_t too?
uint64_t inner_l3_len:9;
uint64_t inner_l2_len:7;  
So it fits inot one uint64_t?

Konstantin

> +			/* uint64_t unused:8; */
>  		};
>  	};
>  } __rte_cache_aligned;
> @@ -631,8 +641,7 @@ static inline void rte_pktmbuf_reset(struct rte_mbuf *m)
>  {
>  	m->next = NULL;
>  	m->pkt_len = 0;
> -	m->l2_l3_len = 0;
> -	m->inner_l2_l3_len = 0;
> +	m->tx_offload = 0;
>  	m->vlan_tci = 0;
>  	m->nb_segs = 1;
>  	m->port = 0xff;
> @@ -701,8 +710,7 @@ static inline void rte_pktmbuf_attach(struct rte_mbuf *mi, struct rte_mbuf *md)
>  	mi->data_len = md->data_len;
>  	mi->port = md->port;
>  	mi->vlan_tci = md->vlan_tci;
> -	mi->l2_l3_len = md->l2_l3_len;
> -	mi->inner_l2_l3_len = md->inner_l2_l3_len;
> +	mi->tx_offload = md->tx_offload;
>  	mi->hash = md->hash;
> 
>  	mi->next = NULL;
> diff --git a/lib/librte_pmd_e1000/igb_rxtx.c b/lib/librte_pmd_e1000/igb_rxtx.c
> index dbf5074..0a9447e 100644
> --- a/lib/librte_pmd_e1000/igb_rxtx.c
> +++ b/lib/librte_pmd_e1000/igb_rxtx.c
> @@ -361,6 +361,13 @@ eth_igb_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
>  	struct rte_mbuf     *tx_pkt;
>  	struct rte_mbuf     *m_seg;
>  	union igb_vlan_macip vlan_macip_lens;
> +	union {
> +		uint16_t u16;
> +		struct {
> +			uint16_t l3_len:9;
> +			uint16_t l2_len:7;
> +		};
> +	} l2_l3_len;
>  	uint64_t buf_dma_addr;
>  	uint32_t olinfo_status;
>  	uint32_t cmd_type_len;
> @@ -398,8 +405,10 @@ eth_igb_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
>  		tx_last = (uint16_t) (tx_id + tx_pkt->nb_segs - 1);
> 
>  		ol_flags = tx_pkt->ol_flags;
> +		l2_l3_len.l2_len = tx_pkt->l2_len;
> +		l2_l3_len.l3_len = tx_pkt->l3_len;
>  		vlan_macip_lens.f.vlan_tci = tx_pkt->vlan_tci;
> -		vlan_macip_lens.f.l2_l3_len = tx_pkt->l2_l3_len;
> +		vlan_macip_lens.f.l2_l3_len = l2_l3_len.u16;
>  		tx_ol_req = ol_flags & (PKT_TX_VLAN_PKT | PKT_TX_IP_CKSUM |
>  			PKT_TX_L4_MASK);
> 
> diff --git a/lib/librte_pmd_ixgbe/ixgbe_rxtx.c b/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
> index 70ca254..54a0fc1 100644
> --- a/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
> +++ b/lib/librte_pmd_ixgbe/ixgbe_rxtx.c
> @@ -540,6 +540,13 @@ ixgbe_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
>  	struct rte_mbuf     *tx_pkt;
>  	struct rte_mbuf     *m_seg;
>  	union ixgbe_vlan_macip vlan_macip_lens;
> +	union {
> +		uint16_t u16;
> +		struct {
> +			uint16_t l3_len:9;
> +			uint16_t l2_len:7;
> +		};
> +	} l2_l3_len;
>  	uint64_t buf_dma_addr;
>  	uint32_t olinfo_status;
>  	uint32_t cmd_type_len;
> @@ -583,8 +590,10 @@ ixgbe_xmit_pkts(void *tx_queue, struct rte_mbuf **tx_pkts,
>  		tx_ol_req = ol_flags & (PKT_TX_VLAN_PKT | PKT_TX_IP_CKSUM |
>  			PKT_TX_L4_MASK);
>  		if (tx_ol_req) {
> +			l2_l3_len.l2_len = tx_pkt->l2_len;
> +			l2_l3_len.l3_len = tx_pkt->l3_len;
>  			vlan_macip_lens.f.vlan_tci = tx_pkt->vlan_tci;
> -			vlan_macip_lens.f.l2_l3_len = tx_pkt->l2_l3_len;
> +			vlan_macip_lens.f.l2_l3_len = l2_l3_len.u16;
> 
>  			/* If new context need be built or reuse the exist ctx. */
>  			ctx = what_advctx_update(txq, tx_ol_req,
> --
> 2.1.0