Re: [dpdk-dev] [PATCH v2 1/3] gso: support UDP/IPv4 fragmentation

["Wang, Xiao W" <xiao.w.wang@intel.com>]

Hi,

> -----Original Message-----
> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Jiayu Hu
> Sent: Sunday, June 17, 2018 11:13 AM
> To: dev@dpdk.org
> Cc: Ananyev, Konstantin <konstantin.ananyev@intel.com>; Zhang, Yuwei1
> <yuwei1.zhang@intel.com>; Iremonger, Bernard
> <bernard.iremonger@intel.com>; Hu, Jiayu <jiayu.hu@intel.com>
> Subject: [dpdk-dev] [PATCH v2 1/3] gso: support UDP/IPv4 fragmentation
> 
> This patch adds GSO support for UDP/IPv4 packets. Supported packets
> may include a single VLAN tag. UDP/IPv4 GSO doesn't check if input
> packets have correct checksums, and doesn't update checksums for
> output packets (the responsibility for this lies with the application).
> Additionally, UDP/IPv4 GSO doesn't process IP fragmented packets.
> 
> UDP/IPv4 GSO uses two chained MBUFs, one direct MBUF and one indrect
> MBUF, to organize an output packet. The direct MBUF stores the packet
> header, while the indirect mbuf simply points to a location within the
> original packet's payload. Consequently, use of UDP GSO requires
> multi-segment MBUF support in the TX functions of the NIC driver.
> 
> If a packet is GSO'd, UDP/IPv4 GSO reduces its MBUF refcnt by 1. As a
> result, when all of its GSOed segments are freed, the packet is freed
> automatically.
> 
> Signed-off-by: Jiayu Hu <jiayu.hu@intel.com>
> ---
>  lib/librte_gso/Makefile     |  1 +
>  lib/librte_gso/gso_common.h |  3 ++
>  lib/librte_gso/gso_udp4.c   | 81
> +++++++++++++++++++++++++++++++++++++++++++++
>  lib/librte_gso/gso_udp4.h   | 42 +++++++++++++++++++++++
>  lib/librte_gso/rte_gso.c    | 24 +++++++++++---
>  lib/librte_gso/rte_gso.h    |  6 +++-
>  6 files changed, 151 insertions(+), 6 deletions(-)
>  create mode 100644 lib/librte_gso/gso_udp4.c
>  create mode 100644 lib/librte_gso/gso_udp4.h
> 
> diff --git a/lib/librte_gso/Makefile b/lib/librte_gso/Makefile
> index 3648ec0..1fac53a 100644
> --- a/lib/librte_gso/Makefile
> +++ b/lib/librte_gso/Makefile
> @@ -19,6 +19,7 @@ SRCS-$(CONFIG_RTE_LIBRTE_GSO) += rte_gso.c
>  SRCS-$(CONFIG_RTE_LIBRTE_GSO) += gso_common.c
>  SRCS-$(CONFIG_RTE_LIBRTE_GSO) += gso_tcp4.c
>  SRCS-$(CONFIG_RTE_LIBRTE_GSO) += gso_tunnel_tcp4.c
> +SRCS-$(CONFIG_RTE_LIBRTE_GSO) += gso_udp4.c
> 

meson should be updated accordingly.

>  # install this header file
>  SYMLINK-$(CONFIG_RTE_LIBRTE_GSO)-include += rte_gso.h
> diff --git a/lib/librte_gso/gso_common.h b/lib/librte_gso/gso_common.h
> index 5ca5974..6cd764f 100644
> --- a/lib/librte_gso/gso_common.h
> +++ b/lib/librte_gso/gso_common.h
> @@ -31,6 +31,9 @@
>  		(PKT_TX_TCP_SEG | PKT_TX_IPV4 | PKT_TX_OUTER_IPV4 | \
>  		 PKT_TX_TUNNEL_GRE))
> 
> +#define IS_IPV4_UDP(flag) (((flag) & (PKT_TX_UDP_SEG | PKT_TX_IPV4)) == \
> +		(PKT_TX_UDP_SEG | PKT_TX_IPV4))
> +
>  /**
>   * Internal function which updates the UDP header of a packet, following
>   * segmentation. This is required to update the header's datagram length field.
> diff --git a/lib/librte_gso/gso_udp4.c b/lib/librte_gso/gso_udp4.c
> new file mode 100644
> index 0000000..a3db329
> --- /dev/null
> +++ b/lib/librte_gso/gso_udp4.c
> @@ -0,0 +1,81 @@
> +/* SPDX-License-Identifier: BSD-3-Clause
> + * Copyright(c) 2018 Intel Corporation
> + */
> +
> +#include "gso_common.h"
> +#include "gso_udp4.h"
> +
> +#define IPV4_HDR_MF_BIT (1U << 13)
> +
> +static inline void
> +update_ipv4_udp_headers(struct rte_mbuf *pkt, struct rte_mbuf **segs,
> +		uint16_t nb_segs)
> +{
> +	struct ipv4_hdr *ipv4_hdr;
> +	uint16_t frag_offset = 0, is_mf;
> +	uint16_t l2_hdrlen = pkt->l2_len, l3_hdrlen = pkt->l3_len;
> +	uint16_t tail_idx = nb_segs - 1, length, i;
> +
> +	/*
> +	 * Update IP header fields for output segments. Specifically,
> +	 * keep the same IP id, update fragment offset and total
> +	 * length.
> +	 */
> +	for (i = 0; i < nb_segs; i++) {
> +		ipv4_hdr = (struct ipv4_hdr *)(rte_pktmbuf_mtod(segs[i],
> +					char *) + l2_hdrlen);

You could use rte_pktmbuf_mtod_offset to simplify the code.

> +		length = segs[i]->pkt_len - l2_hdrlen;
> +		ipv4_hdr->total_length = rte_cpu_to_be_16(length);
> +
> +		is_mf = i < tail_idx ? IPV4_HDR_MF_BIT : 0;
> +		ipv4_hdr->fragment_offset =
> +			rte_cpu_to_be_16(frag_offset | is_mf);
> +		frag_offset += ((length - l3_hdrlen) >> 3);
> +	}
> +}
> +
> +int
> +gso_udp4_segment(struct rte_mbuf *pkt,
> +		uint16_t gso_size,
> +		struct rte_mempool *direct_pool,
> +		struct rte_mempool *indirect_pool,
> +		struct rte_mbuf **pkts_out,
> +		uint16_t nb_pkts_out)
> +{
> +	struct ipv4_hdr *ipv4_hdr;
> +	uint16_t pyld_unit_size, hdr_offset;
> +	uint16_t frag_off;
> +	int ret;
> +
> +	/* Don't process the fragmented packet */
> +	ipv4_hdr = (struct ipv4_hdr *)(rte_pktmbuf_mtod(pkt, char *) +
> +			pkt->l2_len);

Ditto.

BRs,
Xiao