Re: [PATCH v4] app/testpmd: txonly multiflow port change support

["Singh, Aman Deep" <aman.deep.singh@intel.com>]

On 4/12/2023 11:46 PM, Joshua Washington wrote:
> Google cloud routes traffic using IP addresses without the support of MAC
> addresses, so changing source IP address for txonly-multi-flow can have
> negative performance implications for net/gve when using testpmd. This
> patch updates txonly multiflow mode to modify source ports instead of
> source IP addresses.

Generally routing is based on DST IP addresses, was SRC IP also having an
impact in your case ?

>
> The change can be tested with the following command:
> dpdk-testpmd -- --forward-mode=txonly --txonly-multi-flow \
>      --txip=<SRC>,<DST>

Missing "-" in command: --tx-ip=<SRC>,<DST>

>
> Signed-off-by: Joshua Washington <joshwash@google.com>
> Reviewed-by: Rushil Gupta <rushilg@google.com>
> ---
>   app/test-pmd/txonly.c | 34 ++++++++++++++++++----------------
>   1 file changed, 18 insertions(+), 16 deletions(-)
>
> diff --git a/app/test-pmd/txonly.c b/app/test-pmd/txonly.c
> index b3d6873104..7fc743b508 100644
> --- a/app/test-pmd/txonly.c
> +++ b/app/test-pmd/txonly.c
> @@ -56,7 +56,7 @@ uint32_t tx_ip_dst_addr = (198U << 24) | (18 << 16) | (0 << 8) | 2;
>   #define IP_DEFTTL  64   /* from RFC 1340. */
>   
>   static struct rte_ipv4_hdr pkt_ip_hdr; /**< IP header of transmitted packets. */
> -RTE_DEFINE_PER_LCORE(uint8_t, _ip_var); /**< IP address variation */
> +RTE_DEFINE_PER_LCORE(uint16_t, _src_var); /**< Source port variation */
>   static struct rte_udp_hdr pkt_udp_hdr; /**< UDP header of tx packets. */
>   
>   static uint64_t timestamp_mask; /**< Timestamp dynamic flag mask */
> @@ -230,28 +230,30 @@ pkt_burst_prepare(struct rte_mbuf *pkt, struct rte_mempool *mbp,
>   	copy_buf_to_pkt(eth_hdr, sizeof(*eth_hdr), pkt, 0);
>   	copy_buf_to_pkt(&pkt_ip_hdr, sizeof(pkt_ip_hdr), pkt,
>   			sizeof(struct rte_ether_hdr));
> +	copy_buf_to_pkt(&pkt_udp_hdr, sizeof(pkt_udp_hdr), pkt,
> +			sizeof(struct rte_ether_hdr) +
> +			sizeof(struct rte_ipv4_hdr));
>   	if (txonly_multi_flow) {
> -		uint8_t  ip_var = RTE_PER_LCORE(_ip_var);
> -		struct rte_ipv4_hdr *ip_hdr;
> -		uint32_t addr;
> +		uint16_t src_var = RTE_PER_LCORE(_src_var);
> +		struct rte_udp_hdr *udp_hdr;
> +		uint16_t port;
>   
> -		ip_hdr = rte_pktmbuf_mtod_offset(pkt,
> -				struct rte_ipv4_hdr *,
> -				sizeof(struct rte_ether_hdr));
> +		udp_hdr = rte_pktmbuf_mtod_offset(pkt,
> +				struct rte_udp_hdr *,
> +				sizeof(struct rte_ether_hdr) +
> +				sizeof(struct rte_ipv4_hdr));
>   		/*
> -		 * Generate multiple flows by varying IP src addr. This
> -		 * enables packets are well distributed by RSS in
> +		 * Generate multiple flows by varying UDP source port.
> +		 * This enables packets are well distributed by RSS in
>   		 * receiver side if any and txonly mode can be a decent
>   		 * packet generator for developer's quick performance
>   		 * regression test.
>   		 */
> -		addr = (tx_ip_dst_addr | (ip_var++ << 8)) + rte_lcore_id();

Good to have feature where last IP octet had lcore_id.
Helped to identify, packet came from which core.

> -		ip_hdr->src_addr = rte_cpu_to_be_32(addr);
> -		RTE_PER_LCORE(_ip_var) = ip_var;
> +
> +		port = src_var++;
> +		udp_hdr->src_port = rte_cpu_to_be_16(port);
> +		RTE_PER_LCORE(_src_var) = src_var;

To be safe, can we use the Ephemeral port range [49152	to 65535]
and adjust lcore_id within it.

>   	}
> -	copy_buf_to_pkt(&pkt_udp_hdr, sizeof(pkt_udp_hdr), pkt,
> -			sizeof(struct rte_ether_hdr) +
> -			sizeof(struct rte_ipv4_hdr));
>   
>   	if (unlikely(tx_pkt_split == TX_PKT_SPLIT_RND) || txonly_multi_flow)
>   		update_pkt_header(pkt, pkt_len);
> @@ -393,7 +395,7 @@ pkt_burst_transmit(struct fwd_stream *fs)
>   	nb_tx = common_fwd_stream_transmit(fs, pkts_burst, nb_pkt);
>   
>   	if (txonly_multi_flow)
> -		RTE_PER_LCORE(_ip_var) -= nb_pkt - nb_tx;
> +		RTE_PER_LCORE(_src_var) -= nb_pkt - nb_tx;
>   
>   	if (unlikely(nb_tx < nb_pkt)) {
>   		if (verbose_level > 0 && fs->fwd_dropped == 0)