Re: [dpdk-dev] [PATCH] examples/ip_fragmentation: support big packets

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

Hi ,

> 
> In some vendors the RX and TX configuration must be the same, therefore
> the MTU size need to be equal to max_rx_pkt_len.
> The MTU is the largest size packet in bytes that can be sent on the
> network, therefore before changing this parameter, the NIC could not
> receive packets larger than 1500 bytes, which is the default MTU size.
> In addition, scatter-gather need to be enabled in order to receive
> frames bigger than mbuf size.
> 
> Cc: stable@dpdk.org
> 
> Signed-off-by: Noa Ezra <noae@mellanox.com>
> ---
>  examples/ip_fragmentation/main.c | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/examples/ip_fragmentation/main.c b/examples/ip_fragmentation/main.c
> index 17a877d..d294f5f 100644
> --- a/examples/ip_fragmentation/main.c
> +++ b/examples/ip_fragmentation/main.c
> @@ -141,6 +141,7 @@ struct lcore_queue_conf {
>  		.max_rx_pkt_len = JUMBO_FRAME_MAX_SIZE,
>  		.split_hdr_size = 0,
>  		.offloads = (DEV_RX_OFFLOAD_CHECKSUM |
> +			     DEV_RX_OFFLOAD_SCATTER |
>  			     DEV_RX_OFFLOAD_JUMBO_FRAME),
>  	},
>  	.txmode = {
> @@ -892,6 +893,16 @@ struct rte_lpm6_config lpm6_config = {
>  		    dev_info.max_rx_pktlen,
>  		    local_port_conf.rxmode.max_rx_pkt_len);
> 
> +		/* set the mtu to the maximum received packet size */
> +		ret = rte_eth_dev_set_mtu(portid,
> +			local_port_conf.rxmode.max_rx_pkt_len);
> +		if (ret < 0) {
> +			printf("\n");
> +			rte_exit(EXIT_FAILURE, "Set MTU failed: "
> +				"err=%d, port=%d\n",
> +			ret, portid);
> +		}
> +

It probably doesn't matter for that particular case, but
shouldn't set_mtu() be done after dev_configure()?
To avoid situation when max_rx_pkt_len will be set by set_mtu()
and then overwritten by dev_configure().
Konstantin 


>  		/* get the lcore_id for this port */
>  		while (rte_lcore_is_enabled(rx_lcore_id) == 0 ||
>  		       qconf->n_rx_queue == (unsigned)rx_queue_per_lcore) {
> --
> 1.8.3.1