Re: [dpdk-stable] [PATCH v2 3/3] net/pcap: fix concurrent multiseg packet transmits

[Ferruh Yigit <ferruh.yigit@intel.com>]

On 7/25/2019 1:04 PM, David Marchand wrote:
> Two cores can send multi segment packets on two different pcap ports.
> Because of this, we can't have one single buffer to linearize packets.
> 
> Use rte_pktmbuf_read() to copy the packet into a buffer on the stack
> and remove eth_pcap_gather_data() when necessary (if the mbuf is
> contiguous, rte_pktmbuf_read() just points at the buffer address).
> 
> With this change, we won't support mono segment mbuf larger than 16k.
> 
> Fixes: 6db141c91e1f ("pcap: support jumbo frames")
> Cc: stable@dpdk.org
> 
> Signed-off-by: David Marchand <david.marchand@redhat.com>

Thanks David, lgtm, only a few minor syntax issues, please check below.

<...>

> @@ -336,31 +322,27 @@ eth_pcap_tx_dumper(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>  	 * dumper */
>  	for (i = 0; i < nb_pkts; i++) {
>  		mbuf = bufs[i];
> +		len = rte_pktmbuf_pkt_len(mbuf);
> +		if (unlikely(!rte_pktmbuf_is_contiguous(mbuf) &&
> +				len > sizeof(temp_data))) {
> +			PMD_LOG(ERR, "Dropping multi segment PCAP packet. Size (%zd) > max size (%zd).",

Can we break the line to reduce the line length:
PMD_LOG(ERR,
	"Dropping multi segment PCAP packet. Size (%zd) > max size (%zd).",

> +				len, sizeof(temp_data));
> +			rte_pktmbuf_free(mbuf);
> +			continue;
> +		}
> +
>  		calculate_timestamp(&header.ts);
> -		header.len = mbuf->pkt_len;
> +		header.len = len;
>  		header.caplen = header.len;
> -
> -		if (likely(mbuf->nb_segs == 1)) {
> -			pcap_dump((u_char *)dumper, &header,
> -				  rte_pktmbuf_mtod(mbuf, void*));

DPDK coding convention requires a tab, instead of aligning to the parenthesis.

<...>

> +		/* rte_pktmbuf_read() returns a pointer to the data directly
> +		 * in the mbuf (when the mbuf is contiguous) or, otherwise,
> +		 * a pointer to temp_data after copying into it.
> +		 */
> +		pcap_dump((u_char *)dumper, &header,
> +			  rte_pktmbuf_read(mbuf, 0, len, temp_data));

Same here, not need to align to the parenthesis.

<...>

> +		len = rte_pktmbuf_pkt_len(mbuf);
> +		if (unlikely(!rte_pktmbuf_is_contiguous(mbuf) &&
> +				len > sizeof(temp_data))) {
> +			PMD_LOG(ERR, "Dropping multi segment PCAP packet. Size (%zd) > max size (%zd).",
> +				len, sizeof(temp_data));

ditto

> +			rte_pktmbuf_free(mbuf);
> +			continue;
>  		}
>  
> +		/* rte_pktmbuf_read() returns a pointer to the data directly
> +		 * in the mbuf (when the mbuf is contiguous) or, otherwise,
> +		 * a pointer to temp_data after copying into it.
> +		 */
> +		ret = pcap_sendpacket(pcap,
> +				      rte_pktmbuf_read(mbuf, 0, len, temp_data),
> +				      len);

ditto