[PATCH] net/pcap: use pcap_next_ex to track errors

[Ferruh Yigit]

On 9/5/2024 5:10 PM, Stephen Hemminger wrote:
> Use pcap_next_ex rather than just pcap_next because pcap_next
> always blocks if there is no packets to receive.
> 

Hi Stephen,

Do you know if using 'pcap_next_ex()' (instead of 'pcap_next()') has any
dependency impact?
Like can we rely that all libraries that support 'pcap_next()', also
supports 'pcap_next_ex()'?


> Bugzilla ID: 1526
> Reported-by: Ofer Dagan <ofer.d at claroty.com>
> Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
>

Hi Ofer, Can you please verify this fix?


> ---
>  drivers/net/pcap/pcap_ethdev.c | 33 +++++++++++++++++----------------
>  1 file changed, 17 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/net/pcap/pcap_ethdev.c b/drivers/net/pcap/pcap_ethdev.c
> index bfec085045..261997be5c 100644
> --- a/drivers/net/pcap/pcap_ethdev.c
> +++ b/drivers/net/pcap/pcap_ethdev.c
> @@ -274,7 +274,7 @@ static uint16_t
>  eth_pcap_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>  {
>  	unsigned int i;
> -	struct pcap_pkthdr header;
> +	struct pcap_pkthdr *header;
>  	struct pmd_process_private *pp;
>  	const u_char *packet;
>  	struct rte_mbuf *mbuf;
> @@ -294,9 +294,13 @@ eth_pcap_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>  	 */
>  	for (i = 0; i < nb_pkts; i++) {
>  		/* Get the next PCAP packet */
> -		packet = pcap_next(pcap, &header);
> -		if (unlikely(packet == NULL))
> +		int ret = pcap_next_ex(pcap, &header, &packet);
> +		if (ret != 1) {
> +			if (ret == PCAP_ERROR)
> +				pcap_q->rx_stat.err_pkts++;
> +
>  			break;
> +		}
>  
>  		mbuf = rte_pktmbuf_alloc(pcap_q->mb_pool);
>  		if (unlikely(mbuf == NULL)) {
> @@ -304,33 +308,30 @@ eth_pcap_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>  			break;
>  		}
>  
> -		if (header.caplen <= rte_pktmbuf_tailroom(mbuf)) {
> +		uint32_t len = header->caplen;
> +		if (len <= rte_pktmbuf_tailroom(mbuf)) {
>  			/* pcap packet will fit in the mbuf, can copy it */
> -			rte_memcpy(rte_pktmbuf_mtod(mbuf, void *), packet,
> -					header.caplen);
> -			mbuf->data_len = (uint16_t)header.caplen;
> +			rte_memcpy(rte_pktmbuf_mtod(mbuf, void *), packet, len);
> +			mbuf->data_len = len;
>  		} else {
>  			/* Try read jumbo frame into multi mbufs. */
>  			if (unlikely(eth_pcap_rx_jumbo(pcap_q->mb_pool,
> -						       mbuf,
> -						       packet,
> -						       header.caplen) == -1)) {
> +						       mbuf, packet, len) == -1)) {
>  				pcap_q->rx_stat.err_pkts++;
>  				rte_pktmbuf_free(mbuf);
>  				break;
>  			}
>  		}
>  
> -		mbuf->pkt_len = (uint16_t)header.caplen;
> -		*RTE_MBUF_DYNFIELD(mbuf, timestamp_dynfield_offset,
> -			rte_mbuf_timestamp_t *) =
> -				(uint64_t)header.ts.tv_sec * 1000000 +
> -				header.ts.tv_usec;
> +		mbuf->pkt_len = len;
> +		uint64_t us = (uint64_t)header->ts.tv_sec * US_PER_S + header->ts.tv_usec;
> +
> +		*RTE_MBUF_DYNFIELD(mbuf, timestamp_dynfield_offset, rte_mbuf_timestamp_t *) = us;
>  		mbuf->ol_flags |= timestamp_rx_dynflag;
>  		mbuf->port = pcap_q->port_id;
>  		bufs[num_rx] = mbuf;
>  		num_rx++;
> -		rx_bytes += header.caplen;
> +		rx_bytes += len;
>  	}
>  	pcap_q->rx_stat.pkts += num_rx;
>  	pcap_q->rx_stat.bytes += rx_bytes;