[PATCH v20 21/25] net/pcap: add Rx scatter offload

[Bruce Richardson]

On Tue, Mar 10, 2026 at 09:09:59AM -0700, Stephen Hemminger wrote:
> Add RTE_ETH_RX_OFFLOAD_SCATTER to the advertised receive offload
> capabilities. Validate in rx_queue_setup that the mbuf pool data
> room is large enough when scatter is not enabled, following the
> same pattern as the virtio driver.
> 
> Gate the multi-segment receive path on the scatter offload flag
> and drop oversized packets when scatter is disabled.
> Reject scatter with infinite_rx mode since the ring-based replay
> path does not support multi-segment mbufs.
> 
> Signed-off-by: Stephen Hemminger <stephen at networkplumber.org>
> ---
>  drivers/net/pcap/pcap_ethdev.c | 47 +++++++++++++++++++++++++++++++---
>  1 file changed, 44 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/pcap/pcap_ethdev.c b/drivers/net/pcap/pcap_ethdev.c
> index 8a2b5c1b4b..d8a924b0cd 100644
> --- a/drivers/net/pcap/pcap_ethdev.c
> +++ b/drivers/net/pcap/pcap_ethdev.c
> @@ -79,6 +79,7 @@ struct pcap_rx_queue {
>  	uint16_t port_id;
>  	uint16_t queue_id;
>  	bool vlan_strip;
> +	bool rx_scatter;
>  	bool timestamp_offloading;
>  	struct rte_mempool *mb_pool;
>  	struct queue_stat rx_stat;
> @@ -112,6 +113,7 @@ struct pmd_internals {
>  	bool phy_mac;
>  	bool infinite_rx;
>  	bool vlan_strip;
> +	bool rx_scatter;
>  	bool timestamp_offloading;
>  };
>  
> @@ -342,14 +344,19 @@ eth_pcap_rx(void *queue, struct rte_mbuf **bufs, uint16_t nb_pkts)
>  			/* pcap packet will fit in the mbuf, can copy it */
>  			rte_memcpy(rte_pktmbuf_mtod(mbuf, void *), packet, len);
>  			mbuf->data_len = len;
> -		} else {
> -			/* Try read jumbo frame into multi mbufs. */
> +		} else if (pcap_q->rx_scatter) {
> +			/* Scatter into multi-segment mbufs. */
>  			if (unlikely(eth_pcap_rx_jumbo(pcap_q->mb_pool,
>  						       mbuf, packet, len) == -1)) {
>  				pcap_q->rx_stat.err_pkts++;
>  				rte_pktmbuf_free(mbuf);
>  				break;
>  			}
> +		} else {
> +			/* Packet too large and scatter not enabled, drop it. */
> +			pcap_q->rx_stat.err_pkts++;
> +			rte_pktmbuf_free(mbuf);
> +			continue;
>  		}
>  
>  		mbuf->pkt_len = len;
> @@ -907,6 +914,7 @@ eth_dev_configure(struct rte_eth_dev *dev)
>  	const struct rte_eth_rxmode *rxmode = &dev_conf->rxmode;
>  
>  	internals->vlan_strip = !!(rxmode->offloads & RTE_ETH_RX_OFFLOAD_VLAN_STRIP);
> +	internals->rx_scatter = !!(rxmode->offloads & RTE_ETH_RX_OFFLOAD_SCATTER);
>  	internals->timestamp_offloading = !!(rxmode->offloads & RTE_ETH_RX_OFFLOAD_TIMESTAMP);
>  	return 0;
>  }
> @@ -927,7 +935,8 @@ eth_dev_info(struct rte_eth_dev *dev,
>  	dev_info->tx_offload_capa = RTE_ETH_TX_OFFLOAD_MULTI_SEGS |
>  		RTE_ETH_TX_OFFLOAD_VLAN_INSERT;
>  	dev_info->rx_offload_capa = RTE_ETH_RX_OFFLOAD_VLAN_STRIP |
> -		RTE_ETH_RX_OFFLOAD_TIMESTAMP;
> +		RTE_ETH_RX_OFFLOAD_TIMESTAMP |
> +		RTE_ETH_RX_OFFLOAD_SCATTER;
>  

You should check for the infinite_rx mode here and only add the capability
if it's not set.

With that fixed:
Acked-by: Bruce Richardson <bruce.richardson at intel.com>