On Thu, 12 Mar 2026 08:34:03 +0100
Sriram Yagnaraman <[email protected]> wrote:
> Enable jumbo frame reception with default mbuf data room size by
> chaining multiple mbufs when packet exceeds single mbuf tailroom.
>
> Scatter Rx is only enabled when RTE_ETH_RX_OFFLOAD_SCATTER is
> requested. Packets are dropped if they exceed single mbuf size
> and scatter is not enabled, or if mbuf allocation fails during
> chaining. Error counter rx_dropped_pkts tracks all drops.
>
> This allows receiving 9KB jumbo frames using standard 2KB mbufs,
> chaining ~5 segments per jumbo packet.
> ---
Scatter is good, but additional checks are necessary to validate
mbuf pool and buffer constraints. See virtio configure for example.
bool
virtio_rx_check_scatter(uint16_t max_rx_pkt_len, uint16_t rx_buf_size,
bool rx_scatter_enabled, const char **error)
{
if (!rx_scatter_enabled && max_rx_pkt_len > rx_buf_size) {
*error = "Rx scatter is disabled and RxQ mbuf pool object size
is too small";
return false;
}
return true;
}
