From: David Wei This adds the last missing bit to netkit for supporting io_uring with zero-copy mode [0]. Up until this point it was not possible to consume the latter out of containers or Kubernetes Pods where applications are in their own network namespace. Thus, as a last missing bit, implement ndo_queue_get_dma_dev() in netkit to return the physical device of the real rxq for DMA. This allows memory providers like io_uring zero-copy or devmem to bind to the physically mapped rxq in netkit. io_uring example with eth0 being a physical device with 16 queues where netkit is bound to the last queue, iou-zcrx.c is binary from selftests. Flow steering to that queue is based on the service VIP:port of the server utilizing io_uring: # ethtool -X eth0 start 0 equal 15 # ethtool -X eth0 start 15 equal 1 context new # ethtool --config-ntuple eth0 flow-type tcp4 dst-ip 1.2.3.4 dst-port 5000 action 15 # ip netns add foo # ip link add numrxqueues 2 type netkit # ynl-bind eth0 15 nk0 # ip link set nk0 netns foo # ip link set nk1 up # ip netns exec foo ip link set lo up # ip netns exec foo ip link set nk0 up # ip netns exec foo ip addr add 1.2.3.4/32 dev nk0 [ ... setup routing etc to get external traffic into the netns ... ] # ip netns exec foo ./iou-zcrx -s -p 5000 -i nk0 -q 1 Remote io_uring client: # ./iou-zcrx -c -h 1.2.3.4 -p 5000 -l 12840 -z 65536 We have tested the above against a dual-port Nvidia ConnectX-6 (mlx5) 100G NIC as well as Broadcom BCM957504 (bnxt_en) 100G NIC, both supporting TCP header/data split. For Cilium, the plan is to open up support for io_uring in zero-copy mode for regular Kubernetes Pods when Cilium is configured with netkit datapath mode. Signed-off-by: David Wei Co-developed-by: Daniel Borkmann Signed-off-by: Daniel Borkmann Link: https://kernel-recipes.org/en/2024/schedule/efficient-zero-copy-networking-using-io_uring [0] --- drivers/net/netkit.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/drivers/net/netkit.c b/drivers/net/netkit.c index 27ff84833f28..5129b27a7c3c 100644 --- a/drivers/net/netkit.c +++ b/drivers/net/netkit.c @@ -274,6 +274,21 @@ static const struct ethtool_ops netkit_ethtool_ops = { .get_channels = netkit_get_channels, }; +static struct device *netkit_queue_get_dma_dev(struct net_device *dev, int idx) +{ + struct netdev_rx_queue *rxq, *peer_rxq; + unsigned int peer_idx; + + rxq = __netif_get_rx_queue(dev, idx); + if (!rxq->peer) + return NULL; + + peer_rxq = rxq->peer; + peer_idx = get_netdev_rx_queue_index(peer_rxq); + + return netdev_queue_get_dma_dev(peer_rxq->dev, peer_idx); +} + static int netkit_queue_create(struct net_device *dev) { struct netkit *nk = netkit_priv(dev); @@ -299,7 +314,8 @@ static int netkit_queue_create(struct net_device *dev) } static const struct netdev_queue_mgmt_ops netkit_queue_mgmt_ops = { - .ndo_queue_create = netkit_queue_create, + .ndo_queue_get_dma_dev = netkit_queue_get_dma_dev, + .ndo_queue_create = netkit_queue_create, }; static struct net_device *netkit_alloc(struct nlattr *tb[], -- 2.43.0