netdevsim: add HDS feature

HDS options(tcp-data-split, hds-thresh) have dependencies between other
features like XDP. Basic dependencies are checked in the core API.
netdevsim is very useful to check basic dependencies.

The default tcp-data-split mode is UNKNOWN but netdevsim driver
returns ENABLED when ethtool dumps tcp-data-split mode.
The default value of HDS threshold is 0 and the maximum value is 1024.

ethtool shows like this.

ethtool -g eni1np1
Ring parameters for eni1np1:
Pre-set maximums:
...
HDS thresh:             1024
Current hardware settings:
...
TCP data split:         on
HDS thresh:             0

ethtool -G eni1np1 tcp-data-split on hds-thresh 1024
ethtool -g eni1np1
Ring parameters for eni1np1:
Pre-set maximums:
...
HDS thresh:             1024
Current hardware settings:
...
TCP data split:         on
HDS thresh:             1024

Signed-off-by: Taehee Yoo <ap420073@gmail.com>
Link: https://patch.msgid.link/20250114142852.3364986-10-ap420073@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: TaeheeYoo

drivers/net/netdevsim/ethtool.c

@@ -2,7 +2,6 @@
 // Copyright (c) 2020 Facebook
 
 #include <linux/debugfs.h>
-#include <linux/ethtool.h>
 #include <linux/random.h>
 
 #include "netdevsim.h"
@@ -72,6 +71,12 @@ static void nsim_get_ringparam(struct net_device *dev,
 	struct netdevsim *ns = netdev_priv(dev);
 
 	memcpy(ring, &ns->ethtool.ring, sizeof(ns->ethtool.ring));
+	kernel_ring->tcp_data_split = dev->ethtool->hds_config;
+	kernel_ring->hds_thresh = dev->ethtool->hds_thresh;
+	kernel_ring->hds_thresh_max = NSIM_HDS_THRESHOLD_MAX;
+
+	if (kernel_ring->tcp_data_split == ETHTOOL_TCP_DATA_SPLIT_UNKNOWN)
+		kernel_ring->tcp_data_split = ETHTOOL_TCP_DATA_SPLIT_ENABLED;
 }
 
 static int nsim_set_ringparam(struct net_device *dev,
@@ -161,6 +166,8 @@ static int nsim_get_ts_info(struct net_device *dev,
 
 static const struct ethtool_ops nsim_ethtool_ops = {
 	.supported_coalesce_params	= ETHTOOL_COALESCE_ALL_PARAMS,
+	.supported_ring_params		= ETHTOOL_RING_USE_TCP_DATA_SPLIT |
+					  ETHTOOL_RING_USE_HDS_THRS,
 	.get_pause_stats	        = nsim_get_pause_stats,
 	.get_pauseparam		        = nsim_get_pauseparam,
 	.set_pauseparam		        = nsim_set_pauseparam,
@@ -182,6 +189,9 @@ static void nsim_ethtool_ring_init(struct netdevsim *ns)
 	ns->ethtool.ring.rx_jumbo_max_pending = 4096;
 	ns->ethtool.ring.rx_mini_max_pending = 4096;
 	ns->ethtool.ring.tx_max_pending = 4096;
+
+	ns->netdev->ethtool->hds_config = ETHTOOL_TCP_DATA_SPLIT_UNKNOWN;
+	ns->netdev->ethtool->hds_thresh = 0;
 }
 
 void nsim_ethtool_init(struct netdevsim *ns)

drivers/net/netdevsim/netdev.c

@@ -15,6 +15,7 @@
 
 #include <linux/debugfs.h>
 #include <linux/etherdevice.h>
+#include <linux/ethtool_netlink.h>
 #include <linux/kernel.h>
 #include <linux/module.h>
 #include <linux/netdevice.h>
@@ -54,6 +55,7 @@ static int nsim_forward_skb(struct net_device *dev, struct sk_buff *skb,
 static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct netdevsim *ns = netdev_priv(dev);
+	struct ethtool_netdev_state *ethtool;
 	struct net_device *peer_dev;
 	unsigned int len = skb->len;
 	struct netdevsim *peer_ns;
@@ -74,6 +76,13 @@ static netdev_tx_t nsim_start_xmit(struct sk_buff *skb, struct net_device *dev)
 		rxq = rxq % peer_dev->num_rx_queues;
 	rq = peer_ns->rq[rxq];
 
+	ethtool = peer_dev->ethtool;
+	if (skb_is_nonlinear(skb) &&
+	    (ethtool->hds_config != ETHTOOL_TCP_DATA_SPLIT_ENABLED ||
+	     (ethtool->hds_config == ETHTOOL_TCP_DATA_SPLIT_ENABLED &&
+	      ethtool->hds_thresh > len)))
+		skb_linearize(skb);
+
 	skb_tx_timestamp(skb);
 	if (unlikely(nsim_forward_skb(peer_dev, skb, rq) == NET_RX_DROP))
 		goto out_drop_cnt;

drivers/net/netdevsim/netdevsim.h

@@ -16,6 +16,7 @@
 #include <linux/debugfs.h>
 #include <linux/device.h>
 #include <linux/ethtool.h>
+#include <linux/ethtool_netlink.h>
 #include <linux/kernel.h>
 #include <linux/list.h>
 #include <linux/netdevice.h>
@@ -36,6 +37,8 @@
 #define NSIM_IPSEC_VALID		BIT(31)
 #define NSIM_UDP_TUNNEL_N_PORTS		4
 
+#define NSIM_HDS_THRESHOLD_MAX		1024
+
 struct nsim_sa {
 	struct xfrm_state *xs;
 	__be32 ipaddr[4];