netdevsim: Add dummy psample implementation

Allow netdevsim to report "sampled" packets to the psample module by
periodically generating packets from a work queue. The behavior can be
enabled / disabled (default) and the various meta data attributes can be
controlled via debugfs knobs.

This implementation enables both testing of the psample module with all
the optional attributes as well as development of user space
applications on top of psample such as hsflowd and a Wireshark dissector
for psample generic netlink packets.

Signed-off-by: Ido Schimmel <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/Kconfig

···
 	depends on DEBUG_FS
 	depends on INET
 	depends on IPV6 || IPV6=n
+	depends on PSAMPLE || PSAMPLE=n
 	select NET_DEVLINK
 	help
 	  This driver is a developer testing tool and software model that can

drivers/net/netdevsim/Makefile

···
 ifneq ($(CONFIG_XFRM_OFFLOAD),)
 netdevsim-objs += ipsec.o
 endif
+
+ifneq ($(CONFIG_PSAMPLE),)
+netdevsim-objs += psample.o
+endif

drivers/net/netdevsim/dev.c

···
 	if (err)
 		goto err_fib_destroy;
 
-	err = nsim_dev_port_add_all(nsim_dev, nsim_bus_dev->port_count);
+	err = nsim_dev_psample_init(nsim_dev);
 	if (err)
 		goto err_health_exit;
+
+	err = nsim_dev_port_add_all(nsim_dev, nsim_bus_dev->port_count);
+	if (err)
+		goto err_psample_exit;
 
 	nsim_dev->take_snapshot = debugfs_create_file("take_snapshot",
 						      0200,
···
 						&nsim_dev_take_snapshot_fops);
 	return 0;
 
+err_psample_exit:
+	nsim_dev_psample_exit(nsim_dev);
 err_health_exit:
 	nsim_dev_health_exit(nsim_dev);
 err_fib_destroy:
···
 	if (err)
 		goto err_health_exit;
 
-	err = nsim_dev_port_add_all(nsim_dev, nsim_bus_dev->port_count);
+	err = nsim_dev_psample_init(nsim_dev);
 	if (err)
 		goto err_bpf_dev_exit;
+
+	err = nsim_dev_port_add_all(nsim_dev, nsim_bus_dev->port_count);
+	if (err)
+		goto err_psample_exit;
 
 	devlink_params_publish(devlink);
 	devlink_reload_enable(devlink);
 	return 0;
 
+err_psample_exit:
+	nsim_dev_psample_exit(nsim_dev);
 err_bpf_dev_exit:
 	nsim_bpf_dev_exit(nsim_dev);
 err_health_exit:
···
 		return;
 	debugfs_remove(nsim_dev->take_snapshot);
 	nsim_dev_port_del_all(nsim_dev);
+	nsim_dev_psample_exit(nsim_dev);
 	nsim_dev_health_exit(nsim_dev);
 	nsim_fib_destroy(devlink, nsim_dev->fib_data);
 	nsim_dev_traps_exit(devlink);

drivers/net/netdevsim/netdevsim.h

···
 int nsim_dev_health_init(struct nsim_dev *nsim_dev, struct devlink *devlink);
 void nsim_dev_health_exit(struct nsim_dev *nsim_dev);
 
+#if IS_ENABLED(CONFIG_PSAMPLE)
+int nsim_dev_psample_init(struct nsim_dev *nsim_dev);
+void nsim_dev_psample_exit(struct nsim_dev *nsim_dev);
+#else
+static inline int nsim_dev_psample_init(struct nsim_dev *nsim_dev)
+{
+	return 0;
+}
+
+static inline void nsim_dev_psample_exit(struct nsim_dev *nsim_dev)
+{
+}
+#endif
+
 struct nsim_dev_port {
 	struct list_head list;
 	struct devlink_port devlink_port;
···
 		bool static_iana_vxlan;
 		u32 sleep;
 	} udp_ports;
+	struct nsim_dev_psample *psample;
 };
 
 static inline struct net *nsim_dev_net(struct nsim_dev *nsim_dev)

drivers/net/netdevsim/psample.c

···
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) 2021 Mellanox Technologies. All rights reserved */
+
+#include <linux/debugfs.h>
+#include <linux/err.h>
+#include <linux/etherdevice.h>
+#include <linux/inet.h>
+#include <linux/kernel.h>
+#include <linux/random.h>
+#include <linux/slab.h>
+#include <net/devlink.h>
+#include <net/ip.h>
+#include <net/psample.h>
+#include <uapi/linux/ip.h>
+#include <uapi/linux/udp.h>
+
+#include "netdevsim.h"
+
+#define NSIM_PSAMPLE_REPORT_INTERVAL_MS	100
+#define NSIM_PSAMPLE_INVALID_TC		0xFFFF
+#define NSIM_PSAMPLE_L4_DATA_LEN	100
+
+struct nsim_dev_psample {
+	struct delayed_work psample_dw;
+	struct dentry *ddir;
+	struct psample_group *group;
+	u32 rate;
+	u32 group_num;
+	u32 trunc_size;
+	int in_ifindex;
+	int out_ifindex;
+	u16 out_tc;
+	u64 out_tc_occ_max;
+	u64 latency_max;
+	bool is_active;
+};
+
+static struct sk_buff *nsim_dev_psample_skb_build(void)
+{
+	int tot_len, data_len = NSIM_PSAMPLE_L4_DATA_LEN;
+	struct sk_buff *skb;
+	struct udphdr *udph;
+	struct ethhdr *eth;
+	struct iphdr *iph;
+
+	skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
+	if (!skb)
+		return NULL;
+	tot_len = sizeof(struct iphdr) + sizeof(struct udphdr) + data_len;
+
+	skb_reset_mac_header(skb);
+	eth = skb_put(skb, sizeof(struct ethhdr));
+	eth_random_addr(eth->h_dest);
+	eth_random_addr(eth->h_source);
+	eth->h_proto = htons(ETH_P_IP);
+	skb->protocol = htons(ETH_P_IP);
+
+	skb_set_network_header(skb, skb->len);
+	iph = skb_put(skb, sizeof(struct iphdr));
+	iph->protocol = IPPROTO_UDP;
+	iph->saddr = in_aton("192.0.2.1");
+	iph->daddr = in_aton("198.51.100.1");
+	iph->version = 0x4;
+	iph->frag_off = 0;
+	iph->ihl = 0x5;
+	iph->tot_len = htons(tot_len);
+	iph->id = 0;
+	iph->ttl = 100;
+	iph->check = 0;
+	iph->check = ip_fast_csum((unsigned char *)iph, iph->ihl);
+
+	skb_set_transport_header(skb, skb->len);
+	udph = skb_put_zero(skb, sizeof(struct udphdr) + data_len);
+	get_random_bytes(&udph->source, sizeof(u16));
+	get_random_bytes(&udph->dest, sizeof(u16));
+	udph->len = htons(sizeof(struct udphdr) + data_len);
+
+	return skb;
+}
+
+static void nsim_dev_psample_md_prepare(const struct nsim_dev_psample *psample,
+					struct psample_metadata *md)
+{
+	md->trunc_size = psample->trunc_size;
+	md->in_ifindex = psample->in_ifindex;
+	md->out_ifindex = psample->out_ifindex;
+
+	if (psample->out_tc != NSIM_PSAMPLE_INVALID_TC) {
+		md->out_tc = psample->out_tc;
+		md->out_tc_valid = 1;
+	}
+
+	if (psample->out_tc_occ_max) {
+		u64 out_tc_occ;
+
+		get_random_bytes(&out_tc_occ, sizeof(u64));
+		md->out_tc_occ = out_tc_occ & (psample->out_tc_occ_max - 1);
+		md->out_tc_occ_valid = 1;
+	}
+
+	if (psample->latency_max) {
+		u64 latency;
+
+		get_random_bytes(&latency, sizeof(u64));
+		md->latency = latency & (psample->latency_max - 1);
+		md->latency_valid = 1;
+	}
+}
+
+static void nsim_dev_psample_report_work(struct work_struct *work)
+{
+	struct nsim_dev_psample *psample;
+	struct psample_metadata md = {};
+	struct sk_buff *skb;
+	unsigned long delay;
+
+	psample = container_of(work, struct nsim_dev_psample, psample_dw.work);
+
+	skb = nsim_dev_psample_skb_build();
+	if (!skb)
+		goto out;
+
+	nsim_dev_psample_md_prepare(psample, &md);
+	psample_sample_packet(psample->group, skb, psample->rate, &md);
+	consume_skb(skb);
+
+out:
+	delay = msecs_to_jiffies(NSIM_PSAMPLE_REPORT_INTERVAL_MS);
+	schedule_delayed_work(&psample->psample_dw, delay);
+}
+
+static int nsim_dev_psample_enable(struct nsim_dev *nsim_dev)
+{
+	struct nsim_dev_psample *psample = nsim_dev->psample;
+	struct devlink *devlink;
+	unsigned long delay;
+
+	if (psample->is_active)
+		return -EBUSY;
+
+	devlink = priv_to_devlink(nsim_dev);
+	psample->group = psample_group_get(devlink_net(devlink),
+					   psample->group_num);
+	if (!psample->group)
+		return -EINVAL;
+
+	delay = msecs_to_jiffies(NSIM_PSAMPLE_REPORT_INTERVAL_MS);
+	schedule_delayed_work(&psample->psample_dw, delay);
+
+	psample->is_active = true;
+
+	return 0;
+}
+
+static int nsim_dev_psample_disable(struct nsim_dev *nsim_dev)
+{
+	struct nsim_dev_psample *psample = nsim_dev->psample;
+
+	if (!psample->is_active)
+		return -EINVAL;
+
+	psample->is_active = false;
+
+	cancel_delayed_work_sync(&psample->psample_dw);
+	psample_group_put(psample->group);
+
+	return 0;
+}
+
+static ssize_t nsim_dev_psample_enable_write(struct file *file,
+					     const char __user *data,
+					     size_t count, loff_t *ppos)
+{
+	struct nsim_dev *nsim_dev = file->private_data;
+	bool enable;
+	int err;
+
+	err = kstrtobool_from_user(data, count, &enable);
+	if (err)
+		return err;
+
+	if (enable)
+		err = nsim_dev_psample_enable(nsim_dev);
+	else
+		err = nsim_dev_psample_disable(nsim_dev);
+
+	return err ? err : count;
+}
+
+static const struct file_operations nsim_psample_enable_fops = {
+	.open = simple_open,
+	.write = nsim_dev_psample_enable_write,
+	.llseek = generic_file_llseek,
+	.owner = THIS_MODULE,
+};
+
+int nsim_dev_psample_init(struct nsim_dev *nsim_dev)
+{
+	struct nsim_dev_psample *psample;
+	int err;
+
+	psample = kzalloc(sizeof(*psample), GFP_KERNEL);
+	if (!psample)
+		return -ENOMEM;
+	nsim_dev->psample = psample;
+
+	INIT_DELAYED_WORK(&psample->psample_dw, nsim_dev_psample_report_work);
+
+	psample->ddir = debugfs_create_dir("psample", nsim_dev->ddir);
+	if (IS_ERR(psample->ddir)) {
+		err = PTR_ERR(psample->ddir);
+		goto err_psample_free;
+	}
+
+	/* Populate sampling parameters with sane defaults. */
+	psample->rate = 100;
+	debugfs_create_u32("rate", 0600, psample->ddir, &psample->rate);
+
+	psample->group_num = 10;
+	debugfs_create_u32("group_num", 0600, psample->ddir,
+			   &psample->group_num);
+
+	psample->trunc_size = 0;
+	debugfs_create_u32("trunc_size", 0600, psample->ddir,
+			   &psample->trunc_size);
+
+	psample->in_ifindex = 1;
+	debugfs_create_u32("in_ifindex", 0600, psample->ddir,
+			   &psample->in_ifindex);
+
+	psample->out_ifindex = 2;
+	debugfs_create_u32("out_ifindex", 0600, psample->ddir,
+			   &psample->out_ifindex);
+
+	psample->out_tc = 0;
+	debugfs_create_u16("out_tc", 0600, psample->ddir, &psample->out_tc);
+
+	psample->out_tc_occ_max = 10000;
+	debugfs_create_u64("out_tc_occ_max", 0600, psample->ddir,
+			   &psample->out_tc_occ_max);
+
+	psample->latency_max = 50;
+	debugfs_create_u64("latency_max", 0600, psample->ddir,
+			   &psample->latency_max);
+
+	debugfs_create_file("enable", 0200, psample->ddir, nsim_dev,
+			    &nsim_psample_enable_fops);
+
+	return 0;
+
+err_psample_free:
+	kfree(nsim_dev->psample);
+	return err;
+}
+
+void nsim_dev_psample_exit(struct nsim_dev *nsim_dev)
+{
+	debugfs_remove_recursive(nsim_dev->psample->ddir);
+	if (nsim_dev->psample->is_active) {
+		cancel_delayed_work_sync(&nsim_dev->psample->psample_dw);
+		psample_group_put(nsim_dev->psample->group);
+	}
+	kfree(nsim_dev->psample);
+}