net/vdev_netvsc/vdev_netvsc.c

/* SPDX-License-Identifier: BSD-3-Clause
 * Copyright 2017 6WIND S.A.
 * Copyright 2017 Mellanox Technologies, Ltd
 */

#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <linux/sockios.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <net/if.h>
#include <net/if_arp.h>
#include <netinet/ip.h>
#include <stdarg.h>
#include <stddef.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/queue.h>
#include <sys/socket.h>
#include <unistd.h>

#include <rte_alarm.h>
#include <bus_driver.h>
#include <bus_vdev_driver.h>
#include <rte_common.h>
#include <dev_driver.h>
#include <rte_errno.h>
#include <rte_ethdev.h>
#include <rte_ether.h>
#include <rte_hypervisor.h>
#include <rte_kvargs.h>
#include <rte_log.h>
#include <rte_string_fns.h>

#define VDEV_NETVSC_DRIVER net_vdev_netvsc
#define VDEV_NETVSC_DRIVER_NAME RTE_STR(VDEV_NETVSC_DRIVER)
#define VDEV_NETVSC_DRIVER_NAME_LEN 15
#define VDEV_NETVSC_ARG_IFACE "iface"
#define VDEV_NETVSC_ARG_MAC "mac"
#define VDEV_NETVSC_ARG_FORCE "force"
#define VDEV_NETVSC_ARG_IGNORE "ignore"
#define VDEV_NETVSC_PROBE_MS 1000

#define NETVSC_CLASS_ID "{f8615163-df3e-46c5-913f-f2d2f965ed0e}"
#define NETVSC_MAX_ROUTE_LINE_SIZE 300

RTE_LOG_REGISTER_DEFAULT(vdev_netvsc_logtype, NOTICE);
#define RTE_LOGTYPE_VDEV_NETVSC vdev_netvsc_logtype

#define DRV_LOG(level, ...) \
	RTE_LOG_LINE(level, VDEV_NETVSC, __VA_ARGS__)

/** Context structure for a vdev_netvsc instance. */
struct vdev_netvsc_ctx {
	LIST_ENTRY(vdev_netvsc_ctx) entry; /**< Next entry in list. */
	unsigned int id;		   /**< Unique ID. */
	char name[64];			   /**< Unique name. */
	char devname[64];		   /**< Fail-safe instance name. */
	char devargs[256];		   /**< Fail-safe device arguments. */
	char if_name[IF_NAMESIZE];	   /**< NetVSC netdevice name. */
	unsigned int if_index;		   /**< NetVSC netdevice index. */
	struct rte_ether_addr if_addr;	   /**< NetVSC MAC address. */
	int pipe[2];			   /**< Fail-safe communication pipe. */
	char yield[256];		   /**< PCI sub-device arguments. */
};

/** Context list is common to all driver instances. */
static LIST_HEAD(, vdev_netvsc_ctx) vdev_netvsc_ctx_list =
	LIST_HEAD_INITIALIZER(vdev_netvsc_ctx_list);

/** Number of entries in context list. */
static unsigned int vdev_netvsc_ctx_count;

/** Number of driver instances relying on context list. */
static unsigned int vdev_netvsc_ctx_inst;

/**
 * Destroy a vdev_netvsc context instance.
 *
 * @param ctx
 *   Context to destroy.
 */
static void
vdev_netvsc_ctx_destroy(struct vdev_netvsc_ctx *ctx)
{
	if (ctx->pipe[0] != -1)
		close(ctx->pipe[0]);
	if (ctx->pipe[1] != -1)
		close(ctx->pipe[1]);
	free(ctx);
}

/**
 * Determine if a network interface is NetVSC.
 *
 * @param[in] iface
 *   Pointer to netdevice description structure (name and index).
 *
 * @return
 *   A nonzero value when interface is detected as NetVSC. In case of error,
 *   rte_errno is updated and 0 returned.
 */
static int
vdev_netvsc_iface_is_netvsc(const struct if_nameindex *iface)
{
	static const char temp[] = "/sys/class/net/%s/device/class_id";
	char path[sizeof(temp) + IF_NAMESIZE];
	FILE *f;
	int ret;
	int len = 0;

	ret = snprintf(path, sizeof(path), temp, iface->if_name);
	if (ret == -1 || (size_t)ret >= sizeof(path)) {
		rte_errno = ENOBUFS;
		return 0;
	}
	f = fopen(path, "r");
	if (!f) {
		rte_errno = errno;
		return 0;
	}
	ret = fscanf(f, NETVSC_CLASS_ID "%n", &len);
	if (ret == EOF)
		rte_errno = errno;
	ret = len == (int)strlen(NETVSC_CLASS_ID);
	fclose(f);
	return ret;
}

/**
 * Iterate over system network interfaces.
 *
 * This function runs a given callback function for each netdevice found on
 * the system.
 *
 * @param func
 *   Callback function pointer. List traversal is aborted when this function
 *   returns a nonzero value.
 * @param is_netvsc
 *   Indicates the device type to iterate - netvsc or non-netvsc.
 * @param ...
 *   Variable parameter list passed as @p va_list to @p func.
 *
 * @return
 *   0 when the entire list is traversed successfully, a negative error code
 *   in case or failure, or the nonzero value returned by @p func when list
 *   traversal is aborted.
 */
static int
vdev_netvsc_foreach_iface(int (*func)(const struct if_nameindex *iface,
				      const struct rte_ether_addr *eth_addr,
				      va_list ap), int is_netvsc, ...)
{
	struct if_nameindex *iface = if_nameindex();
	int s = socket(PF_INET, SOCK_DGRAM, IPPROTO_IP);
	unsigned int i;
	int ret = 0;

	if (!iface) {
		ret = -ENOBUFS;
		DRV_LOG(ERR, "cannot retrieve system network interfaces");
		goto error;
	}
	if (s == -1) {
		ret = -errno;
		DRV_LOG(ERR, "cannot open socket: %s", rte_strerror(errno));
		goto error;
	}
	for (i = 0; iface[i].if_name; ++i) {
		int is_netvsc_ret;
		struct ifreq req;
		struct rte_ether_addr eth_addr;
		va_list ap;

		is_netvsc_ret = vdev_netvsc_iface_is_netvsc(&iface[i]) ? 1 : 0;
		if (is_netvsc ^ is_netvsc_ret)
			continue;
		strlcpy(req.ifr_name, iface[i].if_name, sizeof(req.ifr_name));
		if (ioctl(s, SIOCGIFHWADDR, &req) == -1) {
			DRV_LOG(WARNING, "cannot retrieve information about"
					 " interface \"%s\": %s",
					 req.ifr_name, rte_strerror(errno));
			continue;
		}
		if (req.ifr_hwaddr.sa_family != ARPHRD_ETHER)
			continue;
		memcpy(eth_addr.addr_bytes, req.ifr_hwaddr.sa_data,
		       RTE_DIM(eth_addr.addr_bytes));
		va_start(ap, is_netvsc);
		ret = func(&iface[i], &eth_addr, ap);
		va_end(ap);
		if (ret)
			break;
	}
error:
	if (s != -1)
		close(s);
	if (iface)
		if_freenameindex(iface);
	return ret;
}

/**
 * Determine if a network interface has a route.
 *
 * @param[in] name
 *   Network device name.
 * @param[in] family
 *   Address family: AF_INET for IPv4 or AF_INET6 for IPv6.
 *
 * @return
 *   1 when interface has a route, negative errno value in case of error and
 *   0 otherwise.
 */
static int
vdev_netvsc_has_route(const struct if_nameindex *iface,
		      const unsigned char family)
{
	/*
	 * The implementation can be simpler by getifaddrs() function usage but
	 * it works for IPv6 only starting from glibc 2.3.3.
	 */
	char buf[4096];
	int len;
	int ret = 0;
	int res;
	int sock;
	struct nlmsghdr *retmsg = (struct nlmsghdr *)buf;
	struct sockaddr_nl sa;
	struct {
		struct nlmsghdr nlhdr;
		struct ifaddrmsg addrmsg;
	} msg;

	if (!iface || (family != AF_INET && family != AF_INET6)) {
		DRV_LOG(ERR, "%s", rte_strerror(EINVAL));
		return -EINVAL;
	}
	sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
	if (sock == -1) {
		DRV_LOG(ERR, "cannot open socket: %s", rte_strerror(errno));
		return -errno;
	}
	memset(&sa, 0, sizeof(sa));
	sa.nl_family = AF_NETLINK;
	sa.nl_groups = RTMGRP_LINK | RTMGRP_IPV4_IFADDR;
	res = bind(sock, (struct sockaddr *)&sa, sizeof(sa));
	if (res == -1) {
		ret = -errno;
		DRV_LOG(ERR, "cannot bind socket: %s", rte_strerror(errno));
		goto close;
	}
	memset(&msg, 0, sizeof(msg));
	msg.nlhdr.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifaddrmsg));
	msg.nlhdr.nlmsg_flags = NLM_F_REQUEST | NLM_F_DUMP;
	msg.nlhdr.nlmsg_type = RTM_GETADDR;
	msg.nlhdr.nlmsg_pid = getpid();
	msg.addrmsg.ifa_family = family;
	msg.addrmsg.ifa_index = iface->if_index;
	res = send(sock, &msg, msg.nlhdr.nlmsg_len, 0);
	if (res == -1) {
		ret = -errno;
		DRV_LOG(ERR, "cannot send socket message: %s",
			rte_strerror(errno));
		goto close;
	}
	memset(buf, 0, sizeof(buf));
	len = recv(sock, buf, sizeof(buf), 0);
	if (len == -1) {
		ret = -errno;
		DRV_LOG(ERR, "cannot receive socket message: %s",
			rte_strerror(errno));
		goto close;
	}
	while (NLMSG_OK(retmsg, (unsigned int)len)) {
		struct ifaddrmsg *retaddr =
				(struct ifaddrmsg *)NLMSG_DATA(retmsg);

		if (retaddr->ifa_family == family &&
		    retaddr->ifa_index == iface->if_index) {
			struct rtattr *retrta = IFA_RTA(retaddr);
			int attlen = IFA_PAYLOAD(retmsg);

			while (RTA_OK(retrta, attlen)) {
				if (retrta->rta_type == IFA_ADDRESS) {
					ret = 1;
					DRV_LOG(DEBUG, "interface %s has IP",
						iface->if_name);
					goto close;
				}
				retrta = RTA_NEXT(retrta, attlen);
			}
		}
		retmsg = NLMSG_NEXT(retmsg, len);
	}
close:
	close(sock);
	return ret;
}

/**
 * Retrieve network interface data from sysfs symbolic link.
 *
 * @param[out] buf
 *   Output data buffer.
 * @param size
 *   Output buffer size.
 * @param[in] if_name
 *   Netdevice name.
 * @param[in] relpath
 *   Symbolic link path relative to netdevice sysfs entry.
 *
 * @return
 *   0 on success, a negative error code otherwise.
 */
static int
vdev_netvsc_sysfs_readlink(char *buf, size_t size, const char *if_name,
			   const char *relpath)
{
	struct vdev_netvsc_ctx *ctx;
	char in[RTE_MAX(sizeof(ctx->yield), 256u)];
	int ret;

	ret = snprintf(in, sizeof(in), "/sys/class/net/%s/%s",
		       if_name, relpath);
	if (ret == -1 || (size_t)ret >= sizeof(in))
		return -ENOBUFS;
	ret = readlink(in, buf, size);
	if (ret == -1)
		return -errno;
	if ((size_t)ret >= size - 1)
		return -ENOBUFS;
	buf[ret] = '\0';
	return 0;
}

/**
 * Probe a network interface to associate with vdev_netvsc context.
 *
 * This function determines if the network device matches the properties of
 * the NetVSC interface associated with the vdev_netvsc context and
 * communicates its bus address to the fail-safe PMD instance if so.
 *
 * It is normally used with vdev_netvsc_foreach_iface().
 *
 * @param[in] iface
 *   Pointer to netdevice description structure (name and index).
 * @param[in] eth_addr
 *   MAC address associated with @p iface.
 * @param ap
 *   Variable arguments list comprising:
 *
 *   - struct vdev_netvsc_ctx *ctx:
 *     Context to associate network interface with.
 *
 * @return
 *   A nonzero value when interface matches, 0 otherwise or in case of
 *   error.
 */
static int
vdev_netvsc_device_probe(const struct if_nameindex *iface,
		    const struct rte_ether_addr *eth_addr,
		    va_list ap)
{
	struct vdev_netvsc_ctx *ctx = va_arg(ap, struct vdev_netvsc_ctx *);
	char buf[RTE_MAX(sizeof(ctx->yield), 256u)];
	const char *addr;
	size_t len;
	int ret;

	/* Skip non-matching or unwanted NetVSC interfaces. */
	if (ctx->if_index == iface->if_index) {
		if (!strcmp(ctx->if_name, iface->if_name))
			return 0;
		DRV_LOG(DEBUG,
			"NetVSC interface \"%s\" (index %u) renamed \"%s\"",
			ctx->if_name, ctx->if_index, iface->if_name);
		strlcpy(ctx->if_name, iface->if_name, sizeof(ctx->if_name));
		return 0;
	}
	if (!rte_is_same_ether_addr(eth_addr, &ctx->if_addr))
		return 0;
	/* Look for associated PCI device. */
	ret = vdev_netvsc_sysfs_readlink(buf, sizeof(buf), iface->if_name,
					 "device/subsystem");
	if (ret)
		return 0;
	addr = strrchr(buf, '/');
	addr = addr ? addr + 1 : buf;
	if (strcmp(addr, "pci"))
		return 0;
	ret = vdev_netvsc_sysfs_readlink(buf, sizeof(buf), iface->if_name,
					 "device");
	if (ret)
		return 0;
	addr = strrchr(buf, '/');
	addr = addr ? addr + 1 : buf;
	len = strlen(addr);
	if (!len)
		return 0;
	/* Send PCI device argument to fail-safe PMD instance. */
	if (strcmp(addr, ctx->yield))
		DRV_LOG(DEBUG, "associating PCI device \"%s\" with NetVSC"
			" interface \"%s\" (index %u)", addr, ctx->if_name,
			ctx->if_index);
	memmove(buf, addr, len + 1);
	addr = buf;
	buf[len] = '\n';
	ret = write(ctx->pipe[1], addr, len + 1);
	buf[len] = '\0';
	if (ret == -1) {
		if (errno == EINTR || errno == EAGAIN)
			return 1;
		DRV_LOG(WARNING, "cannot associate PCI device name \"%s\" with"
			" interface \"%s\": %s", addr, ctx->if_name,
			rte_strerror(errno));
		return 1;
	}
	if ((size_t)ret != len + 1) {
		/*
		 * Attempt to override previous partial write, no need to
		 * recover if that fails.
		 */
		ret = write(ctx->pipe[1], "\n", 1);
		(void)ret;
		return 1;
	}
	fsync(ctx->pipe[1]);
	memcpy(ctx->yield, addr, len + 1);
	return 1;
}

/**
 * Alarm callback that regularly probes system network interfaces.
 *
 * This callback runs at a frequency determined by VDEV_NETVSC_PROBE_MS as
 * long as an vdev_netvsc context instance exists.
 *
 * @param arg
 *   Ignored.
 */
static void
vdev_netvsc_alarm(__rte_unused void *arg)
{
	struct vdev_netvsc_ctx *ctx;
	int ret;

	LIST_FOREACH(ctx, &vdev_netvsc_ctx_list, entry) {
		ret = vdev_netvsc_foreach_iface(vdev_netvsc_device_probe, 0,
		      ctx);
		if (ret < 0)
			break;
	}
	if (!vdev_netvsc_ctx_count)
		return;
	ret = rte_eal_alarm_set(VDEV_NETVSC_PROBE_MS * 1000,
				vdev_netvsc_alarm, NULL);
	if (ret < 0) {
		DRV_LOG(ERR, "unable to reschedule alarm callback: %s",
			rte_strerror(-ret));
	}
}

/**
 * Probe a NetVSC interface to generate a vdev_netvsc context from.
 *
 * This function instantiates vdev_netvsc contexts either for all NetVSC
 * devices found on the system or only a subset provided as device
 * arguments.
 *
 * It is normally used with vdev_netvsc_foreach_iface().
 *
 * @param[in] iface
 *   Pointer to netdevice description structure (name and index).
 * @param[in] eth_addr
 *   MAC address associated with @p iface.
 * @param ap
 *   Variable arguments list comprising:
 *
 *   - const char *name:
 *     Name associated with current driver instance.
 *
 *   - struct rte_kvargs *kvargs:
 *     Device arguments provided to current driver instance.
 *
 *   - int force:
 *     Accept specified interface even if not detected as NetVSC.
 *
 *   - unsigned int specified:
 *     Number of specific netdevices provided as device arguments.
 *
 *   - unsigned int *matched:
 *     The number of specified netdevices matched by this function.
 *
 * @return
 *   A nonzero value when interface matches, 0 otherwise or in case of
 *   error.
 */
static int
vdev_netvsc_netvsc_probe(const struct if_nameindex *iface,
			 const struct rte_ether_addr *eth_addr,
			 va_list ap)
{
	const char *name = va_arg(ap, const char *);
	struct rte_kvargs *kvargs = va_arg(ap, struct rte_kvargs *);
	unsigned int specified = va_arg(ap, unsigned int);
	unsigned int *matched = va_arg(ap, unsigned int *);
	unsigned int i;
	struct vdev_netvsc_ctx *ctx;
	int ret;

	/* Probe all interfaces when none are specified. */
	if (specified) {
		for (i = 0; i != kvargs->count; ++i) {
			const struct rte_kvargs_pair *pair = &kvargs->pairs[i];

			if (!strcmp(pair->key, VDEV_NETVSC_ARG_IFACE)) {
				if (!strcmp(pair->value, iface->if_name))
					break;
			} else if (!strcmp(pair->key, VDEV_NETVSC_ARG_MAC)) {
				struct rte_ether_addr tmp;

				if (rte_ether_unformat_addr(pair->value, &tmp) != 0) {
					DRV_LOG(ERR,
						"invalid MAC address format"
						" \"%s\"",
						pair->value);
					return -EINVAL;
				}
				if (rte_is_same_ether_addr(eth_addr, &tmp))
					break;
			}
		}
		if (i == kvargs->count)
			return 0;
		++(*matched);
	}
	/* Weed out interfaces already handled. */
	LIST_FOREACH(ctx, &vdev_netvsc_ctx_list, entry)
		if (ctx->if_index == iface->if_index)
			break;
	if (ctx) {
		if (!specified)
			return 0;
		DRV_LOG(WARNING,
			"interface \"%s\" (index %u) is already handled,"
			" skipping",
			iface->if_name, iface->if_index);
		return 0;
	}
	/* Routed NetVSC should not be probed. */
	if (vdev_netvsc_has_route(iface, AF_INET) ||
	    vdev_netvsc_has_route(iface, AF_INET6)) {
		if (!specified)
			return 0;
		DRV_LOG(WARNING, "probably using routed NetVSC interface \"%s\""
			" (index %u)", iface->if_name, iface->if_index);
	}
	/* Create interface context. */
	ctx = calloc(1, sizeof(*ctx));
	if (!ctx) {
		ret = -errno;
		DRV_LOG(ERR, "cannot allocate context for interface \"%s\": %s",
			iface->if_name, rte_strerror(errno));
		goto error;
	}
	ctx->id = vdev_netvsc_ctx_count;
	strlcpy(ctx->if_name, iface->if_name, sizeof(ctx->if_name));
	ctx->if_index = iface->if_index;
	ctx->if_addr = *eth_addr;
	ctx->pipe[0] = -1;
	ctx->pipe[1] = -1;
	ctx->yield[0] = '\0';
	if (pipe(ctx->pipe) == -1) {
		ret = -errno;
		DRV_LOG(ERR,
			"cannot allocate control pipe for interface \"%s\": %s",
			ctx->if_name, rte_strerror(errno));
		goto error;
	}
	for (i = 0; i != RTE_DIM(ctx->pipe); ++i) {
		int flf = fcntl(ctx->pipe[i], F_GETFL);

		if (flf != -1 &&
		    fcntl(ctx->pipe[i], F_SETFL, flf | O_NONBLOCK) != -1)
			continue;
		ret = -errno;
		DRV_LOG(ERR, "cannot toggle non-blocking flag on control file"
			" descriptor #%u (%d): %s", i, ctx->pipe[i],
			rte_strerror(errno));
		goto error;
	}
	/* Generate virtual device name and arguments. */
	i = 0;
	ret = snprintf(ctx->name, sizeof(ctx->name), "%s_id%u",
		       name, ctx->id);
	if (ret == -1 || (size_t)ret >= sizeof(ctx->name))
		++i;
	ret = snprintf(ctx->devname, sizeof(ctx->devname), "net_failsafe_vsc%u",
		       ctx->id);
	if (ret == -1 || (size_t)ret >= sizeof(ctx->devname))
		++i;
	ret = snprintf(ctx->devargs, sizeof(ctx->devargs),
		       "fd(%d),dev(net_tap_vsc%u,remote=%s)",
		       ctx->pipe[0], ctx->id, ctx->if_name);
	if (ret == -1 || (size_t)ret >= sizeof(ctx->devargs))
		++i;
	if (i) {
		ret = -ENOBUFS;
		DRV_LOG(ERR, "generated virtual device name or argument list"
			" too long for interface \"%s\"", ctx->if_name);
		goto error;
	}
	/* Request virtual device generation. */
	DRV_LOG(DEBUG, "generating virtual device \"%s\" with arguments \"%s\"",
		ctx->devname, ctx->devargs);
	vdev_netvsc_foreach_iface(vdev_netvsc_device_probe, 0, ctx);
	ret = rte_eal_hotplug_add("vdev", ctx->devname, ctx->devargs);
	if (ret < 0)
		goto error;
	LIST_INSERT_HEAD(&vdev_netvsc_ctx_list, ctx, entry);
	++vdev_netvsc_ctx_count;
	DRV_LOG(DEBUG, "added NetVSC interface \"%s\" to context list",
		ctx->if_name);
	return 0;
error:
	if (ctx)
		vdev_netvsc_ctx_destroy(ctx);
	return ret;
}

/**
 * Probe NetVSC interfaces.
 *
 * This function probes system netdevices according to the specified device
 * arguments and starts a periodic alarm callback to notify the resulting
 * fail-safe PMD instances of their sub-devices whereabouts.
 *
 * @param dev
 *   Virtual device context for driver instance.
 *
 * @return
 *    Always 0, even in case of errors.
 */
static int
vdev_netvsc_vdev_probe(struct rte_vdev_device *dev)
{
	static const char *const vdev_netvsc_arg[] = {
		VDEV_NETVSC_ARG_IFACE,
		VDEV_NETVSC_ARG_MAC,
		VDEV_NETVSC_ARG_FORCE,
		VDEV_NETVSC_ARG_IGNORE,
		NULL,
	};
	const char *name = rte_vdev_device_name(dev);
	const char *args = rte_vdev_device_args(dev);
	struct rte_kvargs *kvargs = rte_kvargs_parse(args ? args : "",
						     vdev_netvsc_arg);
	unsigned int specified = 0;
	unsigned int matched = 0;
	int force = 0;
	int ignore = 0;
	unsigned int i;
	int ret;

	DRV_LOG(DEBUG, "invoked as \"%s\", using arguments \"%s\"", name, args);
	rte_eal_alarm_cancel(vdev_netvsc_alarm, NULL);
	if (!kvargs) {
		DRV_LOG(ERR, "cannot parse arguments list");
		goto error;
	}
	for (i = 0; i != kvargs->count; ++i) {
		const struct rte_kvargs_pair *pair = &kvargs->pairs[i];

		if (!strcmp(pair->key, VDEV_NETVSC_ARG_FORCE))
			force = !!atoi(pair->value);
		else if (!strcmp(pair->key, VDEV_NETVSC_ARG_IGNORE))
			ignore = !!atoi(pair->value);
		else if (!strcmp(pair->key, VDEV_NETVSC_ARG_IFACE) ||
			 !strcmp(pair->key, VDEV_NETVSC_ARG_MAC))
			++specified;
	}
	if (ignore)
		goto ignore;
	if (specified > 1) {
		DRV_LOG(ERR, "More than one way used to specify the netvsc"
			" device.");
		goto error;
	}
	/* Gather interfaces. */
	ret = vdev_netvsc_foreach_iface(vdev_netvsc_netvsc_probe, 1, name,
					kvargs, specified, &matched);
	if (ret < 0)
		goto error;
	if (specified && matched < specified) {
		if (!force) {
			DRV_LOG(ERR, "Cannot find the specified netvsc device");
			goto error;
		}
		/* Try to force probing on non-netvsc specified device. */
		if (vdev_netvsc_foreach_iface(vdev_netvsc_netvsc_probe, 0, name,
					      kvargs, specified, &matched) < 0)
			goto error;
		if (matched < specified) {
			DRV_LOG(ERR, "Cannot find the specified device");
			goto error;
		}
		DRV_LOG(WARNING, "non-netvsc device was probed as netvsc");
	}
error:
	++vdev_netvsc_ctx_inst;
ignore:
	rte_kvargs_free(kvargs);
	/* Reset alarm if there are device context created */
	if (vdev_netvsc_ctx_count) {
		ret = rte_eal_alarm_set(VDEV_NETVSC_PROBE_MS * 1000,
					vdev_netvsc_alarm, NULL);
		if (ret < 0)
			DRV_LOG(ERR, "unable to schedule alarm callback: %s",
				rte_strerror(-ret));
	}
	return 0;
}

/**
 * Remove driver instance.
 *
 * The alarm callback and underlying vdev_netvsc context instances are only
 * destroyed after the last PMD instance is removed.
 *
 * @param dev
 *   Virtual device context for driver instance.
 *
 * @return
 *   Always 0.
 */
static int
vdev_netvsc_vdev_remove(__rte_unused struct rte_vdev_device *dev)
{
	if (--vdev_netvsc_ctx_inst)
		return 0;
	rte_eal_alarm_cancel(vdev_netvsc_alarm, NULL);
	while (!LIST_EMPTY(&vdev_netvsc_ctx_list)) {
		struct vdev_netvsc_ctx *ctx = LIST_FIRST(&vdev_netvsc_ctx_list);

		LIST_REMOVE(ctx, entry);
		--vdev_netvsc_ctx_count;
		vdev_netvsc_ctx_destroy(ctx);
	}
	return 0;
}

/** Virtual device descriptor. */
static struct rte_vdev_driver vdev_netvsc_vdev = {
	.probe = vdev_netvsc_vdev_probe,
	.remove = vdev_netvsc_vdev_remove,
};

RTE_PMD_REGISTER_VDEV(VDEV_NETVSC_DRIVER, vdev_netvsc_vdev);
RTE_PMD_REGISTER_ALIAS(VDEV_NETVSC_DRIVER, eth_vdev_netvsc);
RTE_PMD_REGISTER_PARAM_STRING(net_vdev_netvsc,
			      VDEV_NETVSC_ARG_IFACE "=<string> "
			      VDEV_NETVSC_ARG_MAC "=<string> "
			      VDEV_NETVSC_ARG_FORCE "=<int> "
			      VDEV_NETVSC_ARG_IGNORE "=<int>");

/** Compare function for vdev find device operation. */
static int
vdev_netvsc_cmp_rte_device(const struct rte_device *dev1,
			   __rte_unused const void *_dev2)
{
	return strncmp(dev1->devargs->name, VDEV_NETVSC_DRIVER_NAME,
		       VDEV_NETVSC_DRIVER_NAME_LEN);
}

/**
 * A callback called by vdev bus scan function to ensure this driver probing
 * automatically in Hyper-V VM system unless it already exists in the
 * devargs list.
 */
static void
vdev_netvsc_scan_callback(__rte_unused void *arg)
{
	struct rte_device *dev;
	struct rte_devargs *devargs;
	struct rte_bus *vbus = rte_bus_find_by_name("vdev");

	RTE_EAL_DEVARGS_FOREACH("vdev", devargs)
		if (!strncmp(devargs->name, VDEV_NETVSC_DRIVER_NAME,
			     VDEV_NETVSC_DRIVER_NAME_LEN))
			return;

	dev = vbus->find_device(NULL, vdev_netvsc_cmp_rte_device,
				VDEV_NETVSC_DRIVER_NAME);
	if (dev)
		return;
	if (rte_devargs_add(RTE_DEVTYPE_VIRTUAL, VDEV_NETVSC_DRIVER_NAME))
		DRV_LOG(ERR, "unable to add netvsc devargs.");
}

/** Initialize the custom scan. */
RTE_INIT(vdev_netvsc_custom_scan_add)
{
	if (rte_hypervisor_get() == RTE_HYPERVISOR_HYPERV)
		rte_vdev_add_custom_scan(vdev_netvsc_scan_callback, NULL);
}