net/vmnet-common.m - qemu - Git at Google

 /*
  * vmnet-common.m - network client wrapper for Apple vmnet.framework
  *
  * Copyright(c) 2022 Vladislav Yaroshchuk <vladislav.yaroshchuk@jetbrains.com>
  * Copyright(c) 2021 Phillip Tennen <phillip@axleos.com>
  *
  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  * See the COPYING file in the top-level directory.
  *
  */

 #include "qemu/osdep.h"
 #include "qemu/main-loop.h"
 #include "qemu/log.h"
 #include "qapi/qapi-types-net.h"
 #include "vmnet_int.h"
 #include "clients.h"
 #include "qemu/error-report.h"
 #include "qapi/error.h"
 #include "sysemu/runstate.h"

 #include <vmnet/vmnet.h>
 #include <dispatch/dispatch.h>


 static void vmnet_send_completed(NetClientState *nc, ssize_t len);


 const char *vmnet_status_map_str(vmnet_return_t status)
 {
     switch (status) {
     case VMNET_SUCCESS:
         return "success";
     case VMNET_FAILURE:
         return "general failure (possibly not enough privileges)";
     case VMNET_MEM_FAILURE:
         return "memory allocation failure";
     case VMNET_INVALID_ARGUMENT:
         return "invalid argument specified";
     case VMNET_SETUP_INCOMPLETE:
         return "interface setup is not complete";
     case VMNET_INVALID_ACCESS:
         return "invalid access, permission denied";
     case VMNET_PACKET_TOO_BIG:
         return "packet size is larger than MTU";
     case VMNET_BUFFER_EXHAUSTED:
         return "buffers exhausted in kernel";
     case VMNET_TOO_MANY_PACKETS:
         return "packet count exceeds limit";
 #if defined(MAC_OS_VERSION_11_0) && \
     MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_VERSION_11_0
     case VMNET_SHARING_SERVICE_BUSY:
         return "conflict, sharing service is in use";
 #endif
     default:
         return "unknown vmnet error";
     }
 }


 /**
  * Write packets from QEMU to vmnet interface.
  *
  * vmnet.framework supports iov, but writing more than
  * one iov into vmnet interface fails with
  * 'VMNET_INVALID_ARGUMENT'. Collecting provided iovs into
  * one and passing it to vmnet works fine. That's the
  * reason why receive_iov() left unimplemented. But it still
  * works with good performance having .receive() only.
  */
 ssize_t vmnet_receive_common(NetClientState *nc,
                              const uint8_t *buf,
                              size_t size)
 {
     VmnetState *s = DO_UPCAST(VmnetState, nc, nc);
     struct vmpktdesc packet;
     struct iovec iov;
     int pkt_cnt;
     vmnet_return_t if_status;

     if (size > s->max_packet_size) {
         warn_report("vmnet: packet is too big, %zu > %" PRIu64,
             packet.vm_pkt_size,
             s->max_packet_size);
         return -1;
     }

     iov.iov_base = (char *) buf;
     iov.iov_len = size;

     packet.vm_pkt_iovcnt = 1;
     packet.vm_flags = 0;
     packet.vm_pkt_size = size;
     packet.vm_pkt_iov = &iov;
     pkt_cnt = 1;

     if_status = vmnet_write(s->vmnet_if, &packet, &pkt_cnt);
     if (if_status != VMNET_SUCCESS) {
         error_report("vmnet: write error: %s\n",
                      vmnet_status_map_str(if_status));
         return -1;
     }

     if (pkt_cnt) {
         return size;
     }
     return 0;
 }


 /**
  * Read packets from vmnet interface and write them
  * to temporary buffers in VmnetState.
  *
  * Returns read packets number (may be 0) on success,
  * -1 on error
  */
 static int vmnet_read_packets(VmnetState *s)
 {
     assert(s->packets_send_current_pos == s->packets_send_end_pos);

     struct vmpktdesc *packets = s->packets_buf;
     vmnet_return_t status;
     int i;

     /* Read as many packets as present */
     s->packets_send_current_pos = 0;
     s->packets_send_end_pos = VMNET_PACKETS_LIMIT;
     for (i = 0; i < s->packets_send_end_pos; ++i) {
         packets[i].vm_pkt_size = s->max_packet_size;
         packets[i].vm_pkt_iovcnt = 1;
         packets[i].vm_flags = 0;
     }

     status = vmnet_read(s->vmnet_if, packets, &s->packets_send_end_pos);
     if (status != VMNET_SUCCESS) {
         error_printf("vmnet: read failed: %s\n",
                      vmnet_status_map_str(status));
         s->packets_send_current_pos = 0;
         s->packets_send_end_pos = 0;
         return -1;
     }
     return s->packets_send_end_pos;
 }


 /**
  * Write packets from temporary buffers in VmnetState
  * to QEMU.
  */
 static void vmnet_write_packets_to_qemu(VmnetState *s)
 {
     while (s->packets_send_current_pos < s->packets_send_end_pos) {
         ssize_t size = qemu_send_packet_async(&s->nc,
                                       s->iov_buf[s->packets_send_current_pos].iov_base,
                                       s->packets_buf[s->packets_send_current_pos].vm_pkt_size,
                                       vmnet_send_completed);

         if (size == 0) {
             /* QEMU is not ready to consume more packets -
              * stop and wait for completion callback call */
             return;
         }
         ++s->packets_send_current_pos;
     }
 }


 /**
  * Bottom half callback that transfers packets from vmnet interface
  * to QEMU.
  *
  * The process of transferring packets is three-staged:
  * 1. Handle vmnet event;
  * 2. Read packets from vmnet interface into temporary buffer;
  * 3. Write packets from temporary buffer to QEMU.
  *
  * QEMU may suspend this process on the last stage, returning 0 from
  * qemu_send_packet_async function. If this happens, we should
  * respectfully wait until it is ready to consume more packets,
  * write left ones in temporary buffer and only after this
  * continue reading more packets from vmnet interface.
  *
  * Packets to be transferred are stored into packets_buf,
  * in the window [packets_send_current_pos..packets_send_end_pos)
  * including current_pos, excluding end_pos.
  *
  * Thus, if QEMU is not ready, buffer is not read and
  * packets_send_current_pos < packets_send_end_pos.
  */
 static void vmnet_send_bh(void *opaque)
 {
     NetClientState *nc = (NetClientState *) opaque;
     VmnetState *s = DO_UPCAST(VmnetState, nc, nc);

     /*
      * Do nothing if QEMU is not ready - wait
      * for completion callback invocation
      */
     if (s->packets_send_current_pos < s->packets_send_end_pos) {
         return;
     }

     /* Read packets from vmnet interface */
     if (vmnet_read_packets(s) > 0) {
         /* Send them to QEMU */
         vmnet_write_packets_to_qemu(s);
     }
 }


 /**
  * Completion callback to be invoked by QEMU when it becomes
  * ready to consume more packets.
  */
 static void vmnet_send_completed(NetClientState *nc, ssize_t len)
 {
     VmnetState *s = DO_UPCAST(VmnetState, nc, nc);

     /* Callback is invoked eq queued packet is sent */
     ++s->packets_send_current_pos;

     /* Complete sending packets left in VmnetState buffers */
     vmnet_write_packets_to_qemu(s);

     /* And read new ones from vmnet if VmnetState buffer is ready */
     if (s->packets_send_current_pos < s->packets_send_end_pos) {
         qemu_bh_schedule(s->send_bh);
     }
 }


 static void vmnet_bufs_init(VmnetState *s)
 {
     struct vmpktdesc *packets = s->packets_buf;
     struct iovec *iov = s->iov_buf;
     int i;

     for (i = 0; i < VMNET_PACKETS_LIMIT; ++i) {
         iov[i].iov_len = s->max_packet_size;
         iov[i].iov_base = g_malloc0(iov[i].iov_len);
         packets[i].vm_pkt_iov = iov + i;
     }
 }

 /**
  * Called on state change to un-register/re-register handlers
  */
 static void vmnet_vm_state_change_cb(void *opaque, bool running, RunState state)
 {
     VmnetState *s = opaque;

     if (running) {
         vmnet_interface_set_event_callback(
             s->vmnet_if,
             VMNET_INTERFACE_PACKETS_AVAILABLE,
             s->if_queue,
             ^(interface_event_t event_id, xpc_object_t event) {
                 assert(event_id == VMNET_INTERFACE_PACKETS_AVAILABLE);
                 /*
                  * This function is being called from a non qemu thread, so
                  * we only schedule a BH, and do the rest of the io completion
                  * handling from vmnet_send_bh() which runs in a qemu context.
                  */
                 qemu_bh_schedule(s->send_bh);
             });
     } else {
         vmnet_interface_set_event_callback(
             s->vmnet_if,
             VMNET_INTERFACE_PACKETS_AVAILABLE,
             NULL,
             NULL);
     }
 }

 int vmnet_if_create(NetClientState *nc,
                     xpc_object_t if_desc,
                     Error **errp)
 {
     VmnetState *s = DO_UPCAST(VmnetState, nc, nc);
     dispatch_semaphore_t if_created_sem = dispatch_semaphore_create(0);
     __block vmnet_return_t if_status;

     s->if_queue = dispatch_queue_create(
         "org.qemu.vmnet.if_queue",
         DISPATCH_QUEUE_SERIAL
     );

     xpc_dictionary_set_bool(
         if_desc,
         vmnet_allocate_mac_address_key,
         false
     );

 #ifdef DEBUG
     qemu_log("vmnet.start.interface_desc:\n");
     xpc_dictionary_apply(if_desc,
                          ^bool(const char *k, xpc_object_t v) {
                              char *desc = xpc_copy_description(v);
                              qemu_log("  %s=%s\n", k, desc);
                              free(desc);
                              return true;
                          });
 #endif /* DEBUG */

     s->vmnet_if = vmnet_start_interface(
         if_desc,
         s->if_queue,
         ^(vmnet_return_t status, xpc_object_t interface_param) {
             if_status = status;
             if (status != VMNET_SUCCESS || !interface_param) {
                 dispatch_semaphore_signal(if_created_sem);
                 return;
             }

 #ifdef DEBUG
             qemu_log("vmnet.start.interface_param:\n");
             xpc_dictionary_apply(interface_param,
                                  ^bool(const char *k, xpc_object_t v) {
                                      char *desc = xpc_copy_description(v);
                                      qemu_log("  %s=%s\n", k, desc);
                                      free(desc);
                                      return true;
                                  });
 #endif /* DEBUG */

             s->mtu = xpc_dictionary_get_uint64(
                 interface_param,
                 vmnet_mtu_key);
             s->max_packet_size = xpc_dictionary_get_uint64(
                 interface_param,
                 vmnet_max_packet_size_key);

             dispatch_semaphore_signal(if_created_sem);
         });

     if (s->vmnet_if == NULL) {
         dispatch_release(s->if_queue);
         dispatch_release(if_created_sem);
         error_setg(errp,
                    "unable to create interface with requested params");
         return -1;
     }

     dispatch_semaphore_wait(if_created_sem, DISPATCH_TIME_FOREVER);
     dispatch_release(if_created_sem);

     if (if_status != VMNET_SUCCESS) {
         dispatch_release(s->if_queue);
         error_setg(errp,
                    "cannot create vmnet interface: %s",
                    vmnet_status_map_str(if_status));
         return -1;
     }

     s->send_bh = aio_bh_new(qemu_get_aio_context(), vmnet_send_bh, nc);
     vmnet_bufs_init(s);

     s->packets_send_current_pos = 0;
     s->packets_send_end_pos = 0;

     vmnet_vm_state_change_cb(s, 1, RUN_STATE_RUNNING);

     s->change = qemu_add_vm_change_state_handler(vmnet_vm_state_change_cb, s);

     return 0;
 }


 void vmnet_cleanup_common(NetClientState *nc)
 {
     VmnetState *s = DO_UPCAST(VmnetState, nc, nc);
     dispatch_semaphore_t if_stopped_sem;

     if (s->vmnet_if == NULL) {
         return;
     }

     vmnet_vm_state_change_cb(s, 0, RUN_STATE_SHUTDOWN);
     qemu_del_vm_change_state_handler(s->change);
     if_stopped_sem = dispatch_semaphore_create(0);
     vmnet_stop_interface(
         s->vmnet_if,
         s->if_queue,
         ^(vmnet_return_t status) {
             assert(status == VMNET_SUCCESS);
             dispatch_semaphore_signal(if_stopped_sem);
         });
     dispatch_semaphore_wait(if_stopped_sem, DISPATCH_TIME_FOREVER);

     qemu_purge_queued_packets(nc);

     qemu_bh_delete(s->send_bh);
     dispatch_release(if_stopped_sem);
     dispatch_release(s->if_queue);

     for (int i = 0; i < VMNET_PACKETS_LIMIT; ++i) {
         g_free(s->iov_buf[i].iov_base);
     }
 }
	/*
	* vmnet-common.m - network client wrapper for Apple vmnet.framework
	*
	* Copyright(c) 2022 Vladislav Yaroshchuk <vladislav.yaroshchuk@jetbrains.com>
	* Copyright(c) 2021 Phillip Tennen <phillip@axleos.com>
	*
	* This work is licensed under the terms of the GNU GPL, version 2 or later.
	* See the COPYING file in the top-level directory.
	*
	*/

	#include "qemu/osdep.h"
	#include "qemu/main-loop.h"
	#include "qemu/log.h"
	#include "qapi/qapi-types-net.h"
	#include "vmnet_int.h"
	#include "clients.h"
	#include "qemu/error-report.h"
	#include "qapi/error.h"
	#include "sysemu/runstate.h"

	#include <vmnet/vmnet.h>
	#include <dispatch/dispatch.h>


	static void vmnet_send_completed(NetClientState *nc, ssize_t len);


	const char *vmnet_status_map_str(vmnet_return_t status)
	{
	switch (status) {
	case VMNET_SUCCESS:
	return "success";
	case VMNET_FAILURE:
	return "general failure (possibly not enough privileges)";
	case VMNET_MEM_FAILURE:
	return "memory allocation failure";
	case VMNET_INVALID_ARGUMENT:
	return "invalid argument specified";
	case VMNET_SETUP_INCOMPLETE:
	return "interface setup is not complete";
	case VMNET_INVALID_ACCESS:
	return "invalid access, permission denied";
	case VMNET_PACKET_TOO_BIG:
	return "packet size is larger than MTU";
	case VMNET_BUFFER_EXHAUSTED:
	return "buffers exhausted in kernel";
	case VMNET_TOO_MANY_PACKETS:
	return "packet count exceeds limit";
	#if defined(MAC_OS_VERSION_11_0) && \
	MAC_OS_X_VERSION_MIN_REQUIRED >= MAC_OS_VERSION_11_0
	case VMNET_SHARING_SERVICE_BUSY:
	return "conflict, sharing service is in use";
	#endif
	default:
	return "unknown vmnet error";
	}
	}


	/**
	* Write packets from QEMU to vmnet interface.
	*
	* vmnet.framework supports iov, but writing more than
	* one iov into vmnet interface fails with
	* 'VMNET_INVALID_ARGUMENT'. Collecting provided iovs into
	* one and passing it to vmnet works fine. That's the
	* reason why receive_iov() left unimplemented. But it still
	* works with good performance having .receive() only.
	*/
	ssize_t vmnet_receive_common(NetClientState *nc,
	const uint8_t *buf,
	size_t size)
	{
	VmnetState *s = DO_UPCAST(VmnetState, nc, nc);
	struct vmpktdesc packet;
	struct iovec iov;
	int pkt_cnt;
	vmnet_return_t if_status;

	if (size > s->max_packet_size) {
	warn_report("vmnet: packet is too big, %zu > %" PRIu64,
	packet.vm_pkt_size,
	s->max_packet_size);
	return -1;
	}

	iov.iov_base = (char *) buf;
	iov.iov_len = size;

	packet.vm_pkt_iovcnt = 1;
	packet.vm_flags = 0;
	packet.vm_pkt_size = size;
	packet.vm_pkt_iov = &iov;
	pkt_cnt = 1;

	if_status = vmnet_write(s->vmnet_if, &packet, &pkt_cnt);
	if (if_status != VMNET_SUCCESS) {
	error_report("vmnet: write error: %s\n",
	vmnet_status_map_str(if_status));
	return -1;
	}

	if (pkt_cnt) {
	return size;
	}
	return 0;
	}


	/**
	* Read packets from vmnet interface and write them
	* to temporary buffers in VmnetState.
	*
	* Returns read packets number (may be 0) on success,
	* -1 on error
	*/
	static int vmnet_read_packets(VmnetState *s)
	{
	assert(s->packets_send_current_pos == s->packets_send_end_pos);

	struct vmpktdesc *packets = s->packets_buf;
	vmnet_return_t status;
	int i;

	/* Read as many packets as present */
	s->packets_send_current_pos = 0;
	s->packets_send_end_pos = VMNET_PACKETS_LIMIT;
	for (i = 0; i < s->packets_send_end_pos; ++i) {
	packets[i].vm_pkt_size = s->max_packet_size;
	packets[i].vm_pkt_iovcnt = 1;
	packets[i].vm_flags = 0;
	}

	status = vmnet_read(s->vmnet_if, packets, &s->packets_send_end_pos);
	if (status != VMNET_SUCCESS) {
	error_printf("vmnet: read failed: %s\n",
	vmnet_status_map_str(status));
	s->packets_send_current_pos = 0;
	s->packets_send_end_pos = 0;
	return -1;
	}
	return s->packets_send_end_pos;
	}


	/**
	* Write packets from temporary buffers in VmnetState
	* to QEMU.
	*/
	static void vmnet_write_packets_to_qemu(VmnetState *s)
	{
	while (s->packets_send_current_pos < s->packets_send_end_pos) {
	ssize_t size = qemu_send_packet_async(&s->nc,
	s->iov_buf[s->packets_send_current_pos].iov_base,
	s->packets_buf[s->packets_send_current_pos].vm_pkt_size,
	vmnet_send_completed);

	if (size == 0) {
	/* QEMU is not ready to consume more packets -
	* stop and wait for completion callback call */
	return;
	}
	++s->packets_send_current_pos;
	}
	}


	/**
	* Bottom half callback that transfers packets from vmnet interface
	* to QEMU.
	*
	* The process of transferring packets is three-staged:
	* 1. Handle vmnet event;
	* 2. Read packets from vmnet interface into temporary buffer;
	* 3. Write packets from temporary buffer to QEMU.
	*
	* QEMU may suspend this process on the last stage, returning 0 from
	* qemu_send_packet_async function. If this happens, we should
	* respectfully wait until it is ready to consume more packets,
	* write left ones in temporary buffer and only after this
	* continue reading more packets from vmnet interface.
	*
	* Packets to be transferred are stored into packets_buf,
	* in the window [packets_send_current_pos..packets_send_end_pos)
	* including current_pos, excluding end_pos.
	*
	* Thus, if QEMU is not ready, buffer is not read and
	* packets_send_current_pos < packets_send_end_pos.
	*/
	static void vmnet_send_bh(void *opaque)
	{
	NetClientState nc = (NetClientState ) opaque;
	VmnetState *s = DO_UPCAST(VmnetState, nc, nc);

	/*
	* Do nothing if QEMU is not ready - wait
	* for completion callback invocation
	*/
	if (s->packets_send_current_pos < s->packets_send_end_pos) {
	return;
	}

	/* Read packets from vmnet interface */
	if (vmnet_read_packets(s) > 0) {
	/* Send them to QEMU */
	vmnet_write_packets_to_qemu(s);
	}
	}


	/**
	* Completion callback to be invoked by QEMU when it becomes
	* ready to consume more packets.
	*/
	static void vmnet_send_completed(NetClientState *nc, ssize_t len)
	{
	VmnetState *s = DO_UPCAST(VmnetState, nc, nc);

	/* Callback is invoked eq queued packet is sent */
	++s->packets_send_current_pos;

	/* Complete sending packets left in VmnetState buffers */
	vmnet_write_packets_to_qemu(s);

	/* And read new ones from vmnet if VmnetState buffer is ready */
	if (s->packets_send_current_pos < s->packets_send_end_pos) {
	qemu_bh_schedule(s->send_bh);
	}
	}


	static void vmnet_bufs_init(VmnetState *s)
	{
	struct vmpktdesc *packets = s->packets_buf;
	struct iovec *iov = s->iov_buf;
	int i;

	for (i = 0; i < VMNET_PACKETS_LIMIT; ++i) {
	iov[i].iov_len = s->max_packet_size;
	iov[i].iov_base = g_malloc0(iov[i].iov_len);
	packets[i].vm_pkt_iov = iov + i;
	}
	}

	/**
	* Called on state change to un-register/re-register handlers
	*/
	static void vmnet_vm_state_change_cb(void *opaque, bool running, RunState state)
	{
	VmnetState *s = opaque;

	if (running) {
	vmnet_interface_set_event_callback(
	s->vmnet_if,
	VMNET_INTERFACE_PACKETS_AVAILABLE,
	s->if_queue,
	^(interface_event_t event_id, xpc_object_t event) {
	assert(event_id == VMNET_INTERFACE_PACKETS_AVAILABLE);
	/*
	* This function is being called from a non qemu thread, so
	* we only schedule a BH, and do the rest of the io completion
	* handling from vmnet_send_bh() which runs in a qemu context.
	*/
	qemu_bh_schedule(s->send_bh);
	});
	} else {
	vmnet_interface_set_event_callback(
	s->vmnet_if,
	VMNET_INTERFACE_PACKETS_AVAILABLE,
	NULL,
	NULL);
	}
	}

	int vmnet_if_create(NetClientState *nc,
	xpc_object_t if_desc,
	Error **errp)
	{
	VmnetState *s = DO_UPCAST(VmnetState, nc, nc);
	dispatch_semaphore_t if_created_sem = dispatch_semaphore_create(0);
	__block vmnet_return_t if_status;

	s->if_queue = dispatch_queue_create(
	"org.qemu.vmnet.if_queue",
	DISPATCH_QUEUE_SERIAL
	);

	xpc_dictionary_set_bool(
	if_desc,
	vmnet_allocate_mac_address_key,
	false
	);

	#ifdef DEBUG
	qemu_log("vmnet.start.interface_desc:\n");
	xpc_dictionary_apply(if_desc,
	^bool(const char *k, xpc_object_t v) {
	char *desc = xpc_copy_description(v);
	qemu_log(" %s=%s\n", k, desc);
	free(desc);
	return true;
	});
	#endif /* DEBUG */

	s->vmnet_if = vmnet_start_interface(
	if_desc,
	s->if_queue,
	^(vmnet_return_t status, xpc_object_t interface_param) {
	if_status = status;
	if (status != VMNET_SUCCESS \|\| !interface_param) {
	dispatch_semaphore_signal(if_created_sem);
	return;
	}

	#ifdef DEBUG
	qemu_log("vmnet.start.interface_param:\n");
	xpc_dictionary_apply(interface_param,
	^bool(const char *k, xpc_object_t v) {
	char *desc = xpc_copy_description(v);
	qemu_log(" %s=%s\n", k, desc);
	free(desc);
	return true;
	});
	#endif /* DEBUG */

	s->mtu = xpc_dictionary_get_uint64(
	interface_param,
	vmnet_mtu_key);
	s->max_packet_size = xpc_dictionary_get_uint64(
	interface_param,
	vmnet_max_packet_size_key);

	dispatch_semaphore_signal(if_created_sem);
	});

	if (s->vmnet_if == NULL) {
	dispatch_release(s->if_queue);
	dispatch_release(if_created_sem);
	error_setg(errp,
	"unable to create interface with requested params");
	return -1;
	}

	dispatch_semaphore_wait(if_created_sem, DISPATCH_TIME_FOREVER);
	dispatch_release(if_created_sem);

	if (if_status != VMNET_SUCCESS) {
	dispatch_release(s->if_queue);
	error_setg(errp,
	"cannot create vmnet interface: %s",
	vmnet_status_map_str(if_status));
	return -1;
	}

	s->send_bh = aio_bh_new(qemu_get_aio_context(), vmnet_send_bh, nc);
	vmnet_bufs_init(s);

	s->packets_send_current_pos = 0;
	s->packets_send_end_pos = 0;

	vmnet_vm_state_change_cb(s, 1, RUN_STATE_RUNNING);

	s->change = qemu_add_vm_change_state_handler(vmnet_vm_state_change_cb, s);

	return 0;
	}


	void vmnet_cleanup_common(NetClientState *nc)
	{
	VmnetState *s = DO_UPCAST(VmnetState, nc, nc);
	dispatch_semaphore_t if_stopped_sem;

	if (s->vmnet_if == NULL) {
	return;
	}

	vmnet_vm_state_change_cb(s, 0, RUN_STATE_SHUTDOWN);
	qemu_del_vm_change_state_handler(s->change);
	if_stopped_sem = dispatch_semaphore_create(0);
	vmnet_stop_interface(
	s->vmnet_if,
	s->if_queue,
	^(vmnet_return_t status) {
	assert(status == VMNET_SUCCESS);
	dispatch_semaphore_signal(if_stopped_sem);
	});
	dispatch_semaphore_wait(if_stopped_sem, DISPATCH_TIME_FOREVER);

	qemu_purge_queued_packets(nc);

	qemu_bh_delete(s->send_bh);
	dispatch_release(if_stopped_sem);
	dispatch_release(s->if_queue);

	for (int i = 0; i < VMNET_PACKETS_LIMIT; ++i) {
	g_free(s->iov_buf[i].iov_base);
	}
	}