[PATCH 19/24] vhost-user: introduce vhost-user API

[Laurent Vivier <lvivier@redhat.com>]

Add vhost_user.c and vhost_user.h that define the functions needed
to implement vhost-user backend.

Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
 Makefile     |    4 +-
 passt.c      |    2 +
 passt.h      |    8 +
 tap.c        |    2 +-
 tap.h        |    3 +
 vhost_user.c | 1050 ++++++++++++++++++++++++++++++++++++++++++++++++++
 vhost_user.h |  139 +++++++
 7 files changed, 1205 insertions(+), 3 deletions(-)
 create mode 100644 vhost_user.c
 create mode 100644 vhost_user.h

diff --git a/Makefile b/Makefile
index ae1daa6b2b50..2016b071ddf2 100644
--- a/Makefile
+++ b/Makefile
@@ -47,7 +47,7 @@ FLAGS += -DDUAL_STACK_SOCKETS=$(DUAL_STACK_SOCKETS)
 PASST_SRCS = arch.c arp.c checksum.c conf.c dhcp.c dhcpv6.c flow.c icmp.c \
 	igmp.c isolation.c lineread.c log.c mld.c ndp.c netlink.c packet.c \
 	passt.c pasta.c pcap.c pif.c port_fwd.c tap.c tcp.c tcp_splice.c \
-	tcp_buf.c udp.c util.c iov.c ip.c virtio.c
+	tcp_buf.c udp.c util.c iov.c ip.c virtio.c vhost_user.c
 QRAP_SRCS = qrap.c
 SRCS = $(PASST_SRCS) $(QRAP_SRCS)
 
@@ -57,7 +57,7 @@ PASST_HEADERS = arch.h arp.h checksum.h conf.h dhcp.h dhcpv6.h flow.h \
 	flow_table.h icmp.h inany.h isolation.h lineread.h log.h ndp.h \
 	netlink.h packet.h passt.h pasta.h pcap.h pif.h port_fwd.h siphash.h \
 	tap.h tcp.h tcp_conn.h tcp_splice.h tcp_buf.h tcp_internal.h udp.h \
-	util.h iov.h ip.h virtio.h
+	util.h iov.h ip.h virtio.h vhost_user.h
 HEADERS = $(PASST_HEADERS) seccomp.h
 
 C := \#include <linux/tcp.h>\nstruct tcp_info x = { .tcpi_snd_wnd = 0 };
diff --git a/passt.c b/passt.c
index 5056a49dec95..95034d73381f 100644
--- a/passt.c
+++ b/passt.c
@@ -72,6 +72,8 @@ char *epoll_type_str[] = {
 	[EPOLL_TYPE_TAP_PASTA]	= "/dev/net/tun device",
 	[EPOLL_TYPE_TAP_PASST]	= "connected qemu socket",
 	[EPOLL_TYPE_TAP_LISTEN]	= "listening qemu socket",
+	[EPOLL_TYPE_VHOST_CMD]	= "vhost-user command socket",
+	[EPOLL_TYPE_VHOST_KICK]	= "vhost-user kick socket",
 };
 static_assert(ARRAY_SIZE(epoll_type_str) == EPOLL_NUM_TYPES,
 	      "epoll_type_str[] doesn't match enum epoll_type");
diff --git a/passt.h b/passt.h
index a9e8f15af0e1..6ed1d0b19e82 100644
--- a/passt.h
+++ b/passt.h
@@ -42,6 +42,7 @@ union epoll_ref;
 #include "port_fwd.h"
 #include "tcp.h"
 #include "udp.h"
+#include "vhost_user.h"
 
 /**
  * enum epoll_type - Different types of fds we poll over
@@ -71,6 +72,10 @@ enum epoll_type {
 	EPOLL_TYPE_TAP_PASST,
 	/* socket listening for qemu socket connections */
 	EPOLL_TYPE_TAP_LISTEN,
+	/* vhost-user command socket */
+	EPOLL_TYPE_VHOST_CMD,
+	/* vhost-user kick event socket */
+	EPOLL_TYPE_VHOST_KICK,
 
 	EPOLL_NUM_TYPES,
 };
@@ -303,6 +308,9 @@ struct ctx {
 
 	int low_wmem;
 	int low_rmem;
+
+	/* vhost-user */
+	struct VuDev vdev;
 };
 
 void proto_update_l2_buf(const unsigned char *eth_d,
diff --git a/tap.c b/tap.c
index ebe52247ad87..936206e53637 100644
--- a/tap.c
+++ b/tap.c
@@ -954,7 +954,7 @@ void packet_add_all_do(struct ctx *c, ssize_t len, char *p,
  * tap_sock_reset() - Handle closing or failure of connect AF_UNIX socket
  * @c:		Execution context
  */
-static void tap_sock_reset(struct ctx *c)
+void tap_sock_reset(struct ctx *c)
 {
 	if (c->one_off) {
 		info("Client closed connection, exiting");
diff --git a/tap.h b/tap.h
index 7157ef37ee6e..ee839d4f09dc 100644
--- a/tap.h
+++ b/tap.h
@@ -81,12 +81,15 @@ void tap_handler_pasta(struct ctx *c, uint32_t events,
 		       const struct timespec *now);
 void tap_handler_passt(struct ctx *c, uint32_t events,
 		       const struct timespec *now);
+void tap_sock_reset(struct ctx *c);
 void tap_sock_init(struct ctx *c);
 void pool_flush_all(void);
 void tap_handler_all(struct ctx *c, const struct timespec *now);
 
 void packet_add_do(struct pool *p, size_t len, const char *start,
 		   const char *func, int line);
+void packet_add_all_do(struct ctx *c, ssize_t len, char *p,
+		       const char *func, int line);
 #define packet_add_all(p, len, start)					\
 	packet_add_all_do(p, len, start, __func__, __LINE__)
 
diff --git a/vhost_user.c b/vhost_user.c
new file mode 100644
index 000000000000..2acd72398e3a
--- /dev/null
+++ b/vhost_user.c
@@ -0,0 +1,1050 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/* some parts from QEMU subprojects/libvhost-user/libvhost-user.c */
+
+#include <errno.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stddef.h>
+#include <string.h>
+#include <assert.h>
+#include <stdbool.h>
+#include <inttypes.h>
+#include <time.h>
+#include <net/ethernet.h>
+#include <netinet/in.h>
+#include <sys/epoll.h>
+#include <sys/eventfd.h>
+#include <sys/mman.h>
+#include <linux/vhost_types.h>
+#include <linux/virtio_net.h>
+
+#include "util.h"
+#include "passt.h"
+#include "tap.h"
+#include "vhost_user.h"
+
+#define VHOST_USER_VERSION 1
+
+static unsigned char buffer[65536][VHOST_USER_MAX_QUEUES];
+
+void vu_print_capabilities(void)
+{
+	printf("{\n");
+	printf("  \"type\": \"net\"\n");
+	printf("}\n");
+	exit(EXIT_SUCCESS);
+}
+
+static const char *
+vu_request_to_string(unsigned int req)
+{
+#define REQ(req) [req] = #req
+	static const char *vu_request_str[] = {
+		REQ(VHOST_USER_NONE),
+		REQ(VHOST_USER_GET_FEATURES),
+		REQ(VHOST_USER_SET_FEATURES),
+		REQ(VHOST_USER_SET_OWNER),
+		REQ(VHOST_USER_RESET_OWNER),
+		REQ(VHOST_USER_SET_MEM_TABLE),
+		REQ(VHOST_USER_SET_LOG_BASE),
+		REQ(VHOST_USER_SET_LOG_FD),
+		REQ(VHOST_USER_SET_VRING_NUM),
+		REQ(VHOST_USER_SET_VRING_ADDR),
+		REQ(VHOST_USER_SET_VRING_BASE),
+		REQ(VHOST_USER_GET_VRING_BASE),
+		REQ(VHOST_USER_SET_VRING_KICK),
+		REQ(VHOST_USER_SET_VRING_CALL),
+		REQ(VHOST_USER_SET_VRING_ERR),
+		REQ(VHOST_USER_GET_PROTOCOL_FEATURES),
+		REQ(VHOST_USER_SET_PROTOCOL_FEATURES),
+		REQ(VHOST_USER_GET_QUEUE_NUM),
+		REQ(VHOST_USER_SET_VRING_ENABLE),
+		REQ(VHOST_USER_SEND_RARP),
+		REQ(VHOST_USER_NET_SET_MTU),
+		REQ(VHOST_USER_SET_BACKEND_REQ_FD),
+		REQ(VHOST_USER_IOTLB_MSG),
+		REQ(VHOST_USER_SET_VRING_ENDIAN),
+		REQ(VHOST_USER_GET_CONFIG),
+		REQ(VHOST_USER_SET_CONFIG),
+		REQ(VHOST_USER_POSTCOPY_ADVISE),
+		REQ(VHOST_USER_POSTCOPY_LISTEN),
+		REQ(VHOST_USER_POSTCOPY_END),
+		REQ(VHOST_USER_GET_INFLIGHT_FD),
+		REQ(VHOST_USER_SET_INFLIGHT_FD),
+		REQ(VHOST_USER_GPU_SET_SOCKET),
+		REQ(VHOST_USER_VRING_KICK),
+		REQ(VHOST_USER_GET_MAX_MEM_SLOTS),
+		REQ(VHOST_USER_ADD_MEM_REG),
+		REQ(VHOST_USER_REM_MEM_REG),
+		REQ(VHOST_USER_MAX),
+	};
+#undef REQ
+
+	if (req < VHOST_USER_MAX) {
+		return vu_request_str[req];
+	} else {
+		return "unknown";
+	}
+}
+
+/* Translate qemu virtual address to our virtual address.  */
+static void *qva_to_va(VuDev *dev, uint64_t qemu_addr)
+{
+	unsigned int i;
+
+	/* Find matching memory region.  */
+	for (i = 0; i < dev->nregions; i++) {
+		VuDevRegion *r = &dev->regions[i];
+
+		if ((qemu_addr >= r->qva) && (qemu_addr < (r->qva + r->size))) {
+			return (void *)(uintptr_t)
+			(qemu_addr - r->qva + r->mmap_addr + r->mmap_offset);
+		}
+	}
+
+	return NULL;
+}
+
+static void
+vmsg_close_fds(VhostUserMsg *vmsg)
+{
+	int i;
+
+	for (i = 0; i < vmsg->fd_num; i++)
+		close(vmsg->fds[i]);
+}
+
+static void vu_remove_watch(VuDev *vdev, int fd)
+{
+	struct ctx *c = (struct ctx *) ((char *)vdev - offsetof(struct ctx, vdev));
+
+	epoll_ctl(c->epollfd, EPOLL_CTL_DEL, fd, NULL);
+}
+
+/* Set reply payload.u64 and clear request flags and fd_num */
+static void vmsg_set_reply_u64(struct VhostUserMsg *vmsg, uint64_t val)
+{
+	vmsg->hdr.flags = 0; /* defaults will be set by vu_send_reply() */
+	vmsg->hdr.size = sizeof(vmsg->payload.u64);
+	vmsg->payload.u64 = val;
+	vmsg->fd_num = 0;
+}
+
+static ssize_t vu_message_read_default(VuDev *dev, int conn_fd, struct VhostUserMsg *vmsg)
+{
+	char control[CMSG_SPACE(VHOST_MEMORY_BASELINE_NREGIONS *
+		     sizeof(int))] = { 0 };
+	struct iovec iov = {
+		.iov_base = (char *)vmsg,
+		.iov_len = VHOST_USER_HDR_SIZE,
+	};
+	struct msghdr msg = {
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+		.msg_control = control,
+		.msg_controllen = sizeof(control),
+	};
+	size_t fd_size;
+	struct cmsghdr *cmsg;
+	ssize_t ret, sz_payload;
+
+	ret = recvmsg(conn_fd, &msg, MSG_DONTWAIT);
+	if (ret < 0) {
+		if (errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)
+			return 0;
+		vu_panic(dev, "Error while recvmsg: %s", strerror(errno));
+		goto out;
+	}
+
+	vmsg->fd_num = 0;
+	for (cmsg = CMSG_FIRSTHDR(&msg); cmsg != NULL;
+	     cmsg = CMSG_NXTHDR(&msg, cmsg)) {
+		if (cmsg->cmsg_level == SOL_SOCKET &&
+		    cmsg->cmsg_type == SCM_RIGHTS) {
+			fd_size = cmsg->cmsg_len - CMSG_LEN(0);
+			vmsg->fd_num = fd_size / sizeof(int);
+			memcpy(vmsg->fds, CMSG_DATA(cmsg), fd_size);
+			break;
+		}
+	}
+
+	sz_payload = vmsg->hdr.size;
+	if ((size_t)sz_payload > sizeof(vmsg->payload)) {
+		vu_panic(dev,
+			 "Error: too big message request: %d, size: vmsg->size: %zd, "
+			 "while sizeof(vmsg->payload) = %zu",
+			 vmsg->hdr.request, sz_payload, sizeof(vmsg->payload));
+		goto out;
+	}
+
+	if (sz_payload) {
+		do {
+			ret = recv(conn_fd, &vmsg->payload, sz_payload, 0);
+		} while (ret < 0 && (errno == EINTR || errno == EAGAIN));
+
+		if (ret < sz_payload) {
+			vu_panic(dev, "Error while reading: %s", strerror(errno));
+			goto out;
+		}
+	}
+
+	return 1;
+out:
+	vmsg_close_fds(vmsg);
+
+	return -ECONNRESET;
+}
+
+static int vu_message_write(VuDev *dev, int conn_fd, struct VhostUserMsg *vmsg)
+{
+	int rc;
+	uint8_t *p = (uint8_t *)vmsg;
+	char control[CMSG_SPACE(VHOST_MEMORY_BASELINE_NREGIONS * sizeof(int))] = { 0 };
+	struct iovec iov = {
+		.iov_base = (char *)vmsg,
+		.iov_len = VHOST_USER_HDR_SIZE,
+	};
+	struct msghdr msg = {
+		.msg_iov = &iov,
+		.msg_iovlen = 1,
+		.msg_control = control,
+	};
+	struct cmsghdr *cmsg;
+
+	memset(control, 0, sizeof(control));
+	assert(vmsg->fd_num <= VHOST_MEMORY_BASELINE_NREGIONS);
+	if (vmsg->fd_num > 0) {
+		size_t fdsize = vmsg->fd_num * sizeof(int);
+		msg.msg_controllen = CMSG_SPACE(fdsize);
+		cmsg = CMSG_FIRSTHDR(&msg);
+		cmsg->cmsg_len = CMSG_LEN(fdsize);
+		cmsg->cmsg_level = SOL_SOCKET;
+		cmsg->cmsg_type = SCM_RIGHTS;
+		memcpy(CMSG_DATA(cmsg), vmsg->fds, fdsize);
+	} else {
+		msg.msg_controllen = 0;
+	}
+
+	do {
+		rc = sendmsg(conn_fd, &msg, 0);
+	} while (rc < 0 && (errno == EINTR || errno == EAGAIN));
+
+	if (vmsg->hdr.size) {
+		do {
+			if (vmsg->data) {
+				rc = write(conn_fd, vmsg->data, vmsg->hdr.size);
+			} else {
+				rc = write(conn_fd, p + VHOST_USER_HDR_SIZE, vmsg->hdr.size);
+			}
+		} while (rc < 0 && (errno == EINTR || errno == EAGAIN));
+	}
+
+	if (rc <= 0) {
+		vu_panic(dev, "Error while writing: %s", strerror(errno));
+		return false;
+	}
+
+	return true;
+}
+
+static int vu_send_reply(VuDev *dev, int conn_fd, struct VhostUserMsg *msg)
+{
+	msg->hdr.flags &= ~VHOST_USER_VERSION_MASK;
+	msg->hdr.flags |= VHOST_USER_VERSION;
+	msg->hdr.flags |= VHOST_USER_REPLY_MASK;
+
+	return vu_message_write(dev, conn_fd, msg);
+}
+
+static bool vu_get_features_exec(struct VhostUserMsg *msg)
+{
+	uint64_t features =
+		1ULL << VIRTIO_F_VERSION_1 |
+		1ULL << VIRTIO_NET_F_MRG_RXBUF |
+		1ULL << VHOST_USER_F_PROTOCOL_FEATURES;
+
+	vmsg_set_reply_u64(msg, features);
+
+	debug("Sending back to guest u64: 0x%016"PRIx64, msg->payload.u64);
+
+	return true;
+}
+
+static void
+vu_set_enable_all_rings(VuDev *vdev, bool enabled)
+{
+	uint16_t i;
+
+	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++) {
+		vdev->vq[i].enable = enabled;
+	}
+}
+
+static bool
+vu_set_features_exec(VuDev *vdev, struct VhostUserMsg *msg)
+{
+	debug("u64: 0x%016"PRIx64, msg->payload.u64);
+
+	vdev->features = msg->payload.u64;
+	if (!vu_has_feature(vdev, VIRTIO_F_VERSION_1)) {
+		/*
+		 * We only support devices conforming to VIRTIO 1.0 or
+		 * later
+		 */
+		vu_panic(vdev, "virtio legacy devices aren't supported by passt");
+		return false;
+	}
+
+	if (!vu_has_feature(vdev, VHOST_USER_F_PROTOCOL_FEATURES)) {
+		vu_set_enable_all_rings(vdev, true);
+	}
+
+	/* virtio-net features */
+
+	if (vu_has_feature(vdev, VIRTIO_F_VERSION_1) ||
+	    vu_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF)) {
+		vdev->hdrlen = sizeof(struct virtio_net_hdr_mrg_rxbuf);
+	} else {
+		vdev->hdrlen = sizeof(struct virtio_net_hdr);
+	}
+
+	return false;
+}
+
+static bool
+vu_set_owner_exec(void)
+{
+	return false;
+}
+
+static bool map_ring(VuDev *vdev, VuVirtq *vq)
+{
+	vq->vring.desc = qva_to_va(vdev, vq->vra.desc_user_addr);
+	vq->vring.used = qva_to_va(vdev, vq->vra.used_user_addr);
+	vq->vring.avail = qva_to_va(vdev, vq->vra.avail_user_addr);
+
+	debug("Setting virtq addresses:");
+	debug("    vring_desc  at %p", (void *)vq->vring.desc);
+	debug("    vring_used  at %p", (void *)vq->vring.used);
+	debug("    vring_avail at %p", (void *)vq->vring.avail);
+
+	return !(vq->vring.desc && vq->vring.used && vq->vring.avail);
+}
+
+/*
+ * #syscalls:passt mmap munmap
+ */
+
+static bool vu_set_mem_table_exec(VuDev *vdev,
+				  struct VhostUserMsg *msg)
+{
+	unsigned int i;
+	struct VhostUserMemory m = msg->payload.memory, *memory = &m;
+
+	for (i = 0; i < vdev->nregions; i++) {
+		VuDevRegion *r = &vdev->regions[i];
+		void *m = (void *) (uintptr_t) r->mmap_addr;
+
+		if (m)
+			munmap(m, r->size + r->mmap_offset);
+	}
+	vdev->nregions = memory->nregions;
+
+	debug("Nregions: %u", memory->nregions);
+	for (i = 0; i < vdev->nregions; i++) {
+		void *mmap_addr;
+		VhostUserMemory_region *msg_region = &memory->regions[i];
+		VuDevRegion *dev_region = &vdev->regions[i];
+
+		debug("Region %d", i);
+		debug("    guest_phys_addr: 0x%016"PRIx64,
+		      msg_region->guest_phys_addr);
+		debug("    memory_size:     0x%016"PRIx64,
+		      msg_region->memory_size);
+		debug("    userspace_addr   0x%016"PRIx64,
+		      msg_region->userspace_addr);
+		debug("    mmap_offset      0x%016"PRIx64,
+		      msg_region->mmap_offset);
+
+		dev_region->gpa = msg_region->guest_phys_addr;
+		dev_region->size = msg_region->memory_size;
+		dev_region->qva = msg_region->userspace_addr;
+		dev_region->mmap_offset = msg_region->mmap_offset;
+
+		/* We don't use offset argument of mmap() since the
+		 * mapped address has to be page aligned, and we use huge
+		 * pages.  */
+		mmap_addr = mmap(0, dev_region->size + dev_region->mmap_offset,
+				 PROT_READ | PROT_WRITE, MAP_SHARED | MAP_NORESERVE,
+				 msg->fds[i], 0);
+
+		if (mmap_addr == MAP_FAILED) {
+			vu_panic(vdev, "region mmap error: %s", strerror(errno));
+		} else {
+			dev_region->mmap_addr = (uint64_t)(uintptr_t)mmap_addr;
+			debug("    mmap_addr:       0x%016"PRIx64,
+			      dev_region->mmap_addr);
+		}
+
+		close(msg->fds[i]);
+	}
+
+	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++) {
+		if (vdev->vq[i].vring.desc) {
+			if (map_ring(vdev, &vdev->vq[i])) {
+				vu_panic(vdev, "remapping queue %d during setmemtable", i);
+			}
+		}
+	}
+
+	return false;
+}
+
+static bool vu_set_vring_num_exec(VuDev *vdev,
+				  struct VhostUserMsg *msg)
+{
+	unsigned int index = msg->payload.state.index;
+	unsigned int num = msg->payload.state.num;
+
+	debug("State.index: %u", index);
+	debug("State.num:   %u", num);
+	vdev->vq[index].vring.num = num;
+
+	return false;
+}
+
+static bool vu_set_vring_addr_exec(VuDev *vdev,
+				   struct VhostUserMsg *msg)
+{
+	struct vhost_vring_addr addr = msg->payload.addr, *vra = &addr;
+	unsigned int index = vra->index;
+	VuVirtq *vq = &vdev->vq[index];
+
+	debug("vhost_vring_addr:");
+	debug("    index:  %d", vra->index);
+	debug("    flags:  %d", vra->flags);
+	debug("    desc_user_addr:   0x%016" PRIx64, (uint64_t)vra->desc_user_addr);
+	debug("    used_user_addr:   0x%016" PRIx64, (uint64_t)vra->used_user_addr);
+	debug("    avail_user_addr:  0x%016" PRIx64, (uint64_t)vra->avail_user_addr);
+	debug("    log_guest_addr:   0x%016" PRIx64, (uint64_t)vra->log_guest_addr);
+
+	vq->vra = *vra;
+	vq->vring.flags = vra->flags;
+	vq->vring.log_guest_addr = vra->log_guest_addr;
+
+	if (map_ring(vdev, vq)) {
+		vu_panic(vdev, "Invalid vring_addr message");
+		return false;
+	}
+
+	vq->used_idx = le16toh(vq->vring.used->idx);
+
+	if (vq->last_avail_idx != vq->used_idx) {
+		debug("Last avail index != used index: %u != %u",
+		      vq->last_avail_idx, vq->used_idx);
+	}
+
+	return false;
+}
+
+static bool vu_set_vring_base_exec(VuDev *vdev,
+				   struct VhostUserMsg *msg)
+{
+	unsigned int index = msg->payload.state.index;
+	unsigned int num = msg->payload.state.num;
+
+	debug("State.index: %u", index);
+	debug("State.num:   %u", num);
+	vdev->vq[index].shadow_avail_idx = vdev->vq[index].last_avail_idx = num;
+
+	return false;
+}
+
+static bool vu_get_vring_base_exec(VuDev *vdev,
+				   struct VhostUserMsg *msg)
+{
+	unsigned int index = msg->payload.state.index;
+
+	debug("State.index: %u", index);
+	msg->payload.state.num = vdev->vq[index].last_avail_idx;
+	msg->hdr.size = sizeof(msg->payload.state);
+
+	vdev->vq[index].started = false;
+
+	if (vdev->vq[index].call_fd != -1) {
+		close(vdev->vq[index].call_fd);
+		vdev->vq[index].call_fd = -1;
+	}
+	if (vdev->vq[index].kick_fd != -1) {
+		vu_remove_watch(vdev,  vdev->vq[index].kick_fd);
+		close(vdev->vq[index].kick_fd);
+		vdev->vq[index].kick_fd = -1;
+	}
+
+	return true;
+}
+
+static void vu_set_watch(VuDev *vdev, int fd)
+{
+	struct ctx *c = (struct ctx *) ((char *)vdev - offsetof(struct ctx, vdev));
+	union epoll_ref ref = { .type = EPOLL_TYPE_VHOST_KICK, .fd = fd };
+	struct epoll_event ev = { 0 };
+
+	ev.data.u64 = ref.u64;
+	ev.events = EPOLLIN;
+	epoll_ctl(c->epollfd, EPOLL_CTL_ADD, fd, &ev);
+}
+
+int vu_send(const struct ctx *c, const void *buf, size_t size)
+{
+	VuDev *vdev = (VuDev *)&c->vdev;
+	size_t hdrlen = vdev->hdrlen;
+	VuVirtq *vq = &vdev->vq[VHOST_USER_RX_QUEUE];
+	unsigned int indexes[VIRTQUEUE_MAX_SIZE];
+	size_t lens[VIRTQUEUE_MAX_SIZE];
+	size_t offset;
+	int i, j;
+	__virtio16 *num_buffers_ptr;
+
+	debug("vu_send size %zu hdrlen %zu", size, hdrlen);
+
+	if (!vu_queue_enabled(vq) || !vu_queue_started(vq)) {
+		err("Got packet, but no available descriptors on RX virtq.");
+		return 0;
+	}
+
+	offset = 0;
+	i = 0;
+	num_buffers_ptr = NULL;
+	while (offset < size) {
+		VuVirtqElement *elem;
+		size_t len;
+		int total;
+
+		total = 0;
+
+		if (i == VIRTQUEUE_MAX_SIZE) {
+			err("virtio-net unexpected long buffer chain");
+			goto err;
+		}
+
+		elem = vu_queue_pop(vdev, vq, sizeof(VuVirtqElement),
+				    buffer[VHOST_USER_RX_QUEUE]);
+		if (!elem) {
+			if (!vdev->broken) {
+				eventfd_t kick_data;
+				ssize_t rc;
+				int status;
+
+				/* wait the kernel to put new entries in the queue */
+
+				status = fcntl(vq->kick_fd, F_GETFL);
+				if (status != -1) {
+					fcntl(vq->kick_fd, F_SETFL, status & ~O_NONBLOCK);
+					rc =  eventfd_read(vq->kick_fd, &kick_data);
+					fcntl(vq->kick_fd, F_SETFL, status);
+					if (rc != -1)
+						continue;
+				}
+			}
+			if (i) {
+				err("virtio-net unexpected empty queue: "
+				    "i %d mergeable %d offset %zd, size %zd, "
+				    "features 0x%" PRIx64,
+				    i, vu_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF),
+				    offset, size, vdev->features);
+			}
+			offset = -1;
+			goto err;
+		}
+
+		if (elem->in_num < 1) {
+			err("virtio-net receive queue contains no in buffers");
+			vu_queue_detach_element(vdev, vq, elem->index, 0);
+			offset = -1;
+			goto err;
+		}
+
+		if (i == 0) {
+			struct virtio_net_hdr hdr = {
+				.flags = VIRTIO_NET_HDR_F_DATA_VALID,
+				.gso_type = VIRTIO_NET_HDR_GSO_NONE,
+			};
+
+			ASSERT(offset == 0);
+			ASSERT(elem->in_sg[0].iov_len >= hdrlen);
+
+			len = iov_from_buf(elem->in_sg, elem->in_num, 0, &hdr, sizeof hdr);
+
+			num_buffers_ptr = (__virtio16 *)((char *)elem->in_sg[0].iov_base +
+							 len);
+
+			total += hdrlen;
+		}
+
+		len = iov_from_buf(elem->in_sg, elem->in_num, total, (char *)buf + offset,
+				   size - offset);
+
+		total += len;
+		offset += len;
+
+		/* If buffers can't be merged, at this point we
+		 * must have consumed the complete packet.
+		 * Otherwise, drop it.
+		 */
+		if (!vu_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF) && offset < size) {
+			vu_queue_unpop(vdev, vq, elem->index, total);
+			goto err;
+		}
+
+		indexes[i] = elem->index;
+		lens[i] = total;
+		i++;
+	}
+
+	if (num_buffers_ptr && vu_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF)) {
+		*num_buffers_ptr = htole16(i);
+	}
+
+	for (j = 0; j < i; j++) {
+		debug("filling total %zd idx %d", lens[j], j);
+		vu_queue_fill_by_index(vdev, vq, indexes[j], lens[j], j);
+	}
+
+	vu_queue_flush(vdev, vq, i);
+	vu_queue_notify(vdev, vq);
+
+	debug("sent %zu", offset);
+
+	return offset;
+err:
+	for (j = 0; j < i; j++) {
+		vu_queue_detach_element(vdev, vq, indexes[j], lens[j]);
+	}
+
+	return offset;
+}
+
+size_t tap_send_frames_vu(const struct ctx *c, const struct iovec *iov, size_t n)
+{
+	size_t i;
+	int ret;
+
+	debug("tap_send_frames_vu n %zd", n);
+
+	for (i = 0; i < n; i++) {
+		ret = vu_send(c, iov[i].iov_base, iov[i].iov_len);
+		if (ret < 0)
+			break;
+	}
+	debug("count %zd", i);
+	return i;
+}
+
+static void vu_handle_tx(VuDev *vdev, int index)
+{
+	struct ctx *c = (struct ctx *) ((char *)vdev - offsetof(struct ctx, vdev));
+	VuVirtq *vq = &vdev->vq[index];
+	int hdrlen = vdev->hdrlen;
+	struct timespec now;
+	char *p;
+	size_t n;
+
+	if (index % 2 != VHOST_USER_TX_QUEUE) {
+		debug("index %d is not an TX queue", index);
+		return;
+	}
+
+	clock_gettime(CLOCK_MONOTONIC, &now);
+
+	p = pkt_buf;
+
+	pool_flush_all();
+
+	while (1) {
+		VuVirtqElement *elem;
+		unsigned int out_num;
+		struct iovec sg[VIRTQUEUE_MAX_SIZE], *out_sg;
+
+		ASSERT(index == VHOST_USER_TX_QUEUE);
+		elem = vu_queue_pop(vdev, vq, sizeof(VuVirtqElement), buffer[index]);
+		if (!elem) {
+			break;
+		}
+
+		out_num = elem->out_num;
+		out_sg = elem->out_sg;
+		if (out_num < 1) {
+			debug("virtio-net header not in first element");
+			break;
+		}
+
+		if (hdrlen) {
+			unsigned sg_num;
+
+			sg_num = iov_copy(sg, ARRAY_SIZE(sg), out_sg, out_num,
+					  hdrlen, -1);
+			out_num = sg_num;
+			out_sg = sg;
+		}
+
+		n = iov_to_buf(out_sg, out_num, 0, p, TAP_BUF_FILL);
+
+		packet_add_all(c, n, p);
+
+		p += n;
+
+		vu_queue_push(vdev, vq, elem, 0);
+		vu_queue_notify(vdev, vq);
+	}
+	tap_handler_all(c, &now);
+}
+
+void vu_kick_cb(struct ctx *c, union epoll_ref ref)
+{
+	VuDev *vdev = &c->vdev;
+	eventfd_t kick_data;
+	ssize_t rc;
+	int index;
+
+	for (index = 0; index < VHOST_USER_MAX_QUEUES; index++)
+		if (c->vdev.vq[index].kick_fd == ref.fd)
+			break;
+
+	if (index == VHOST_USER_MAX_QUEUES)
+		return;
+
+	rc =  eventfd_read(ref.fd, &kick_data);
+	if (rc == -1) {
+		vu_panic(vdev, "kick eventfd_read(): %s", strerror(errno));
+		vu_remove_watch(vdev, ref.fd);
+	} else {
+		debug("Got kick_data: %016"PRIx64" idx:%d",
+		      kick_data, index);
+		if (index % 2 == VHOST_USER_TX_QUEUE)
+			vu_handle_tx(vdev, index);
+	}
+}
+
+static bool vu_check_queue_msg_file(VuDev *vdev, struct VhostUserMsg *msg)
+{
+	int index = msg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
+	bool nofd = msg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
+
+	if (index >= VHOST_USER_MAX_QUEUES) {
+		vmsg_close_fds(msg);
+		vu_panic(vdev, "Invalid queue index: %u", index);
+		return false;
+	}
+
+	if (nofd) {
+		vmsg_close_fds(msg);
+		return true;
+	}
+
+	if (msg->fd_num != 1) {
+		vmsg_close_fds(msg);
+		vu_panic(vdev, "Invalid fds in request: %d", msg->hdr.request);
+		return false;
+	}
+
+	return true;
+}
+
+static bool vu_set_vring_kick_exec(VuDev *vdev,
+				   struct VhostUserMsg *msg)
+{
+	int index = msg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
+	bool nofd = msg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
+
+	debug("u64: 0x%016"PRIx64, msg->payload.u64);
+
+	if (!vu_check_queue_msg_file(vdev, msg))
+		return false;
+
+	if (vdev->vq[index].kick_fd != -1) {
+		vu_remove_watch(vdev, vdev->vq[index].kick_fd);
+		close(vdev->vq[index].kick_fd);
+		vdev->vq[index].kick_fd = -1;
+	}
+
+	vdev->vq[index].kick_fd = nofd ? -1 : msg->fds[0];
+	debug("Got kick_fd: %d for vq: %d", vdev->vq[index].kick_fd, index);
+
+	vdev->vq[index].started = true;
+
+	if (vdev->vq[index].kick_fd != -1 && index % 2 == VHOST_USER_TX_QUEUE) {
+		vu_set_watch(vdev, vdev->vq[index].kick_fd);
+		debug("Waiting for kicks on fd: %d for vq: %d",
+		      vdev->vq[index].kick_fd, index);
+	}
+
+	return false;
+}
+
+static bool vu_set_vring_call_exec(VuDev *vdev,
+				   struct VhostUserMsg *msg)
+{
+	int index = msg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
+	bool nofd = msg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
+
+	debug("u64: 0x%016"PRIx64, msg->payload.u64);
+
+	if (!vu_check_queue_msg_file(vdev, msg))
+		return false;
+
+	if (vdev->vq[index].call_fd != -1) {
+		close(vdev->vq[index].call_fd);
+		vdev->vq[index].call_fd = -1;
+	}
+
+	vdev->vq[index].call_fd = nofd ? -1 : msg->fds[0];
+
+	/* in case of I/O hang after reconnecting */
+	if (vdev->vq[index].call_fd != -1) {
+		eventfd_write(msg->fds[0], 1);
+	}
+
+	debug("Got call_fd: %d for vq: %d", vdev->vq[index].call_fd, index);
+
+	return false;
+}
+
+static bool vu_set_vring_err_exec(VuDev *vdev,
+				  struct VhostUserMsg *msg)
+{
+	int index = msg->payload.u64 & VHOST_USER_VRING_IDX_MASK;
+	bool nofd = msg->payload.u64 & VHOST_USER_VRING_NOFD_MASK;
+
+	debug("u64: 0x%016"PRIx64, msg->payload.u64);
+
+	if (!vu_check_queue_msg_file(vdev, msg))
+		return false;
+
+	if (vdev->vq[index].err_fd != -1) {
+		close(vdev->vq[index].err_fd);
+		vdev->vq[index].err_fd = -1;
+	}
+
+	vdev->vq[index].err_fd = nofd ? -1 : msg->fds[0];
+
+	return false;
+}
+
+static bool vu_get_protocol_features_exec(struct VhostUserMsg *msg)
+{
+	uint64_t features = 1ULL << VHOST_USER_PROTOCOL_F_REPLY_ACK;
+
+	vmsg_set_reply_u64(msg, features);
+
+	return true;
+}
+
+static bool vu_set_protocol_features_exec(VuDev *vdev, struct VhostUserMsg *msg)
+{
+	uint64_t features = msg->payload.u64;
+
+	debug("u64: 0x%016"PRIx64, features);
+
+	vdev->protocol_features = msg->payload.u64;
+
+	if (vu_has_protocol_feature(vdev,
+				    VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS) &&
+	    (!vu_has_protocol_feature(vdev, VHOST_USER_PROTOCOL_F_BACKEND_REQ) ||
+	     !vu_has_protocol_feature(vdev, VHOST_USER_PROTOCOL_F_REPLY_ACK))) {
+		/*
+		 * The use case for using messages for kick/call is simulation, to make
+		 * the kick and call synchronous. To actually get that behaviour, both
+		 * of the other features are required.
+		 * Theoretically, one could use only kick messages, or do them without
+		 * having F_REPLY_ACK, but too many (possibly pending) messages on the
+		 * socket will eventually cause the master to hang, to avoid this in
+		 * scenarios where not desired enforce that the settings are in a way
+		 * that actually enables the simulation case.
+		 */
+		vu_panic(vdev,
+			 "F_IN_BAND_NOTIFICATIONS requires F_BACKEND_REQ && F_REPLY_ACK");
+		return false;
+	}
+
+	return false;
+}
+
+
+static bool vu_get_queue_num_exec(struct VhostUserMsg *msg)
+{
+	vmsg_set_reply_u64(msg, VHOST_USER_MAX_QUEUES);
+	return true;
+}
+
+static bool vu_set_vring_enable_exec(VuDev *vdev, struct VhostUserMsg *msg)
+{
+	unsigned int index = msg->payload.state.index;
+	unsigned int enable = msg->payload.state.num;
+
+	debug("State.index:  %u", index);
+	debug("State.enable: %u", enable);
+
+	if (index >= VHOST_USER_MAX_QUEUES) {
+		vu_panic(vdev, "Invalid vring_enable index: %u", index);
+		return false;
+	}
+
+	vdev->vq[index].enable = enable;
+	return false;
+}
+
+void vu_init(struct ctx *c)
+{
+	int i;
+
+	c->vdev.hdrlen = 0;
+	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++)
+		c->vdev.vq[i] = (VuVirtq){
+			.call_fd = -1,
+			.kick_fd = -1,
+			.err_fd = -1,
+			.notification = true,
+		};
+}
+
+static void vu_cleanup(VuDev *vdev)
+{
+	unsigned int i;
+
+	for (i = 0; i < VHOST_USER_MAX_QUEUES; i++) {
+		VuVirtq *vq = &vdev->vq[i];
+
+		vq->started = false;
+		vq->notification = true;
+
+		if (vq->call_fd != -1) {
+			close(vq->call_fd);
+			vq->call_fd = -1;
+		}
+		if (vq->err_fd != -1) {
+			close(vq->err_fd);
+			vq->err_fd = -1;
+		}
+		if (vq->kick_fd != -1) {
+			vu_remove_watch(vdev,  vq->kick_fd);
+			close(vq->kick_fd);
+			vq->kick_fd = -1;
+		}
+
+		vq->vring.desc = 0;
+		vq->vring.used = 0;
+		vq->vring.avail = 0;
+	}
+	vdev->hdrlen = 0;
+
+	for (i = 0; i < vdev->nregions; i++) {
+		VuDevRegion *r = &vdev->regions[i];
+		void *m = (void *) (uintptr_t) r->mmap_addr;
+
+		if (m)
+			munmap(m, r->size + r->mmap_offset);
+	}
+	vdev->nregions = 0;
+}
+
+/**
+ * tap_handler_vu() - Packet handler for vhost-user
+ * @c:		Execution context
+ * @events:	epoll events
+ */
+void tap_handler_vu(struct ctx *c, uint32_t events)
+{
+	VuDev *dev = &c->vdev;
+	struct VhostUserMsg msg = { 0 };
+	bool need_reply, reply_requested;
+	int ret;
+
+	if (events & (EPOLLRDHUP | EPOLLHUP | EPOLLERR)) {
+		tap_sock_reset(c);
+		return;
+	}
+
+
+	ret = vu_message_read_default(dev, c->fd_tap, &msg);
+	if (ret <= 0) {
+		if (errno != EINTR && errno != EAGAIN && errno != EWOULDBLOCK)
+			tap_sock_reset(c);
+		return;
+	}
+	debug("================ Vhost user message ================");
+	debug("Request: %s (%d)", vu_request_to_string(msg.hdr.request),
+		msg.hdr.request);
+	debug("Flags:   0x%x", msg.hdr.flags);
+	debug("Size:    %u", msg.hdr.size);
+
+	need_reply = msg.hdr.flags & VHOST_USER_NEED_REPLY_MASK;
+	switch (msg.hdr.request) {
+	case VHOST_USER_GET_FEATURES:
+		reply_requested = vu_get_features_exec(&msg);
+		break;
+	case VHOST_USER_SET_FEATURES:
+		reply_requested = vu_set_features_exec(dev, &msg);
+		break;
+	case VHOST_USER_GET_PROTOCOL_FEATURES:
+		reply_requested = vu_get_protocol_features_exec(&msg);
+		break;
+	case VHOST_USER_SET_PROTOCOL_FEATURES:
+		reply_requested = vu_set_protocol_features_exec(dev, &msg);
+		break;
+	case VHOST_USER_GET_QUEUE_NUM:
+		reply_requested = vu_get_queue_num_exec(&msg);
+		break;
+	case VHOST_USER_SET_OWNER:
+		reply_requested = vu_set_owner_exec();
+		break;
+	case VHOST_USER_SET_MEM_TABLE:
+		reply_requested = vu_set_mem_table_exec(dev, &msg);
+		break;
+	case VHOST_USER_SET_VRING_NUM:
+		reply_requested = vu_set_vring_num_exec(dev, &msg);
+		break;
+	case VHOST_USER_SET_VRING_ADDR:
+		reply_requested = vu_set_vring_addr_exec(dev, &msg);
+		break;
+	case VHOST_USER_SET_VRING_BASE:
+		reply_requested = vu_set_vring_base_exec(dev, &msg);
+		break;
+	case VHOST_USER_GET_VRING_BASE:
+		reply_requested = vu_get_vring_base_exec(dev, &msg);
+		break;
+	case VHOST_USER_SET_VRING_KICK:
+		reply_requested = vu_set_vring_kick_exec(dev, &msg);
+		break;
+	case VHOST_USER_SET_VRING_CALL:
+		reply_requested = vu_set_vring_call_exec(dev, &msg);
+		break;
+	case VHOST_USER_SET_VRING_ERR:
+		reply_requested = vu_set_vring_err_exec(dev, &msg);
+		break;
+	case VHOST_USER_SET_VRING_ENABLE:
+		reply_requested = vu_set_vring_enable_exec(dev, &msg);
+		break;
+	case VHOST_USER_NONE:
+		vu_cleanup(dev);
+		return;
+	default:
+		vu_panic(dev, "Unhandled request: %d", msg.hdr.request);
+		return;
+	}
+
+	if (!reply_requested && need_reply) {
+		msg.payload.u64 = 0;
+		msg.hdr.flags = 0;
+		msg.hdr.size = sizeof(msg.payload.u64);
+		msg.fd_num = 0;
+		reply_requested = true;
+	}
+
+	if (reply_requested)
+		ret = vu_send_reply(dev, c->fd_tap, &msg);
+	free(msg.data);
+}
diff --git a/vhost_user.h b/vhost_user.h
new file mode 100644
index 000000000000..25f0b617ab40
--- /dev/null
+++ b/vhost_user.h
@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/* some parts from subprojects/libvhost-user/libvhost-user.h */
+
+#ifndef VHOST_USER_H
+#define VHOST_USER_H
+
+#include "virtio.h"
+#include "iov.h"
+
+#define VHOST_USER_F_PROTOCOL_FEATURES 30
+
+#define VHOST_MEMORY_BASELINE_NREGIONS 8
+
+enum vhost_user_protocol_feature {
+	VHOST_USER_PROTOCOL_F_MQ = 0,
+	VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1,
+	VHOST_USER_PROTOCOL_F_RARP = 2,
+	VHOST_USER_PROTOCOL_F_REPLY_ACK = 3,
+	VHOST_USER_PROTOCOL_F_NET_MTU = 4,
+	VHOST_USER_PROTOCOL_F_BACKEND_REQ = 5,
+	VHOST_USER_PROTOCOL_F_CROSS_ENDIAN = 6,
+	VHOST_USER_PROTOCOL_F_CRYPTO_SESSION = 7,
+	VHOST_USER_PROTOCOL_F_PAGEFAULT = 8,
+	VHOST_USER_PROTOCOL_F_CONFIG = 9,
+	VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD = 10,
+	VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
+	VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
+	VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS = 14,
+	VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS = 15,
+
+	VHOST_USER_PROTOCOL_F_MAX
+};
+
+enum vhost_user_request {
+	VHOST_USER_NONE = 0,
+	VHOST_USER_GET_FEATURES = 1,
+	VHOST_USER_SET_FEATURES = 2,
+	VHOST_USER_SET_OWNER = 3,
+	VHOST_USER_RESET_OWNER = 4,
+	VHOST_USER_SET_MEM_TABLE = 5,
+	VHOST_USER_SET_LOG_BASE = 6,
+	VHOST_USER_SET_LOG_FD = 7,
+	VHOST_USER_SET_VRING_NUM = 8,
+	VHOST_USER_SET_VRING_ADDR = 9,
+	VHOST_USER_SET_VRING_BASE = 10,
+	VHOST_USER_GET_VRING_BASE = 11,
+	VHOST_USER_SET_VRING_KICK = 12,
+	VHOST_USER_SET_VRING_CALL = 13,
+	VHOST_USER_SET_VRING_ERR = 14,
+	VHOST_USER_GET_PROTOCOL_FEATURES = 15,
+	VHOST_USER_SET_PROTOCOL_FEATURES = 16,
+	VHOST_USER_GET_QUEUE_NUM = 17,
+	VHOST_USER_SET_VRING_ENABLE = 18,
+	VHOST_USER_SEND_RARP = 19,
+	VHOST_USER_NET_SET_MTU = 20,
+	VHOST_USER_SET_BACKEND_REQ_FD = 21,
+	VHOST_USER_IOTLB_MSG = 22,
+	VHOST_USER_SET_VRING_ENDIAN = 23,
+	VHOST_USER_GET_CONFIG = 24,
+	VHOST_USER_SET_CONFIG = 25,
+	VHOST_USER_CREATE_CRYPTO_SESSION = 26,
+	VHOST_USER_CLOSE_CRYPTO_SESSION = 27,
+	VHOST_USER_POSTCOPY_ADVISE  = 28,
+	VHOST_USER_POSTCOPY_LISTEN  = 29,
+	VHOST_USER_POSTCOPY_END     = 30,
+	VHOST_USER_GET_INFLIGHT_FD = 31,
+	VHOST_USER_SET_INFLIGHT_FD = 32,
+	VHOST_USER_GPU_SET_SOCKET = 33,
+	VHOST_USER_VRING_KICK = 35,
+	VHOST_USER_GET_MAX_MEM_SLOTS = 36,
+	VHOST_USER_ADD_MEM_REG = 37,
+	VHOST_USER_REM_MEM_REG = 38,
+	VHOST_USER_MAX
+};
+
+typedef struct {
+	enum vhost_user_request request;
+
+#define VHOST_USER_VERSION_MASK     0x3
+#define VHOST_USER_REPLY_MASK       (0x1 << 2)
+#define VHOST_USER_NEED_REPLY_MASK  (0x1 << 3)
+	uint32_t flags;
+	uint32_t size; /* the following payload size */
+} __attribute__ ((__packed__)) vhost_user_header;
+
+typedef struct VhostUserMemory_region {
+	uint64_t guest_phys_addr;
+	uint64_t memory_size;
+	uint64_t userspace_addr;
+	uint64_t mmap_offset;
+} VhostUserMemory_region;
+
+struct VhostUserMemory {
+	uint32_t nregions;
+	uint32_t padding;
+	struct VhostUserMemory_region regions[VHOST_MEMORY_BASELINE_NREGIONS];
+};
+
+typedef union {
+#define VHOST_USER_VRING_IDX_MASK   0xff
+#define VHOST_USER_VRING_NOFD_MASK  (0x1 << 8)
+	uint64_t u64;
+	struct vhost_vring_state state;
+	struct vhost_vring_addr addr;
+	struct VhostUserMemory memory;
+} vhost_user_payload;
+
+typedef struct VhostUserMsg {
+	vhost_user_header hdr;
+	vhost_user_payload payload;
+
+	int fds[VHOST_MEMORY_BASELINE_NREGIONS];
+	int fd_num;
+	uint8_t *data;
+} __attribute__ ((__packed__)) VhostUserMsg;
+#define VHOST_USER_HDR_SIZE sizeof(vhost_user_header)
+
+#define VHOST_USER_RX_QUEUE 0
+#define VHOST_USER_TX_QUEUE 1
+
+static inline bool vu_queue_enabled(VuVirtq *vq)
+{
+	return vq->enable;
+}
+
+static inline bool vu_queue_started(const VuVirtq *vq)
+{
+	return vq->started;
+}
+
+size_t tap_send_frames_vu(const struct ctx *c, const struct iovec *iov,
+			  size_t n);
+int vu_send(const struct ctx *c, const void *data, size_t len);
+void vu_print_capabilities(void);
+void vu_init(struct ctx *c);
+void vu_kick_cb(struct ctx *c, union epoll_ref ref);
+void tap_handler_vu(struct ctx *c, uint32_t events);
+#endif /* VHOST_USER_H */
-- 
@@ -0,0 +1,139 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/* some parts from subprojects/libvhost-user/libvhost-user.h */
+
+#ifndef VHOST_USER_H
+#define VHOST_USER_H
+
+#include "virtio.h"
+#include "iov.h"
+
+#define VHOST_USER_F_PROTOCOL_FEATURES 30
+
+#define VHOST_MEMORY_BASELINE_NREGIONS 8
+
+enum vhost_user_protocol_feature {
+	VHOST_USER_PROTOCOL_F_MQ = 0,
+	VHOST_USER_PROTOCOL_F_LOG_SHMFD = 1,
+	VHOST_USER_PROTOCOL_F_RARP = 2,
+	VHOST_USER_PROTOCOL_F_REPLY_ACK = 3,
+	VHOST_USER_PROTOCOL_F_NET_MTU = 4,
+	VHOST_USER_PROTOCOL_F_BACKEND_REQ = 5,
+	VHOST_USER_PROTOCOL_F_CROSS_ENDIAN = 6,
+	VHOST_USER_PROTOCOL_F_CRYPTO_SESSION = 7,
+	VHOST_USER_PROTOCOL_F_PAGEFAULT = 8,
+	VHOST_USER_PROTOCOL_F_CONFIG = 9,
+	VHOST_USER_PROTOCOL_F_SLAVE_SEND_FD = 10,
+	VHOST_USER_PROTOCOL_F_HOST_NOTIFIER = 11,
+	VHOST_USER_PROTOCOL_F_INFLIGHT_SHMFD = 12,
+	VHOST_USER_PROTOCOL_F_INBAND_NOTIFICATIONS = 14,
+	VHOST_USER_PROTOCOL_F_CONFIGURE_MEM_SLOTS = 15,
+
+	VHOST_USER_PROTOCOL_F_MAX
+};
+
+enum vhost_user_request {
+	VHOST_USER_NONE = 0,
+	VHOST_USER_GET_FEATURES = 1,
+	VHOST_USER_SET_FEATURES = 2,
+	VHOST_USER_SET_OWNER = 3,
+	VHOST_USER_RESET_OWNER = 4,
+	VHOST_USER_SET_MEM_TABLE = 5,
+	VHOST_USER_SET_LOG_BASE = 6,
+	VHOST_USER_SET_LOG_FD = 7,
+	VHOST_USER_SET_VRING_NUM = 8,
+	VHOST_USER_SET_VRING_ADDR = 9,
+	VHOST_USER_SET_VRING_BASE = 10,
+	VHOST_USER_GET_VRING_BASE = 11,
+	VHOST_USER_SET_VRING_KICK = 12,
+	VHOST_USER_SET_VRING_CALL = 13,
+	VHOST_USER_SET_VRING_ERR = 14,
+	VHOST_USER_GET_PROTOCOL_FEATURES = 15,
+	VHOST_USER_SET_PROTOCOL_FEATURES = 16,
+	VHOST_USER_GET_QUEUE_NUM = 17,
+	VHOST_USER_SET_VRING_ENABLE = 18,
+	VHOST_USER_SEND_RARP = 19,
+	VHOST_USER_NET_SET_MTU = 20,
+	VHOST_USER_SET_BACKEND_REQ_FD = 21,
+	VHOST_USER_IOTLB_MSG = 22,
+	VHOST_USER_SET_VRING_ENDIAN = 23,
+	VHOST_USER_GET_CONFIG = 24,
+	VHOST_USER_SET_CONFIG = 25,
+	VHOST_USER_CREATE_CRYPTO_SESSION = 26,
+	VHOST_USER_CLOSE_CRYPTO_SESSION = 27,
+	VHOST_USER_POSTCOPY_ADVISE  = 28,
+	VHOST_USER_POSTCOPY_LISTEN  = 29,
+	VHOST_USER_POSTCOPY_END     = 30,
+	VHOST_USER_GET_INFLIGHT_FD = 31,
+	VHOST_USER_SET_INFLIGHT_FD = 32,
+	VHOST_USER_GPU_SET_SOCKET = 33,
+	VHOST_USER_VRING_KICK = 35,
+	VHOST_USER_GET_MAX_MEM_SLOTS = 36,
+	VHOST_USER_ADD_MEM_REG = 37,
+	VHOST_USER_REM_MEM_REG = 38,
+	VHOST_USER_MAX
+};
+
+typedef struct {
+	enum vhost_user_request request;
+
+#define VHOST_USER_VERSION_MASK     0x3
+#define VHOST_USER_REPLY_MASK       (0x1 << 2)
+#define VHOST_USER_NEED_REPLY_MASK  (0x1 << 3)
+	uint32_t flags;
+	uint32_t size; /* the following payload size */
+} __attribute__ ((__packed__)) vhost_user_header;
+
+typedef struct VhostUserMemory_region {
+	uint64_t guest_phys_addr;
+	uint64_t memory_size;
+	uint64_t userspace_addr;
+	uint64_t mmap_offset;
+} VhostUserMemory_region;
+
+struct VhostUserMemory {
+	uint32_t nregions;
+	uint32_t padding;
+	struct VhostUserMemory_region regions[VHOST_MEMORY_BASELINE_NREGIONS];
+};
+
+typedef union {
+#define VHOST_USER_VRING_IDX_MASK   0xff
+#define VHOST_USER_VRING_NOFD_MASK  (0x1 << 8)
+	uint64_t u64;
+	struct vhost_vring_state state;
+	struct vhost_vring_addr addr;
+	struct VhostUserMemory memory;
+} vhost_user_payload;
+
+typedef struct VhostUserMsg {
+	vhost_user_header hdr;
+	vhost_user_payload payload;
+
+	int fds[VHOST_MEMORY_BASELINE_NREGIONS];
+	int fd_num;
+	uint8_t *data;
+} __attribute__ ((__packed__)) VhostUserMsg;
+#define VHOST_USER_HDR_SIZE sizeof(vhost_user_header)
+
+#define VHOST_USER_RX_QUEUE 0
+#define VHOST_USER_TX_QUEUE 1
+
+static inline bool vu_queue_enabled(VuVirtq *vq)
+{
+	return vq->enable;
+}
+
+static inline bool vu_queue_started(const VuVirtq *vq)
+{
+	return vq->started;
+}
+
+size_t tap_send_frames_vu(const struct ctx *c, const struct iovec *iov,
+			  size_t n);
+int vu_send(const struct ctx *c, const void *data, size_t len);
+void vu_print_capabilities(void);
+void vu_init(struct ctx *c);
+void vu_kick_cb(struct ctx *c, union epoll_ref ref);
+void tap_handler_vu(struct ctx *c, uint32_t events);
+#endif /* VHOST_USER_H */
-- 
2.42.0