Merge pull request #145 from djs55/tap-vsockd-tool

tuntap vsock tool

alpine/Dockerfile

@@ -40,6 +40,7 @@ COPY packages/proxy/proxy /sbin/
 COPY packages/proxy/etc /etc/
 COPY packages/transfused/transfused /sbin/
 COPY packages/transfused/etc /etc/
+COPY packages/tap-vsockd/tap-vsockd /sbin/
 COPY packages/llmnrd/llmnrd /sbin/
 COPY packages/llmnrd/etc /etc/
 COPY packages/llmnrd/llmnrd.tar.gz /usr/share/src/

alpine/packages/Makefile

@@ -2,6 +2,7 @@ all:
 	$(MAKE) -C proxy OS=linux
 	$(MAKE) -C diagnostics OS=linux
 	$(MAKE) -C transfused OS=linux
+	$(MAKE) -C tap-vsockd OS=linux
 	$(MAKE) -C hupper OS=linux
 	$(MAKE) -C hvtools OS=linux
 	$(MAKE) -C docker OS=Linux
@@ -16,6 +17,7 @@ arm:
 	$(MAKE) -C hupper OS=linux ARCH=arm
 	$(MAKE) -C docker arm OS=Linux ARCH=arm
 	# Not cross building at present (C code)
+	# $(MAKE) -C tap-vsockd OS=linux ARCH=arm
 	# $(MAKE) -C diagnostics OS=linux ARCH=arm
 	# $(MAKE) -C proxy OS=linux ARCH=arm
 	# $(MAKE) -C nc-vsock OS=linux ARCH=arm
@@ -25,6 +27,7 @@ clean:
 	$(MAKE) -C proxy clean
 	$(MAKE) -C diagnostics clean
 	$(MAKE) -C transfused clean
+	$(MAKE) -C tap-vsockd clean
 	$(MAKE) -C docker clean
 	$(MAKE) -C hupper clean
 	$(MAKE) -C hvtools clean

alpine/packages/diagnostics/diagnostics

@@ -9,6 +9,8 @@ INET=$(ifconfig eth0 2> /dev/null | grep 'inet addr')
 [ $? -eq 0 ] && printf "✓ Network connected: $INET\n" || printf "✗ No network connection\n"
 FUSE=$(ps -eo args | grep '^/sbin/transfused')
 [ $? -eq 0 ] && printf "✓ Process transfused running\n" || printf "✗ No transfused process\n"
+FUSE=$(ps -eo args | grep '^/sbin/tap-vsockd')
+[ $? -eq 0 ] && printf "✓ Process tap-vsockd running\n" || printf "✗ No tap-vsockd process\n"
 HUPPER=$(ps -eo args | grep '^/bin/hupper')
 [ $? -eq 0 ] && printf "✓ Process hupper running: $HUPPER\n" || printf "✗ No hupper process\n"
 DOCKER=$(ps -eo args | grep '^/usr/bin/docker')

alpine/packages/tap-vsockd/.gitignore

@@ -0,0 +1 @@
+tap-vsockd

alpine/packages/tap-vsockd/Dockerfile

@@ -0,0 +1,10 @@
+FROM alpine:3.3
+
+RUN apk update && apk upgrade && apk add alpine-sdk util-linux-dev linux-headers
+
+RUN mkdir -p /tap-vsockd
+WORKDIR /tap-vsockd
+
+COPY . /tap-vsockd
+
+RUN make tap-vsockd

alpine/packages/tap-vsockd/Makefile

@@ -0,0 +1,24 @@
+.PHONY: all
+
+DEPS=tap-vsockd.c hvsock.c hvsock.h protocol.c protocol.h
+
+all: Dockerfile $(DEPS)
+	docker build -t tap-vsockd:build .
+	docker run --rm tap-vsockd:build cat tap-vsockd > tap-vsockd
+	chmod 755 tap-vsockd
+
+tap-vsockd: hvsock.o protocol.o tap-vsockd.o
+	gcc -Wall -Werror -o tap-vsockd tap-vsockd.o protocol.o hvsock.o -lpthread
+
+hvsock.o: hvsock.c hvsock.h
+	gcc -Wall -Werror -c hvsock.c
+
+protocol.o: protocol.c
+	gcc -Wall -Werror -c protocol.c
+
+tap-vsockd.o: tap-vsockd.c hvsock.h
+	gcc -Wall -Werror -c tap-vsockd.c
+
+clean:
+	rm -f tap-vsockd
+	docker images -q tap-vsockd:build | xargs docker rmi -f

alpine/packages/tap-vsockd/hvsock.c

@@ -0,0 +1,38 @@
+#include <stdio.h>
+
+#include "hvsock.h"
+
+int parseguid(const char *s, GUID *g)
+{
+    int res;
+    int p0, p1, p2, p3, p4, p5, p6, p7;
+
+    res = sscanf(s, GUID_FMT,
+                 &g->Data1, &g->Data2, &g->Data3,
+                 &p0, &p1, &p2, &p3, &p4, &p5, &p6, &p7);
+    if (res != 11)
+        return 1;
+    g->Data4[0] = p0;
+    g->Data4[1] = p1;
+    g->Data4[2] = p2;
+    g->Data4[3] = p3;
+    g->Data4[4] = p4;
+    g->Data4[5] = p5;
+    g->Data4[6] = p6;
+    g->Data4[7] = p7;
+    return 0;
+}
+
+DEFINE_GUID(HV_GUID_ZERO,
+    0x00000000, 0x0000, 0x0000, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00);
+DEFINE_GUID(HV_GUID_BROADCAST,
+    0xFFFFFFFF, 0xFFFF, 0xFFFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF);
+DEFINE_GUID(HV_GUID_WILDCARD,
+    0x00000000, 0x0000, 0x0000, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00);
+
+DEFINE_GUID(HV_GUID_CHILDREN,
+    0x90db8b89, 0x0d35, 0x4f79, 0x8c, 0xe9, 0x49, 0xea, 0x0a, 0xc8, 0xb7, 0xcd);
+DEFINE_GUID(HV_GUID_LOOPBACK,
+    0xe0e16197, 0xdd56, 0x4a10, 0x91, 0x95, 0x5e, 0xe7, 0xa1, 0x55, 0xa8, 0x38);
+DEFINE_GUID(HV_GUID_PARENT,
+    0xa42e7cda, 0xd03f, 0x480c, 0x9c, 0xc2, 0xa4, 0xde, 0x20, 0xab, 0xb8, 0x78);

alpine/packages/tap-vsockd/hvsock.h

@@ -0,0 +1,49 @@
+/* AF_HYPERV definitions and utilities */
+
+#include <errno.h>
+#include <stdint.h>
+#include <unistd.h>
+#include <sys/socket.h>
+
+/* GUID handling  */
+typedef struct _GUID {
+    uint32_t Data1;
+    uint16_t Data2;
+    uint16_t Data3;
+    uint8_t  Data4[8];
+} GUID;
+
+#define DEFINE_GUID(name, l, w1, w2, b1, b2, b3, b4, b5, b6, b7, b8) \
+    const GUID name = {l, w1, w2, {b1, b2,  b3,  b4,  b5,  b6,  b7,  b8}}
+
+/* Helper macros for parsing/printing GUIDs */
+#define GUID_FMT "%08x-%04hx-%04hx-%02x%02x-%02x%02x%02x%02x%02x%02x"
+#define GUID_ARGS(_g)                                               \
+    (_g).Data1, (_g).Data2, (_g).Data3,                             \
+    (_g).Data4[0], (_g).Data4[1], (_g).Data4[2], (_g).Data4[3],     \
+    (_g).Data4[4], (_g).Data4[5], (_g).Data4[6], (_g).Data4[7]
+#define GUID_SARGS(_g)                                              \
+    &(_g).Data1, &(_g).Data2, &(_g).Data3,                          \
+    &(_g).Data4[0], &(_g).Data4[1], &(_g).Data4[2], &(_g).Data4[3], \
+    &(_g).Data4[4], &(_g).Data4[5], &(_g).Data4[6], &(_g).Data4[7]
+
+extern int parseguid(const char *s, GUID *g);
+
+/* HV Socket definitions */
+#define AF_HYPERV 43
+#define HV_PROTOCOL_RAW 1
+
+typedef struct _SOCKADDR_HV
+{
+    unsigned short Family;
+    unsigned short Reserved;
+    GUID VmId;
+    GUID ServiceId;
+} SOCKADDR_HV;
+
+extern const GUID HV_GUID_ZERO;
+extern const GUID HV_GUID_BROADCAST;
+extern const GUID HV_GUID_WILDCARD;
+extern const GUID HV_GUID_CHILDREN;
+extern const GUID HV_GUID_LOOPBACK;
+extern const GUID HV_GUID_PARENT;

alpine/packages/tap-vsockd/protocol.c

@@ -0,0 +1,171 @@
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+#include <syslog.h>
+
+#include "protocol.h"
+
+/* Version 0 of the protocol used this */
+char expected_hello_old[5] = { 'V', 'M', 'N', 'E', 'T' };
+
+/* Version 1 and later of the protocol used this */
+char expected_hello[5] = { 'V', 'M', 'N', '3', 'T' };
+
+int really_read(int fd, uint8_t *buffer, size_t total){
+  size_t remaining = total;
+	ssize_t n;
+  while (remaining > 0){
+    n = read(fd, buffer, remaining);
+    if (n == 0){
+      syslog(LOG_CRIT, "EOF reading from socket: closing\n");
+      goto err;
+    }
+    if (n < 0){
+      syslog(LOG_CRIT, "Failure reading from socket: closing: %s", strerror(errno));
+      goto err;
+    }
+    remaining -= (size_t)n;
+    buffer = buffer + n;
+  }
+  return 0;
+err:
+  /* On error: stop reading from the socket and trigger a clean shutdown */
+  shutdown(fd, SHUT_RD);
+  return -1;
+}
+
+int really_write(int fd, uint8_t *buffer, size_t total){
+	size_t remaining = total;
+  ssize_t n;
+  while (remaining > 0){
+    n = write(fd, buffer, remaining);
+    if (n == 0){
+      syslog(LOG_CRIT, "EOF writing to socket: closing");
+      goto err;
+    }
+    if (n < 0){
+      syslog(LOG_CRIT, "Failure writing to socket: closing: %s", strerror(errno));
+      goto err;
+    }
+    remaining -= (size_t) n;
+    buffer = buffer + n;
+  }
+  return 0;
+err:
+  /* On error: stop listening to the socket */
+  shutdown(fd, SHUT_WR);
+  return -1;
+}
+
+struct init_message *create_init_message(){
+  struct init_message *m = (struct init_message*) malloc(sizeof(struct init_message));
+  bzero(m, sizeof(struct init_message));
+  memcpy(&m->hello[0], &expected_hello[0], sizeof(m->hello));
+  m->version = CURRENT_VERSION;
+  memset(&m->commit[0], 0, sizeof(m->commit));
+  return m;
+}
+
+char *print_init_message(struct init_message *m) {
+  char tmp[41];
+  memcpy(&tmp[0], &m->commit[0], 40);
+  tmp[40] = '\000';
+  char *buffer = (char*) malloc(80);
+  int n = snprintf(buffer, 80, "version %d, commit %s", m->version, tmp);
+  if (n < 0) {
+    perror("Failed to format init_message");
+    exit(1);
+  }
+  return buffer;
+}
+
+int read_init_message(int fd, struct init_message *ci) {
+  bzero(ci, sizeof(struct init_message));
+  if (really_read(fd, (uint8_t*) &ci->hello[0], sizeof(ci->hello)) == -1){
+    syslog(LOG_CRIT, "Failed to read hello from client");
+    return -1;
+  }
+  if (memcmp(&ci->hello[0], &expected_hello_old[0], sizeof(expected_hello_old)) == 0) {
+      ci->version = 0;
+      return 0;
+  }
+  if (memcmp(&ci->hello[0], &expected_hello[0], sizeof(expected_hello)) != 0) {
+    syslog(LOG_CRIT, "Failed to read header magic from client");
+    return -1;
+  }
+  if (really_read(fd, (uint8_t*) &ci->version, sizeof(ci->version)) == -1){
+    syslog(LOG_CRIT, "Failed to read header version from client");
+    return -1;
+  }
+  if (really_read(fd, (uint8_t*) &ci->commit[0], sizeof(ci->commit)) == -1){
+    syslog(LOG_CRIT, "Failed to read header hash from client");
+    return -1;
+  }
+  return 0;
+}
+
+int write_init_message(int fd, struct init_message *ci) {
+  if (really_write(fd, (uint8_t*) &ci->hello[0], sizeof(ci->hello)) == -1){
+    syslog(LOG_CRIT, "Failed to write hello to client");
+    return -1;
+  }
+  if (ci->version > 0) {
+    if (really_write(fd, (uint8_t*) &ci->version, sizeof(ci->version)) == -1){
+      syslog(LOG_CRIT, "Failed to write version to client");
+      return -1;
+    }
+    if (really_write(fd, (uint8_t*) &ci->commit[0], sizeof(ci->commit)) == -1){
+      syslog(LOG_CRIT, "Failed to write header hash to client");
+      return -1;
+    }
+  }
+  return 0;
+}
+
+int read_vif_info(int fd, struct vif_info *vif) {
+  uint8_t buffer[10];
+  if (really_read(fd, &buffer[0], sizeof(buffer)) == -1){
+    syslog(LOG_CRIT, "Failed to read vif info from client");
+    return -1;
+  }
+  vif->mtu = (size_t) (buffer[0] | (buffer[1] << 8));
+  vif->max_packet_size = (size_t) (buffer[2] | (buffer[3] << 8));
+  memcpy(vif->mac, &buffer[4], 6);
+  return 0;
+}
+
+
+int write_vif_info(int fd, struct vif_info *vif) {
+  uint8_t buffer[10];
+  buffer[0] = (uint8_t) ((vif->mtu >> 0) & 0xff);
+  buffer[1] = (uint8_t) ((vif->mtu >> 8) & 0xff);
+  buffer[2] = (uint8_t) ((vif->max_packet_size >> 0) & 0xff);
+  buffer[3] = (uint8_t) ((vif->max_packet_size >> 8) & 0xff);
+  memcpy(&buffer[0] + 4, &(vif->mac)[0], 6);
+  if (really_write(fd, &buffer[0], sizeof(buffer)) == -1){
+    syslog(LOG_CRIT, "Failed to write vif into to client");
+    return -1;
+  }
+  return 0;
+}
+
+int write_command(int fd, enum command *c) {
+  uint8_t command = *c;
+  if (really_write(fd, (uint8_t*) &command, sizeof(command)) == -1){
+    syslog(LOG_CRIT, "Failed to write command to client");
+    return -1;
+  }
+  return 0;
+}
+
+int write_ethernet_args(int fd, struct ethernet_args *args){
+  if (really_write(fd, (uint8_t*) &args->uuid_string[0], 36) == -1){
+    syslog(LOG_CRIT, "Failed to write ethernet args to client");
+    return -1;
+  }
+  return 0;
+}

alpine/packages/tap-vsockd/protocol.h

@@ -0,0 +1,56 @@
+#ifndef _VMNET_PROTOCOL_H_
+#define _VMNET_PROTOCOL_H_
+
+#include <errno.h>
+#include <stdint.h>
+
+/* Client -> Server init_message */
+/* Server -> Client init_message */
+struct init_message {
+  char hello[5];
+  uint8_t _padding[3];
+  uint32_t version;
+  char commit[40]; /* git sha of the compiled commit */
+};
+
+/* This should be bumped whenever we add something (like a feature or a bugfix)
+   and we wish the UI to be able to detect when to trigger a reinstall. */
+#define CURRENT_VERSION 13
+
+extern struct init_message *create_init_message(void);
+extern int read_init_message(int fd, struct init_message *ci);
+extern int write_init_message(int fd, struct init_message *ci);
+extern char *print_init_message(struct init_message *m);
+
+/* Client -> Server command */
+enum command {
+  ethernet = 1,
+};
+
+extern int write_command(int fd, enum command *c);
+
+/* Client -> Server command arguments */
+struct ethernet_args {
+  char uuid_string[36];
+};
+
+extern int write_ethernet_args(int fd, struct ethernet_args *args);
+
+/* Server -> Client: details of a vif */
+struct vif_info {
+  uint8_t mac[6];
+  short _padding;
+  size_t max_packet_size;
+  size_t mtu;
+};
+
+extern int read_vif_info(int fd, struct vif_info *vif);
+extern int write_vif_info(int fd, struct vif_info *vif);
+
+extern char expected_hello[5];
+extern char expected_hello_old[5];
+
+extern int really_read(int fd, uint8_t *buffer, size_t total);
+extern int really_write(int fd, uint8_t *buffer, size_t total);
+
+#endif /* _VMNET_PROTOCOL_H_ */

alpine/packages/tap-vsockd/tap-vsockd.c

@@ -0,0 +1,432 @@
+/*
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <getopt.h>
+#include <syslog.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <err.h>
+#include <pthread.h>
+#include <arpa/inet.h>
+#include <sys/ioctl.h>
+#include <net/if.h>
+#include <linux/if_tun.h>
+#include <net/if_arp.h>
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <ifaddrs.h>
+
+
+#include "hvsock.h"
+#include "protocol.h"
+
+int daemon_flag = 0;
+int listen_flag = 0;
+int connect_flag = 0;
+
+char *default_sid = "30D48B34-7D27-4B0B-AAAF-BBBED334DD59";
+
+void fatal(const char *msg)
+{
+    syslog(LOG_CRIT, "%s Error: %d. %s", msg, errno, strerror(errno));
+    exit(1);
+}
+
+int alloc_tap(const char *dev) {
+  int fd;
+  struct ifreq ifr;
+  const char *clonedev = "/dev/net/tun";
+  if ((fd = open(clonedev, O_RDWR)) == -1) {
+    fatal("Failed to open /dev/net/tun");
+  }
+  memset(&ifr, 0, sizeof(ifr));
+  ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
+  strncpy(ifr.ifr_name, dev, IFNAMSIZ);
+  if (ioctl(fd, TUNSETIFF, (void*) &ifr) < 0) {
+    fatal("TUNSETIFF failed");
+  }
+  int persist = 1;
+  if (ioctl(fd, TUNSETPERSIST, persist) < 0) {
+    fatal("TUNSETPERSIST failed");
+  }
+  syslog(LOG_INFO, "successfully created TAP device %s", dev);
+  return fd;
+}
+
+void set_macaddr(const char *dev, uint8_t *mac) {
+  int fd;
+  struct ifreq ifq;
+
+  fd = socket(PF_INET, SOCK_DGRAM, 0);
+  strcpy(ifq.ifr_name, dev);
+  memcpy(&ifq.ifr_hwaddr.sa_data[0], mac, 6);
+  ifq.ifr_hwaddr.sa_family = ARPHRD_ETHER;
+
+  if (ioctl(fd, SIOCSIFHWADDR, &ifq) == -1) {
+    fatal("SIOCSIFHWADDR failed");
+  }
+
+  close(fd);
+}
+
+/* Negotiate a vmnet connection, returns 0 on success and 1 on error. */
+int negotiate(int fd, struct vif_info *vif)
+{
+    /* Negotiate with com.docker.slirp */
+    struct init_message *me = create_init_message();
+    if (write_init_message(fd, me) == -1) {
+      goto err;
+    }
+    struct init_message you;
+    if (read_init_message(fd, &you) == -1) {
+      goto err;
+    }
+    char *txt = print_init_message(&you);
+    syslog(LOG_INFO, "Server reports %s", txt);
+    free(txt);
+    enum command command = ethernet;
+    if (write_command(fd, &command) == -1) {
+      goto err;
+    }
+    struct ethernet_args args;
+    /* We don't need a uuid */
+    memset(&args.uuid_string[0], 0, sizeof(args.uuid_string));
+    if (write_ethernet_args(fd, &args) == -1) {
+      goto err;
+    }
+    if (read_vif_info(fd, vif) == -1) {
+      goto err;
+    }
+    return 0;
+err:
+    syslog(LOG_CRIT, "Failed to negotiate vmnet connection");
+    return 1;
+}
+
+
+/* Argument passed to proxy threads */
+struct connection {
+    int fd; /* Hyper-V socket with vmnet protocol */
+    int tapfd; /* TAP device with ethernet frames */
+    struct vif_info vif; /* Contains VIF MAC, MTU etc, received from server */
+};
+
+static void* vmnet_to_tap(void *arg)
+{
+  int length, n;
+  struct connection *connection = (struct connection*) arg;
+  uint8_t header[2];
+  uint8_t buffer[2048];
+
+  for (;;) {
+    if (really_read(connection->fd, &header[0], 2) == -1){
+      fatal("Failed to read a packet header from host");
+    }
+    length = (header[0] & 0xff) | ((header[1] & 0xff) << 8);
+    if (length > sizeof(buffer)) {
+      syslog(LOG_CRIT, "Received an over-large packet: %d > %ld", length, sizeof(buffer));
+      exit(1);
+    }
+    if (really_read(connection->fd, &buffer[0], length) == -1){
+      syslog(LOG_CRIT, "Failed to read packet contents from host");
+      exit(1);
+    }
+    n = write(connection->tapfd, &buffer[0], length);
+    if (n != length) {
+      syslog(LOG_CRIT, "Failed to write %d bytes to tap device (wrote %d)", length, n);
+      exit(1);
+    }
+  }
+}
+
+static void* tap_to_vmnet(void *arg)
+{
+  int length;
+  struct connection *connection = (struct connection*) arg;
+  uint8_t header[2];
+  uint8_t buffer[2048];
+
+  for (;;) {
+    length = read(connection->tapfd, &buffer[0], sizeof(buffer));
+    if (length == -1) {
+      if (errno == ENXIO) {
+        fatal("tap device has gone down");
+      }
+      syslog(LOG_WARNING, "ignoring error %d", errno);
+      /* This is what mirage-net-unix does. Is it a good idea really? */
+      continue;
+    }
+    header[0] = (length >> 0) & 0xff;
+    header[1] = (length >> 8) & 0xff;
+    if (really_write(connection->fd, &header[0], 2) == -1){
+      fatal("Failed to write packet header");
+    }
+    if (really_write(connection->fd, &buffer[0], length) == -1) {
+      fatal("Failed to write packet body");
+    }
+  }
+  return NULL;
+}
+
+/* Handle a connection by exchanging ethernet frames forever.
+ */
+static void handle(struct connection *connection)
+{
+    pthread_t v2t, t2v;
+
+    if (pthread_create(&v2t, NULL, vmnet_to_tap, connection) != 0){
+      fatal("Failed to create the vmnet_to_tap thread");
+    }
+    if (pthread_create(&t2v, NULL, tap_to_vmnet, connection) != 0){
+      fatal("Failed to create the tap_to_vmnet thread");
+    }
+    if (pthread_join(v2t, NULL) != 0){
+      fatal("Failed to join the vmnet_to_tap thread");
+    }
+    if (pthread_join(t2v, NULL) != 0){
+      fatal("Failed to join the tap_to_vmnet thread");
+    }
+}
+
+static int create_listening_socket(GUID serviceid) {
+  int lsock = -1;
+  SOCKADDR_HV sa;
+  int res;
+
+  lsock = socket(AF_HYPERV, SOCK_STREAM, HV_PROTOCOL_RAW);
+  if (lsock == -1) {
+      fatal("socket()");
+  }
+
+  sa.Family = AF_HYPERV;
+  sa.Reserved = 0;
+  sa.VmId = HV_GUID_WILDCARD;
+  sa.ServiceId = serviceid;
+
+  res = bind(lsock, (const struct sockaddr *)&sa, sizeof(sa));
+  if (res == -1) {
+      fatal("bind()");
+  }
+
+  res = listen(lsock, SOMAXCONN);
+  if (res == -1) {
+      fatal("listen()");
+  }
+  return lsock;
+}
+
+static int connect_socket(GUID serviceid) {
+  int sock = -1;
+  SOCKADDR_HV sa;
+  int res;
+
+  sock = socket(AF_HYPERV, SOCK_STREAM, HV_PROTOCOL_RAW);
+  if (sock == -1) {
+      fatal("socket()");
+  }
+
+  sa.Family = AF_HYPERV;
+  sa.Reserved = 0;
+  sa.VmId = HV_GUID_PARENT;
+  sa.ServiceId = serviceid;
+
+  res = connect(sock, (const struct sockaddr *)&sa, sizeof(sa));
+  if (res == -1) {
+      fatal("connect()");
+  }
+
+  return sock;
+}
+
+static int accept_socket(int lsock) {
+  int csock = -1;
+  SOCKADDR_HV sac;
+  socklen_t socklen = sizeof(sac);
+
+  csock = accept(lsock, (struct sockaddr *)&sac, &socklen);
+  if (csock == -1) {
+    fatal("accept()");
+  }
+
+  syslog(LOG_INFO, "Connect from: "GUID_FMT":"GUID_FMT"\n",
+    GUID_ARGS(sac.VmId), GUID_ARGS(sac.ServiceId));
+  return csock;
+}
+
+void write_pidfile(const char *pidfile) {
+  pid_t pid = getpid();
+  char * pid_s;
+  FILE *file;
+  int len;
+
+  if (asprintf(&pid_s, "%lld", (long long) pid) == -1) {
+    fatal("Failed to allocate pidfile string");
+  }
+  len = strlen(pid_s);
+  file = fopen(pidfile, "w");
+  if (file == NULL) {
+    syslog(LOG_CRIT, "Failed to open pidfile %s", pidfile);
+    exit(1);
+  }
+
+  if (fwrite(pid_s, 1, len, file) != len) {
+    fatal("Failed to write pid to pidfile");
+  }
+  fclose(file);
+  free(pid_s);
+}
+
+void daemonize(const char *pidfile){
+  pid_t pid = fork ();
+  if (pid == -1) {
+    fatal("Failed to fork()");
+  }
+  else if (pid != 0)
+    exit(0);
+  if (setsid () == -1) {
+    fatal("Failed to setsid()");
+  }
+  if (chdir ("/") == -1) {
+    fatal("Failed to chdir()");
+  }
+  int null = open("/dev/null", O_RDWR);
+  dup2(null, STDIN_FILENO);
+  dup2(null, STDOUT_FILENO);
+  dup2(null, STDERR_FILENO);
+  close(null);
+  if (pidfile) write_pidfile(pidfile);
+}
+
+void usage(char *name)
+{
+    printf("%s usage:\n", name);
+    printf("\t[--daemon] [--tap <name>] [--serviceid <guid>] [--pid <file>]\n");
+    printf("\t[--listen | --connect]\n\n");
+    printf("where\n");
+    printf("\t--daemonize: run as a background daemon\n");
+    printf("\t--tap <name>: create a tap device with the given name\n");
+    printf("\t  (defaults to eth1)\n");
+    printf("\t--serviceid <guid>: use <guid> as the well-known service GUID\n");
+    printf("\t  (defaults to %s)\n", default_sid);
+    printf("\t--pid <file>: write a pid to the given file\n");
+    printf("\t--listen: listen forever for incoming AF_HVSOCK connections\n");
+    printf("\t--connect: connect to the parent partition\n");
+}
+
+int main(int argc, char **argv)
+{
+    int res = 0;
+    GUID sid;
+    int c;
+    /* Defaults to a testing GUID */
+    char *serviceid = default_sid;
+    char *tap = "eth1";
+    char *pidfile = NULL;
+
+    opterr = 0;
+    while (1) {
+      static struct option long_options[] = {
+        /* These options set a flag. */
+        {"daemon",    no_argument,       &daemon_flag, 1},
+        {"serviceid", required_argument, NULL, 's'},
+        {"tap",       required_argument, NULL, 't'},
+        {"pidfile",   required_argument, NULL, 'p'},
+        {"listen",    no_argument,       &listen_flag, 1},
+        {"connect",   no_argument,       &connect_flag, 1},
+        {0, 0, 0, 0}
+      };
+      int option_index = 0;
+
+      c = getopt_long (argc, argv, "ds:t:p:", long_options, &option_index);
+      if (c == -1) break;
+
+      switch (c) {
+        case 'd':
+          daemon_flag = 1;
+          break;
+        case 's':
+          serviceid = optarg;
+          break;
+        case 't':
+          tap = optarg;
+          break;
+        case 'p':
+          pidfile = optarg;
+          break;
+        case 0:
+          break;
+        default:
+          usage (argv[0]);
+          exit (1);
+      }
+    }
+    if ((listen_flag && connect_flag) || !(listen_flag || connect_flag)){
+      fprintf(stderr, "Please supply either the --listen or --connect flag, but not both.\n");
+      exit(1);
+    }
+    if (daemon_flag && !pidfile){
+      fprintf(stderr, "For daemon mode, please supply a --pidfile argument.\n");
+      exit(1);
+    }
+    res = parseguid(serviceid, &sid);
+    if (res) {
+      fprintf(stderr, "Failed to parse serviceid as GUID: %s\n", serviceid);
+      usage(argv[0]);
+      exit(1);
+    }
+
+    int log_flags = LOG_CONS | LOG_NDELAY;
+    if (!daemon_flag) {
+      log_flags |= LOG_PERROR;
+    }
+    openlog(argv[0], log_flags, LOG_DAEMON);
+
+    int tapfd = alloc_tap(tap);
+
+    struct connection connection;
+    connection.tapfd = tapfd;
+
+    int sock = -1;
+
+    for (;;) {
+      if (sock != -1) {
+        close(sock);
+        sock = -1;
+      }
+      if (listen_flag) {
+        syslog(LOG_INFO, "starting in listening mode with serviceid=%s and tap=%s", serviceid, tap);
+        int lsocket = create_listening_socket(sid);
+        sock = accept_socket(lsocket);
+        close(lsocket);
+      } else {
+        syslog(LOG_INFO, "starting in connect mode with serviceid=%s and tap=%s", serviceid, tap);
+        sock = connect_socket(sid);
+      }
+
+      connection.fd = sock;
+      if (negotiate(sock, &connection.vif) != 0) {
+        sleep(1);
+        continue;
+      }
+      syslog(LOG_INFO, "VMNET VIF has MAC %02x:%02x:%02x:%02x:%02x:%02x",
+        connection.vif.mac[0], connection.vif.mac[1], connection.vif.mac[2],
+        connection.vif.mac[3], connection.vif.mac[4], connection.vif.mac[5]
+      );
+      set_macaddr(tap, &connection.vif.mac[0]);
+
+      /* Daemonize after we've made our first reliable connection */
+      if (daemon_flag) {
+        daemon_flag = 0;
+        daemonize(pidfile);
+      }
+      handle(&connection);
+    }
+}