Index: src/dnsmasq.h
===================================================================
--- a/src/dnsmasq.h
+++ b/src/dnsmasq.h
@@ -734,6 +734,8 @@ struct dhcp_lease {
   unsigned char *clid;   /* clientid */
   char *hostname, *fqdn; /* name from client-hostname option or config */
   char *old_hostname;    /* hostname before it moved to another lease */
+  char *fingerprint;     /* DHCP fingerprint  */
+  char *vendor_class;    /* DHCP vendor class */
   int flags;
   time_t expires;        /* lease expiry */
 #ifdef HAVE_BROKEN_RTC
@@ -1458,6 +1460,8 @@ void lease_find_interfaces(time_t now);
 void lease_add_extradata(struct dhcp_lease *lease, unsigned char *data, 
 			 unsigned int len, int delim);
 #endif
+void lease_add_fingerprint(struct dhcp_lease *lease, unsigned char *req_options);
+void lease_add_vendor_class(struct dhcp_lease *lease, unsigned char *data, unsigned int len);
 #endif
 
 /* rfc2131.c */
Index: src/lease.c
===================================================================
--- a/src/lease.c
+++ b/src/lease.c
@@ -21,8 +21,11 @@
 static struct dhcp_lease *leases = NULL, *old_leases = NULL;
 static int dns_dirty, file_dirty, leases_left;
 
+#define SZ_FINGERPRINT  (256)
 static int read_leases(time_t now, FILE *leasestream)
 {
+  char finger_buf[SZ_FINGERPRINT];
+  char vendor_buf[256];
   unsigned long ei;
   union all_addr addr;
   struct dhcp_lease *lease;
@@ -57,9 +60,10 @@ static int read_leases(time_t now, FILE
 	    continue;
 	  }
 #endif
-	
-	if (fscanf(leasestream, " %64s %255s %764s",
-		   daemon->namebuff, daemon->dhcp_buff, daemon->packet) != 3)
+
+	if (fscanf(leasestream, " %64s %255s %255s \"%255[^\"]\" %764s",
+		   daemon->namebuff, daemon->dhcp_buff, finger_buf, vendor_buf, daemon->packet) != 3)
+
 	  {
 	    my_syslog(MS_DHCP | LOG_WARNING, _("ignoring invalid line in lease database: %s %s %s %s ..."),
 		      daemon->dhcp_buff3, daemon->dhcp_buff2,
@@ -116,6 +120,16 @@ static int read_leases(time_t now, FILE
 	if (strcmp(daemon->dhcp_buff, "*") !=  0)
 	  lease_set_hostname(lease, daemon->dhcp_buff, 0, domain, NULL);
 
+	if (strcmp(finger_buf, "*") != 0)
+	{
+	    lease->fingerprint = whine_malloc(SZ_FINGERPRINT);
+	    if (lease->fingerprint)
+	      strncpy(lease->fingerprint, finger_buf, SZ_FINGERPRINT);
+	 }
+
+	if (strcmp(vendor_buf, "*") != 0)
+	   lease->vendor_class = strdup(vendor_buf);
+
 	ei = atol(daemon->dhcp_buff3);
 
 #ifdef HAVE_BROKEN_RTC
@@ -248,6 +262,23 @@ static void ourprintf(int *errp, char *f
   va_end(ap);
 }
 
+int lock_file(int fd, int lock)
+{
+  struct flock fl;
+
+  fl.l_type = lock ? F_WRLCK : F_UNLCK;
+  fl.l_whence = SEEK_SET;
+  fl.l_start = 0;
+  fl.l_len = 0;
+
+  if (fcntl(fd, F_SETLKW, &fl) == -1)
+  {
+      return 1;
+  }
+
+  return 0;
+}
+
 void lease_update_file(time_t now)
 {
   struct dhcp_lease *lease;
@@ -257,6 +288,11 @@ void lease_update_file(time_t now)
   if (file_dirty != 0 && daemon->lease_stream)
     {
       errno = 0;
+	  if (lock_file(fileno(daemon->lease_stream), 1) != 0)
+      {
+          err = errno;
+      }
+
       rewind(daemon->lease_stream);
       if (errno != 0 || ftruncate(fileno(daemon->lease_stream), 0) != 0)
 	err = errno;
@@ -288,6 +324,9 @@ void lease_update_file(time_t now)
 
 	  ourprintf(&err, " %s ", daemon->addrbuff);
 	  ourprintf(&err, "%s ", lease->hostname ? lease->hostname : "*");
+	  ourprintf(&err, "%s ", lease->fingerprint ? lease->fingerprint : "*");
+	  // Here we use double quotes since vendor-class can contain spaces
+	  ourprintf(&err, "\"%s\" ", lease->vendor_class ? lease->vendor_class : "*");
 	  	  
 	  if (lease->clid && lease->clid_len != 0)
 	    {
@@ -324,6 +363,10 @@ void lease_update_file(time_t now)
 	      ourprintf(&err, "%s%u %s ", (lease->flags & LEASE_TA) ? "T" : "",
 			lease->iaid, daemon->addrbuff);
 	      ourprintf(&err, "%s ", lease->hostname ? lease->hostname : "*");
+		  /* DHCPv6 doesn't support fingerprinting, add a dummy entry */
+	      ourprintf(&err, "%s ", "*");
+		  // Here we use double quotes since vendor-class can contain spaces
+	      ourprintf(&err, "\"%s\" ", lease->vendor_class ? lease->vendor_class : "*");
 	      
 	      if (lease->clid && lease->clid_len != 0)
 		{
@@ -340,6 +383,10 @@ void lease_update_file(time_t now)
       if (fflush(daemon->lease_stream) != 0 ||
 	  fsync(fileno(daemon->lease_stream)) < 0)
 	err = errno;
+
+	   /* Unlock file */
+      if (lock_file(fileno(daemon->lease_stream), 0) != 0)
+        err = errno;
       
       if (!err)
 	file_dirty = 0;
@@ -564,6 +611,18 @@ void lease_prune(struct dhcp_lease *targ
 	  if (lease->hostname)
 	    dns_dirty = 1;
 
+	  if (lease->fingerprint)
+      {
+         free(lease->fingerprint);
+         lease->fingerprint = NULL;
+      }
+
+	  if (lease->vendor_class)
+      {
+        free(lease->vendor_class);
+        lease->vendor_class = NULL;
+      }
+
 	  daemon->metrics[lease->addr.s_addr ? METRIC_LEASES_PRUNED_4 : METRIC_LEASES_PRUNED_6]++;
 
  	  *up = lease->next; /* unlink */
@@ -1201,6 +1260,81 @@ void lease_add_extradata(struct dhcp_lea
 }
 #endif
 
+void lease_add_fingerprint(struct dhcp_lease *lease, unsigned char *req_options)
+{
+  unsigned int i, len, left;
+
+  if (req_options == NULL || req_options[0] == OPTION_END)
+  {
+    /*
+     * We were given empty options -- we are not allowed to generate an empty fingerprint string, in such case
+     * it should be set to NULL instead of ""
+     */
+    if (lease->fingerprint != NULL)
+      free(lease->fingerprint);
+
+    lease->fingerprint = NULL;
+    return;
+  }
+
+  if (lease->fingerprint == NULL)
+  {
+    lease->fingerprint = whine_malloc(SZ_FINGERPRINT);
+    if (lease->fingerprint == NULL)
+      return;
+  }
+
+  char *q = lease->fingerprint;
+  for (i = 0; req_options[i] != OPTION_END; i++)
+  {
+    left = (SZ_FINGERPRINT - (q - lease->fingerprint));
+    len  = snprintf(q,
+                    left,
+                    "%d%s",
+                    req_options[i],
+                    req_options[i+1] == OPTION_END ? "" : ",");
+    /*
+     * snprintf returns len that would have been written, not
+     * how much was actually written. This means return value
+     * can be higher then max length provided
+     */
+    if (len > left) {
+      /*
+       * Not enough room to append the entire otpion,
+       * so truncate after last option
+       */
+      *(q-1) = '\0';
+      break;
+    }
+    q += len;
+  }
+}
+
+void lease_add_vendor_class(struct dhcp_lease *lease, unsigned char *data, unsigned int len)
+{
+  unsigned int i;
+
+  if (lease->vendor_class != NULL)
+  {
+    free(lease->vendor_class);
+    lease->vendor_class = NULL;
+  }
+
+  if (len > 0)
+  {
+    lease->vendor_class = whine_malloc(len + 1);
+    memcpy(lease->vendor_class, data, len);
+    lease->vendor_class[len]    = '\0';
+
+    // Escape quotes (") and 0 in vendor-class by replacing them with space just to be safe
+    for (i = 0; i < len; i++)
+    {
+        if (lease->vendor_class[i] == '\"' || lease->vendor_class[i] == '\0')
+            lease->vendor_class[i] = ' ';
+    }
+  }
+}
+
 #endif