Add support for unique TFTP root per MAC.

It is currently only possible to let the TFTP server serve a different
folder depending on the client's IP address.
However it isn't always possible to predict what the client's
IP address will be, especially in situations in which we are not
responsible for handing them out (e.g. proxy dhcp setups).

Extend the current --tftp-unique-root parameter to support having a
separate folder per MAC address instead.

src/dnsmasq.h

@@ -211,7 +211,7 @@ struct event_desc {
 #define OPT_TFTP_SECURE    26
 #define OPT_TFTP_NOBLOCK   27
 #define OPT_LOG_OPTS       28
-#define OPT_TFTP_APREF     29
+#define OPT_TFTP_APREF_IP  29
 #define OPT_NO_OVERRIDE    30
 #define OPT_NO_REBIND      31
 #define OPT_ADD_MAC        32
@@ -238,7 +238,8 @@ struct event_desc {
 #define OPT_SCRIPT_ARP     53
 #define OPT_MAC_B64        54
 #define OPT_MAC_HEX        55
-#define OPT_LAST           56
+#define OPT_TFTP_APREF_MAC 56
+#define OPT_LAST           57
 
 /* extra flags for my_syslog, we use a couple of facilities since they are known 
    not to occupy the same bits as priorities, no matter how syslog.h is set up. */

src/option.c

@@ -242,7 +242,7 @@ static const struct myoption opts[] =
     { "enable-tftp", 2, 0, LOPT_TFTP },
     { "tftp-secure", 0, 0, LOPT_SECURE },
     { "tftp-no-fail", 0, 0, LOPT_TFTP_NO_FAIL },
-    { "tftp-unique-root", 0, 0, LOPT_APREF },
+    { "tftp-unique-root", 2, 0, LOPT_APREF },
     { "tftp-root", 1, 0, LOPT_PREFIX },
     { "tftp-max", 1, 0, LOPT_TFTP_MAX },
     { "tftp-mtu", 1, 0, LOPT_TFTP_MTU },
@@ -430,7 +430,7 @@ static struct {
   { LOPT_OVERRIDE, OPT_NO_OVERRIDE, NULL, gettext_noop("Do NOT reuse filename and server fields for extra DHCP options."), NULL },
   { LOPT_TFTP, ARG_DUP, "[=<intr>[,<intr>]]", gettext_noop("Enable integrated read-only TFTP server."), NULL },
   { LOPT_PREFIX, ARG_DUP, "<dir>[,<iface>]", gettext_noop("Export files by TFTP only from the specified subtree."), NULL },
-  { LOPT_APREF, OPT_TFTP_APREF, NULL, gettext_noop("Add client IP address to tftp-root."), NULL },
+  { LOPT_APREF, ARG_DUP, "[=ip|mac]", gettext_noop("Add client IP or hardware address to tftp-root."), NULL },
   { LOPT_SECURE, OPT_TFTP_SECURE, NULL, gettext_noop("Allow access only to files owned by the user running dnsmasq."), NULL },
   { LOPT_TFTP_NO_FAIL, OPT_TFTP_NO_FAIL, NULL, gettext_noop("Do not terminate the service if TFTP directories are inaccessible."), NULL },
   { LOPT_TFTP_MAX, ARG_ONE, "<integer>", gettext_noop("Maximum number of concurrent TFTP transfers (defaults to %s)."), "#" },
@@ -2717,6 +2717,15 @@ static int one_opt(int option, char *arg, char *errstr, char *gen_err, int comma
 	} 
       
       break;
+
+    case LOPT_APREF: /* --tftp-unique-root */
+      if (!arg || strcasecmp(arg, "ip") == 0)
+        set_option_bool(OPT_TFTP_APREF_IP);
+      else if (strcasecmp(arg, "mac") == 0)
+        set_option_bool(OPT_TFTP_APREF_MAC);
+      else
+        ret_err(gen_err);
+      break;
 #endif
 	      
     case LOPT_BRIDGE:   /* --bridge-interface */

src/tftp.c

@@ -382,7 +382,7 @@ void tftp_request(struct listener *listen, time_t now)
 	  if (prefix[strlen(prefix)-1] != '/')
 	    strncat(daemon->namebuff, "/", (MAXDNAME-1) - strlen(daemon->namebuff));
 
-	  if (option_bool(OPT_TFTP_APREF))
+	  if (option_bool(OPT_TFTP_APREF_IP))
 	    {
 	      size_t oldlen = strlen(daemon->namebuff);
 	      struct stat statbuf;
@@ -394,6 +394,38 @@ void tftp_request(struct listener *listen, time_t now)
 	      if (stat(daemon->namebuff, &statbuf) == -1 || !S_ISDIR(statbuf.st_mode))
 		daemon->namebuff[oldlen] = 0;
 	    }
+	  if (option_bool(OPT_TFTP_APREF_MAC))
+	    {
+	      unsigned char *macaddr = NULL;
+	      unsigned char macbuf[DHCP_CHADDR_MAX];
+
+#ifdef HAVE_DHCP
+	      if (daemon->dhcp && peer.sa.sa_family == AF_INET)
+	        {
+		  /* Check if the client IP is in our lease database */
+		  struct dhcp_lease *lease = lease_find_by_addr(peer.in.sin_addr);
+		  if (lease && lease->hwaddr_type == ARPHRD_ETHER && lease->hwaddr_len == ETHER_ADDR_LEN)
+		    macaddr = lease->hwaddr;
+		}
+#endif
+
+	      /* If no luck, try to find in ARP table. This only works if client is in same (V)LAN */
+	      if (!macaddr && find_mac(&peer, macbuf, 1, now) > 0)
+		  macaddr = macbuf;
+
+	      if (macaddr)
+	        {
+		  size_t oldlen = strlen(daemon->namebuff);
+		  struct stat statbuf;
+
+		  snprintf(daemon->namebuff + oldlen, (MAXDNAME-1) - oldlen, "%.2x-%.2x-%.2x-%.2x-%.2x-%.2x/",
+			   macaddr[0], macaddr[1], macaddr[2], macaddr[3], macaddr[4], macaddr[5]);
+
+		  /* remove unique-directory if it doesn't exist */
+		  if (stat(daemon->namebuff, &statbuf) == -1 || !S_ISDIR(statbuf.st_mode))
+		    daemon->namebuff[oldlen] = 0;
+		}
+	    }
 		
 	  /* Absolute pathnames OK if they match prefix */
 	  if (filename[0] == '/')