--- relay/dhcrelay.c.org	2007-02-14 17:41:23.000000000 -0500
+++ relay/dhcrelay.c	2007-11-25 14:28:24.000000000 -0500
@@ -53,6 +53,7 @@
 char *tlname;
 
 const char *path_dhcrelay_pid = _PATH_DHCRELAY_PID;
+const char *path_dhcrelay_hosts = NULL;
 
 int bogus_agent_drops = 0;	/* Packets dropped because agent option
 				   field was specified and we're not relaying
@@ -98,11 +99,19 @@
 	struct sockaddr_in to;
 } *servers;
 
+struct hosts_list {
+  struct hosts_list *next;
+  unsigned char MACaddress[17];  /* Including : */
+  struct server_list *servers;
+} *hosts;
+
 static char copyright [] = "Copyright 2004-2007 Internet Systems Consortium.";
 static char arr [] = "All rights reserved.";
 static char message [] = "Internet Systems Consortium DHCP Relay Agent";
 static char url [] = "For info, please visit http://www.isc.org/sw/dhcp/";
 
+isc_result_t readhosts ();
+
 int main (argc, argv, envp)
 	int argc;
 	char **argv, **envp;
@@ -115,6 +124,7 @@
 	int quiet = 0;
 	isc_result_t status;
 	char *s;
+	int no_dhcrelay_hosts = 0;
 
         /* Make sure that file descriptors 0 (stdin), 1, (stdout), and
            2 (stderr) are open. To do this, we assume that when we
@@ -186,7 +196,12 @@
 				max_hop_count= hcount;
 			else
 				usage ();
-		} else if (!strcmp (argv [i], "-A")) {
+		} else if (!strcmp (argv [i], "-ch")) {
+			if (++i == argc)
+				usage ();
+			path_dhcrelay_hosts = argv [i];
+			no_dhcrelay_hosts = 1;
+                } else if (!strcmp (argv [i], "-A")) {
 			if (++i == argc)
 				usage ();
 			dhcp_max_agent_option_packet_length = atoi (argv [i]);
@@ -268,6 +283,10 @@
 		usage ();
 	}
 
+	/* Read the dhcrelay.hosts file... */
+	if (readhosts () != ISC_R_SUCCESS)
+		log_fatal ("Hosts file errors encountered -- exiting");
+
 	/* Set up the server sockaddrs. */
 	for (sp = servers; sp; sp = sp -> next) {
 		sp -> to.sin_port = local_port;
@@ -337,7 +356,8 @@
 	struct hardware *hfrom;
 {
 	struct server_list *sp;
-	struct sockaddr_in to;
+        struct hosts_list *hp = NULL;
+        struct sockaddr_in to;
 	struct interface_info *out;
 	struct hardware hto, *htop;
 
@@ -440,7 +460,29 @@
 
 	/* Otherwise, it's a BOOTREQUEST, so forward it to all the
 	   servers. */
-	for (sp = servers; sp; sp = sp -> next) {
+
+        /* Check for entry in hosts file first */
+        for (hp = hosts; hp; hp = hp -> next) {
+          /*log_debug("Comparing BOOTREQUEST MAC %s with %s\n", print_hw_addr (packet -> htype, 
+               packet -> hlen, packet -> chaddr), hp->MACaddress); */
+          
+          if (strcasestr(hp->MACaddress, print_hw_addr (packet -> htype, 
+                packet -> hlen, packet -> chaddr))) {
+            /* log_debug("MAC address matches\n"); */
+
+            for (sp = hp->servers; sp; sp = sp -> next) {
+              /* log_debug(" Server: %s\n", inet_ntoa (sp -> to.sin_addr)); */
+            }
+            sp = hp->servers;
+            break;
+          }
+          else {
+            sp = servers;
+          }
+        }
+
+        /*for (sp = servers; sp; sp = sp -> next) { */
+        for (; sp; sp = sp -> next) {
 		if (send_packet ((fallback_interface
 				  ? fallback_interface : interfaces),
 				 (struct packet *)0,
@@ -464,7 +506,7 @@
 		"interface] [-q] [-a]\n                ",
 		"[-c count] [-A length] ",
 		"[-m append|replace|forward|discard]\n",
-		"                [server1 [... serverN]]");
+                "                [-ch hosts-file] [server1 [... serverN]]");
 }
 
 int write_lease (lease)
@@ -915,3 +957,109 @@
 
 	return length;
 }
+
+/* Read in dhcrelay.hosts file */
+isc_result_t readhosts ()
+{
+  FILE *hostsfile;
+  char buffer[255];
+  char *tokenize = NULL;
+  char *comment = NULL;
+  struct hosts_list *hp = NULL;
+  struct server_list *sp = NULL;
+
+  if (!path_dhcrelay_hosts)
+    return 1;
+  
+  log_debug ("\nLoading hosts file %s\n",path_dhcrelay_hosts);
+  
+  hostsfile = fopen(path_dhcrelay_hosts, "r");
+  if (!hostsfile) {
+    log_fatal ("Can't open %s: %m", path_dhcrelay_hosts);
+    return 1;
+  }
+
+  while(fgets(buffer,255,hostsfile)) {
+    comment = strchr(buffer, '#');
+    if (comment) {
+      *comment = '\0';
+      }
+
+    tokenize = strtok(buffer," \t");
+    if (!tokenize)
+      continue;
+
+    if (strlen(tokenize) <= 1)
+      continue;
+
+    if (strlen(tokenize) != 17) {
+      log_debug (" Invalid MAC address detected.  Skipping line: %s.\n", buffer);
+      continue;
+    }
+
+    /* Allocate memory for MAC list structure */
+    hp = ((struct hosts_list *) malloc (sizeof *hp));
+    if (!hp) {
+      log_fatal("no memory for hosts list\n");
+    }
+
+    /* Add a structure */
+    hp->next = hosts;
+    hosts = hp;
+    strncpy(hp->MACaddress, tokenize, 17);
+    
+    /* Add server(s) to structure */
+    while (tokenize != NULL) {
+      tokenize = strtok(NULL," \t");
+
+      if (tokenize == NULL)
+        continue;
+
+      struct hostent *he;
+      struct in_addr ia, *iap = (struct in_addr *)0;
+      if (inet_aton (tokenize, &ia)) {
+        iap = &ia;
+      } else {
+        he = gethostbyname (tokenize);
+        if (!he) {
+          log_error ("%s: host unknown",
+              tokenize);
+        } else {
+          iap = ((struct in_addr *)
+              he -> h_addr_list [0]);
+        }
+      }
+      
+      if (iap) {
+        sp = ((struct server_list *)
+            dmalloc (sizeof *sp, MDL));
+        if (!sp)
+          log_fatal ("no memory for server.\n");
+        sp -> next = hp->servers;
+        hp->servers = sp;
+        memcpy (&sp -> to.sin_addr,
+            iap, sizeof *iap);      
+      }
+    }
+    
+    /* Set up the server sockaddrs. */
+    for (sp = hp->servers; sp; sp = sp -> next) {
+      sp -> to.sin_port = local_port;
+      sp -> to.sin_family = AF_INET;
+#ifdef HAVE_SA_LEN
+      sp -> to.sin_len = sizeof sp -> to;
+#endif
+    }
+  }
+
+  /*
+  for (hp = hosts; hp; hp = hp -> next) {
+    printf("MAC: %s\n",hp->MACaddress);    
+    for (sp = hp->servers; sp; sp = sp -> next) {
+      printf(" Server: %s\n", inet_ntoa (sp -> to.sin_addr));
+    }
+  }*/
+
+  return 0;
+}
+