Change the rules for sending DHCP responses

giaddr -> giaddr
broadcast -> broadcast
nak -> broadcast
!ciaddr -> broadcast
ciaddr -> ciaddr BUT
   if the request was not *from* ciaddr, we need to send a "raw"
   response.

Many DHCP clients can handle a broadcast DHCP OFFER / ACK when first
assigning an address.  Some clients expect a response unicast to
their MAC address.

diff --git a/src/lib/dhcp.c b/src/lib/dhcp.c
index 603c07fb6ba9873ea1f7b2d958e3b87a2710da4f..105db0eb3260ed4fe653456b7aa37dde6989db9b 100644 (file)
--- a/src/lib/dhcp.c
+++ b/src/lib/dhcp.c
@@ -375,6 +375,17 @@ int fr_dhcp_send(RADIUS_PACKET *packet)
        fr_ipaddr2sockaddr(&packet->dst_ipaddr, packet->dst_port,
                           &dst, &sizeof_dst);
 
+       /*
+        *      The client doesn't yet have an IP address, but is
+        *      expecting an ethernet packet unicast to it's MAC
+        *      address.  We need to build a raw frame.
+        */
+       if (packet->offset == 0) {
+               /*
+                *      FIXME: Insert code here!
+                */
+       }
+
 #ifndef WITH_UDPFROMTO
        /*
         *      Assume that the packet is encoded before sending it.
@@ -978,11 +989,10 @@ int fr_dhcp_encode(RADIUS_PACKET *packet, RADIUS_PACKET *original)
                 *      to the client.
                 *
                 *      if giaddr, send to giaddr.
-                *      if NAK, send broadcast packet
-                *      if ciaddr, unicast to ciaddr
-                *      if flags & 0x8000, broadcast (client request)
-                *      if sent from 0.0.0.0, broadcast response
-                *      unicast to client yiaddr
+                *      if NAK, send broadcast.
+                *      if broadcast flag, send broadcast.
+                *      if ciaddr is empty, send broadcast.
+                *      otherwise unicast to ciaddr.
                 */
                
                /*
@@ -991,6 +1001,12 @@ int fr_dhcp_encode(RADIUS_PACKET *packet, RADIUS_PACKET *original)
                 */
                dhcp = (dhcp_packet_t *) original->data;
                
+               /*
+                *      Default to sending it via sendto(), without using
+                *      raw sockets.
+                */
+               packet->offset = 1;
+
                if (dhcp->giaddr != htonl(INADDR_ANY)) {
                        packet->dst_ipaddr.ipaddr.ip4addr.s_addr = dhcp->giaddr;
                        
@@ -1000,23 +1016,24 @@ int fr_dhcp_encode(RADIUS_PACKET *packet, RADIUS_PACKET *original)
                                packet->dst_port = original->src_port; /* debugging */
                        }
                        
-               } else if (packet->code == PW_DHCP_NAK) {
-                       packet->dst_ipaddr.ipaddr.ip4addr.s_addr = htonl(INADDR_BROADCAST);
-                       
-               } else if (dhcp->ciaddr != htonl(INADDR_ANY)) {
-                       packet->dst_ipaddr.ipaddr.ip4addr.s_addr = dhcp->ciaddr;
-                       
-               } else if ((dhcp->flags & 0x8000) != 0) {
-                       packet->dst_ipaddr.ipaddr.ip4addr.s_addr = htonl(INADDR_BROADCAST);
-                       
-               } else if (packet->dst_ipaddr.ipaddr.ip4addr.s_addr == htonl(INADDR_ANY)) {
+               } else if ((packet->code == PW_DHCP_NAK) ||
+                          ((dhcp->flags & 0x8000) != 0) ||
+                          (dhcp->ciaddr == htonl(INADDR_ANY))) {
+                       /*
+                        *      The kernel will take care of sending it to
+                        *      the broadcast MAC.
+                        */
                        packet->dst_ipaddr.ipaddr.ip4addr.s_addr = htonl(INADDR_BROADCAST);
                        
-               } else if (dhcp->yiaddr != htonl(INADDR_ANY)) {
-                       packet->dst_ipaddr.ipaddr.ip4addr.s_addr = dhcp->yiaddr;
-                       
                } else {
-                       /* leave destination IP alone. */
+                       /*
+                        *      It was broadcast to us: we need to
+                        *      broadcast the response.
+                        */
+                       if (packet->src_ipaddr.ipaddr.ip4addr.s_addr != dhcp->ciaddr) {
+                               packet->offset = 0;
+                       }
+                       packet->dst_ipaddr.ipaddr.ip4addr.s_addr = dhcp->ciaddr;
                }
 
                /*