Preliminary implementation of DHCP relay

For now, it can only relay packets if giaddr = 0.
If giaddr != 0, we are required to cache the packet by XID/MAC, so that
we can capture the response on the DHCP port, look up the XID/MAC, and
respond to the client.

We will also need to update the fr_dhcp_encode function, which can
currently only respond to clients, and not originate packets.

diff --git a/share/dictionary.dhcp b/share/dictionary.dhcp
index 966379e..aac3952 100644 (file)
--- a/share/dictionary.dhcp
+++ b/share/dictionary.dhcp
@@ -46,6 +46,8 @@ ATTRIBUTE     DHCP-Client-Hardware-Address            267     ether     # 16 octets
 ATTRIBUTE      DHCP-Server-Host-Name                   268     string    # 64 octets
 ATTRIBUTE      DHCP-Boot-Filename                      269     string    # 128 octets
 
+ATTRIBUTE      DHCP-Relay-To-IP-Address                270     ipaddr
+
 VALUE  DHCP-Flags                      Broadcast               0x8000
 
 

diff --git a/src/main/dhcpd.c b/src/main/dhcpd.c
index 9db6c96..50123d5 100644 (file)
--- a/src/main/dhcpd.c
+++ b/src/main/dhcpd.c
@@ -56,8 +56,71 @@ static int dhcp_process(REQUEST *request)
        }
 
        /*
-        *      Look for Relay attribute, and forward it if so...
+        *      Look for Relay attribute, and forward it if necessary.
         */
+       vp = pairfind(request->config_items, DHCP2ATTR(270));
+       if (vp) {
+               VALUE_PAIR *giaddr;
+               RADIUS_PACKET relayed;
+               
+               request->reply->code = 0; /* don't reply to the client */
+
+               /*
+                *      Find the original giaddr.
+                *      FIXME: Maybe look in the original packet?
+                *
+                *      It's invalid to have giaddr=0 AND a relay option
+                */
+               giaddr = pairfind(request->packet->vps, 266);
+               if (giaddr && (giaddr->vp_ipaddr == htonl(INADDR_ANY))) {
+                       if (pairfind(request->packet->vps, DHCP2ATTR(82))) {
+                               RDEBUG("DHCP: Received packet with giaddr = 0 and containing relay option: Discarding packet");
+                               return 1;
+                       }
+
+                       /*
+                        *      FIXME: Add cache by XID.
+                        */
+                       RDEBUG("DHCP: Cannot yet relay packets with giaddr = 0");
+                       return 1;
+               }
+
+               if (packet->data[3] > 10) {
+                       RDEBUG("DHCP: Number of hops is greater than 10: not relaying");
+                       return 1;
+               }
+
+               /*
+                *      Forward it VERBATIM to the next server, rather
+                *      than to the client.
+                */
+               memcpy(&relayed, packet, sizeof(relayed));
+
+               relayed.dst_ipaddr.af = AF_INET;
+               relayed.dst_ipaddr.ipaddr.s_addr = vp->vp_ipaddr;
+               relayed.dst_port = request->packet->dst_port;
+
+               relayed.src_ipaddr = request->packet->dst_ipaddr;
+               relayed.src_port = request->packet->dst_port;
+
+               relayed.data = rad_malloc(relayed.data_len);
+               memcpy(relayed.data, request->packet->data, data_len);
+               relayed.vps = NULL;
+
+               /*
+                *      The only field that changes is the number of hops
+                */
+               relayed.data[3]++; /* number of hops */
+               
+               /*
+                *      Forward the relayed packet VERBATIM, don't
+                *      respond to the client, and forget completely
+                *      about this request.
+                */
+               fr_dhcp_send(&relayed);
+               free(relayed.data);
+               return 1;
+       }
 
        vp = pairfind(request->reply->vps, DHCP2ATTR(53)); /* DHCP-Message-Type */
        if (vp) {