Merge pull request #23 from mehlis/nak-to-broadcast

dhcpv4: send Nak to broadcast address

diff --git a/src/dhcpv4.c b/src/dhcpv4.c
index 9b9b528..92a1397 100644 (file)
--- a/src/dhcpv4.c
+++ b/src/dhcpv4.c
@@ -439,16 +439,36 @@ static void handle_dhcpv4(void *addr, void *data, size_t len,
 
        struct sockaddr_in dest = *((struct sockaddr_in*)addr);
        if (req->giaddr.s_addr) {
+               /*
+                * relay agent is configured, send reply to the agent
+                */
                dest.sin_addr = req->giaddr;
                dest.sin_port = htons(DHCPV4_SERVER_PORT);
        } else if (req->ciaddr.s_addr && req->ciaddr.s_addr != dest.sin_addr.s_addr) {
+               /*
+                * client has existing configuration (ciaddr is set) AND this address is
+                * not the address it used for the dhcp message
+                */
                dest.sin_addr = req->ciaddr;
                dest.sin_port = htons(DHCPV4_CLIENT_PORT);
        } else if ((ntohs(req->flags) & DHCPV4_FLAG_BROADCAST) ||
                        req->hlen != reply.hlen || !reply.yiaddr.s_addr) {
+               /*
+                * client requests a broadcast reply OR we can't offer an IP
+                */
+               dest.sin_addr.s_addr = INADDR_BROADCAST;
+               dest.sin_port = htons(DHCPV4_CLIENT_PORT);
+       } else if (!req->ciaddr.s_addr && msg == DHCPV4_MSG_NAK) {
+               /*
+                * client has no previous configuration -> no IP, so we need to reply
+                * with a broadcast packet
+                */
                dest.sin_addr.s_addr = INADDR_BROADCAST;
                dest.sin_port = htons(DHCPV4_CLIENT_PORT);
        } else {
+               /*
+                * send reply to the newly (in this proccess) allocated IP
+                */
                dest.sin_addr = reply.yiaddr;
                dest.sin_port = htons(DHCPV4_CLIENT_PORT);
 
@@ -459,10 +479,24 @@ static void handle_dhcpv4(void *addr, void *data, size_t len,
                ioctl(sock, SIOCSARP, &arp);
        }
 
-       syslog(LOG_WARNING, "sending %s to %x:%x:%x:%x:%x:%x",
-                       dhcpv4_msg_to_string(msg),
-                       req->chaddr[0],req->chaddr[1],req->chaddr[2],
-                       req->chaddr[3],req->chaddr[4],req->chaddr[5]);
+       if (dest.sin_addr.s_addr == INADDR_BROADCAST) {
+               /*
+                * reply goes to IP broadcast -> MAC broadcast
+                */
+               syslog(LOG_WARNING, "sending %s to ff:ff:ff:ff:ff:ff - %s",
+                               dhcpv4_msg_to_string(msg),
+                               inet_ntoa(dest.sin_addr));
+       } else {
+               /*
+                * reply is send directly to IP,
+                * MAC is assumed to be the same as the request
+                */
+               syslog(LOG_WARNING, "sending %s to %x:%x:%x:%x:%x:%x - %s",
+                               dhcpv4_msg_to_string(msg),
+                               req->chaddr[0],req->chaddr[1],req->chaddr[2],
+                               req->chaddr[3],req->chaddr[4],req->chaddr[5],
+                               inet_ntoa(dest.sin_addr));
+       }
 
        sendto(sock, &reply, sizeof(reply), MSG_DONTWAIT,
                        (struct sockaddr*)&dest, sizeof(dest));