dhcpv4: send NAK to broacast address

[project/odhcpd.git] / src / dhcpv4.c

diff --git a/src/dhcpv4.c b/src/dhcpv4.c
index 7fe5bd8..ebddb22 100644 (file)
--- a/src/dhcpv4.c
+++ b/src/dhcpv4.c
@@ -357,7 +357,16 @@ static void handle_dhcpv4(void *addr, void *data, size_t len,
        } else if (reqmsg == DHCPV4_MSG_REQUEST && reqaddr.s_addr &&
                        reqaddr.s_addr != htonl(lease->addr)) {
                msg = DHCPV4_MSG_NAK;
-               lease = NULL;
+               /*
+                * DHCP client requested an IP which we can't offer to him. Probably the
+                * client changed the network. The reply type is set to DHCPV4_MSG_NAK,
+                * because the client should not use that IP.
+                *
+                * For modern devices we build an answer that includes a valid IP, like
+                * a DHCPV4_MSG_ACK. The client will use that IP and doesn't need to
+                * perform additional DHCP round trips.
+                *
+                */
        }
 
        syslog(LOG_WARNING, "received %s from %x:%x:%x:%x:%x:%x",
@@ -412,8 +421,11 @@ static void handle_dhcpv4(void *addr, void *data, size_t len,
                                        len, search_buf);
        }
 
-       dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
-
+       if (iface->dhcpv4_router_cnt == 0)
+               dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER, 4, &ifaddr.sin_addr);
+       else
+               dhcpv4_put(&reply, &cookie, DHCPV4_OPT_ROUTER,
+                               4 * iface->dhcpv4_router_cnt, iface->dhcpv4_router);
 
 
        if (iface->dhcpv4_dns_cnt == 0)
@@ -427,16 +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);