Abstract uses of get_option_data() outside of ifchange.c and options.c.

The eventual goal is to eliminate uses of get_option_data() in ifchange.c and
will make it a static function in options.c.

ndhc/arp.c

@@ -486,12 +486,7 @@ void arp_success(struct client_state_t *cs)
     if (cs->arpPrevState == DS_RENEWING || cs->arpPrevState == DS_REBINDING) {
         arp_switch_state(cs, AS_DEFENSE);
     } else {
-        ssize_t ol;
+        cs->routerAddr = get_option_router(&arp_dhcp_packet);
-        uint8_t *od = get_option_data(&arp_dhcp_packet, DCODE_ROUTER, &ol);
-        if (ol == 4) {
-            memcpy(&cs->routerAddr, od, 4);
-        } else
-            cs->routerAddr = 0;
         arp_get_gw_hwaddr(cs);
     }
     set_listen_none(cs);

ndhc/dhcp.c

@@ -503,13 +503,11 @@ static int validate_dhcp_packet(struct client_state_t *cs, int len,
                  packet->xid, cs->xid);
         return 0;
     }
-    ssize_t optlen;
+    *msgtype = get_option_msgtype(packet);
-    uint8_t *temp = get_option_data(packet, DCODE_MSGTYPE, &optlen);
+    if (!*msgtype) {
-    if (!temp) {
         log_line("Packet does not specify a DHCP message type.  Ignoring.");
         return 0;
     }
-    *msgtype = *temp;
     return 1;
 }
 

ndhc/options.c

@@ -372,3 +372,49 @@ void add_option_hostname(struct dhcpmsg *packet)
         add_option_string(packet, DCODE_HOSTNAME, client_config.hostname, len);
 }
 
+uint32_t get_option_router(struct dhcpmsg *packet)
+{
+    ssize_t ol;
+    uint32_t ret = 0;
+    uint8_t *od = get_option_data(packet, DCODE_ROUTER, &ol);
+    if (ol == sizeof ret)
+        memcpy(&ret, od, sizeof ret);
+    return ret;
+}
+
+uint8_t get_option_msgtype(struct dhcpmsg *packet)
+{
+    ssize_t ol;
+    uint8_t ret = 0;
+    uint8_t *t = get_option_data(packet, DCODE_MSGTYPE, &ol);
+    if (t)
+        ret = *t;
+    return ret;
+}
+
+uint32_t get_option_serverid(struct dhcpmsg *packet, int *found)
+{
+    ssize_t ol;
+    uint8_t *t;
+    uint32_t ret = 0;
+    *found = 0;
+    t = get_option_data(packet, DCODE_SERVER_ID, &ol);
+    if (ol == sizeof ret) {
+        *found = 1;
+        memcpy(&ret, t, sizeof ret);
+    }
+    return ret;
+}
+
+uint32_t get_option_leasetime(struct dhcpmsg *packet)
+{
+    ssize_t ol;
+    uint8_t *t;
+    uint32_t ret = 0;
+    t = get_option_data(packet, DCODE_LEASET, &ol);
+    if (ol == sizeof ret) {
+        memcpy(&ret, t, sizeof ret);
+        ret = ntohl(ret);
+    }
+    return ret;
+}

ndhc/options.h

@@ -82,4 +82,9 @@ void add_option_vendor(struct dhcpmsg *packet);
 void add_option_clientid(struct dhcpmsg *packet);
 void add_option_hostname(struct dhcpmsg *packet);
 
+uint32_t get_option_router(struct dhcpmsg *packet);
+uint8_t get_option_msgtype(struct dhcpmsg *packet);
+uint32_t get_option_serverid(struct dhcpmsg *packet, int *found);
+uint32_t get_option_leasetime(struct dhcpmsg *packet);
+
 #endif

ndhc/state.c

@@ -192,17 +192,15 @@ static void released_timeout(struct client_state_t *cs, long long nowts)
 static int validate_serverid(struct client_state_t *cs, struct dhcpmsg *packet,
                              char *typemsg)
 {
-    uint8_t *temp = NULL;
+    int found;
-    ssize_t optlen;
+    uint32_t sid = get_option_serverid(packet, &found);
-    if (!(temp = get_option_data(packet, DCODE_SERVER_ID, &optlen))) {
+    if (!found) {
         log_line("Received %s with no server id.  Ignoring it.");
         return 0;
     }
-    if (memcmp(&cs->serverAddr, temp, 4)) {
+    if (cs->serverAddr != sid) {
         char svrbuf[INET_ADDRSTRLEN];
-        uint32_t iptmp;
+        inet_ntop(AF_INET, &(struct in_addr){.s_addr=sid},
-        memcpy(&iptmp, temp, 4);
-        inet_ntop(AF_INET, &(struct in_addr){.s_addr=iptmp},
                   svrbuf, sizeof svrbuf);
         log_line("Received %s with an unexpected server id: %s.  Ignoring it.",
                  typemsg, svrbuf);
@@ -218,15 +216,12 @@ static void an_packet(struct client_state_t *cs, struct dhcpmsg *packet,
     if (msgtype == DHCPACK) {
         if (!validate_serverid(cs, packet, "a DHCP ACK"))
             return;
-        ssize_t optlen;
+        cs->lease = get_option_leasetime(packet);
-        uint8_t *temp = get_option_data(packet, DCODE_LEASET, &optlen);
         cs->leaseStartTime = curms();
-        if (!temp) {
+        if (!cs->lease) {
             log_line("No lease time received, assuming 1h.");
             cs->lease = 60 * 60;
         } else {
-            memcpy(&cs->lease, temp, 4);
-            cs->lease = ntohl(cs->lease);
             if (cs->lease < 60) {
                 log_warning("Server sent lease of <1m.  Forcing lease to 1m.");
                 cs->lease = 60;
@@ -269,12 +264,12 @@ static void selecting_packet(struct client_state_t *cs, struct dhcpmsg *packet,
                              uint8_t msgtype)
 {
     if (msgtype == DHCPOFFER) {
-        uint8_t *temp = NULL;
+        int found;
-        ssize_t optlen;
+        uint32_t sid = get_option_serverid(packet, &found);
-        if ((temp = get_option_data(packet, DCODE_SERVER_ID, &optlen))) {
+        if (found) {
             char clibuf[INET_ADDRSTRLEN];
             char svrbuf[INET_ADDRSTRLEN];
-            memcpy(&cs->serverAddr, temp, 4);
+            cs->serverAddr = sid;
             cs->xid = packet->xid;
             cs->clientAddr = packet->yiaddr;
             cs->dhcpState = DS_REQUESTING;