udhcpc: ignore NAKs from "wrong" servers. Closes 4267

function                                             old     new   delta
udhcpc_main                                         2716    2814     +98

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index 25f18b35dccd6e927c192769ea46f5a336feca82..7dfc160e2dc801234bdc3060f661c92e007a43b4 100644 (file)
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -1232,7 +1232,7 @@ static void client_background(void)
 int udhcpc_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int udhcpc_main(int argc UNUSED_PARAM, char **argv)
 {
-       uint8_t *temp, *message;
+       uint8_t *message;
        const char *str_V, *str_h, *str_F, *str_r;
        IF_FEATURE_UDHCP_PORT(char *str_P;)
        void *clientid_mac_ptr;
@@ -1640,6 +1640,8 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                case INIT_SELECTING:
                        /* Must be a DHCPOFFER */
                        if (*message == DHCPOFFER) {
+                               uint8_t *temp;
+
 /* What exactly is server's IP? There are several values.
  * Example DHCP offer captured with tchdump:
  *
@@ -1689,6 +1691,7 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                        if (*message == DHCPACK) {
                                uint32_t lease_seconds;
                                struct in_addr temp_addr;
+                               uint8_t *temp;
 
                                temp = udhcp_get_option(&packet, DHCP_LEASE_TIME);
                                if (!temp) {
@@ -1766,6 +1769,26 @@ int udhcpc_main(int argc UNUSED_PARAM, char **argv)
                                continue; /* back to main loop */
                        }
                        if (*message == DHCPNAK) {
+                               /* If network has more than one DHCP server,
+                                * "wrong" server can reply first, with a NAK.
+                                * Do not interpret it as a NAK from "our" server.
+                                */
+                               if (server_addr != 0) {
+                                       uint32_t svid;
+                                       uint8_t *temp;
+
+                                       temp = udhcp_get_option(&packet, DHCP_SERVER_ID);
+                                       if (!temp) {
+ non_matching_svid:
+                                               log1("%s with wrong server ID, ignoring packet",
+                                                       "Received DHCP NAK"
+                                               );
+                                               continue;
+                                       }
+                                       move_from_unaligned32(svid, temp);
+                                       if (svid != server_addr)
+                                               goto non_matching_svid;
+                               }
                                /* return to init state */
                                bb_info_msg("Received DHCP NAK");
                                udhcp_run_script(&packet, "nak");