Fix for name resolution responses containing 0.0.0.0 (#1127)

* Ignores name resolution responses that contain 0.0.0.0 Prevents sending name resolution responses with 0.0.0.0 --------- Co-authored-by: Emil Popov <epopov@cardinalkinetic.com> Co-authored-by: Tony Josi <tonyjosi@amazon.com>
FreeRTOS · Apr 18, 2024 · a53e71a · a53e71a
1 parent 1bc37d3
commit a53e71a
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Showing 2 changed files with 242 additions and 9 deletions.
diff --git a/source/FreeRTOS_DNS_Parser.c b/source/FreeRTOS_DNS_Parser.c
@@ -442,6 +442,13 @@
                             xDNSHookReturn = xApplicationDNSQueryHook_Multi( &xEndPoint, xSet.pcName );
                         #endif
 
+                        /* During the early stages of boot or after a DHCP lease expires, our end-point
+                         * may have an IP address of 0.0.0.0. Do not respond to name queries with that address. */
+                        if( ( xDNSHookReturn != pdFALSE ) && ( xEndPoint.bits.bIPv6 == pdFALSE ) && ( xEndPoint.ipv4_settings.ulIPAddress == 0U ) )
+                        {
+                            xDNSHookReturn = pdFALSE;
+                        }
+
                         if( xDNSHookReturn != pdFALSE )
                         {
                             int16_t usLength;
@@ -655,7 +662,21 @@
 
                 if( pxSet->uxSourceBytesRemaining >= ( sizeof( DNSAnswerRecord_t ) + pxSet->uxAddressLength ) )
                 {
-                    xDoAccept = pdTRUE;
+                    /* Ignore responses containing an IP of 0.0.0.0.
+                     * If we don't stop parsing this now, the code below will
+                     * invoke the user callback and also store this invalid address in our cache. */
+                    void * pvCopyDest;
+                    const void * pvCopySource;
+                    uint32_t ulTestAddress;
+
+                    pvCopySource = &( pxSet->pucByte[ sizeof( DNSAnswerRecord_t ) ] );
+                    pvCopyDest = &( ulTestAddress );
+                    ( void ) memcpy( pvCopyDest, pvCopySource, pxSet->uxAddressLength );
+
+                    if( ulTestAddress != 0U )
+                    {
+                        xDoAccept = pdTRUE;
+                    }
                 }
             }
             else
@@ -798,8 +819,10 @@
                     }
                     #endif /* ipconfigUSE_DNS_CACHE */
 
-                    if( ( ulReturnIPAddress == 0U ) && ( pxSet->ulIPAddress != 0U ) )
+                    if( ulReturnIPAddress == 0U )
                     {
+                        /* Here pxSet->ulIPAddress should be not equal tp 0 since pxSet->ulIPAddress is copied from
+                         * pxSet->pucByte[ sizeof( DNSAnswerRecord_t ) ] and os verified to be non zero above. */
                         /* Remember the first IP-address that is found. */
                         ulReturnIPAddress = pxSet->ulIPAddress;
                     }
@@ -1121,6 +1144,13 @@
                     break;
                 }
 
+                /* During the early stages of boot or after a DHCP lease expires, our end-point
+                 * may have an IP address of 0.0.0.0. Do not respond to name queries with that address. */
+                if( xEndPoint.ipv4_settings.ulIPAddress == 0U )
+                {
+                    break;
+                }
+
                 /* Someone is looking for a device with ucNBNSName,
                  * prepare a positive reply.
                  * The reply will be a bit longer than the request, so make some space.