Minor change: move DNS_MSG_SIZE in opt.h, add comments.

src/core/dns.c

@@ -102,9 +102,6 @@
 #define DNS_MAX_TTL               604800
 #endif
 
-/** DNS message max. size */
-#define DNS_MSG_SIZE              512
-
 /* DNS protocol flags */
 #define DNS_FLAG1_RESPONSE        0x80
 #define DNS_FLAG1_OPCODE_STATUS   0x10

src/include/lwip/opt.h

@@ -580,11 +580,17 @@
 #endif
 
 /** DNS use a local buffer if DNS_USES_STATIC_BUF=0, a static one if
-    DNS_USES_STATIC_BUF=1, or a dynamic one if DNS_USES_STATIC_BUF=2. */
+    DNS_USES_STATIC_BUF=1, or a dynamic one if DNS_USES_STATIC_BUF=2.
+    The buffer will be of size DNS_MSG_SIZE */
 #ifndef DNS_USES_STATIC_BUF
 #define DNS_USES_STATIC_BUF             1
 #endif
 
+/** DNS message max. size. Default value is RFC compliant. */
+#ifndef DNS_MSG_SIZE
+#define DNS_MSG_SIZE                    512
+#endif
+
 /*
    ---------------------------------
    ---------- UDP options ----------