pull out struct types of complex rdata fields

examples/dns.h

@@ -35,35 +35,22 @@ typedef struct dns_question {
   uint16_t qclass;
 } dns_question_t;
 
-typedef struct dns_rr {
+typedef struct {
-  char* name;
-  uint16_t type;
-  uint16_t class;
-  uint32_t ttl; // cmos is also acceptable.
-  uint16_t rdlength;
-  union {
-    char* cname;
-    struct {
   uint8_t* cpu;
   uint8_t* os;
-    } hinfo;
+} dns_rr_hinfo_t;
-    char* mb;
+
-    char* md;
+typedef struct {
-    char* mf;
-    char* mg;
-    struct {
   char* rmailbx;
   char* emailbx;
-    } minfo;
+} dns_rr_minfo_t;
-    char* mr;
+
-    struct {
+typedef struct {
   uint16_t preference;
   char* exchange;
-    } mx;
+} dns_rr_mx_t;
-    uint8_t* null;
+
-    char* ns;
+typedef struct {
-    char* ptr;
-    struct {
   char* mname;
   char* rname;
   uint32_t serial;
@@ -71,18 +58,43 @@ typedef struct dns_rr {
   uint32_t retry;
   uint32_t expire;
   uint32_t minimum;
-    } soa;
+} dns_rr_soa_t;
-    struct {
+
+typedef struct {
   size_t count;
   uint8_t** txt_data;
-    } txt;
+} dns_rr_txt_t;
-    uint32_t a;
+
-    struct {
+typedef struct {
   uint32_t address;
   uint8_t protocol;
   size_t len;
   uint8_t* bit_map;
-    } wks;
+} dns_rr_wks_t;
+
+typedef struct dns_rr {
+  char* name;
+  uint16_t type;
+  uint16_t class;
+  uint32_t ttl; // cmos is also acceptable.
+  uint16_t rdlength;
+  union {
+    uint32_t       a;
+    char*          ns;
+    char*          md;
+    char*          mf;
+    char*          cname;
+    dns_rr_soa_t   soa;
+    char*          mb;
+    char*          mg;
+    char*          mr;
+    uint8_t*       null;
+    dns_rr_wks_t   wks;
+    char*          ptr;
+    dns_rr_hinfo_t hinfo;
+    dns_rr_minfo_t minfo;
+    dns_rr_mx_t    mx;
+    dns_rr_txt_t   txt;
   };
 } dns_rr_t;