Fix propagation of implicit TTL

Use value specified in $TTL directive if available, use the last stated
explicit TTL otherwise.

Fixes NLnetLabs/nsd#375.

Author: k0ekk0ek

include/zone.h

@@ -279,8 +279,6 @@ struct zone_rdata_buffer {
  */
 #define ZONE_TAPE_SIZE ((100 * ZONE_BLOCK_SIZE) + ZONE_BLOCK_SIZE)
 
-// @private
-
 typedef struct zone_file zone_file_t;
 struct zone_file {
   /** @private */
@@ -290,7 +288,9 @@ struct zone_file {
   /** @private */
   uint16_t last_type;
   /** @private */
-  uint32_t last_ttl, default_ttl;
+  uint32_t last_ttl, dollar_ttl;
+  /** @private */
+  uint32_t *ttl, *default_ttl;
   /** @private */
   uint16_t last_class;
   /** Number of lines spanned by RR. */

src/generic/format.h

@@ -161,11 +161,13 @@ static really_inline int32_t parse_rr(
 
   int32_t code;
   const type_info_t *descriptor;
+  const mnemonic_t *mnemonic;
   rdata_t rdata = { parser->rdata->octets, parser->rdata->octets + 65535 };
 
-  const mnemonic_t *mnemonic;
+  parser->file->ttl = parser->file->default_ttl;
 
   if ((uint8_t)token->data[0] - '0' < 10) {
+    parser->file->ttl = &parser->file->last_ttl;
     if (!scan_ttl(token->data, token->length, parser->options.pretty_ttls, &parser->file->last_ttl))
       SYNTAX_ERROR(parser, "Invalid %s in %s", NAME(&fields[3]), NAME(&rr));
     if (parser->file->last_ttl & (1u << 31))
@@ -187,6 +189,7 @@ static really_inline int32_t parse_rr(
   if ((code = take_contiguous(parser, &rr, &fields[1], token)) < 0)
     return code;
   if ((uint8_t)token->data[0] - '0' < 10) {
+    parser->file->ttl = &parser->file->last_ttl;
     if (!scan_ttl(token->data, token->length, parser->options.pretty_ttls, &parser->file->last_ttl))
       SYNTAX_ERROR(parser, "Invalid %s in %s", NAME(&fields[3]), NAME(&rr));
     if (parser->file->last_ttl & (1u << 31))
@@ -337,14 +340,14 @@ static really_inline int32_t parse_dollar_ttl(
 
   if ((code = take_contiguous(parser, &ttl, &fields[0], token)) < 0)
     return code;
-  if (!scan_ttl(token->data, token->length, parser->options.pretty_ttls, &parser->file->default_ttl))
+  if (!scan_ttl(token->data, token->length, parser->options.pretty_ttls, &parser->file->dollar_ttl))
     SYNTAX_ERROR(parser, "Invalid %s in %s", NAME(&fields[0]), NAME(&ttl));
-  if (parser->file->default_ttl & (1u << 31))
+  if (parser->file->dollar_ttl & (1u << 31))
     SEMANTIC_ERROR(parser, "Invalid %s in %s", NAME(&fields[0]), NAME(&ttl));
   if ((code = take_delimiter(parser, &ttl, token)) < 0)
     return code;
 
-  parser->file->last_ttl = parser->file->default_ttl;
+  parser->file->ttl = parser->file->default_ttl = &parser->file->dollar_ttl;
   adjust_line_count(parser->file);
   return 0;
 }

src/generic/types.h

@@ -216,7 +216,7 @@ static really_inline int32_t accept_rr(
     &(zone_name_t){ (uint8_t)parser->owner->length, parser->owner->octets },
     parser->file->last_type,
     parser->file->last_class,
-    parser->file->last_ttl,
+    *parser->file->ttl,
     (uint16_t)length,
     parser->rdata->octets,
     parser->user_data);

src/zone.c

@@ -255,14 +255,24 @@ static void initialize_file(
            parser->options.origin.length);
     file->origin.length = parser->options.origin.length;
     file->last_class = parser->options.default_class;
+    file->dollar_ttl = parser->options.default_ttl;
     file->last_ttl = parser->options.default_ttl;
+    file->ttl = file->default_ttl = &file->last_ttl;
   } else {
     assert(parser->file);
     file->includer = parser->file;
     memcpy(&file->origin, &parser->file->origin, sizeof(file->origin));
-    // retain class and TTL
+    // Retain class and TTL values.
     file->last_class = parser->file->last_class;
+    file->dollar_ttl = parser->file->dollar_ttl;
     file->last_ttl = parser->file->last_ttl;
+    // RRs appearing after the $TTL directive that do not explicitly include
+    // a TTL value, have their TTL set to the TTL in the $TTL directive. RRs
+    // appearing before a $TTL directive use the last explicitly stated value.
+    if (parser->file->default_ttl == &parser->file->last_ttl)
+      file->ttl = file->default_ttl = &file->dollar_ttl;
+    else
+      file->ttl = file->default_ttl = &file->last_ttl;
   }
 
   file->line = 1;