resolved: add code to generate the wire format for a single RR

This adds dns_resource_record_to_wire_format() that generates the raw
wire-format of a single DnsResourceRecord object, and caches it in the
object, optionally in DNSSEC canonical form. This call is used later to
generate the RR serialization of RRs to verify.

This adds four new fields to DnsResourceRecord objects:

- wire_format points to the buffer with the wire-format version of the
  RR
- wire_format_size stores the size of that buffer
- wire_format_rdata_offset specifies the index into the buffer where the
  RDATA of the RR begins (i.e. the size of the key part of the RR).
- wire_format_canonical is a boolean that stores whether the cached wire
  format is in DNSSEC canonical form or not.

Note that this patch adds a mode where a DnsPacket is allocated on the
stack (instead of on the heap), so that it is cheaper to reuse the
DnsPacket object for generating this wire format. After all we reuse the
DnsPacket object for this, since it comes with all the dynamic memory
management, and serialization calls we need anyway.

1 files changed, 7 insertions, 1 deletions

diff --git a/src/resolve/resolved-dns-rr.h b/src/resolve/resolved-dns-rr.h
index ac4256b882..c51419cb94 100644
--- a/src/resolve/resolved-dns-rr.h
+++ b/src/resolve/resolved-dns-rr.h
@@ -57,7 +57,11 @@ struct DnsResourceRecord {
         unsigned n_ref;
         DnsResourceKey *key;
         uint32_t ttl;
-        bool unparseable;
+        bool unparseable:1;
+        bool wire_format_canonical:1;
+        void *wire_format;
+        size_t wire_format_size;
+        size_t wire_format_rdata_offset;
         union {
                 struct {
                         void *data;
@@ -209,6 +213,8 @@ int dns_resource_record_equal(const DnsResourceRecord *a, const DnsResourceRecor
 int dns_resource_record_to_string(const DnsResourceRecord *rr, char **ret);
 DEFINE_TRIVIAL_CLEANUP_FUNC(DnsResourceRecord*, dns_resource_record_unref);
 
+int dns_resource_record_to_wire_format(DnsResourceRecord *rr, bool canonical);
+
 DnsTxtItem *dns_txt_item_free_all(DnsTxtItem *i);
 bool dns_txt_item_equal(DnsTxtItem *a, DnsTxtItem *b);