1 files changed, 74 insertions, 0 deletions
diff --git a/resolv/ns_rr_cursor_next.c b/resolv/ns_rr_cursor_next.c
new file mode 100644
index 0000000000..33652fc5da
--- /dev/null
+++ b/resolv/ns_rr_cursor_next.c
@@ -0,0 +1,74 @@
+/* Simple DNS record parser without textual name decoding.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <arpa/nameser.h>
+#include <errno.h>
+#include <stdbool.h>
+#include <string.h>
+
+bool
+__ns_rr_cursor_next (struct ns_rr_cursor *c, struct ns_rr_wire *rr)
+{
+  rr->rdata = NULL;
+
+  /* Extract the record owner name.  */
+  int consumed = __ns_name_unpack (c->begin, c->end, c->current,
+                                   rr->rname, sizeof (rr->rname));
+  if (consumed < 0)
+    {
+      memset (rr, 0, sizeof (*rr));
+      __set_errno (EMSGSIZE);
+      return false;
+    }
+  c->current += consumed;
+
+  /* Extract the metadata.  */
+  struct
+  {
+    uint16_t rtype;
+    uint16_t rclass;
+    uint32_t ttl;
+    uint16_t rdlength;
+  } __attribute__ ((packed)) metadata;
+  _Static_assert (sizeof (metadata) == 10, "sizeof metadata");
+  if (c->end - c->current < sizeof (metadata))
+    {
+      memset (rr, 0, sizeof (*rr));
+      __set_errno (EMSGSIZE);
+      return false;
+    }
+  memcpy (&metadata, c->current, sizeof (metadata));
+  c->current += sizeof (metadata);
+  /* Endianess conversion.  */
+  rr->rtype = ntohs (metadata.rtype);
+  rr->rclass = ntohs (metadata.rclass);
+  rr->ttl = ntohl (metadata.ttl);
+  rr->rdlength = ntohs (metadata.rdlength);
+
+  /* Extract record data.  */
+  if (c->end - c->current < rr->rdlength)
+    {
+      memset (rr, 0, sizeof (*rr));
+      __set_errno (EMSGSIZE);
+      return false;
+    }
+  rr->rdata = c->current;
+  c->current += rr->rdlength;
+
+  return true;
+}