1 files changed, 45 insertions, 0 deletions
diff --git a/edns0.c b/edns0.c
new file mode 100644
index 0000000..0487b2b
--- /dev/null
+++ b/edns0.c
@@ -0,0 +1,45 @@
+/* (C) 2012 Peter Conrad <conrad@quisquis.de>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 3 as
+ * published by the Free Software Foundation.
+ * 
+ * This program 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 General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "dns.h"
+#include "edns0.h"
+#include "response.h"
+#include "uint16.h"
+
+unsigned int check_edns0(const char header[12], const char *buf, const int len, unsigned int pos)
+{
+char opt_class[2];
+char opt_ttl[4];
+
+  max_response_len = 512;
+  do_dnssec = 0;
+  if (!header[6] && !header[7] && !header[8] && !header[9]
+	&& !header[10] && header[11] == 1) {
+    char nametype[3];
+    uint16 size, min_len;
+    pos = dns_packet_copy(buf,len,pos,nametype,3); if (!pos) return pos;
+    if (nametype[0] || nametype[1] || nametype[2] != DNS_T_OPT[1]) return pos;
+    pos = dns_packet_copy(buf,len,pos,opt_class,2); if (!pos) return pos;
+    pos = dns_packet_copy(buf,len,pos,opt_ttl,4); if (!pos) return pos;
+    if (opt_ttl[0]) return pos; // unsupported RCODE in query
+    if (opt_ttl[1]) return pos; // unsupported version
+    do_dnssec = opt_ttl[2] & 0x80;
+    uint16_unpack_big(opt_class, &size);
+    min_len = do_dnssec ? 1220 : 512;
+    max_response_len = size > 4000 ? 4000 : size;
+    if (max_response_len < min_len) { max_response_len = min_len; }
+  }
+  return pos;
+}