1 files changed, 59 insertions, 0 deletions
diff --git a/dnsstub/dns_cname.c b/dnsstub/dns_cname.c
new file mode 100644
index 0000000..408949a
--- /dev/null
+++ b/dnsstub/dns_cname.c
@@ -0,0 +1,59 @@
+#include "stralloc.h"
+#include "uint_t.h"
+#include "byte.h"
+#include "ip.h"
+#include "case.h"
+#include "dnsresolv.h"
+
+/**
+	@file dns_cname.c
+	@author feh
+	@brief DNS cname lookup
+*/
+
+static char *q = 0;
+
+int dns_cname_packet(stralloc *out,const char *buf,unsigned int len)
+{
+  unsigned int pos;
+  char header[12];
+  uint16 numanswers;
+  uint16 datalen;
+  int ranswers = 0;
+
+  if (!stralloc_copys(out,"")) return DNS_MEM;
+
+  pos = dns_packet_copy(buf,len,0,header,12); if (!pos) return DNS_ERR;
+  uint16_unpack_big(header + 6,&numanswers);
+  pos = dns_packet_skipname(buf,len,pos); if (!pos) return DNS_ERR;
+  pos += 4;
+
+  while (numanswers--) {
+    pos = dns_packet_skipname(buf,len,pos); if (!pos) return DNS_ERR;
+    pos = dns_packet_copy(buf,len,pos,header,10); if (!pos) return DNS_ERR;
+    uint16_unpack_big(header + 8,&datalen);
+    if (byte_equal(header,2,DNS_T_CNAME))
+      if (byte_equal(header + 2,2,DNS_C_IN)) {
+        if (!dns_packet_getname(buf,len,pos,&q)) return DNS_ERR;
+        if (dns_domain_todot_cat(out,q) <= 0) return DNS_ERR;
+      }
+    pos += datalen;
+    ++ranswers;
+  }
+
+  return ranswers;
+}
+
+int dns_cname(stralloc *out,stralloc *fqdn)
+{
+  int rc; 
+
+  if (dns_domain_fromdot(&q,fqdn->s,fqdn->len) <= 0) return DNS_ERR;
+  if (dns_resolve(q,DNS_T_CNAME) < 0) return DNS_ERR;
+  if ((rc = dns_cname_packet(out,dns_resolve_tx.packet,dns_resolve_tx.packetlen)) < 0) return DNS_ERR;
+  dns_transmit_free(&dns_resolve_tx);
+  dns_domain_free(&q);
+	if (case_equals(out->s,fqdn->s)) rc = -6; // loop DNS_HARD
+
+  return rc;
+}