Added dns-utils for functions not found in ldns.

Currently only a function for matching labels in two domain names
  is implemented. May need some revision and testing!

CuteDNS.files

@@ -3,6 +3,8 @@ src/common.h
 src/main.c
 src/dns/dns-simple.c
 src/dns/dns-simple.h
+src/dns/dns-utils.h
+src/dns/dns-utils.c
 src/hash/cuckoo-hash-table.c
 src/hash/cuckoo-hash-table.h
 src/hash/hash-functions.c

src/dns/dns-utils.c

+#include "dns-utils.h"
+#include <ldns/rdata.h>
+#include "common.h"
+#include <string.h>
+#include <assert.h>
+#include <ctype.h>
+
+static const uint MAX_LABELS = 127;
+
+/*----------------------------------------------------------------------------*/
+
+uint dnsu_subdomain_labels( const ldns_rdf *sub, const ldns_rdf *parent )
+{
+	uint8_t *labels_sub[MAX_LABELS], *labels_par[MAX_LABELS];	// 254 B
+
+	assert(ldns_rdf_get_type(sub) == LDNS_RDF_TYPE_DNAME);
+	assert(ldns_rdf_get_type(parent) == LDNS_RDF_TYPE_DNAME);
+
+	size_t sub_size = ldns_rdf_size(sub);
+	size_t par_size = ldns_rdf_size(parent);
+
+	if (sub_size == 0 || par_size == 0) {
+		return 0;
+	}
+
+	uint8_t *sub_data = ldns_rdf_data(sub);
+	uint8_t *par_data = ldns_rdf_data(parent);
+
+	/*
+	 * walk the domain names from left to right and save labels start/end
+	 * positions
+	 */
+	// walk sub
+	uint8_t *pos_sub = sub_data;
+	uint8_t len = *pos_sub;
+	uint label_sub_i = 0;
+
+	assert(sub_data[sub_size - 1] == '\0');
+
+	while (len != 0) {
+		++pos_sub;
+		labels_sub[label_sub_i++] = pos_sub;
+		pos_sub += len;
+		len = *pos_sub;
+	}
+	// save the pointer to the terminating 0
+	labels_sub[label_sub_i] = pos_sub;
+
+	assert(labels_sub[label_sub_i] == sub_data + sub_size - 1);
+	assert(len == 0);
+	assert(pos_sub == sub_data + sub_size - 1);
+
+	// walk parent
+	uint8_t *pos_par = par_data;
+	len = *pos_par;
+	uint label_par_i = 0;
+
+	assert(par_data[par_size - 1] == '\0');
+
+	while (len != 0) {
+		labels_par[label_par_i++] = pos_par;
+		++pos_par;
+		pos_par += len;
+		len = *pos_par;
+	}
+	// save the pointer to the terminating 0
+	labels_par[label_par_i] = pos_par;
+
+	assert(labels_par[label_par_i] == par_data + par_size - 1);
+	assert(len == 0);
+	assert(pos_par == par_data + par_size - 1);
+
+	// if parent has more labels than sub, then sub cannot be subdomain or the
+	// same domain
+	if (label_par_i > label_sub_i) {
+		return 0;
+	}
+
+	/*
+	 * Now we know that sub may be a subdomain of parent.
+	 * Walk through labels from end to start and count labels which are equal
+	 * case-insensitive. The characters in labels are walked from right to left.
+	 */
+	uint matched = 0;
+	while (label_par_i > 0) {
+		// set positions on the end of labels
+		pos_sub = labels_sub[label_sub_i];
+		pos_par = labels_par[label_par_i];
+
+		--label_par_i;
+		--label_sub_i;
+
+		uint8_t *pos_par_next = labels_par[label_par_i];
+
+		do {
+			// in first iteration we skip the labels' length / the last 0
+			--pos_sub;
+			--pos_par;
+		} while (pos_par != pos_par_next
+				 && (tolower(*pos_par) == tolower(*pos_sub)));
+
+		// if the whole label was matched, we should be at the end of the next
+		// label
+		if (pos_par != pos_par_next) {
+			return matched;
+		}
+		// so just continue
+		++matched;
+	}
+
+	return matched;
+}

src/dns/dns-utils.h

+#ifndef DNS_UTILS
+#define DNS_UTILS
+
+#include <ldns/rdata.h>
+#include "common.h"
+
+uint dnsu_subdomain_labels( const ldns_rdf *sub, const ldns_rdf *parent );
+
+#endif /* DNS_UTILS */