Reduce duplication of common DNS code.

The NAPTR and SRV branches were worked on independently and
resulted in some code being duplicated in each. Since both
have been merged into trunk now, this patch reduces the
duplication by factoring out common code into its own
source files.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@434490 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 70 insertions, 13 deletions

diff --git a/main/dns_core.c b/main/dns_core.c
index 228147bbf..53ea1d09e 100644
--- a/main/dns_core.c
+++ b/main/dns_core.c
@@ -426,6 +426,20 @@ static struct ast_dns_record *generic_record_alloc(struct ast_dns_query *query,
 	return record;
 }
 
+typedef struct ast_dns_record *(*dns_alloc_fn)(struct ast_dns_query *query, const char *data, const size_t size);
+
+static dns_alloc_fn dns_alloc_table [] = {
+	[ns_t_naptr] = dns_naptr_alloc,
+	[ns_t_srv] = dns_srv_alloc,
+};
+
+static struct ast_dns_record *allocate_dns_record(int rr_type, struct ast_dns_query *query, const char *data, const size_t size)
+{
+	dns_alloc_fn allocator = dns_alloc_table[rr_type] ?: generic_record_alloc;
+
+	return allocator(query, data, size);
+}
+
 int ast_dns_resolver_add_record(struct ast_dns_query *query, int rr_type, int rr_class, int ttl, const char *data, const size_t size)
 {
 	struct ast_dns_record *record;
@@ -460,14 +474,7 @@ int ast_dns_resolver_add_record(struct ast_dns_query *query, int rr_type, int rr
 		return -1;
 	}
 
-	if (rr_type == ns_t_naptr) {
-		record = dns_naptr_alloc(query, data, size);
-	} else if (rr_type == ns_t_srv) {
-		record = ast_dns_srv_alloc(query, data, size);
-	} else {
-		record = generic_record_alloc(query, data, size);
-	}
-
+	record = allocate_dns_record(rr_type, query, data, size);
 	if (!record) {
 		return -1;
 	}
@@ -483,13 +490,23 @@ int ast_dns_resolver_add_record(struct ast_dns_query *query, int rr_type, int rr
 	return 0;
 }
 
-void ast_dns_resolver_completed(struct ast_dns_query *query)
+typedef void (*dns_sort_fn)(struct ast_dns_result *result);
+
+static dns_sort_fn dns_sort_table [] = {
+	[ns_t_naptr] = dns_naptr_sort,
+	[ns_t_srv] = dns_srv_sort,
+};
+
+static void sort_result(int rr_type, struct ast_dns_result *result)
 {
-	if (ast_dns_query_get_rr_type(query) == ns_t_naptr) {
-		dns_naptr_sort(query->result);
-	} else if (ast_dns_query_get_rr_type(query) == ns_t_srv) {
-		ast_dns_srv_sort(query->result);
+	if (dns_sort_table[rr_type]) {
+		dns_sort_table[rr_type](result);
 	}
+}
+
+void ast_dns_resolver_completed(struct ast_dns_query *query)
+{
+	sort_result(ast_dns_query_get_rr_type(query), query->result);
 
 	query->callback(query);
 }
@@ -593,3 +610,43 @@ void ast_dns_resolver_unregister(struct ast_dns_resolver *resolver)
 
 	ast_verb(2, "Unregistered DNS resolver '%s'\n", resolver->name);
 }
+
+char *dns_find_record(const char *record, size_t record_size, const char *response, size_t response_size)
+{
+	size_t remaining_size = response_size;
+	const char *search_base = response;
+	char *record_offset;
+
+	while (1) {
+		record_offset = memchr(search_base, record[0], remaining_size);
+
+		ast_assert(record_offset != NULL);
+		ast_assert(search_base + remaining_size - record_offset >= record_size);
+
+		if (!memcmp(record_offset, record, record_size)) {
+			return record_offset;
+		}
+
+		remaining_size -= record_offset - search_base;
+		search_base = record_offset + 1;
+	}
+}
+
+int dns_parse_short(unsigned char *cur, uint16_t *val)
+{
+	/* This assignment takes a big-endian 16-bit value and stores it in the
+	 * machine's native byte order. Using this method allows us to avoid potential
+	 * alignment issues in case the order is not on a short-addressable boundary.
+	 * See http://commandcenter.blogspot.com/2012/04/byte-order-fallacy.html for
+	 * more information
+	 */
+	*val = (cur[1] << 0) | (cur[0] << 8);
+	return sizeof(*val);
+}
+
+int dns_parse_string(char *cur, uint8_t *size, char **val)
+{
+	*size = *cur++;
+	*val = cur;
+	return *size + 1;
+}