sock_dns: add debug output

sys/net/application_layer/sock_dns/dns.c

@@ -20,13 +20,17 @@
 #include <string.h>
 
 #include <arpa/inet.h>
+#include <string.h>
 
 #include "net/dns.h"
 #include "net/dns/cache.h"
 #include "net/dns/msg.h"
 #include "net/sock/udp.h"
 #include "net/sock/dns.h"
 
+#define ENABLE_DEBUG 0
+#include "debug.h"
+
 /* min domain name length is 1, so minimum record length is 7 */
 #define DNS_MIN_REPLY_LEN (unsigned)(sizeof(dns_hdr_t) + 7)
 
@@ -87,7 +91,7 @@ int sock_dns_query(const char *domain_name, void *addr_out, int family)
 
  res = sock_udp_create(&sock_dns, NULL, &sock_dns_server, 0);
  if (res) {
- goto out;
+ return res;
  }
 
  uint16_t id = 0;
@@ -96,25 +100,30 @@ int sock_dns_query(const char *domain_name, void *addr_out, int family)
 
  res = sock_udp_send(&sock_dns, dns_buf, buflen, NULL);
  if (res <= 0) {
+ DEBUG("sock_dns: can't send: %s\n", strerror(-res));
  continue;
  }
  res = sock_udp_recv(&sock_dns, dns_buf, sizeof(dns_buf), 1000000LU, NULL);
- if (res > 0) {
- if (res > (int)DNS_MIN_REPLY_LEN) {
- uint32_t ttl;
- if ((res = dns_msg_parse_reply(dns_buf, res, family,
- addr_out, &ttl)) > 0) {
- dns_cache_add(domain_name, addr_out, res, ttl);
- goto out;
- }
- }
- else {
- res = -EBADMSG;
- }
+ if (res < 0) {
+ DEBUG("sock_dns: can't receive %s\n", strerror(-res));
+ continue;
+ }
+ if (res < (int)DNS_MIN_REPLY_LEN) {
+ DEBUG("sock_dns: reply too small (%d byte)\n", res);
+ res = -EBADMSG;
+ continue;
+ }
+
+ uint32_t ttl;
+ if ((res = dns_msg_parse_reply(dns_buf, res, family,
+ addr_out, &ttl)) > 0) {
+ dns_cache_add(domain_name, addr_out, res, ttl);
+ break;
+ } else {
+ DEBUG("sock_dns: can't parse response\n");
  }
  }
 
-out:
  sock_udp_close(&sock_dns);
  return res;
 }