linux: add error logs to ipadapter

port/linux/ipadapter.c

@@ -254,7 +254,7 @@ get_data_size(int sock)
       if (errno == EINTR) {
         continue;
       }
-      return -1;
+      return -errno;
     }
   } while ((size_t)response_len == guess);
   return response_len;
@@ -270,7 +270,7 @@ get_data(int sock, uint8_t *buffer, size_t buffer_size)
       if (errno == EINTR) {
         continue;
       }
-      return -1;
+      return -errno;
     }
     break;
   } while (true);
@@ -327,12 +327,14 @@ get_interface_addresses(ip_context_t *dev, unsigned char family, int port,
   while (!done) {
     ssize_t response_len = get_data_size(nl_sock);
     if (response_len < 0) {
+      OC_ERR("failed to get data size: %d", (int)-response_len);
       close(nl_sock);
       return false;
     }
     uint8_t buffer[response_len];
     response_len = get_data(nl_sock, buffer, sizeof(buffer));
     if (response_len < 0) {
+      OC_ERR("failed to get data: %d", (int)-response_len);
       close(nl_sock);
       return false;
     }
@@ -546,13 +548,15 @@ process_interface_change_event(void)
 {
   ssize_t response_len = get_data_size(g_ifchange_sock);
   if (response_len < 0) {
-    OC_ERR("reading payload size from netlink interface");
+    OC_ERR("failed reading payload size from netlink interface: error(%d)",
+           (int)-response_len);
     return -1;
   }
   uint8_t buffer[response_len];
   response_len = get_data(g_ifchange_sock, buffer, sizeof(buffer));
   if (response_len < 0) {
-    OC_ERR("reading payload from netlink interface");
+    OC_ERR("failed reading payload from netlink interface: error(%d)",
+           (int)-response_len);
     return -1;
   }