rpcd-mod-rrdns: add new rpcd plugin for rapid reverse DNS lookups

The plugin provides a new ubus procedure "network.rrdns.lookup" which
allows looking up the names of a large chunk of IP addresses at once,
within a fixed global timeout.

This is useful to have a guaranteed maximum query time even if the
local DNS setup is broken or timing out.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

1 files changed, 51 insertions, 0 deletions

diff --git a/libs/rpcd-mod-rrdns/src/rrdns.h b/libs/rpcd-mod-rrdns/src/rrdns.h
new file mode 100644
index 0000000000..3f95116f08
--- /dev/null
+++ b/libs/rpcd-mod-rrdns/src/rrdns.h
@@ -0,0 +1,51 @@
+/*
+ * rrdns - Rapid Reverse DNS lookup plugin for the UBUS RPC server
+ *
+ *   Copyright (C) 2016-2017 Jo-Philipp Wich <jo@mein.io>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+#include <libubus.h>
+#include <libubox/avl.h>
+#include <libubox/uloop.h>
+
+#define RRDNS_MAX_TIMEOUT 5000
+#define RRDNS_DEF_TIMEOUT 250
+
+#define RRDNS_MAX_LIMIT 1000
+#define RRDNS_DEF_LIMIT 10
+
+
+struct rrdns_request {
+	struct avl_node by_id;
+	struct avl_node by_addr;
+	uint16_t id;
+	uint16_t family;
+	union {
+		struct in_addr in;
+		struct in6_addr in6;
+	} addr;
+};
+
+struct rrdns_context {
+	struct ubus_context *context;
+	struct ubus_request_data request;
+	struct uloop_timeout timeout;
+	struct blob_attr *addr_cur;
+	int addr_rem;
+	struct uloop_fd socket;
+	struct blob_buf blob;
+	struct avl_tree request_ids;
+	struct avl_tree request_addrs;
+};