Asynchronous DNS resolver
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Latest commit a8ee174 Mar 14, 2016 @vstakhov Sync from rspamd
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test Fix regression test. Aug 25, 2014
.project Initial version. Feb 7, 2014

Rapid DNS resolver

Asynchronous pluggable DNS resolver with many features.

Features list

  • can work with libev and libevent asynchronous cores (and this could be extended in future)
  • follows secure resolver principles:
    • randomize source port for outgoing requests (based on periodic IO sockets updates)
    • use secure random generator for DNS ID
    • compare request and reply
    • support pool of sockets per server
  • supports multiple DNS servers (unlimited amount actually)
  • can parse resolv.conf file
  • supports edns0 by default
  • can include multiple queries in a packet
  • RDNS supports plugins and DNSCurve in particular to encrypt DNS traffic
  • can automatically handle IDN queries (encoded in UTF8)

TODO list

  • DNSSec support
  • Recursion support
  • TCP fallback
  • Documentation and tests

Typical usage example

Here is a simple example of using RDNS library with libev backend.

#include <stdlib.h>
#include <stdio.h>
#include "rdns.h"
#include "rdns_curve.h"
#include "rdns_ev.h"

static int remain_tests = 0;

static void
rdns_regress_callback (struct rdns_reply *reply, void *arg)
    printf ("got result for host: %s\n", (const char *)arg);

    if (--remain_tests == 0) {
        rdns_resolver_release (reply->resolver);

static void
rdns_test_a (struct rdns_resolver *resolver)
    char *names[] = {
    char **cur;

    for (cur = names; *cur != NULL; cur ++) {
        rdns_make_request_full (resolver, rdns_regress_callback, *cur, 1.0, 2, 1, *cur, RDNS_REQUEST_A);
        remain_tests ++;

main(int argc, char **argv)
    struct rdns_resolver *resolver_ev;
    struct ev_loop *loop;

    loop = ev_default_loop (0);
    resolver_ev = rdns_resolver_new ();
    rdns_bind_libev (resolver_ev, loop);

    rdns_resolver_add_server (resolver_ev, argv[1], strtoul (argv[2], NULL, 10), 0, 8);

    rdns_resolver_init (resolver_ev);

    rdns_test_a (resolver_ev);
    ev_loop (loop, 0);

    return 0;