libuv dns example

libuv_dns_example.c

//
// Adapted from https://github.com/Elzair/libuv-examples/blob/master/dns/dns.c
// to also loop through all results.
//
#include <stdio.h>
#include <stdlib.h>
#include <uv.h>

#include <string>

uv_loop_t *loop;

uv_buf_t alloc_buffer(uv_handle_t *handle, size_t suggested_size) {
  return uv_buf_init((char*) malloc(suggested_size), suggested_size);
}

void on_resolved(uv_getaddrinfo_t *resolver, int status, struct addrinfo *res) {
  if (status == -1) {
    fprintf(stderr, "getaddrinfo callback error\n");
    return;
  }

  // iterate through the records to find a working peer
  struct addrinfo* address;
  for (address = res; address != nullptr; address = address->ai_next)
  {
    char addr[17] = {'\0'};
    uv_ip4_name((struct sockaddr_in*) res->ai_addr, addr, 16);
    fprintf(stderr, "%s\n", addr);
  }

  uv_freeaddrinfo(res);
}

int main() {
   loop = uv_default_loop();

   struct addrinfo hints;
   hints.ai_family = PF_INET;
   hints.ai_socktype = SOCK_STREAM;
   hints.ai_protocol = IPPROTO_TCP;
   hints.ai_flags = 0;

   std::string host("www.google.com");

   uv_getaddrinfo_t resolver;
   fprintf(stderr, "%s is... ", host.c_str());
   int r = uv_getaddrinfo(loop, &resolver, on_resolved, host.c_str(), "80", &hints);
   
   if (r) {
     fprintf(stderr, "getaddrinfo call error\n");
     return 1;
   }
   return uv_run(loop, UV_RUN_DEFAULT);
}