jnk/dns.cpp

   1 // scratch program to mess with getaddrinfo
   2
   3 #include <cstdlib>
   4 #include <iostream>
   5
   6 #include <arpa/inet.h>
   7 #include <netdb.h>
   8
   9 #include <glog/logging.h>
  10
  11 using namespace google;
  12 using namespace std;
  13
  14 int main(int argc, char* argv[])
  15 {
  16   InitGoogleLogging(argv[0]);
  17   InstallFailureSignalHandler();
  18
  19   if (1 == argc) {
  20     return 0;
  21   }
  22
  23   addrinfo hints{};
  24   hints.ai_family = AF_UNSPEC;
  25   hints.ai_socktype = SOCK_STREAM;
  26   hints.ai_flags = AI_CANONNAME;
  27   hints.ai_protocol = 0; // any protocol
  28
  29   addrinfo* result;
  30   int err = getaddrinfo(argv[1], nullptr, &hints, &result);
  31   if (err) {
  32     cerr << "getaddrinfo failure: " << gai_strerror(err) << '\n';
  33     return 1;
  34   }
  35
  36   if (0 == result) {
  37     cerr << "no results\n";
  38     return 2;
  39   }
  40
  41   for (addrinfo* rp = result; rp; rp = rp->ai_next) {
  42     switch (rp->ai_family) {
  43     case AF_INET:
  44       cout << "AF_INET";
  45       break;
  46     case AF_INET6:
  47       cout << "AF_INET6";
  48       break;
  49     default:
  50       cout << "unknown ai_family " << rp->ai_family << '\n';
  51       return 3;
  52     }
  53
  54     switch (rp->ai_socktype) {
  55     case SOCK_STREAM:
  56       cout << " SOCK_STREAM";
  57       break;
  58     case SOCK_DGRAM:
  59       cout << " SOCK_DGRAM";
  60       break;
  61     default:
  62       cout << "unknown ai_socktype " << rp->ai_socktype << '\n';
  63       return 4;
  64     }
  65
  66     switch (rp->ai_protocol) {
  67     case IPPROTO_TCP:
  68       cout << " IPPROTO_TCP";
  69       break;
  70     case IPPROTO_UDP:
  71       cout << " IPPROTO_UDP";
  72       break;
  73     default:
  74       cout << "unknown ai_protocol " << rp->ai_protocol << '\n';
  75       return 5;
  76     }
  77
  78     cout << '\n';
  79
  80     if (rp->ai_canonname)
  81       cout << "canonname == " << rp->ai_canonname << '\n';
  82
  83     char net_addr[INET6_ADDRSTRLEN];
  84
  85     switch (rp->ai_addrlen) {
  86     case sizeof(sockaddr_in): {
  87       CHECK(rp->ai_family == AF_INET);
  88       sockaddr_in* sa = reinterpret_cast<struct sockaddr_in*>(rp->ai_addr);
  89       inet_ntop(AF_INET, &(sa->sin_addr), net_addr, sizeof net_addr);
  90       break;
  91     }
  92     case sizeof(sockaddr_in6): {
  93       CHECK(rp->ai_family == AF_INET6);
  94       sockaddr_in6* sa = reinterpret_cast<struct sockaddr_in6*>(rp->ai_addr);
  95       inet_ntop(AF_INET6, &(sa->sin6_addr), net_addr, sizeof net_addr);
  96       break;
  97     }
  98     default:
  99       cout << "unknown ai_addrlen" << rp->ai_addrlen << '\n';
 100       return 6;
 101     }
 102
 103     char host[NI_MAXHOST];
 104     char serv[NI_MAXSERV];
 105
 106     cout << "addr      == " << net_addr << '\n';
 107
 108     if (AF_INET == rp->ai_family) {
 109       sockaddr_in adr;
 110       adr.sin_family = AF_INET;
 111       PCHECK(inet_pton(AF_INET, net_addr, &adr.sin_addr) == 1);
 112       err = getnameinfo(reinterpret_cast<sockaddr*>(&adr), sizeof adr, host,
 113                         sizeof host, serv, sizeof serv, 0);
 114       if (err) {
 115         cerr << "4 getnameinfo failure: " << gai_strerror(err) << '\n';
 116         return 7;
 117       }
 118     }
 119
 120     if (AF_INET6 == rp->ai_family) {
 121       sockaddr_in6 adr;
 122       adr.sin6_family = AF_INET6;
 123       PCHECK(inet_pton(AF_INET6, net_addr, &adr.sin6_addr) == 1);
 124       err = getnameinfo(reinterpret_cast<sockaddr*>(&adr), sizeof adr, host,
 125                         sizeof host, serv, sizeof serv, 0);
 126       if (err) {
 127         cerr << "6 getnameinfo failure: " << gai_strerror(err) << '\n';
 128         return 8;
 129       }
 130     }
 131
 132     cout << "reverse   == " << host << '\n';
 133   }
 134
 135   freeaddrinfo(result);
 136 }