xapian-core/net/resolver.h

   1 /** @file
   2  * @brief Resolve hostnames and ip addresses
   3  */
   4 /* Copyright (C) 2017 Olly Betts
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * along with this program; if not, write to the Free Software
  18  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  19  */
  20
  21 #ifndef XAPIAN_INCLUDED_RESOLVER_H
  22 #define XAPIAN_INCLUDED_RESOLVER_H
  23
  24 #include <cstring>
  25 #include "safenetdb.h"
  26 #include "safesyssocket.h"
  27 #include "str.h"
  28 #include "xapian/error.h"
  29
  30 using namespace std;
  31
  32 class Resolver {
  33     struct addrinfo* result = NULL;
  34
  35   public:
  36     class const_iterator {
  37         struct addrinfo* p;
  38       public:
  39         explicit const_iterator(struct addrinfo* p_) : p(p_) { }
  40
  41         struct addrinfo& operator*() const {
  42             return *p;
  43         }
  44
  45         void operator++() {
  46             p = p->ai_next;
  47         }
  48
  49         const_iterator operator++(int) {
  50             struct addrinfo* old_p = p;
  51             operator++();
  52             return const_iterator(old_p);
  53         }
  54
  55         bool operator==(const const_iterator& o) {
  56             return p == o.p;
  57         }
  58
  59         bool operator!=(const const_iterator& o) {
  60             return !(*this == o);
  61         }
  62     };
  63
  64     Resolver(const std::string& host, int port, int flags = 0) {
  65         // RFC 3493 has an extra sentence in its definition of
  66         // AI_ADDRCONFIG which POSIX doesn't:
  67         //
  68         //   "The loopback address is not considered for this case as valid
  69         //   as a configured address."
  70         //
  71         // Some platforms implement this version rather than POSIX (notably
  72         // glibc on Linux).  Others implement POSIX (from looking at the
  73         // man pages, these include FreeBSD 11.0).
  74         //
  75         // In most cases, this extra sentence is arguably helpful - e.g. it
  76         // means that you won't get IPv6 addresses just because the system
  77         // has IPv6 loopback (and similarly for IPv4).
  78         //
  79         // However, it behaves unhelpfully if the *only* interface
  80         // configured is loopback - in this situation, AI_ADDRCONFIG means
  81         // that you won't get an IPv4 address (as there's no IPv4 address
  82         // configured ignoring loopback) and you won't get an IPv6 address
  83         // (as there's no IPv6 address configured ignoring loopback).
  84         //
  85         // It's generally rare that systems with only loopback would want
  86         // to use the remote backend, but a real example is testsuites
  87         // (including our own) running on autobuilders which deliberately
  88         // close off network access.
  89         //
  90         // To allow such cases to work on Linux (and other platforms which
  91         // follow the RFC rather than POSIX in this detail) we avoid using
  92         // AI_ADDRCONFIG for 127.0.0.1, ::1 and localhost.  There are
  93         // other ways to write these IP addresses and other hostnames may
  94         // map onto them, but this just needs to work for the standard
  95         // cases which a testsuite might use.
  96         if (host != "::1" && host != "127.0.0.1" && host != "localhost") {
  97             flags |= AI_ADDRCONFIG;
  98         }
  99         flags |= AI_NUMERICSERV;
 100
 101         struct addrinfo hints;
 102         std::memset(&hints, 0, sizeof(struct addrinfo));
 103         hints.ai_family = AF_INET;
 104         hints.ai_socktype = SOCK_STREAM;
 105         hints.ai_flags = flags;
 106         hints.ai_protocol = 0;
 107
 108         const char * node = host.empty() ? NULL : host.c_str();
 109         int r = getaddrinfo(node, str(port).c_str(), &hints, &result);
 110         if (r != 0) {
 111             throw Xapian::NetworkError("Couldn't resolve host " + host,
 112                                        eai_to_xapian(r));
 113         }
 114     }
 115
 116     ~Resolver() {
 117         if (result) freeaddrinfo(result);
 118     }
 119
 120     const_iterator begin() const {
 121         return const_iterator(result);
 122     }
 123
 124     const_iterator end() const {
 125         return const_iterator(NULL);
 126     }
 127 };
 128
 129 #endif // XAPIAN_INCLUDED_RESOLVER_H