wownero/src/common/dns_utils.cpp

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// Copyright (c) 2014, The Monero Project
//
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without modification, are
// permitted provided that the following conditions are met:
//
// 1. Redistributions of source code must retain the above copyright notice, this list of
// conditions and the following disclaimer.
//
// 2. Redistributions in binary form must reproduce the above copyright notice, this list
// of conditions and the following disclaimer in the documentation and/or other
// materials provided with the distribution.
//
// 3. Neither the name of the copyright holder nor the names of its contributors may be
// used to endorse or promote products derived from this software without specific
// prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
// EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
// MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
// THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
// PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
// STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
// THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
#include "common/dns_utils.h"
#include <ldns/rr.h> // for RR type and class defs
#include <unbound.h>
#include <arpa/inet.h> // for inet_ntoa (bytes to text for IPs)
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namespace tools
{
// custom smart pointer.
// TODO: see if std::auto_ptr and the like support custom destructors
class ub_result_ptr
{
public:
ub_result_ptr()
{
ptr = nullptr;
}
~ub_result_ptr()
{
ub_resolve_free(ptr);
}
ub_result* ptr;
};
struct DNSResolverData
{
ub_ctx* m_ub_context;
};
DNSResolver::DNSResolver() : m_data(new DNSResolverData())
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{
// init libunbound context
m_data->m_ub_context = ub_ctx_create();
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// look for "/etc/resolv.conf" and "/etc/hosts" or platform equivalent
ub_ctx_resolvconf(m_data->m_ub_context, "");
ub_ctx_hosts(m_data->m_ub_context, "");
}
DNSResolver::~DNSResolver()
{
if (m_data)
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{
if (m_data->m_ub_context != NULL)
{
ub_ctx_delete(m_data->m_ub_context);
}
delete m_data;
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}
}
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std::vector<std::string> DNSResolver::get_ipv4(const std::string& url)
{
std::vector<std::string> addresses;
if (!check_address_syntax(url))
{
return addresses;
}
// destructor takes care of cleanup
ub_result_ptr result;
// call DNS resolver, blocking. if return value not zero, something went wrong
if (!ub_resolve(m_data->m_ub_context, url.c_str(), LDNS_RR_TYPE_A, LDNS_RR_CLASS_IN, &(result.ptr)))
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{
if (result.ptr->havedata)
{
for (size_t i=0; result.ptr->data[i] != NULL; i++)
{
char as_str[INET_ADDRSTRLEN];
// convert bytes to string, append if no error
if (inet_ntop(AF_INET, result.ptr->data[i], as_str, sizeof(as_str)))
{
addresses.push_back(as_str);
}
}
}
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}
return addresses;
}
std::vector<std::string> DNSResolver::get_ipv6(const std::string& url)
{
std::vector<std::string> addresses;
if (!check_address_syntax(url))
{
return addresses;
}
ub_result_ptr result;
// call DNS resolver, blocking. if return value not zero, something went wrong
if (!ub_resolve(m_data->m_ub_context, url.c_str(), LDNS_RR_TYPE_AAAA, LDNS_RR_CLASS_IN, &(result.ptr)))
{
if (result.ptr->havedata)
{
for (size_t i=0; result.ptr->data[i] != NULL; i++)
{
char as_str[INET6_ADDRSTRLEN];
// convert bytes to string, append if no error
if (inet_ntop(AF_INET6, result.ptr->data[i], as_str, sizeof(as_str)))
{
addresses.push_back(as_str);
}
}
}
}
return addresses;
}
std::vector<std::string> DNSResolver::get_txt_record(const std::string& url)
{
std::vector<std::string> records;
if (!check_address_syntax(url))
{
return records;
}
ub_result_ptr result;
// call DNS resolver, blocking. if return value not zero, something went wrong
if (!ub_resolve(m_data->m_ub_context, url.c_str(), LDNS_RR_TYPE_TXT, LDNS_RR_CLASS_IN, &(result.ptr)))
{
if (result.ptr->havedata)
{
for (size_t i=0; result.ptr->data[i] != NULL; i++)
{
records.push_back(result.ptr->data[i]);
}
}
}
return records;
}
DNSResolver& DNSResolver::instance()
{
static DNSResolver* staticInstance = NULL;
if (staticInstance == NULL)
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{
staticInstance = new DNSResolver();
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}
return *staticInstance;
}
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bool DNSResolver::check_address_syntax(const std::string& addr)
{
// if string doesn't contain a dot, we won't consider it a url for now.
if (addr.find(".") == std::string::npos)
{
return false;
}
return true;
}
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} // namespace tools