Adding upstream version 1.8.3.upstream/1.8.3

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 637 insertions, 0 deletions

diff --git a/dnsname.cc b/dnsname.cc
new file mode 100644
index 0000000..3bfbf30
--- /dev/null
+++ b/dnsname.cc
@@ -0,0 +1,637 @@
+/*
+ * This file is part of PowerDNS or dnsdist.
+ * Copyright -- PowerDNS.COM B.V. and its contributors
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * In addition, for the avoidance of any doubt, permission is granted to
+ * link this program with OpenSSL and to (re)distribute the binaries
+ * produced as the result of such linking.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+#include "dnsname.hh"
+#include <boost/format.hpp>
+#include <string>
+#include <cinttypes>
+
+#include "dnswriter.hh"
+#include "misc.hh"
+
+#include <boost/functional/hash.hpp>
+
+const DNSName g_rootdnsname("."), g_wildcarddnsname("*");
+
+/* raw storage
+   in DNS label format, with trailing 0. W/o trailing 0, we are 'empty'
+   www.powerdns.com = 3www8powerdns3com0
+*/
+
+std::ostream & operator<<(std::ostream &os, const DNSName& d)
+{
+  return os <<d.toLogString();
+}
+
+void DNSName::throwSafeRangeError(const std::string& msg, const char* buf, size_t length)
+{
+  std::string dots;
+  if (length > s_maxDNSNameLength) {
+    length = s_maxDNSNameLength;
+    dots = "...";
+  }
+  std::string label;
+  DNSName::appendEscapedLabel(label, buf, length);
+  throw std::range_error(msg + label + dots);
+}
+
+DNSName::DNSName(const std::string_view sw)
+{
+  const char* p = sw.data();
+  size_t length = sw.length();
+
+  if(length == 0 || (length == 1 && p[0]=='.')) {
+    d_storage.assign(1, '\0');
+  } else {
+    if(!std::memchr(p, '\\', length)) {
+      unsigned char lenpos=0;
+      unsigned char labellen=0;
+      const char* const pbegin=p, *pend=p+length;
+
+      d_storage.reserve(length+1);
+      for(auto iter = pbegin; iter != pend; ) {
+        lenpos = d_storage.size();
+        if(*iter=='.')
+          throwSafeRangeError("Found . in wrong position in DNSName: ", p, length);
+        d_storage.append(1, '\0');
+        labellen=0;
+        auto begiter=iter;
+        for(; iter != pend && *iter!='.'; ++iter) {
+          labellen++;
+        }
+        d_storage.append(begiter,iter);
+        if(iter != pend)
+          ++iter;
+        if(labellen > 63)
+          throwSafeRangeError("label too long to append: ", p, length);
+
+        if(iter-pbegin > static_cast<ptrdiff_t>(s_maxDNSNameLength - 1)) // reserve two bytes, one for length and one for the root label
+          throwSafeRangeError("name too long to append: ", p, length);
+
+        d_storage[lenpos]=labellen;
+      }
+      d_storage.append(1, '\0');
+    }
+    else {
+      d_storage=segmentDNSNameRaw(p, length);
+      if(d_storage.size() > s_maxDNSNameLength) {
+        throwSafeRangeError("name too long: ", p, length);
+      }
+    }
+  }
+}
+
+
+DNSName::DNSName(const char* pos, int len, int offset, bool uncompress, uint16_t* qtype, uint16_t* qclass, unsigned int* consumed, uint16_t minOffset)
+{
+  if (offset >= len)
+    throw std::range_error("Trying to read past the end of the buffer ("+std::to_string(offset)+ " >= "+std::to_string(len)+")");
+
+  if(!uncompress) {
+    if(const void * fnd=memchr(pos+offset, 0, len-offset)) {
+      d_storage.reserve(2+(const char*)fnd-(pos+offset));
+    }
+  }
+
+  packetParser(pos, len, offset, uncompress, qtype, qclass, consumed, 0, minOffset);
+}
+
+// this should be the __only__ dns name parser in PowerDNS.
+void DNSName::packetParser(const char* qpos, int len, int offset, bool uncompress, uint16_t* qtype, uint16_t* qclass, unsigned int* consumed, int depth, uint16_t minOffset)
+{
+  const unsigned char* pos=(const unsigned char*)qpos;
+  unsigned char labellen;
+  const unsigned char *opos = pos;
+
+  if (offset >= len)
+    throw std::range_error("Trying to read past the end of the buffer ("+std::to_string(offset)+ " >= "+std::to_string(len)+")");
+  if (offset < (int) minOffset)
+    throw std::range_error("Trying to read before the beginning of the buffer ("+std::to_string(offset)+ " < "+std::to_string(minOffset)+")");
+
+  const unsigned char* end = pos + len;
+  pos += offset;
+  while((labellen=*pos++) && pos < end) { // "scan and copy"
+    if(labellen >= 0xc0) {
+      if(!uncompress)
+        throw std::range_error("Found compressed label, instructed not to follow");
+
+      labellen &= (~0xc0);
+      int newpos = (labellen << 8) + *(const unsigned char*)pos;
+
+      if(newpos < offset) {
+        if(newpos < (int) minOffset)
+          throw std::range_error("Invalid label position during decompression ("+std::to_string(newpos)+ " < "+std::to_string(minOffset)+")");
+        if (++depth > 100)
+          throw std::range_error("Abort label decompression after 100 redirects");
+        packetParser((const char*)opos, len, newpos, true, nullptr, nullptr, nullptr, depth, minOffset);
+      } else
+        throw std::range_error("Found a forward reference during label decompression");
+      pos++;
+      break;
+    } else if(labellen & 0xc0) {
+      throw std::range_error("Found an invalid label length in qname (only one of the first two bits is set)");
+    }
+    if (pos + labellen < end) {
+      appendRawLabel((const char*)pos, labellen);
+    }
+    else
+      throw std::range_error("Found an invalid label length in qname");
+    pos+=labellen;
+  }
+  if(d_storage.empty())
+    d_storage.append(1, (char)0); // we just parsed the root
+  if(consumed)
+    *consumed = pos - opos - offset;
+  if(qtype) {
+    if (pos + 2 > end) {
+      throw std::range_error("Trying to read qtype past the end of the buffer ("+std::to_string((pos - opos) + 2)+ " > "+std::to_string(len)+")");
+    }
+    *qtype=(*(const unsigned char*)pos)*256 + *((const unsigned char*)pos+1);
+  }
+  pos+=2;
+  if(qclass) {
+    if (pos + 2 > end) {
+      throw std::range_error("Trying to read qclass past the end of the buffer ("+std::to_string((pos - opos) + 2)+ " > "+std::to_string(len)+")");
+    }
+    *qclass=(*(const unsigned char*)pos)*256 + *((const unsigned char*)pos+1);
+  }
+}
+
+std::string DNSName::toString(const std::string& separator, const bool trailing) const
+{
+  std::string ret;
+  toString(ret, separator, trailing);
+  return ret;
+}
+
+void DNSName::toString(std::string& output, const std::string& separator, const bool trailing) const
+{
+  if (empty()) {
+    throw std::out_of_range("Attempt to print an unset dnsname");
+  }
+
+  if (isRoot()) {
+    output += (trailing ? separator : "");
+    return;
+  }
+
+  if (output.capacity() < (output.size() + d_storage.size())) {
+    output.reserve(output.size() + d_storage.size());
+  }
+
+  {
+    // iterate over the raw labels
+    const char* p = d_storage.c_str();
+    const char* end = p + d_storage.size();
+
+    while (p < end && *p) {
+      appendEscapedLabel(output, p + 1, static_cast<size_t>(*p));
+      output += separator;
+      p += *p + 1;
+    }
+  }
+
+  if (!trailing) {
+    output.resize(output.size() - separator.size());
+  }
+}
+
+std::string DNSName::toLogString() const
+{
+  if (empty()) {
+    return "(empty)";
+  }
+
+  return toStringRootDot();
+}
+
+std::string DNSName::toDNSString() const
+{
+  if (empty())
+    throw std::out_of_range("Attempt to DNSString an unset dnsname");
+
+  return std::string(d_storage.c_str(), d_storage.length());
+}
+
+std::string DNSName::toDNSStringLC() const
+{
+  auto result = toDNSString();
+  toLowerInPlace(result); // label lengths are always < 'A'
+  return result;
+}
+
+/**
+ * Get the length of the DNSName on the wire
+ *
+ * @return the total wirelength of the DNSName
+ */
+size_t DNSName::wirelength() const {
+  return d_storage.length();
+}
+
+// Are WE part of parent
+bool DNSName::isPartOf(const DNSName& parent) const
+{
+  if(parent.empty() || empty())
+    throw std::out_of_range("empty dnsnames aren't part of anything");
+
+  if(parent.d_storage.size() > d_storage.size())
+    return false;
+
+  // this is slightly complicated since we can't start from the end, since we can't see where a label begins/ends then
+  for(auto us=d_storage.cbegin(); us<d_storage.cend(); us+=*us+1) {
+    auto distance = std::distance(us,d_storage.cend());
+    if (distance < 0 || static_cast<size_t>(distance) < parent.d_storage.size()) {
+      break;
+    }
+    if (static_cast<size_t>(distance) == parent.d_storage.size()) {
+      auto p = parent.d_storage.cbegin();
+      for(; us != d_storage.cend(); ++us, ++p) {
+        if(dns_tolower(*p) != dns_tolower(*us))
+          return false;
+      }
+      return true;
+    }
+    if (static_cast<uint8_t>(*us) > 63) {
+      throw std::out_of_range("illegal label length in dnsname");
+    }
+  }
+  return false;
+}
+
+DNSName DNSName::makeRelative(const DNSName& zone) const
+{
+  DNSName ret(*this);
+  ret.makeUsRelative(zone);
+  return ret;
+}
+
+void DNSName::makeUsRelative(const DNSName& zone) 
+{
+  if (isPartOf(zone)) {
+    d_storage.erase(d_storage.size()-zone.d_storage.size());
+    d_storage.append(1, (char)0); // put back the trailing 0
+  } 
+  else
+    clear();
+}
+
+DNSName DNSName::getCommonLabels(const DNSName& other) const
+{
+  DNSName result;
+
+  const std::vector<std::string> ours = getRawLabels();
+  const std::vector<std::string> others = other.getRawLabels();
+
+  for (size_t pos = 0; ours.size() > pos && others.size() > pos; pos++) {
+    const std::string& ourLabel = ours.at(ours.size() - pos - 1);
+    const std::string& otherLabel = others.at(others.size() - pos - 1);
+
+    if (!pdns_iequals(ourLabel, otherLabel)) {
+      break;
+    }
+
+    result.prependRawLabel(ourLabel);
+  }
+
+  return result;
+}
+
+DNSName DNSName::labelReverse() const
+{
+  DNSName ret;
+
+  if(isRoot())
+    return *this; // we don't create the root automatically below
+
+  if (!empty()) {
+    vector<string> l=getRawLabels();
+    while(!l.empty()) {
+      ret.appendRawLabel(l.back());
+      l.pop_back();
+    }
+  }
+  return ret;
+}
+
+void DNSName::appendRawLabel(const std::string& label)
+{
+  appendRawLabel(label.c_str(), label.length());
+}
+
+void DNSName::appendRawLabel(const char* start, unsigned int length)
+{
+  if(length==0)
+    throw std::range_error("no such thing as an empty label to append");
+  if(length > 63)
+    throw std::range_error("label too long to append");
+  if(d_storage.size() + length > s_maxDNSNameLength - 1) // reserve one byte for the label length
+    throw std::range_error("name too long to append");
+
+  if(d_storage.empty()) {
+    d_storage.append(1, (char)length);
+  }
+  else {
+    *d_storage.rbegin()=(char)length;
+  }
+  d_storage.append(start, length);
+  d_storage.append(1, (char)0);
+}
+
+void DNSName::prependRawLabel(const std::string& label)
+{
+  if(label.empty())
+    throw std::range_error("no such thing as an empty label to prepend");
+  if(label.size() > 63)
+    throw std::range_error("label too long to prepend");
+  if(d_storage.size() + label.size() > s_maxDNSNameLength - 1) // reserve one byte for the label length
+    throw std::range_error("name too long to prepend");
+
+  if(d_storage.empty())
+    d_storage.append(1, (char)0);
+
+  string_t prep(1, (char)label.size());
+  prep.append(label.c_str(), label.size());
+  d_storage = prep+d_storage;
+}
+
+bool DNSName::slowCanonCompare(const DNSName& rhs) const 
+{
+  auto ours=getRawLabels(), rhsLabels = rhs.getRawLabels();
+  return std::lexicographical_compare(ours.rbegin(), ours.rend(), rhsLabels.rbegin(), rhsLabels.rend(), CIStringCompare());
+}
+
+vector<std::string> DNSName::getRawLabels() const
+{
+  vector<std::string> ret;
+  ret.reserve(countLabels());
+  // 3www4ds9a2nl0
+  for(const unsigned char* p = (const unsigned char*) d_storage.c_str(); p < ((const unsigned char*) d_storage.c_str()) + d_storage.size() && *p; p+=*p+1) {
+    ret.push_back({(const char*)p+1, (size_t)*p}); // XXX FIXME
+  }
+  return ret;
+}
+
+std::string DNSName::getRawLabel(unsigned int pos) const
+{
+  unsigned int currentPos = 0;
+  for(const unsigned char* p = (const unsigned char*) d_storage.c_str(); p < ((const unsigned char*) d_storage.c_str()) + d_storage.size() && *p; p+=*p+1, currentPos++) {
+    if (currentPos == pos) {
+      return std::string((const char*)p+1, (size_t)*p);
+    }
+  }
+
+  throw std::out_of_range("trying to get label at position "+std::to_string(pos)+" of a DNSName that only has "+std::to_string(currentPos)+" labels");
+}
+
+DNSName DNSName::getLastLabel() const
+{
+  DNSName ret(*this);
+  ret.trimToLabels(1);
+  return ret;
+}
+
+bool DNSName::chopOff()
+{
+  if(d_storage.empty() || d_storage[0]==0)
+    return false;
+  d_storage.erase(0, (unsigned int)d_storage[0]+1);
+  return true;
+}
+
+bool DNSName::isWildcard() const
+{
+  if(d_storage.size() < 2)
+    return false;
+  auto p = d_storage.begin();
+  return (*p == 0x01 && *++p == '*');
+}
+
+/*
+ * Returns true if the DNSName is a valid RFC 1123 hostname, this function uses
+ * a regex on the string, so it is probably best not used when speed is essential.
+ */
+bool DNSName::isHostname() const
+{
+  static Regex hostNameRegex = Regex("^(([A-Za-z0-9]([A-Za-z0-9-]*[A-Za-z0-9])?)\\.)+$");
+  return hostNameRegex.match(this->toString());
+}
+
+unsigned int DNSName::countLabels() const
+{
+  unsigned int count=0;
+  const unsigned char* p = reinterpret_cast<const unsigned char*>(d_storage.c_str());
+  const unsigned char* end = reinterpret_cast<const unsigned char*>(p + d_storage.size());
+
+  while (p < end && *p) {
+    ++count;
+    p += *p + 1;
+  }
+  return count;
+}
+
+void DNSName::trimToLabels(unsigned int to)
+{
+  while(countLabels() > to && chopOff())
+    ;
+}
+
+
+size_t hash_value(DNSName const& d)
+{
+  return d.hash();
+}
+
+void DNSName::appendEscapedLabel(std::string& appendTo, const char* orig, size_t len)
+{
+  size_t pos = 0;
+
+  while (pos < len) {
+    auto p = static_cast<uint8_t>(orig[pos]);
+    if(p=='.')
+      appendTo+="\\.";
+    else if(p=='\\')
+      appendTo+="\\\\";
+    else if(p > 0x20 && p < 0x7f)
+      appendTo.append(1, (char)p);
+    else {
+      char buf[] = "000";
+      auto got = snprintf(buf, sizeof(buf), "%03" PRIu8, p);
+      if (got < 0 || static_cast<size_t>(got) >= sizeof(buf)) {
+        throw std::runtime_error("Error, snprintf returned " + std::to_string(got) + " while escaping label " + std::string(orig, len));
+      }
+      appendTo.append(1, '\\');
+      appendTo += buf;
+    }
+    ++pos;
+  }
+}
+
+bool DNSName::has8bitBytes() const
+{
+  const auto& s = d_storage;
+  string::size_type pos = 0;
+  uint8_t length = s.at(pos);
+  while (length > 0) {
+    for (size_t idx = 0; idx < length; idx++) {
+      ++pos;
+      char c = s.at(pos);
+      if(!((c >= 'a' && c <= 'z') ||
+           (c >= 'A' && c <= 'Z') ||
+           (c >= '0' && c <= '9') ||
+           c =='-' || c == '_' || c=='*' || c=='.' || c=='/' || c=='@' || c==' ' || c=='\\' || c==':'))
+        return true;
+    }
+    ++pos;
+    length = s.at(pos);
+  }
+
+  return false;
+}
+
+// clang-format off
+const unsigned char dns_toupper_table[256] = {
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+  0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+  0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
+  0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
+  0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
+  0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
+  0x40, 0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47,
+  0x48, 0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f,
+  0x50, 0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57,
+  0x58, 0x59, 0x5a, 0x5b, 0x5c, 0x5d, 0x5e, 0x5f,
+  0x60, 'A',  'B',  'C',  'D',  'E',  'F',  'G',
+  'H',  'I',  'J',  'K',  'L',  'M',  'N',  'O',
+  'P',  'Q',  'R',  'S',  'T',  'U',  'V',  'W',
+  'X',  'Y',  'Z',  0x7b, 0x7c, 0x7d, 0x7e, 0x7f,
+  0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
+  0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
+  0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
+  0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
+  0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
+  0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
+  0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
+  0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
+  0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
+  0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
+  0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
+  0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
+  0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
+  0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
+  0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
+  0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff
+};
+
+const unsigned char dns_tolower_table[256] = {
+  0x00, 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07,
+  0x08, 0x09, 0x0a, 0x0b, 0x0c, 0x0d, 0x0e, 0x0f,
+  0x10, 0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17,
+  0x18, 0x19, 0x1a, 0x1b, 0x1c, 0x1d, 0x1e, 0x1f,
+  0x20, 0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27,
+  0x28, 0x29, 0x2a, 0x2b, 0x2c, 0x2d, 0x2e, 0x2f,
+  0x30, 0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37,
+  0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f,
+  0x40, 'a',  'b',  'c',  'd',  'e',  'f',  'g',
+  'h',  'i',  'j',  'k',  'l',  'm',  'n',  'o',
+  'p',  'q',  'r',  's',  't',  'u',  'v',  'w',
+  'x',  'y',  'z',  0x5b, 0x5c, 0x5d, 0x5e, 0x5f,
+  0x60, 0x61, 0x62, 0x63, 0x64, 0x65, 0x66, 0x67,
+  0x68, 0x69, 0x6a, 0x6b, 0x6c, 0x6d, 0x6e, 0x6f,
+  0x70, 0x71, 0x72, 0x73, 0x74, 0x75, 0x76, 0x77,
+  0x78, 0x79, 0x7a, 0x7b, 0x7c, 0x7d, 0x7e, 0x7f,
+  0x80, 0x81, 0x82, 0x83, 0x84, 0x85, 0x86, 0x87,
+  0x88, 0x89, 0x8a, 0x8b, 0x8c, 0x8d, 0x8e, 0x8f,
+  0x90, 0x91, 0x92, 0x93, 0x94, 0x95, 0x96, 0x97,
+  0x98, 0x99, 0x9a, 0x9b, 0x9c, 0x9d, 0x9e, 0x9f,
+  0xa0, 0xa1, 0xa2, 0xa3, 0xa4, 0xa5, 0xa6, 0xa7,
+  0xa8, 0xa9, 0xaa, 0xab, 0xac, 0xad, 0xae, 0xaf,
+  0xb0, 0xb1, 0xb2, 0xb3, 0xb4, 0xb5, 0xb6, 0xb7,
+  0xb8, 0xb9, 0xba, 0xbb, 0xbc, 0xbd, 0xbe, 0xbf,
+  0xc0, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7,
+  0xc8, 0xc9, 0xca, 0xcb, 0xcc, 0xcd, 0xce, 0xcf,
+  0xd0, 0xd1, 0xd2, 0xd3, 0xd4, 0xd5, 0xd6, 0xd7,
+  0xd8, 0xd9, 0xda, 0xdb, 0xdc, 0xdd, 0xde, 0xdf,
+  0xe0, 0xe1, 0xe2, 0xe3, 0xe4, 0xe5, 0xe6, 0xe7,
+  0xe8, 0xe9, 0xea, 0xeb, 0xec, 0xed, 0xee, 0xef,
+  0xf0, 0xf1, 0xf2, 0xf3, 0xf4, 0xf5, 0xf6, 0xf7,
+  0xf8, 0xf9, 0xfa, 0xfb, 0xfc, 0xfd, 0xfe, 0xff
+};
+
+DNSName::RawLabelsVisitor::RawLabelsVisitor(const DNSName::string_t& storage): d_storage(storage)
+{
+  size_t position = 0;
+  while (position < storage.size()) {
+    auto labelLength = static_cast<uint8_t>(storage.at(position));
+    if (labelLength == 0) {
+      break;
+    }
+    d_labelPositions.at(d_position) = position;
+    d_position++;
+    position += labelLength + 1;
+  }
+}
+
+DNSName::RawLabelsVisitor DNSName::getRawLabelsVisitor() const
+{
+  return DNSName::RawLabelsVisitor(getStorage());
+}
+
+std::string_view DNSName::RawLabelsVisitor::front() const
+{
+  if (d_position == 0) {
+    throw std::out_of_range("trying to access the front of an empty DNSName::RawLabelsVisitor");
+  }
+  uint8_t length = d_storage.at(0);
+  if (length == 0) {
+    return std::string_view();
+  }
+  return std::string_view(&d_storage.at(1), length);
+}
+
+std::string_view DNSName::RawLabelsVisitor::back() const
+{
+  if (d_position == 0) {
+    throw std::out_of_range("trying to access the back of an empty DNSName::RawLabelsVisitor");
+  }
+  size_t offset = d_labelPositions.at(d_position-1);
+  uint8_t length = d_storage.at(offset);
+  if (length == 0) {
+    return std::string_view();
+  }
+  return std::string_view(&d_storage.at(offset + 1), length);
+}
+
+bool DNSName::RawLabelsVisitor::pop_back()
+{
+  if (d_position > 0) {
+    d_position--;
+    return true;
+  }
+  return false;
+}
+
+bool DNSName::RawLabelsVisitor::empty() const
+{
+  return d_position == 0;
+}