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/*
* 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.
*/
#pragma once
#include "ednsoptions.hh"
#include "misc.hh"
#include "iputils.hh"
class PacketCache : public boost::noncopyable
{
public:
/* hash the packet from the provided position, which should point right after tje qname. This skips:
- the query ID ;
- EDNS Cookie options, if any ;
- Any given option code present in optionsToSkip
*/
static uint32_t hashAfterQname(const std::string_view& packet, uint32_t currentHash, size_t pos, const std::unordered_set<uint16_t>& optionsToSkip = {EDNSOptionCode::COOKIE})
{
const size_t packetSize = packet.size();
assert(packetSize >= sizeof(dnsheader));
/* we need at least 2 (QTYPE) + 2 (QCLASS)
+ OPT root label (1), type (2), class (2) and ttl (4)
+ the OPT RR rdlen (2)
= 15
*/
const dnsheader_aligned dnsheaderdata(packet.data());
const struct dnsheader *dh = dnsheaderdata.get();
if (ntohs(dh->qdcount) != 1 || ntohs(dh->ancount) != 0 || ntohs(dh->nscount) != 0 || ntohs(dh->arcount) != 1 || (pos + 15) >= packetSize) {
if (packetSize > pos) {
currentHash = burtle(reinterpret_cast<const unsigned char*>(&packet.at(pos)), packetSize - pos, currentHash);
}
return currentHash;
}
currentHash = burtle(reinterpret_cast<const unsigned char*>(&packet.at(pos)), 15, currentHash);
/* skip the qtype (2), qclass (2) */
/* root label (1), type (2), class (2) and ttl (4) */
/* already hashed above */
pos += 13;
const uint16_t rdLen = ((static_cast<uint16_t>(packet.at(pos)) * 256) + static_cast<uint16_t>(packet.at(pos + 1)));
/* skip the rd length */
/* already hashed above */
pos += 2;
if (rdLen > (packetSize - pos)) {
if (pos < packetSize) {
currentHash = burtle(reinterpret_cast<const unsigned char*>(&packet.at(pos)), packetSize - pos, currentHash);
}
return currentHash;
}
uint16_t rdataRead = 0;
uint16_t optionCode;
uint16_t optionLen;
while (pos < packetSize && rdataRead < rdLen && getNextEDNSOption(&packet.at(pos), rdLen - rdataRead, optionCode, optionLen)) {
if (optionLen > (rdLen - rdataRead - 4)) {
if (packetSize > pos) {
currentHash = burtle(reinterpret_cast<const unsigned char*>(&packet.at(pos)), packetSize - pos, currentHash);
}
return currentHash;
}
if (optionsToSkip.count(optionCode) == 0) {
/* hash the option code, length and content */
currentHash = burtle(reinterpret_cast<const unsigned char*>(&packet.at(pos)), 4 + optionLen, currentHash);
}
else {
/* skip option: hash only its code and length */
currentHash = burtle(reinterpret_cast<const unsigned char*>(&packet.at(pos)), 4, currentHash);
}
pos += 4 + optionLen;
rdataRead += 4 + optionLen;
}
if (pos < packetSize) {
currentHash = burtle(reinterpret_cast<const unsigned char*>(&packet.at(pos)), packetSize - pos, currentHash);
}
return currentHash;
}
static uint32_t hashHeaderAndQName(const std::string& packet, size_t& pos)
{
const size_t packetSize = packet.size();
assert(packetSize >= sizeof(dnsheader));
// Quite some bits in the header are actually irrelevant for
// incoming queries. If we ever change that and ignore them for
// hashing, don't forget to also adapt the `queryHeaderMatches`
// code, as it should be consistent with the hash function.
uint32_t currentHash = burtle(reinterpret_cast<const unsigned char*>(&packet.at(2)), sizeof(dnsheader) - 2, 0); // rest of dnsheader, skip id
for (pos = sizeof(dnsheader); pos < packetSize; ) {
const unsigned char labelLen = static_cast<unsigned char>(packet.at(pos));
++pos;
if (labelLen == 0) {
break;
}
pos = std::min(pos + labelLen, packetSize);
}
return burtleCI(reinterpret_cast<const unsigned char*>(&packet.at(sizeof(dnsheader))), pos - sizeof(dnsheader), currentHash);
}
/* hash the packet from the beginning, including the qname. This skips:
- the query ID ;
- EDNS Cookie options, if any ;
- Any given option code present in optionsToSkip
*/
static uint32_t canHashPacket(const std::string& packet, const std::unordered_set<uint16_t>& optionsToSkip = {EDNSOptionCode::COOKIE})
{
size_t pos = 0;
uint32_t currentHash = hashHeaderAndQName(packet, pos);
if (pos >= packet.size()) {
return currentHash;
}
return hashAfterQname(packet, currentHash, pos, optionsToSkip);
}
static bool queryHeaderMatches(const std::string& cachedQuery, const std::string& query)
{
if (cachedQuery.size() != query.size()) {
return false;
}
return (cachedQuery.compare(/* skip the ID */ 2, sizeof(dnsheader) - 2, query, 2, sizeof(dnsheader) - 2) == 0);
}
static bool queryMatches(const std::string& cachedQuery, const std::string& query, const DNSName& qname, const std::unordered_set<uint16_t>& optionsToIgnore)
{
const size_t querySize = query.size();
const size_t cachedQuerySize = cachedQuery.size();
if (querySize != cachedQuerySize) {
return false;
}
if (!queryHeaderMatches(cachedQuery, query)) {
return false;
}
size_t pos = sizeof(dnsheader) + qname.wirelength();
/* we need at least 2 (QTYPE) + 2 (QCLASS)
+ OPT root label (1), type (2), class (2) and ttl (4)
+ the OPT RR rdlen (2)
= 15
*/
const dnsheader_aligned dnsheaderdata(query.data());
const struct dnsheader* dh = dnsheaderdata.get();
if (ntohs(dh->qdcount) != 1 || ntohs(dh->ancount) != 0 || ntohs(dh->nscount) != 0 || ntohs(dh->arcount) != 1 || (pos + 15) >= querySize || optionsToIgnore.empty()) {
return cachedQuery.compare(pos, cachedQuerySize - pos, query, pos, querySize - pos) == 0;
}
/* compare up to the first option, if any */
if (cachedQuery.compare(pos, 15, query, pos, 15) != 0) {
return false;
}
/* skip the qtype (2), qclass (2) */
/* root label (1), type (2), class (2) and ttl (4) */
/* already compared above */
pos += 13;
const uint16_t rdLen = ((static_cast<unsigned char>(query.at(pos)) * 256) + static_cast<unsigned char>(query.at(pos + 1)));
/* skip the rd length */
/* already compared above */
pos += sizeof(uint16_t);
if (rdLen > (querySize - pos)) {
/* something is wrong, let's just compare everything */
return cachedQuery.compare(pos, cachedQuerySize - pos, query, pos, querySize - pos) == 0;
}
uint16_t rdataRead = 0;
uint16_t optionCode;
uint16_t optionLen;
while (pos < querySize && rdataRead < rdLen && getNextEDNSOption(&query.at(pos), rdLen - rdataRead, optionCode, optionLen)) {
if (optionLen > (rdLen - rdataRead)) {
return cachedQuery.compare(pos, cachedQuerySize - pos, query, pos, querySize - pos) == 0;
}
/* compare the option code and length */
if (cachedQuery.compare(pos, 4, query, pos, 4) != 0) {
return false;
}
pos += 4;
rdataRead += 4;
if (optionLen > 0 && optionsToIgnore.count(optionCode) == 0) {
if (cachedQuery.compare(pos, optionLen, query, pos, optionLen) != 0) {
return false;
}
}
pos += optionLen;
rdataRead += optionLen;
}
if (pos >= querySize) {
return true;
}
return cachedQuery.compare(pos, cachedQuerySize - pos, query, pos, querySize - pos) == 0;
}
};
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