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Diffstat (limited to 'src/lib/dns/edns.cc')
| -rw-r--r-- | src/lib/dns/edns.cc | 178 |
1 files changed, 178 insertions, 0 deletions
diff --git a/src/lib/dns/edns.cc b/src/lib/dns/edns.cc new file mode 100644 index 0000000..49253cf --- /dev/null +++ b/src/lib/dns/edns.cc @@ -0,0 +1,178 @@ +// Copyright (C) 2010-2015 Internet Systems Consortium, Inc. ("ISC") +// +// This Source Code Form is subject to the terms of the Mozilla Public +// License, v. 2.0. If a copy of the MPL was not distributed with this +// file, You can obtain one at http://mozilla.org/MPL/2.0/. + +#include <config.h> + +#include <stdint.h> + +#include <cassert> + +#include <boost/lexical_cast.hpp> + +#include <exceptions/exceptions.h> + +#include <dns/edns.h> +#include <dns/exceptions.h> +#include <dns/message.h> +#include <dns/messagerenderer.h> +#include <dns/name.h> +#include <dns/rdata.h> +#include <dns/rdataclass.h> +#include <dns/rrclass.h> +#include <dns/rrttl.h> +#include <dns/rrtype.h> + +using namespace std; +using boost::lexical_cast; +using namespace isc::dns::rdata; +using namespace isc::util; + +namespace isc { +namespace dns { + +namespace { +// This diagram shows the wire-format representation of the TTL field of +// OPT RR and its relationship with implementation specific parameters. +// +// 0 7 15 31 +// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +// | EXTENDED-RCODE| VERSION |D| Z | +// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +// <= VERSION_SHIFT (16 bits) +// <= EXTRCODE_SHIFT (24 bits) +//EXTFLAG_DO:0 0 0 ....................... 0 1 0 0 0 0.....................0 +//VER_MASK: 0 0 0 ........0 1 1 1 1 1 1 1 1 0 0 ..........................0 + +const unsigned int VERSION_SHIFT = 16; +const unsigned int EXTRCODE_SHIFT = 24; +const uint32_t VERSION_MASK = 0x00ff0000; +const uint32_t EXTFLAG_DO = 0x00008000; +} + +EDNS::EDNS(const uint8_t version) : + version_(version), + udp_size_(Message::DEFAULT_MAX_UDPSIZE), + dnssec_aware_(false) +{ + if (version_ > SUPPORTED_VERSION) { + isc_throw(isc::InvalidParameter, + "failed to construct EDNS: unsupported version: " << + static_cast<unsigned int>(version_)); + } +} + +EDNS::EDNS(const Name& name, const RRClass& rrclass, const RRType& rrtype, + const RRTTL& ttl, const Rdata&) : + version_((ttl.getValue() & VERSION_MASK) >> VERSION_SHIFT) +{ + if (rrtype != RRType::OPT()) { + isc_throw(isc::InvalidParameter, + "EDNS is being created with incompatible RR type: " + << rrtype); + } + + if (version_ > EDNS::SUPPORTED_VERSION) { + isc_throw(DNSMessageBADVERS, "unsupported EDNS version: " << + static_cast<unsigned int>(version_)); + } + + if (name != Name::ROOT_NAME()) { + isc_throw(DNSMessageFORMERR, "invalid owner name for EDNS OPT RR: " << + name); + } + + dnssec_aware_ = ((ttl.getValue() & EXTFLAG_DO) != 0); + udp_size_ = rrclass.getCode(); +} + +string +EDNS::toText() const { + string ret = "; EDNS: version: "; + + ret += lexical_cast<string>(static_cast<int>(getVersion())); + ret += ", flags:"; + if (getDNSSECAwareness()) { + ret += " do"; + } + ret += "; udp: " + lexical_cast<string>(getUDPSize()) + "\n"; + + return (ret); +} + +namespace { +/// Helper function to define unified implementation for the public versions +/// of toWire(). +template <typename Output> +int +toWireCommon(Output& output, const uint8_t version, + const uint16_t udp_size, const bool dnssec_aware, + const uint8_t extended_rcode) +{ + // Render EDNS OPT RR + uint32_t extrcode_flags = extended_rcode << EXTRCODE_SHIFT; + extrcode_flags |= (version << VERSION_SHIFT) & VERSION_MASK; + if (dnssec_aware) { + extrcode_flags |= EXTFLAG_DO; + } + + // Construct an RRset corresponding to the EDNS. + // We don't support any options for now, so the OPT RR can be empty. + RRsetPtr edns_rrset(new RRset(Name::ROOT_NAME(), RRClass(udp_size), + RRType::OPT(), RRTTL(extrcode_flags))); + edns_rrset->addRdata(ConstRdataPtr(new generic::OPT())); + + edns_rrset->toWire(output); + + return (1); +} +} + +unsigned int +EDNS::toWire(AbstractMessageRenderer& renderer, + const uint8_t extended_rcode) const +{ + // If adding the OPT RR would exceed the size limit, don't do it. + // 11 = len(".") + type(2byte) + class(2byte) + TTL(4byte) + RDLEN(2byte) + // (RDATA is empty in this simple implementation) + if (renderer.getLength() + 11 > renderer.getLengthLimit()) { + return (0); + } + + return (toWireCommon(renderer, version_, udp_size_, dnssec_aware_, + extended_rcode)); +} + +unsigned int +EDNS::toWire(isc::util::OutputBuffer& buffer, + const uint8_t extended_rcode) const +{ + return (toWireCommon(buffer, version_, udp_size_, dnssec_aware_, + extended_rcode)); +} + +EDNS* +createEDNSFromRR(const Name& name, const RRClass& rrclass, + const RRType& rrtype, const RRTTL& ttl, + const Rdata& rdata, + uint8_t& extended_rcode) +{ + // Create a new EDNS object first for exception guarantee. + EDNS* edns = new EDNS(name, rrclass, rrtype, ttl, rdata); + + // At this point we can update extended_rcode safely. + extended_rcode = ttl.getValue() >> EXTRCODE_SHIFT; + + return (edns); +} + +ostream& +operator<<(std::ostream& os, const EDNS& edns) { + os << edns.toText(); + return (os); +} + +} // end of namespace dns +} // end of namespace isc |