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Tidy up a few minor protocol things, improve documentation in Packet.hpp.

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This commit is contained in:
Adam Ierymenko 2016-08-23 11:29:02 -07:00
parent 77f7dcf40a
commit 0dfc08b317
4 changed files with 120 additions and 68 deletions
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71
node/IncomingPacket.cpp
View file

@ -469,29 +469,40 @@ bool IncomingPacket::_doOK(const RuntimeEnvironment *RR,const SharedPtr<Peer> &p
bool IncomingPacket::_doWHOIS(const RuntimeEnvironment *RR,const SharedPtr<Peer> &peer) bool IncomingPacket::_doWHOIS(const RuntimeEnvironment *RR,const SharedPtr<Peer> &peer)
{ {
try { try {
if (payloadLength() == ZT_ADDRESS_LENGTH) { Packet outp(peer->address(),RR->identity.address(),Packet::VERB_OK);
const Address addr(payload(),ZT_ADDRESS_LENGTH); outp.append((unsigned char)Packet::VERB_WHOIS);
outp.append(packetId());
unsigned int count = 0;
unsigned int ptr = ZT_PACKET_IDX_PAYLOAD;
while ((ptr + ZT_ADDRESS_LENGTH) <= size()) {
const Address addr(field(ptr,ZT_ADDRESS_LENGTH),ZT_ADDRESS_LENGTH);
ptr += ZT_ADDRESS_LENGTH;
const Identity id(RR->topology->getIdentity(addr)); const Identity id(RR->topology->getIdentity(addr));
if (id) { if (id) {
Packet outp(peer->address(),RR->identity.address(),Packet::VERB_OK);
outp.append((unsigned char)Packet::VERB_WHOIS);
outp.append(packetId());
id.serialize(outp,false); id.serialize(outp,false);
outp.armor(peer->key(),true); ++count;
RR->node->putPacket(_localAddress,_remoteAddress,outp.data(),outp.size());
} else { } else {
// If I am not the root and don't know this identity, ask upstream. Downstream
// peer may re-request in the future and if so we will be able to provide it.
if (!RR->topology->amRoot())
RR->sw->requestWhois(addr);
#ifdef ZT_ENABLE_CLUSTER #ifdef ZT_ENABLE_CLUSTER
// Distribute WHOIS queries across a cluster if we do not know the ID.
// This may result in duplicate OKs to the querying peer, which is fine.
if (RR->cluster) if (RR->cluster)
RR->cluster->sendDistributedQuery(*this); RR->cluster->sendDistributedQuery(*this);
#endif #endif
if (!RR->topology->amRoot()) {
RR->sw->requestWhois(addr);
return false; // packet parse will be attempted again if we get a reply from upstream
}
} }
} else {
TRACE("dropped WHOIS from %s(%s): missing or invalid address",source().toString().c_str(),_remoteAddress.toString().c_str());
} }
if (count > 0) {
outp.armor(peer->key(),true);
RR->node->putPacket(_localAddress,_remoteAddress,outp.data(),outp.size());
}
peer->received(_localAddress,_remoteAddress,hops(),packetId(),Packet::VERB_WHOIS,0,Packet::VERB_NOP); peer->received(_localAddress,_remoteAddress,hops(),packetId(),Packet::VERB_WHOIS,0,Packet::VERB_NOP);
} catch ( ... ) { } catch ( ... ) {
TRACE("dropped WHOIS from %s(%s): unexpected exception",source().toString().c_str(),_remoteAddress.toString().c_str()); TRACE("dropped WHOIS from %s(%s): unexpected exception",source().toString().c_str(),_remoteAddress.toString().c_str());
@ -836,11 +847,26 @@ bool IncomingPacket::_doMULTICAST_GATHER(const RuntimeEnvironment *RR,const Shar
{ {
try { try {
const uint64_t nwid = at<uint64_t>(ZT_PROTO_VERB_MULTICAST_GATHER_IDX_NETWORK_ID); const uint64_t nwid = at<uint64_t>(ZT_PROTO_VERB_MULTICAST_GATHER_IDX_NETWORK_ID);
const unsigned int flags = (*this)[ZT_PROTO_VERB_MULTICAST_GATHER_IDX_FLAGS];
const MulticastGroup mg(MAC(field(ZT_PROTO_VERB_MULTICAST_GATHER_IDX_MAC,6),6),at<uint32_t>(ZT_PROTO_VERB_MULTICAST_GATHER_IDX_ADI)); const MulticastGroup mg(MAC(field(ZT_PROTO_VERB_MULTICAST_GATHER_IDX_MAC,6),6),at<uint32_t>(ZT_PROTO_VERB_MULTICAST_GATHER_IDX_ADI));
const unsigned int gatherLimit = at<uint32_t>(ZT_PROTO_VERB_MULTICAST_GATHER_IDX_GATHER_LIMIT); const unsigned int gatherLimit = at<uint32_t>(ZT_PROTO_VERB_MULTICAST_GATHER_IDX_GATHER_LIMIT);
//TRACE("<<MC %s(%s) GATHER up to %u in %.16llx/%s",source().toString().c_str(),_remoteAddress.toString().c_str(),gatherLimit,nwid,mg.toString().c_str()); //TRACE("<<MC %s(%s) GATHER up to %u in %.16llx/%s",source().toString().c_str(),_remoteAddress.toString().c_str(),gatherLimit,nwid,mg.toString().c_str());
if ((flags & 0x01) != 0) {
try {
CertificateOfMembership com;
com.deserialize(*this,ZT_PROTO_VERB_MULTICAST_GATHER_IDX_COM);
if (com) {
SharedPtr<Network> network(RR->node->network(nwid));
if (network)
network->addCredential(com);
}
} catch ( ... ) {
TRACE("MULTICAST_GATHER from %s(%s): discarded invalid COM",peer->address().toString().c_str(),_remoteAddress.toString().c_str());
}
}
if (gatherLimit) { if (gatherLimit) {
Packet outp(peer->address(),RR->identity.address(),Packet::VERB_OK); Packet outp(peer->address(),RR->identity.address(),Packet::VERB_OK);
outp.append((unsigned char)Packet::VERB_MULTICAST_GATHER); outp.append((unsigned char)Packet::VERB_MULTICAST_GATHER);
@ -854,6 +880,7 @@ bool IncomingPacket::_doMULTICAST_GATHER(const RuntimeEnvironment *RR,const Shar
RR->node->putPacket(_localAddress,_remoteAddress,outp.data(),outp.size()); RR->node->putPacket(_localAddress,_remoteAddress,outp.data(),outp.size());
} }
// If we are a member of a cluster, distribute this GATHER across it
#ifdef ZT_ENABLE_CLUSTER #ifdef ZT_ENABLE_CLUSTER
if ((RR->cluster)&&(gatheredLocally < gatherLimit)) if ((RR->cluster)&&(gatheredLocally < gatherLimit))
RR->cluster->sendDistributedQuery(*this); RR->cluster->sendDistributedQuery(*this);
@ -862,7 +889,7 @@ bool IncomingPacket::_doMULTICAST_GATHER(const RuntimeEnvironment *RR,const Shar
peer->received(_localAddress,_remoteAddress,hops(),packetId(),Packet::VERB_MULTICAST_GATHER,0,Packet::VERB_NOP); peer->received(_localAddress,_remoteAddress,hops(),packetId(),Packet::VERB_MULTICAST_GATHER,0,Packet::VERB_NOP);
} catch ( ... ) { } catch ( ... ) {
TRACE("dropped MULTICAST_GATHER from %s(%s): unexpected exception",source().toString().c_str(),_remoteAddress.toString().c_str()); TRACE("dropped MULTICAST_GATHER from %s(%s): unexpected exception",peer->address().toString().c_str(),_remoteAddress.toString().c_str());
} }
return true; return true;
} }
@ -878,7 +905,8 @@ bool IncomingPacket::_doMULTICAST_FRAME(const RuntimeEnvironment *RR,const Share
// Offset -- size of optional fields added to position of later fields // Offset -- size of optional fields added to position of later fields
unsigned int offset = 0; unsigned int offset = 0;
if ((flags & 0x01) != 0) { // deprecated but still used by older peers if ((flags & 0x01) != 0) {
// This is deprecated but may still be sent by old peers
CertificateOfMembership com; CertificateOfMembership com;
offset += com.deserialize(*this,ZT_PROTO_VERB_MULTICAST_FRAME_IDX_COM); offset += com.deserialize(*this,ZT_PROTO_VERB_MULTICAST_FRAME_IDX_COM);
if (com) if (com)
@ -1053,7 +1081,7 @@ bool IncomingPacket::_doCIRCUIT_TEST(const RuntimeEnvironment *RR,const SharedPt
// Tracks total length of variable length fields, initialized to originator credential length below // Tracks total length of variable length fields, initialized to originator credential length below
unsigned int vlf; unsigned int vlf;
// Originator credentials // Originator credentials -- right now only a network ID for which the originator is controller or is authorized by controller is allowed
const unsigned int originatorCredentialLength = vlf = at<uint16_t>(ZT_PACKET_IDX_PAYLOAD + 23); const unsigned int originatorCredentialLength = vlf = at<uint16_t>(ZT_PACKET_IDX_PAYLOAD + 23);
uint64_t originatorCredentialNetworkId = 0; uint64_t originatorCredentialNetworkId = 0;
if (originatorCredentialLength >= 1) { if (originatorCredentialLength >= 1) {
@ -1085,15 +1113,10 @@ bool IncomingPacket::_doCIRCUIT_TEST(const RuntimeEnvironment *RR,const SharedPt
vlf += at<uint16_t>(ZT_PACKET_IDX_PAYLOAD + 29 + vlf); vlf += at<uint16_t>(ZT_PACKET_IDX_PAYLOAD + 29 + vlf);
// Check credentials (signature already verified) // Check credentials (signature already verified)
NetworkConfig originatorCredentialNetworkConfig;
if (originatorCredentialNetworkId) { if (originatorCredentialNetworkId) {
if (Network::controllerFor(originatorCredentialNetworkId) == originatorAddress) { SharedPtr<Network> network(RR->node->network(originatorCredentialNetworkId));
if (!RR->node->network(originatorCredentialNetworkId)) { if ((!network)||(!network->config().circuitTestingAllowed(originatorAddress))) {
TRACE("dropped CIRCUIT_TEST from %s(%s): originator %s specified network ID %.16llx as credential, and we are not a member of that network",source().toString().c_str(),_remoteAddress.toString().c_str(),originatorAddress.toString().c_str(),originatorCredentialNetworkId); TRACE("dropped CIRCUIT_TEST from %s(%s): originator %s specified network ID %.16llx as credential, and we don't belong to that network or originator is not allowed'",source().toString().c_str(),_remoteAddress.toString().c_str(),originatorAddress.toString().c_str(),originatorCredentialNetworkId);
return true;
}
} else {
TRACE("dropped CIRCUIT_TEST from %s(%s): originator %s specified network ID as credential, is not controller for %.16llx",source().toString().c_str(),_remoteAddress.toString().c_str(),originatorAddress.toString().c_str(),originatorCredentialNetworkId);
return true; return true;
} }
} else { } else {

38
node/Multicaster.cpp
View file

@ -224,25 +224,37 @@ void Multicaster::send(
if ((gs.members.empty())||((now - gs.lastExplicitGather) >= ZT_MULTICAST_EXPLICIT_GATHER_DELAY)) { if ((gs.members.empty())||((now - gs.lastExplicitGather) >= ZT_MULTICAST_EXPLICIT_GATHER_DELAY)) {
gs.lastExplicitGather = now; gs.lastExplicitGather = now;
SharedPtr<Peer> explicitGatherPeers[2];
explicitGatherPeers[0] = RR->topology->getBestRoot(); Address explicitGatherPeers[16];
const Address nwidc(Network::controllerFor(nwid)); unsigned int numExplicitGatherPeers = 0;
if (nwidc != RR->identity.address()) SharedPtr<Peer> bestRoot(RR->topology->getBestRoot());
explicitGatherPeers[1] = RR->topology->getPeer(nwidc); if (bestRoot)
for(unsigned int k=0;k<2;++k) { explicitGatherPeers[numExplicitGatherPeers++] = bestRoot->address();
const SharedPtr<Peer> &p = explicitGatherPeers[k]; explicitGatherPeers[numExplicitGatherPeers++] = Network::controllerFor(nwid);
if (!p) SharedPtr<Network> network(RR->node->network(nwid));
continue; if (network) {
//TRACE(">>MC upstream GATHER up to %u for group %.16llx/%s",gatherLimit,nwid,mg.toString().c_str()); std::vector<Address> anchors(network->config().anchors());
Packet outp(p->address(),RR->identity.address(),Packet::VERB_MULTICAST_GATHER); for(std::vector<Address>::const_iterator a(anchors.begin());a!=anchors.end();++a) {
if (*a != RR->identity.address()) {
explicitGatherPeers[numExplicitGatherPeers++] = *a;
if (numExplicitGatherPeers == 16)
break;
}
}
}
for(unsigned int k=0;k<numExplicitGatherPeers;++k) {
const CertificateOfMembership *com = (network) ? (((network->config())&&(network->config().isPrivate())) ? &(network->config().com) : (const CertificateOfMembership *)0) : (const CertificateOfMembership *)0;
Packet outp(explicitGatherPeers[k],RR->identity.address(),Packet::VERB_MULTICAST_GATHER);
outp.append(nwid); outp.append(nwid);
outp.append((uint8_t)0x00); outp.append((uint8_t)((com) ? 0x01 : 0x00));
mg.mac().appendTo(outp); mg.mac().appendTo(outp);
outp.append((uint32_t)mg.adi()); outp.append((uint32_t)mg.adi());
outp.append((uint32_t)gatherLimit); outp.append((uint32_t)gatherLimit);
if (com)
com->serialize(outp);
RR->sw->send(outp,true); RR->sw->send(outp,true);
} }
gatherLimit = 0;
} }
gs.txQueue.push_back(OutboundMulticast()); gs.txQueue.push_back(OutboundMulticast());

20
node/NetworkConfig.hpp
View file

@ -65,6 +65,11 @@
*/ */
#define ZT_NETWORKCONFIG_SPECIALIST_TYPE_ANCHOR 0x0000040000000000ULL #define ZT_NETWORKCONFIG_SPECIALIST_TYPE_ANCHOR 0x0000040000000000ULL
/**
* Device can send CIRCUIT_TESTs for this network
*/
#define ZT_NETWORKCONFIG_SPECIALIST_TYPE_CIRCUIT_TESTER 0x0000080000000000ULL
namespace ZeroTier { namespace ZeroTier {
// Dictionary capacity needed for max size network config // Dictionary capacity needed for max size network config
@ -273,6 +278,21 @@ public:
return false; return false;
} }
/**
* @param byPeer Address to check
* @return True if this peer is allowed to do circuit tests on this network (controller is always true)
*/
inline bool circuitTestingAllowed(const Address &byPeer) const
{
if (byPeer.toInt() == ((networkId >> 24) & 0xffffffffffULL))
return true;
for(unsigned int i=0;i<specialistCount;++i) {
if ((byPeer == specialists[i])&&((specialists[i] & ZT_NETWORKCONFIG_SPECIALIST_TYPE_CIRCUIT_TESTER) != 0))
return true;
}
return false;
}
/** /**
* @return True if this network config is non-NULL * @return True if this network config is non-NULL
*/ */

59
node/Packet.hpp
View file

@ -307,6 +307,7 @@
#define ZT_PROTO_VERB_MULTICAST_GATHER_IDX_MAC (ZT_PROTO_VERB_MULTICAST_GATHER_IDX_FLAGS + 1) #define ZT_PROTO_VERB_MULTICAST_GATHER_IDX_MAC (ZT_PROTO_VERB_MULTICAST_GATHER_IDX_FLAGS + 1)
#define ZT_PROTO_VERB_MULTICAST_GATHER_IDX_ADI (ZT_PROTO_VERB_MULTICAST_GATHER_IDX_MAC + 6) #define ZT_PROTO_VERB_MULTICAST_GATHER_IDX_ADI (ZT_PROTO_VERB_MULTICAST_GATHER_IDX_MAC + 6)
#define ZT_PROTO_VERB_MULTICAST_GATHER_IDX_GATHER_LIMIT (ZT_PROTO_VERB_MULTICAST_GATHER_IDX_ADI + 4) #define ZT_PROTO_VERB_MULTICAST_GATHER_IDX_GATHER_LIMIT (ZT_PROTO_VERB_MULTICAST_GATHER_IDX_ADI + 4)
#define ZT_PROTO_VERB_MULTICAST_GATHER_IDX_COM (ZT_PROTO_VERB_MULTICAST_GATHER_IDX_GATHER_LIMIT + 4)
// Note: COM, GATHER_LIMIT, and SOURCE_MAC are optional, and so are specified without size // Note: COM, GATHER_LIMIT, and SOURCE_MAC are optional, and so are specified without size
#define ZT_PROTO_VERB_MULTICAST_FRAME_IDX_NETWORK_ID (ZT_PACKET_IDX_PAYLOAD) #define ZT_PROTO_VERB_MULTICAST_FRAME_IDX_NETWORK_ID (ZT_PACKET_IDX_PAYLOAD)
@ -538,7 +539,7 @@ public:
* <[8] timestamp (ms since epoch)> * <[8] timestamp (ms since epoch)>
* <[...] binary serialized identity (see Identity)> * <[...] binary serialized identity (see Identity)>
* <[1] destination address type> * <[1] destination address type>
* [<[...] destination address>] * [<[...] destination address to which packet was sent>]
* <[8] 64-bit world ID of current world> * <[8] 64-bit world ID of current world>
* <[8] 64-bit timestamp of current world> * <[8] 64-bit timestamp of current world>
* *
@ -592,20 +593,24 @@ public:
/** /**
* Query an identity by address: * Query an identity by address:
* <[5] address to look up> * <[5] address to look up>
* [<[...] additional addresses to look up>
* *
* OK response payload: * OK response payload:
* <[...] binary serialized identity> * <[...] binary serialized identity>
* [<[...] additional binary serialized identities>]
* *
* If querying a cluster, duplicate OK responses may occasionally occur. * If querying a cluster, duplicate OK responses may occasionally occur.
* These should be discarded. * These must be tolerated, which is easy since they'll have info you
* already have.
* *
* If the address is not found, no response is generated. WHOIS requests * If the address is not found, no response is generated. The semantics
* will time out much like ARP requests and similar do in L2. * of WHOIS is similar to ARP and NDP in that persistent retrying can
* be performed.
*/ */
VERB_WHOIS = 0x04, VERB_WHOIS = 0x04,
/** /**
* Meet another node at a given protocol address: * Relay-mediated NAT traversal or firewall punching initiation:
* <[1] flags (unused, currently 0)> * <[1] flags (unused, currently 0)>
* <[5] ZeroTier address of peer that might be found at this address> * <[5] ZeroTier address of peer that might be found at this address>
* <[2] 16-bit protocol address port> * <[2] 16-bit protocol address port>
@ -619,15 +624,6 @@ public:
* *
* Upon receipt a peer sends HELLO to establish a direct link. * Upon receipt a peer sends HELLO to establish a direct link.
* *
* Nodes should implement rate control, limiting the rate at which they
* respond to these packets to prevent their use in DDOS attacks. Nodes
* may also ignore these messages if a peer is not known or is not being
* actively communicated with.
*
* Unfortunately the physical address format in this message pre-dates
* InetAddress's serialization format. :( ZeroTier is four years old and
* yes we've accumulated a tiny bit of cruft here and there.
*
* No OK or ERROR is generated. * No OK or ERROR is generated.
*/ */
VERB_RENDEZVOUS = 0x05, VERB_RENDEZVOUS = 0x05,
@ -652,7 +648,6 @@ public:
* Full Ethernet frame with MAC addressing and optional fields: * Full Ethernet frame with MAC addressing and optional fields:
* <[8] 64-bit network ID> * <[8] 64-bit network ID>
* <[1] flags> * <[1] flags>
* [<[...] certificate of network membership (DEPRECATED)>]
* <[6] destination MAC or all zero for destination node> * <[6] destination MAC or all zero for destination node>
* <[6] source MAC or all zero for node of origin> * <[6] source MAC or all zero for node of origin>
* <[2] 16-bit ethertype> * <[2] 16-bit ethertype>
@ -715,6 +710,9 @@ public:
* This is sent in response to ERROR_NEED_MEMBERSHIP_CERTIFICATE and may * This is sent in response to ERROR_NEED_MEMBERSHIP_CERTIFICATE and may
* be pushed at any other time to keep exchanged certificates up to date. * be pushed at any other time to keep exchanged certificates up to date.
* *
* COMs and other credentials need not be for the same network, since each
* includes its own network ID and signature.
*
* OK/ERROR are not generated. * OK/ERROR are not generated.
*/ */
VERB_NETWORK_CREDENTIALS = 0x0a, VERB_NETWORK_CREDENTIALS = 0x0a,
@ -762,10 +760,10 @@ public:
* <[6] MAC address of multicast group being queried> * <[6] MAC address of multicast group being queried>
* <[4] 32-bit ADI for multicast group being queried> * <[4] 32-bit ADI for multicast group being queried>
* <[4] 32-bit requested max number of multicast peers> * <[4] 32-bit requested max number of multicast peers>
* [<[...] network certificate of membership (DEPRECATED)>] * [<[...] network certificate of membership>]
* *
* Flags: * Flags:
* 0x01 - COM is attached (DEPRECATED) * 0x01 - COM is attached
* *
* This message asks a peer for additional known endpoints that have * This message asks a peer for additional known endpoints that have
* LIKEd a given multicast group. It's sent when the sender wishes * LIKEd a given multicast group. It's sent when the sender wishes
@ -775,8 +773,8 @@ public:
* More than one OK response can occur if the response is broken up across * More than one OK response can occur if the response is broken up across
* multiple packets or if querying a clustered node. * multiple packets or if querying a clustered node.
* *
* Send VERB_NETWORK_CREDENTIALS prior to GATHERing if doing so from * The COM should be included so that upstream nodes that are not
* upstream nodes like root servers that are not involved in our network. * members of our network can validate our request.
* *
* OK response payload: * OK response payload:
* <[8] 64-bit network ID> * <[8] 64-bit network ID>
@ -795,7 +793,6 @@ public:
* Multicast frame: * Multicast frame:
* <[8] 64-bit network ID> * <[8] 64-bit network ID>
* <[1] flags> * <[1] flags>
* [<[...] network certificate of membership (DEPRECATED)>]
* [<[4] 32-bit implicit gather limit>] * [<[4] 32-bit implicit gather limit>]
* [<[6] source MAC>] * [<[6] source MAC>]
* <[6] destination MAC (multicast address)> * <[6] destination MAC (multicast address)>
@ -890,7 +887,7 @@ public:
* <[...] next hop(s) in path> * <[...] next hop(s) in path>
* *
* Flags: * Flags:
* 0x01 - Report back to originator at middle hops * 0x01 - Report back to originator at all hops
* 0x02 - Report back to originator at last hop * 0x02 - Report back to originator at last hop
* *
* Originator credential types: * Originator credential types:
@ -948,21 +945,21 @@ public:
/** /**
* Circuit test hop report: * Circuit test hop report:
* <[8] 64-bit timestamp (from original test)> * <[8] 64-bit timestamp (echoed from original test)>
* <[8] 64-bit test ID (from original test)> * <[8] 64-bit test ID (echoed from original test)>
* <[8] 64-bit reserved field (set to 0, currently unused)> * <[8] 64-bit reserved field (set to 0, currently unused)>
* <[1] 8-bit vendor ID (set to 0, currently unused)> * <[1] 8-bit vendor ID (set to 0, currently unused)>
* <[1] 8-bit reporter protocol version> * <[1] 8-bit reporter protocol version>
* <[1] 8-bit reporter major version> * <[1] 8-bit reporter software major version>
* <[1] 8-bit reporter minor version> * <[1] 8-bit reporter software minor version>
* <[2] 16-bit reporter revision> * <[2] 16-bit reporter software revision>
* <[2] 16-bit reporter OS/platform> * <[2] 16-bit reporter OS/platform or 0 if not specified>
* <[2] 16-bit reporter architecture> * <[2] 16-bit reporter architecture or 0 if not specified>
* <[2] 16-bit error code (set to 0, currently unused)> * <[2] 16-bit error code (set to 0, currently unused)>
* <[8] 64-bit report flags (set to 0, currently unused)> * <[8] 64-bit report flags (set to 0, currently unused)>
* <[8] 64-bit source packet ID> * <[8] 64-bit packet ID of received CIRCUIT_TEST packet>
* <[5] upstream ZeroTier address from which test was received> * <[5] upstream ZeroTier address from which CIRCUIT_TEST was received>
* <[1] 8-bit source packet hop count (ZeroTier hop count)> * <[1] 8-bit packet hop count of received CIRCUIT_TEST>
* <[...] local wire address on which packet was received> * <[...] local wire address on which packet was received>
* <[...] remote wire address from which packet was received> * <[...] remote wire address from which packet was received>
* <[2] 16-bit length of additional fields> * <[2] 16-bit length of additional fields>