First pass of configurable MTU and max MTU increase.

5 files changed, 21 insertions, 8 deletions

diff --git a/node/Constants.hpp b/node/Constants.hpp
index d3c87491..8aeaef02 100644
--- a/node/Constants.hpp
+++ b/node/Constants.hpp
@@ -159,15 +159,12 @@
 /**
  * Default MTU used for Ethernet tap device
  */
-#define ZT_IF_MTU ZT_MAX_MTU
+#define ZT_DEFAULT_MTU 2800
 
 /**
- * Maximum number of packet fragments we'll support
- *
- * The actual spec allows 16, but this is the most we'll support right
- * now. Packets with more than this many fragments are dropped.
+ * Maximum number of packet fragments we'll support (protocol max: 16)
  */
-#define ZT_MAX_PACKET_FRAGMENTS 4
+#define ZT_MAX_PACKET_FRAGMENTS 7
 
 /**
  * Size of RX queue
diff --git a/node/IncomingPacket.cpp b/node/IncomingPacket.cpp
index 126da53c..7ef2054b 100644
--- a/node/IncomingPacket.cpp
+++ b/node/IncomingPacket.cpp
@@ -1125,7 +1125,7 @@ bool IncomingPacket::_doMULTICAST_FRAME(const RuntimeEnvironment *RR,void *tPtr,
 
 			//TRACE("<<MC FRAME %.16llx/%s from %s@%s flags %.2x length %u",nwid,to.toString().c_str(),from.toString().c_str(),peer->address().toString().c_str(),flags,frameLen);
 
-			if ((frameLen > 0)&&(frameLen <= ZT_IF_MTU)) {
+			if ((frameLen > 0)&&(frameLen <= ZT_MAX_MTU)) {
 				if (!to.mac().isMulticast()) {
 					TRACE("dropped MULTICAST_FRAME from %s@%s(%s) to %s: destination is unicast, must use FRAME or EXT_FRAME",from.toString().c_str(),peer->address().toString().c_str(),_path->address().toString().c_str(),to.toString().c_str());
 					peer->received(tPtr,_path,hops(),packetId(),Packet::VERB_MULTICAST_FRAME,0,Packet::VERB_NOP,true); // trustEstablished because COM is okay
diff --git a/node/Network.cpp b/node/Network.cpp
index ee0f8611..de2ea7d7 100644
--- a/node/Network.cpp
+++ b/node/Network.cpp
@@ -1225,6 +1225,8 @@ void Network::requestConfiguration(void *tPtr)
 			nconf->revision = 1;
 			nconf->issuedTo = RR->identity.address();
 			nconf->flags = ZT_NETWORKCONFIG_FLAG_ENABLE_IPV6_NDP_EMULATION;
+			nconf->mtu = ZT_DEFAULT_MTU;
+			nconf->multicastLimit = 0;
 			nconf->staticIpCount = 1;
 			nconf->ruleCount = 14;
 			nconf->staticIps[0] = InetAddress::makeIpv66plane(_id,RR->identity.address().toInt());
@@ -1495,7 +1497,7 @@ void Network::_externalConfig(ZT_VirtualNetworkConfig *ec) const
 	else ec->name[0] = (char)0;
 	ec->status = _status();
 	ec->type = (_config) ? (_config.isPrivate() ? ZT_NETWORK_TYPE_PRIVATE : ZT_NETWORK_TYPE_PUBLIC) : ZT_NETWORK_TYPE_PRIVATE;
-	ec->mtu = ZT_IF_MTU;
+	ec->mtu = (_config) ? _config.mtu : ZT_DEFAULT_MTU;
 	ec->physicalMtu = ZT_UDP_DEFAULT_PAYLOAD_MTU - (ZT_PACKET_IDX_PAYLOAD + 16);
 	ec->dhcp = 0;
 	std::vector<Address> ab(_config.activeBridges());
diff --git a/node/NetworkConfig.cpp b/node/NetworkConfig.cpp
index 9effe529..c39f6cab 100644
--- a/node/NetworkConfig.cpp
+++ b/node/NetworkConfig.cpp
@@ -51,6 +51,7 @@ bool NetworkConfig::toDictionary(Dictionary<ZT_NETWORKCONFIG_DICT_CAPACITY> &d,b
 		if (!d.add(ZT_NETWORKCONFIG_DICT_KEY_MULTICAST_LIMIT,(uint64_t)this->multicastLimit)) return false;
 		if (!d.add(ZT_NETWORKCONFIG_DICT_KEY_TYPE,(uint64_t)this->type)) return false;
 		if (!d.add(ZT_NETWORKCONFIG_DICT_KEY_NAME,this->name)) return false;
+		if (!d.add(ZT_NETWORKCONFIG_DICT_KEY_MTU,(uint64_t)this->mtu)) return false;
 
 #ifdef ZT_SUPPORT_OLD_STYLE_NETCONF
 		if (includeLegacy) {
@@ -217,6 +218,12 @@ bool NetworkConfig::fromDictionary(const Dictionary<ZT_NETWORKCONFIG_DICT_CAPACI
 		this->multicastLimit = (unsigned int)d.getUI(ZT_NETWORKCONFIG_DICT_KEY_MULTICAST_LIMIT,0);
 		d.get(ZT_NETWORKCONFIG_DICT_KEY_NAME,this->name,sizeof(this->name));
 
+		this->mtu = (unsigned int)d.getUI(ZT_NETWORKCONFIG_DICT_KEY_MTU,ZT_DEFAULT_MTU);
+		if (this->mtu < 1280)
+			this->mtu = 1280; // minimum MTU allowed by IPv6 standard and others
+		else if (this->mtu > ZT_MAX_MTU)
+			this->mtu = ZT_MAX_MTU;
+
 		if (d.getUI(ZT_NETWORKCONFIG_DICT_KEY_VERSION,0) < 6) {
 	#ifdef ZT_SUPPORT_OLD_STYLE_NETCONF
 			char tmp2[1024];
diff --git a/node/NetworkConfig.hpp b/node/NetworkConfig.hpp
index 7bae6a91..fdd078d5 100644
--- a/node/NetworkConfig.hpp
+++ b/node/NetworkConfig.hpp
@@ -167,6 +167,8 @@ namespace ZeroTier {
 #define ZT_NETWORKCONFIG_DICT_KEY_TYPE "t"
 // text
 #define ZT_NETWORKCONFIG_DICT_KEY_NAME "n"
+// network MTU
+#define ZT_NETWORKCONFIG_DICT_KEY_MTU "mtu"
 // credential time max delta in ms
 #define ZT_NETWORKCONFIG_DICT_KEY_CREDENTIAL_TIME_MAX_DELTA "ctmd"
 // binary serialized certificate of membership
@@ -466,6 +468,11 @@ public:
 	uint64_t flags;
 
 	/**
+	 * Network MTU
+	 */
+	unsigned int mtu;
+
+	/**
 	 * Maximum number of recipients per multicast (not including active bridges)
 	 */
 	unsigned int multicastLimit;