Change (discovery) multicast to IPv6

We use ff02::1 as discovery multicast address.

This "all nodes" multicast address is good enough for discovery in the
local network as packets there are likely broadcasted over ethernet
anyways.

src/network/C4NetIO.cpp

@@ -356,6 +356,17 @@ void C4NetIO::HostAddress::SetHost(uint32_t v4addr)
 		memset(&v4.sin_zero, 0, sizeof(v4.sin_zero));
 }
 
+void C4NetIO::HostAddress::SetHost(const StdStrBuf &addr)
+{
+	addrinfo hints = addrinfo();
+	addrinfo *addresses = nullptr;
+	if (getaddrinfo(addr.getData(), nullptr, &hints, &addresses) != 0)
+		// GAI failed
+		return;
+	SetHost(addresses->ai_addr);
+	freeaddrinfo(addresses);
+}
+
 void C4NetIO::EndpointAddress::SetAddress(const StdStrBuf &addr)
 {
 	Clear();
@@ -1767,7 +1778,7 @@ bool C4NetIOSimpleUDP::InitBroadcast(addr_t *pBroadcastAddr)
 	if (fMultiCast) CloseBroadcast();
 
 	// broadcast addr valid?
-	if (pBroadcastAddr->IsMulticast())
+	if (!pBroadcastAddr->IsMulticast())
 	{
 		SetError("invalid broadcast address");
 		return false;
@@ -1779,8 +1790,8 @@ bool C4NetIOSimpleUDP::InitBroadcast(addr_t *pBroadcastAddr)
 	}
 
 	// set mc ttl to somewhat about "same net"
-	int iTTL = 16;
-	if (setsockopt(sock, IPPROTO_IP, IP_MULTICAST_TTL, reinterpret_cast<char*>(&iTTL), sizeof(iTTL)) == SOCKET_ERROR)
+	int TTL = 16;
+	if (setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, reinterpret_cast<char*>(&TTL), sizeof(TTL)) == SOCKET_ERROR)
 	{
 		SetError("could not set mc ttl", true);
 		return false;
@@ -1788,11 +1799,12 @@ bool C4NetIOSimpleUDP::InitBroadcast(addr_t *pBroadcastAddr)
 
 	// set up multicast group information
 	this->MCAddr = *pBroadcastAddr;
-	MCGrpInfo.imr_multiaddr = static_cast<sockaddr_in*>(&MCAddr)->sin_addr;
-	MCGrpInfo.imr_interface.s_addr = INADDR_ANY;
+	MCGrpInfo.ipv6mr_multiaddr = static_cast<sockaddr_in6>(MCAddr).sin6_addr;
+	// TODO: do multicast on all interfaces?
+	MCGrpInfo.ipv6mr_interface = 0; // default interface
 
 	// join multicast group
-	if (setsockopt(sock, IPPROTO_IP, IP_ADD_MEMBERSHIP,
+	if (setsockopt(sock, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP,
 	               reinterpret_cast<const char *>(&MCGrpInfo), sizeof(MCGrpInfo)) == SOCKET_ERROR)
 	{
 		SetError("could not join multicast group"); // to do: more error information
@@ -1854,10 +1866,10 @@ bool C4NetIOSimpleUDP::CloseBroadcast()
 	if (!fMultiCast) return true;
 
 	// leave multicast group
-	if (setsockopt(sock, IPPROTO_IP, IP_DROP_MEMBERSHIP,
+	if (setsockopt(sock, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP,
 	               reinterpret_cast<const char *>(&MCGrpInfo), sizeof(MCGrpInfo)) == SOCKET_ERROR)
 	{
-		SetError("could not join multicast group"); // to do: more error information
+		SetError("could not leave multicast group"); // to do: more error information
 		return false;
 	}
 
@@ -2059,10 +2071,10 @@ enum C4NetIOSimpleUDP::WaitResult C4NetIOSimpleUDP::WaitForSocket(int iTimeout)
 bool C4NetIOSimpleUDP::SetMCLoopback(int fLoopback)
 {
 	// enable/disable MC loopback
-	setsockopt(sock, IPPROTO_IP, IP_MULTICAST_LOOP, reinterpret_cast<char *>(&fLoopback), sizeof fLoopback);
+	setsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, reinterpret_cast<char *>(&fLoopback), sizeof fLoopback);
 	// read result
 	socklen_t iSize = sizeof(fLoopback);
-	if (getsockopt(sock, IPPROTO_IP, IP_MULTICAST_LOOP, reinterpret_cast<char *>(&fLoopback), &iSize) == SOCKET_ERROR)
+	if (getsockopt(sock, IPPROTO_IPV6, IPV6_MULTICAST_LOOP, reinterpret_cast<char *>(&fLoopback), &iSize) == SOCKET_ERROR)
 		return false;
 	fMCLoopback = !! fLoopback;
 	return true;

src/network/C4NetIO.h

@@ -193,8 +193,8 @@ public:
 
 		// conversions
 		operator sockaddr() const { return gen; }
-/*		operator sockaddr_in() const { assert(gen.sa_family == AF_INET); return v4; }
-		operator sockaddr_in6() const { assert(gen.sa_family == AF_INET6); return v6; }*/
+		operator sockaddr_in() const { assert(gen.sa_family == AF_INET); return v4; }
+		operator sockaddr_in6() const { assert(gen.sa_family == AF_INET6); return v6; }
 
 		// StdCompiler
 		void CompileFunc(StdCompiler *comp);
@@ -533,7 +533,7 @@ private:
 #endif
 
 	// multicast
-	addr_t MCAddr; ip_mreq MCGrpInfo;
+	addr_t MCAddr; ipv6_mreq MCGrpInfo;
 	bool fMCLoopback;
 
 	// multibind

src/network/C4Network2Discover.cpp

@@ -17,6 +17,17 @@
 #include "network/C4Network2Discover.h"
 
 // *** C4Network2IODiscover
+//
+// Quick multicast discovery guide by Luchs:
+//
+// All engines in network mode join a multicast group (defined by C4NetDiscoveryAddress).
+//
+// Engines searching for a game ("client") send a single byte c = 3 to that multicast group. This
+// happens while on the network list on each refresh.
+//
+// Engines hosting a game (when going into the lobby) send a byte c = 4 plus their reference server
+// port to the multicast group. Additionally, they listen for the c = 3 bytes and will reply with
+// another multicast answer.
 
 struct C4Network2IODiscoverReply
 {

src/network/C4Network2Discover.h

@@ -20,7 +20,7 @@
 
 const int C4NetMaxDiscover = 64;
 
-const C4NetIO::HostAddress C4NetDiscoveryAddress = C4NetIO::HostAddress(0xef000000); // 239.0.0.0
+const C4NetIO::HostAddress C4NetDiscoveryAddress = C4NetIO::HostAddress(StdStrBuf("ff02::1"));
 
 class C4Network2IODiscover : public C4NetIOSimpleUDP, private C4NetIO::CBClass
 {