Add bind to network interface option

Config.cpp

@@ -27,6 +27,10 @@ namespace config {
   variables_map       m_Options;
 
   void Init() {
+    bool nat = true;
+#ifdef MESHNET
+    nat = false;
+#endif
     options_description general("General options");
     general.add_options()
       ("help",     "Show this message")
@@ -39,6 +43,8 @@ namespace config {
 	  ("family",    value<std::string>()->default_value(""),     "Specify a family, router belongs to")
 	  ("datadir",   value<std::string>()->default_value(""),     "Path to storage of i2pd data (RI, keys, peer profiles, ...)")
       ("host",      value<std::string>()->default_value("0.0.0.0"),     "External IP")
+      ("ifname",    value<std::string>()->default_value(""), "network interface to bind to")
+      ("nat",       value<bool>()->zero_tokens()->default_value(nat), "should we assume we are behind NAT?")
       ("port",      value<uint16_t>()->default_value(0),                "Port to listen for incoming connections (default: auto)")
       ("ipv4",      value<bool>()->zero_tokens()->default_value(true),  "Enable communication through ipv4")
       ("ipv6",      value<bool>()->zero_tokens()->default_value(false), "Enable communication through ipv6")

Daemon.cpp

@@ -22,6 +22,7 @@
 #include "I2PControl.h"
 #include "ClientContext.h"
 #include "Crypto.h"
+#include "util.h"
 
 #ifdef USE_UPNP
 #include "UPnP.h"
@@ -114,7 +115,7 @@ namespace i2p
 			}
 			i2p::log::Logger().Ready();
 
-			LogPrint(eLogInfo,  "i2pd v", VERSION, " starting");
+			LogPrint(eLogInfo,	"i2pd v", VERSION, " starting");
 			LogPrint(eLogDebug, "FS: main config file: ", config);
 			LogPrint(eLogDebug, "FS: data directory: ", datadir);
 
@@ -122,6 +123,14 @@ namespace i2p
 			i2p::crypto::InitCrypto (precomputation);
 			i2p::context.Init ();
 
+			bool ipv6;		i2p::config::GetOption("ipv6", ipv6);
+			bool ipv4;		i2p::config::GetOption("ipv4", ipv4);
+#ifdef MESHNET
+			// manual override for meshnet
+			ipv4 = false;
+			ipv6 = true;
+#endif
+			
 			uint16_t port; i2p::config::GetOption("port", port);
 			if (!i2p::config::IsDefault("port"))
 			{	
@@ -129,20 +138,31 @@ namespace i2p
 				i2p::context.UpdatePort (port);
 			}	
 
-			std::string host; i2p::config::GetOption("host", host);
-			if (!i2p::config::IsDefault("host"))
+			bool nat; i2p::config::GetOption("nat", nat);
+			if (nat)
 			{
-				LogPrint(eLogInfo, "Daemon: setting address for incoming connections to ", host);
-				i2p::context.UpdateAddress (boost::asio::ip::address::from_string (host));	
+				LogPrint(eLogInfo, "Daemon: assuming be are behind NAT");
+				// we are behind nat, try setting via host 
+				std::string host; i2p::config::GetOption("host", host);
+				if (!i2p::config::IsDefault("host"))
+					{
+						LogPrint(eLogInfo, "Daemon: setting address for incoming connections to ", host);
+						i2p::context.UpdateAddress (boost::asio::ip::address::from_string (host));	
+					}
+			}
+			else
+			{
+				// we are not behind nat
+				std::string ifname; i2p::config::GetOption("ifname", ifname);
+				if (ifname.size())
+				{
+					// bind to interface, we have no NAT so set external address too
+					auto addr = i2p::util::net::GetInterfaceAddress(ifname, ipv6);
+					LogPrint(eLogInfo, "Daemon: bind to network interface ", ifname, " with public address ", addr);
+					i2p::context.UpdateAddress(addr);
+				}
 			}
 
-			bool ipv6;		i2p::config::GetOption("ipv6", ipv6);
-			bool ipv4;		i2p::config::GetOption("ipv4", ipv4);
-#ifdef MESHNET
-      // manual override for meshnet
-      ipv4 = false;
-      ipv6 = true;
-#endif
 			bool transit; i2p::config::GetOption("notransit", transit);
 			i2p::context.SetSupportsV6		 (ipv6);
 			i2p::context.SetSupportsV4		 (ipv4);

util.cpp

@@ -413,7 +413,53 @@ namespace net
         return GetMTUUnix(localAddress, fallback);
 #endif
         return fallback;
-    }	
+    }
+  
+	const boost::asio::ip::address GetInterfaceAddress(const std::string & ifname, bool ipv6)
+	{
+#ifdef WIN32
+		LogPrint(eLogError, "NetIface: cannot get address by interface name, not implemented on WIN32");
+		return boost::asio::ip::from_string("127.0.0.1");
+#else
+		int af = (ipv6 ? AF_INET6 : AF_INET);
+		ifaddrs * addrs = nullptr;
+		if(getifaddrs(&addrs) == 0)
+		{
+			// got ifaddrs
+			ifaddrs * cur = addrs;
+			while(cur)
+			{
+				std::string cur_ifname(cur->ifa_name);
+				if (cur_ifname == ifname && cur->ifa_addr->sa_family == af)
+				{
+					// match
+					size_t sz = (ipv6 ? INET6_ADDRSTRLEN : INET_ADDRSTRLEN);
+					char * addr = new char[sz];
+					addr[sz-1] = 0;
+					socklen_t sl = (ipv6 ? sizeof(sockaddr_in6) : sizeof(sockaddr_in));
+					// this probably won't screw up (right?)
+					inet_ntop(af, cur->ifa_addr, addr, sl);
+					std::string cur_ifaddr(addr);
+					delete [] addr;
+					freeifaddrs(addrs);
+					return boost::asio::ip::address::from_string(cur_ifaddr);
+				}
+				cur = cur->ifa_next;
+			}
+		}
+		if(addrs) freeifaddrs(addrs);
+		std::string fallback;
+		if(ipv6) {
+			fallback = "::";
+			LogPrint(eLogWarning, "NetIface: cannot find ipv6 address for interface ", ifname);
+		} else {
+			fallback = "127.0.0.1";
+			LogPrint(eLogWarning, "NetIface: cannot find ipv4 address for interface ", ifname);
+		}
+		return boost::asio::ip::address::from_string(fallback);
+			
+#endif
+	}
 } 
 
 } // util

util.h

@@ -66,6 +66,7 @@ namespace util
 	namespace net
 	{
 		int GetMTU (const boost::asio::ip::address& localAddress);
+		const boost::asio::ip::address GetInterfaceAddress(const std::string & ifname, bool ipv6=false);
 	}
 }
 }