Add IPv6 support

new cli options (RPC ones also apply to wallet):
  --p2p-bind-ipv6-address (default = "::")
  --p2p-bind-port-ipv6    (default same as ipv4 port for given nettype)
  --rpc-bind-ipv6-address (default = "::1")

  --p2p-use-ipv6          (default false)
  --rpc-use-ipv6          (default false)

  --p2p-require-ipv4      (default true, if ipv4 bind fails and this is
                           true, will not continue even if ipv6 bind
                           successful)
  --rpc-require-ipv4      (default true, description as above)

ipv6 addresses are to be specified as "[xx:xx:xx::xx:xx]:port" except
in the cases of the cli args for bind address.  For those the square
braces can be omitted.

1 files changed, 32 insertions, 3 deletions

diff --git a/contrib/epee/src/net_helper.cpp b/contrib/epee/src/net_helper.cpp
index 3543f5716..719f1c8e0 100644
--- a/contrib/epee/src/net_helper.cpp
+++ b/contrib/epee/src/net_helper.cpp
@@ -11,10 +11,39 @@ namespace net_utils
 		//////////////////////////////////////////////////////////////////////////
 		boost::asio::ip::tcp::resolver resolver(GET_IO_SERVICE(timeout));
 		boost::asio::ip::tcp::resolver::query query(boost::asio::ip::tcp::v4(), addr, port, boost::asio::ip::tcp::resolver::query::canonical_name);
-		boost::asio::ip::tcp::resolver::iterator iterator = resolver.resolve(query);
+
+		bool try_ipv6 = false;
+		boost::asio::ip::tcp::resolver::iterator iterator;
 		boost::asio::ip::tcp::resolver::iterator end;
-		if(iterator == end) // Documentation states that successful call is guaranteed to be non-empty
-			throw boost::system::system_error{boost::asio::error::fault, "Failed to resolve " + addr};
+		boost::system::error_code resolve_error;
+		try
+		{
+			iterator = resolver.resolve(query, resolve_error);
+			if(iterator == end) // Documentation states that successful call is guaranteed to be non-empty
+			{
+				// if IPv4 resolution fails, try IPv6.  Unintentional outgoing IPv6 connections should only
+				// be possible if for some reason a hostname was given and that hostname fails IPv4 resolution,
+				// so at least for now there should not be a need for a flag "using ipv6 is ok"
+				try_ipv6 = true;
+			}
+
+		}
+		catch (const boost::system::system_error& e)
+		{
+			if (resolve_error != boost::asio::error::host_not_found &&
+					resolve_error != boost::asio::error::host_not_found_try_again)
+			{
+				throw;
+			}
+			try_ipv6 = true;
+		}
+		if (try_ipv6)
+		{
+			boost::asio::ip::tcp::resolver::query query6(boost::asio::ip::tcp::v6(), addr, port, boost::asio::ip::tcp::resolver::query::canonical_name);
+			iterator = resolver.resolve(query6);
+			if (iterator == end)
+				throw boost::system::system_error{boost::asio::error::fault, "Failed to resolve " + addr};
+		}
 
 		//////////////////////////////////////////////////////////////////////////