1 files changed, 48 insertions, 4 deletions

diff --git a/vendor/github.com/miekg/dns/udp.go b/vendor/github.com/miekg/dns/udp.go
index 12a209678..f3f31a7ac 100644
--- a/vendor/github.com/miekg/dns/udp.go
+++ b/vendor/github.com/miekg/dns/udp.go
@@ -4,6 +4,9 @@ package dns
 
 import (
 	"net"
+
+	"golang.org/x/net/ipv4"
+	"golang.org/x/net/ipv6"
 )
 
 // SessionUDP holds the remote address and the associated
@@ -34,12 +37,53 @@ func WriteToSessionUDP(conn *net.UDPConn, b []byte, session *SessionUDP) (int, e
 	return n, err
 }
 
+func setUDPSocketOptions(conn *net.UDPConn) error {
+	// Try setting the flags for both families and ignore the errors unless they
+	// both error.
+	err6 := ipv6.NewPacketConn(conn).SetControlMessage(ipv6.FlagDst|ipv6.FlagInterface, true)
+	err4 := ipv4.NewPacketConn(conn).SetControlMessage(ipv4.FlagDst|ipv4.FlagInterface, true)
+	if err6 != nil && err4 != nil {
+		return err4
+	}
+	return nil
+}
+
+// parseDstFromOOB takes oob data and returns the destination IP.
+func parseDstFromOOB(oob []byte) net.IP {
+	// Start with IPv6 and then fallback to IPv4
+	// TODO(fastest963): Figure out a way to prefer one or the other. Looking at
+	// the lvl of the header for a 0 or 41 isn't cross-platform.
+	var dst net.IP
+	cm6 := new(ipv6.ControlMessage)
+	if cm6.Parse(oob) == nil {
+		dst = cm6.Dst
+	}
+	if dst == nil {
+		cm4 := new(ipv4.ControlMessage)
+		if cm4.Parse(oob) == nil {
+			dst = cm4.Dst
+		}
+	}
+	return dst
+}
+
 // correctSource takes oob data and returns new oob data with the Src equal to the Dst
 func correctSource(oob []byte) []byte {
-	dst, err := parseUDPSocketDst(oob)
-	// If the destination could not be determined, ignore.
-	if err != nil || dst == nil {
+	dst := parseDstFromOOB(oob)
+	if dst == nil {
 		return nil
 	}
-	return marshalUDPSocketSrc(dst)
+	// If the dst is definitely an IPv6, then use ipv6's ControlMessage to
+	// respond otherwise use ipv4's because ipv6's marshal ignores ipv4
+	// addresses.
+	if dst.To4() == nil {
+		cm := new(ipv6.ControlMessage)
+		cm.Src = dst
+		oob = cm.Marshal()
+	} else {
+		cm := new(ipv4.ControlMessage)
+		cm.Src = dst
+		oob = cm.Marshal()
+	}
+	return oob
 }