Release v0.1.0

vendor/github.com/miekg/dns/udp_linux.go

@@ -0,0 +1,220 @@
+// +build linux,!appengine
+
+package dns
+
+// See:
+// * http://stackoverflow.com/questions/3062205/setting-the-source-ip-for-a-udp-socket and
+// * http://blog.powerdns.com/2012/10/08/on-binding-datagram-udp-sockets-to-the-any-addresses/
+//
+// Why do we need this: When listening on 0.0.0.0 with UDP so kernel decides what is the outgoing
+// interface, this might not always be the correct one. This code will make sure the egress
+// packet's interface matched the ingress' one.
+
+import (
+	"net"
+	"syscall"
+	"unsafe"
+
+	"github.com/miekg/dns/internal/socket"
+)
+
+const (
+	sizeofInet6Pktinfo = 0x14
+	sizeofInetPktinfo  = 0xc
+	protocolIP         = 0
+	protocolIPv6       = 41
+)
+
+type inetPktinfo struct {
+	Ifindex  int32
+	Spec_dst [4]byte /* in_addr */
+	Addr     [4]byte /* in_addr */
+}
+
+type inet6Pktinfo struct {
+	Addr    [16]byte /* in6_addr */
+	Ifindex int32
+}
+
+type inetControlMessage struct {
+	Src net.IP // source address, specifying only
+	Dst net.IP // destination address, receiving only
+}
+
+// setUDPSocketOptions sets the UDP socket options.
+// This function is implemented on a per platform basis. See udp_*.go for more details
+func setUDPSocketOptions(conn *net.UDPConn) error {
+	sa, err := getUDPSocketName(conn)
+	if err != nil {
+		return err
+	}
+	switch sa.(type) {
+	case *syscall.SockaddrInet6:
+		v6only, err := getUDPSocketOptions6Only(conn)
+		if err != nil {
+			return err
+		}
+		setUDPSocketOptions6(conn)
+		if !v6only {
+			setUDPSocketOptions4(conn)
+		}
+	case *syscall.SockaddrInet4:
+		setUDPSocketOptions4(conn)
+	}
+	return nil
+}
+
+// setUDPSocketOptions4 prepares the v4 socket for sessions.
+func setUDPSocketOptions4(conn *net.UDPConn) error {
+	file, err := conn.File()
+	if err != nil {
+		return err
+	}
+	if err := syscall.SetsockoptInt(int(file.Fd()), syscall.IPPROTO_IP, syscall.IP_PKTINFO, 1); err != nil {
+		file.Close()
+		return err
+	}
+	// Calling File() above results in the connection becoming blocking, we must fix that.
+	// See https://github.com/miekg/dns/issues/279
+	err = syscall.SetNonblock(int(file.Fd()), true)
+	if err != nil {
+		file.Close()
+		return err
+	}
+	file.Close()
+	return nil
+}
+
+// setUDPSocketOptions6 prepares the v6 socket for sessions.
+func setUDPSocketOptions6(conn *net.UDPConn) error {
+	file, err := conn.File()
+	if err != nil {
+		return err
+	}
+	if err := syscall.SetsockoptInt(int(file.Fd()), syscall.IPPROTO_IPV6, syscall.IPV6_RECVPKTINFO, 1); err != nil {
+		file.Close()
+		return err
+	}
+	err = syscall.SetNonblock(int(file.Fd()), true)
+	if err != nil {
+		file.Close()
+		return err
+	}
+	file.Close()
+	return nil
+}
+
+// getUDPSocketOption6Only return true if the socket is v6 only and false when it is v4/v6 combined
+// (dualstack).
+func getUDPSocketOptions6Only(conn *net.UDPConn) (bool, error) {
+	file, err := conn.File()
+	if err != nil {
+		return false, err
+	}
+	// dual stack. See http://stackoverflow.com/questions/1618240/how-to-support-both-ipv4-and-ipv6-connections
+	v6only, err := syscall.GetsockoptInt(int(file.Fd()), syscall.IPPROTO_IPV6, syscall.IPV6_V6ONLY)
+	if err != nil {
+		file.Close()
+		return false, err
+	}
+	file.Close()
+	return v6only == 1, nil
+}
+
+func getUDPSocketName(conn *net.UDPConn) (syscall.Sockaddr, error) {
+	file, err := conn.File()
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+	return syscall.Getsockname(int(file.Fd()))
+}
+
+// marshalInetPacketInfo marshals a ipv4 control message, returning
+// the byte slice for the next marshal, if any
+func marshalInetPacketInfo(b []byte, cm *inetControlMessage) []byte {
+	m := socket.ControlMessage(b)
+	m.MarshalHeader(protocolIP, syscall.IP_PKTINFO, sizeofInetPktinfo)
+	if cm != nil {
+		pi := (*inetPktinfo)(unsafe.Pointer(&m.Data(sizeofInetPktinfo)[0]))
+		if ip := cm.Src.To4(); ip != nil {
+			copy(pi.Spec_dst[:], ip)
+		}
+	}
+	return m.Next(sizeofInetPktinfo)
+}
+
+// marshalInet6PacketInfo marshals a ipv6 control message, returning
+// the byte slice for the next marshal, if any
+func marshalInet6PacketInfo(b []byte, cm *inetControlMessage) []byte {
+	m := socket.ControlMessage(b)
+	m.MarshalHeader(protocolIPv6, syscall.IPV6_PKTINFO, sizeofInet6Pktinfo)
+	if cm != nil {
+		pi := (*inet6Pktinfo)(unsafe.Pointer(&m.Data(sizeofInet6Pktinfo)[0]))
+		if ip := cm.Src.To16(); ip != nil && ip.To4() == nil {
+			copy(pi.Addr[:], ip)
+		}
+	}
+	return m.Next(sizeofInet6Pktinfo)
+}
+
+func parseInetPacketInfo(cm *inetControlMessage, b []byte) {
+	pi := (*inetPktinfo)(unsafe.Pointer(&b[0]))
+	if len(cm.Dst) < net.IPv4len {
+		cm.Dst = make(net.IP, net.IPv4len)
+	}
+	copy(cm.Dst, pi.Addr[:])
+}
+
+func parseInet6PacketInfo(cm *inetControlMessage, b []byte) {
+	pi := (*inet6Pktinfo)(unsafe.Pointer(&b[0]))
+	if len(cm.Dst) < net.IPv6len {
+		cm.Dst = make(net.IP, net.IPv6len)
+	}
+	copy(cm.Dst, pi.Addr[:])
+}
+
+// parseUDPSocketDst takes out-of-band data from ReadMsgUDP and parses it for
+// the Dst address
+func parseUDPSocketDst(oob []byte) (net.IP, error) {
+	cm := new(inetControlMessage)
+	ms, err := socket.ControlMessage(oob).Parse()
+	if err != nil {
+		return nil, err
+	}
+	for _, m := range ms {
+		lvl, typ, l, err := m.ParseHeader()
+		if err != nil {
+			return nil, err
+		}
+		if lvl == protocolIPv6 { // IPv6
+			if typ == syscall.IPV6_PKTINFO && l >= sizeofInet6Pktinfo {
+				parseInet6PacketInfo(cm, m.Data(l))
+			}
+		} else if lvl == protocolIP { // IPv4
+			if typ == syscall.IP_PKTINFO && l >= sizeofInetPktinfo {
+				parseInetPacketInfo(cm, m.Data(l))
+			}
+		}
+	}
+	return cm.Dst, nil
+}
+
+// marshalUDPSocketSrc takes the given src address and returns out-of-band data
+// to give to WriteMsgUDP
+func marshalUDPSocketSrc(src net.IP) []byte {
+	var oob []byte
+	// If the dst is definitely an ipv6, then use ipv6 control to respond
+	// otherwise use ipv4 because the ipv6 marshal ignores ipv4 messages.
+	// See marshalInet6PacketInfo
+	cm := new(inetControlMessage)
+	cm.Src = src
+	if src.To4() == nil {
+		oob = make([]byte, socket.ControlMessageSpace(sizeofInet6Pktinfo))
+		marshalInet6PacketInfo(oob, cm)
+	} else {
+		oob = make([]byte, socket.ControlMessageSpace(sizeofInetPktinfo))
+		marshalInetPacketInfo(oob, cm)
+	}
+	return oob
+}