Pull request: UDP OOB darwin

Merge in DNS/dnsproxy from 2807-bind-addr to master

Updates AdguardTeam/AdGuardHome#2807.

Squashed commit of the following:

commit 3cfff15
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Tue Aug 3 17:47:48 2021 +0300

    proxyutil: imp docs

commit 54fbad0
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Tue Aug 3 16:59:31 2021 +0300

    proxyutil: fix comments

commit 722a382
Author: Eugene Burkov <e.burkov@adguard.com>
Date:   Tue Aug 3 16:41:05 2021 +0300

    proxyutil: rm oob writing on darwin

proxyutil/oob_darwin.go

@@ -0,0 +1,28 @@
+//go:build darwin
+// +build darwin
+
+package proxyutil
+
+import (
+	"net"
+
+	"golang.org/x/net/ipv6"
+)
+
+// udpMakeOOBWithSrc makes the OOB data with a specified source IP.
+func udpMakeOOBWithSrc(ip net.IP) []byte {
+	if ip4 := ip.To4(); ip4 != nil {
+		// Do not set the IPv4 source address via OOB, because it can
+		// cause the address to become unspecified on darwin.
+		//
+		// See https://github.com/AdguardTeam/AdGuardHome/issues/2807.
+		//
+		// TODO(e.burkov): Develop a workaround to make it write OOB
+		// only when listening on an unspecified address.
+		return []byte{}
+	}
+
+	return (&ipv6.ControlMessage{
+		Src: ip,
+	}).Marshal()
+}

proxyutil/oob_others.go

@@ -0,0 +1,24 @@
+//go:build aix || dragonfly || linux || netbsd || openbsd || freebsd || solaris
+// +build aix dragonfly linux netbsd openbsd freebsd solaris
+
+package proxyutil
+
+import (
+	"net"
+
+	"golang.org/x/net/ipv4"
+	"golang.org/x/net/ipv6"
+)
+
+// udpMakeOOBWithSrc makes the OOB data with a specified source IP.
+func udpMakeOOBWithSrc(ip net.IP) []byte {
+	if ip4 := ip.To4(); ip4 != nil {
+		return (&ipv4.ControlMessage{
+			Src: ip,
+		}).Marshal()
+	}
+
+	return (&ipv6.ControlMessage{
+		Src: ip,
+	}).Marshal()
+}

proxyutil/udp.go

@@ -0,0 +1,36 @@
+package proxyutil
+
+import "net"
+
+// UDPGetOOBSize returns maximum size of the received OOB data.
+func UDPGetOOBSize() (oobSize int) {
+	return udpGetOOBSize()
+}
+
+// UDPSetOptions sets flag options on a UDP socket to be able to receive the
+// necessary OOB data.
+func UDPSetOptions(c *net.UDPConn) (err error) {
+	return udpSetOptions(c)
+}
+
+// UDPRead udpRead reads the message from c using buf receives payload of size
+// udpOOBSize from the UDP socket.  It returns the number of bytes copied into
+// buf, the number of bytes copied with OOB and the source address of the
+// message.
+func UDPRead(
+	c *net.UDPConn,
+	buf []byte,
+	udpOOBSize int,
+) (n int, localIP net.IP, remoteAddr *net.UDPAddr, err error) {
+	return udpRead(c, buf, udpOOBSize)
+}
+
+// UDPWrite writes the data to the remoteAddr using conn.
+func UDPWrite(
+	data []byte,
+	conn *net.UDPConn,
+	remoteAddr *net.UDPAddr,
+	localIP net.IP,
+) (n int, err error) {
+	return udpWrite(data, conn, remoteAddr, localIP)
+}

proxyutil/udp_unix.go

@@ -1,4 +1,5 @@
-// +build aix darwin dragonfly linux netbsd openbsd solaris freebsd
+//go:build aix || dragonfly || linux || netbsd || openbsd || freebsd || solaris || darwin
+// +build aix dragonfly linux netbsd openbsd freebsd solaris darwin
 
 package proxyutil
 
@@ -10,52 +11,42 @@ import (
 	"golang.org/x/net/ipv6"
 )
 
-// UDPGetOOBSize - get max. size of received OOB data
-// It will then be used in the ReadMsgUDP function
-func UDPGetOOBSize() int {
-	oob4 := ipv4.NewControlMessage(ipv4.FlagDst | ipv4.FlagInterface)
-	oob6 := ipv6.NewControlMessage(ipv6.FlagDst | ipv6.FlagInterface)
+// ipv*Flags is the set of socket option flags for configuring IPv* UDP
+// connection to receive an appropriate OOB data.  For both versions the flags
+// are:
+//
+//   FlagDst
+//   FlagInterface
+//
+const (
+	ipv4Flags ipv4.ControlFlags = ipv4.FlagDst | ipv4.FlagInterface
+	ipv6Flags ipv6.ControlFlags = ipv6.FlagDst | ipv6.FlagInterface
+)
 
-	if len(oob4) > len(oob6) {
-		return len(oob4)
-	}
-	return len(oob6)
-}
+// udpGetOOBSize obtains the destination IP from OOB data.
+func udpGetOOBSize() (oobSize int) {
+	l4, l6 :=
+		len(ipv4.NewControlMessage(ipv4Flags)),
+		len(ipv6.NewControlMessage(ipv6Flags))
 
-// UDPSetOptions - set options on a UDP socket to be able to receive the necessary OOB data
-func UDPSetOptions(c *net.UDPConn) error {
-	err6 := ipv6.NewPacketConn(c).SetControlMessage(ipv6.FlagDst|ipv6.FlagInterface, true)
-	err4 := ipv4.NewPacketConn(c).SetControlMessage(ipv4.FlagDst|ipv4.FlagInterface, true)
-	if err6 != nil && err4 != nil {
-		return fmt.Errorf("failed to call SetControlMessage: ipv4: %v ipv6: %v", err4, err6)
+	if l4 >= l6 {
+		return l4
 	}
-	return nil
+
+	return l6
 }
 
-// UDPRead - receive payload and OOB data from the UDP socket
-func UDPRead(c *net.UDPConn, buf []byte, udpOOBSize int) (int, net.IP, *net.UDPAddr, error) {
-	var oobn int
-	oob := make([]byte, udpOOBSize)
-	var err error
-	var n int
-	var remoteAddr *net.UDPAddr
-	n, oobn, _, remoteAddr, err = c.ReadMsgUDP(buf, oob)
-	if err != nil {
-		return -1, nil, nil, err
+func udpSetOptions(c *net.UDPConn) (err error) {
+	err6 := ipv6.NewPacketConn(c).SetControlMessage(ipv6Flags, true)
+	err4 := ipv4.NewPacketConn(c).SetControlMessage(ipv4Flags, true)
+	if err6 != nil && err4 != nil {
+		return fmt.Errorf("failed to call SetControlMessage: ipv4: %v; ipv6: %v", err4, err6)
 	}
 
-	localIP := udpGetDstFromOOB(oob[:oobn])
-	return n, localIP, remoteAddr, nil
-}
-
-// UDPWrite - writes to the UDP socket and sets local IP to OOB data
-func UDPWrite(bytes []byte, conn *net.UDPConn, remoteAddr *net.UDPAddr, localIP net.IP) (int, error) {
-	n, _, err := conn.WriteMsgUDP(bytes, udpMakeOOBWithSrc(localIP), remoteAddr)
-	return n, err
+	return nil
 }
 
-// udpGetDstFromOOB - get destination IP from OOB data
-func udpGetDstFromOOB(oob []byte) net.IP {
+func udpGetDstFromOOB(oob []byte) (dst net.IP) {
 	cm6 := &ipv6.ControlMessage{}
 	if cm6.Parse(oob) == nil && cm6.Dst != nil {
 		return cm6.Dst
@@ -69,15 +60,30 @@ func udpGetDstFromOOB(oob []byte) net.IP {
 	return nil
 }
 
-// udpMakeOOBWithSrc - make OOB data with a specified source IP
-func udpMakeOOBWithSrc(ip net.IP) []byte {
-	if ip.To4() == nil {
-		cm := &ipv6.ControlMessage{}
-		cm.Src = ip
-		return cm.Marshal()
+func udpRead(
+	c *net.UDPConn,
+	buf []byte,
+	udpOOBSize int,
+) (n int, localIP net.IP, remoteAddr *net.UDPAddr, err error) {
+	var oobn int
+	oob := make([]byte, udpOOBSize)
+	n, oobn, _, remoteAddr, err = c.ReadMsgUDP(buf, oob)
+	if err != nil {
+		return -1, nil, nil, err
 	}
 
-	cm := &ipv4.ControlMessage{}
-	cm.Src = ip
-	return cm.Marshal()
+	localIP = udpGetDstFromOOB(oob[:oobn])
+
+	return n, localIP, remoteAddr, nil
+}
+
+func udpWrite(
+	data []byte,
+	conn *net.UDPConn,
+	remoteAddr *net.UDPAddr,
+	localIP net.IP,
+) (n int, err error) {
+	n, _, err = conn.WriteMsgUDP(data, udpMakeOOBWithSrc(localIP), remoteAddr)
+
+	return n, err
 }

proxyutil/udp_windows.go

@@ -1,30 +1,28 @@
+//go:build windows
+// +build windows
+
 package proxyutil
 
 import "net"
 
-// UDPGetOOBSize - get max. size of received OOB data
-// Does nothing on Windows
-func UDPGetOOBSize() int {
+func udpGetOOBSize() int {
 	return 0
 }
 
-// UDPSetOptions - set options on a UDP socket to be able to receive the necessary OOB data
-// Does nothing on Windows
-func UDPSetOptions(c *net.UDPConn) error {
+func udpSetOptions(c *net.UDPConn) error {
 	return nil
 }
 
-// UDPRead - receive payload from the UDP socket
-func UDPRead(c *net.UDPConn, buf []byte, _ int) (int, net.IP, *net.UDPAddr, error) {
+func udpRead(c *net.UDPConn, buf []byte, _ int) (int, net.IP, *net.UDPAddr, error) {
 	n, addr, err := c.ReadFrom(buf)
 	var udpAddr *net.UDPAddr
 	if addr != nil {
 		udpAddr = addr.(*net.UDPAddr)
 	}
+
 	return n, nil, udpAddr, err
 }
 
-// UDPWrite - writes to the UDP socket
-func UDPWrite(bytes []byte, conn *net.UDPConn, remoteAddr *net.UDPAddr, _ net.IP) (int, error) {
+func udpWrite(bytes []byte, conn *net.UDPConn, remoteAddr *net.UDPAddr, _ net.IP) (int, error) {
 	return conn.WriteTo(bytes, remoteAddr)
 }