iptables: remove unused min/max NAT range fields

PiperOrigin-RevId: 334531794

pkg/sentry/socket/netfilter/targets.go

@@ -194,11 +194,9 @@ func (*redirectTargetMaker) marshal(target stack.Target) []byte {
 
 	ret := make([]byte, 0, linux.SizeOfXTRedirectTarget)
 	xt.NfRange.RangeSize = 1
-	if rt.RangeProtoSpecified {
-		xt.NfRange.RangeIPV4.Flags |= linux.NF_NAT_RANGE_PROTO_SPECIFIED
-	}
-	xt.NfRange.RangeIPV4.MinPort = htons(rt.MinPort)
-	xt.NfRange.RangeIPV4.MaxPort = htons(rt.MaxPort)
+	xt.NfRange.RangeIPV4.Flags |= linux.NF_NAT_RANGE_PROTO_SPECIFIED
+	xt.NfRange.RangeIPV4.MinPort = htons(rt.Port)
+	xt.NfRange.RangeIPV4.MaxPort = xt.NfRange.RangeIPV4.MinPort
 	return binary.Marshal(ret, usermem.ByteOrder, xt)
 }
 
@@ -231,23 +229,23 @@ func (*redirectTargetMaker) unmarshal(buf []byte, filter stack.IPHeaderFilter) (
 	// Also check if we need to map ports or IP.
 	// For now, redirect target only supports destination port change.
 	// Port range and IP range are not supported yet.
-	if nfRange.RangeIPV4.Flags&linux.NF_NAT_RANGE_PROTO_SPECIFIED == 0 {
+	if nfRange.RangeIPV4.Flags != linux.NF_NAT_RANGE_PROTO_SPECIFIED {
 		nflog("redirectTargetMaker: invalid range flags %d", nfRange.RangeIPV4.Flags)
 		return nil, syserr.ErrInvalidArgument
 	}
-	target.RangeProtoSpecified = true
-
-	target.MinIP = tcpip.Address(nfRange.RangeIPV4.MinIP[:])
-	target.MaxIP = tcpip.Address(nfRange.RangeIPV4.MaxIP[:])
 
 	// TODO(gvisor.dev/issue/170): Port range is not supported yet.
 	if nfRange.RangeIPV4.MinPort != nfRange.RangeIPV4.MaxPort {
 		nflog("redirectTargetMaker: MinPort != MaxPort (%d, %d)", nfRange.RangeIPV4.MinPort, nfRange.RangeIPV4.MaxPort)
 		return nil, syserr.ErrInvalidArgument
 	}
+	if nfRange.RangeIPV4.MinIP != nfRange.RangeIPV4.MaxIP {
+		nflog("redirectTargetMaker: MinIP != MaxIP (%d, %d)", nfRange.RangeIPV4.MinPort, nfRange.RangeIPV4.MaxPort)
+		return nil, syserr.ErrInvalidArgument
+	}
 
-	target.MinPort = ntohs(nfRange.RangeIPV4.MinPort)
-	target.MaxPort = ntohs(nfRange.RangeIPV4.MaxPort)
+	target.Addr = tcpip.Address(nfRange.RangeIPV4.MinIP[:])
+	target.Port = ntohs(nfRange.RangeIPV4.MinPort)
 
 	return &target, nil
 }

pkg/tcpip/stack/conntrack.go

@@ -281,8 +281,8 @@ func (ct *ConnTrack) insertRedirectConn(pkt *PacketBuffer, hook Hook, rt Redirec
 	// rule. This tuple will be used to manipulate the packet in
 	// handlePacket.
 	replyTID := tid.reply()
-	replyTID.srcAddr = rt.MinIP
-	replyTID.srcPort = rt.MinPort
+	replyTID.srcAddr = rt.Addr
+	replyTID.srcPort = rt.Port
 	var manip manipType
 	switch hook {
 	case Prerouting:

pkg/tcpip/stack/iptables_targets.go

@@ -128,26 +128,14 @@ func (ReturnTarget) Action(*PacketBuffer, *ConnTrack, Hook, *GSO, *Route, tcpip.
 const RedirectTargetName = "REDIRECT"
 
 // RedirectTarget redirects the packet by modifying the destination port/IP.
-// Min and Max values for IP and Ports in the struct indicate the range of
-// values which can be used to redirect.
+// TODO(gvisor.dev/issue/170): Other flags need to be added after we support
+// them.
 type RedirectTarget struct {
-	// TODO(gvisor.dev/issue/170): Other flags need to be added after
-	// we support them.
-	// RangeProtoSpecified flag indicates single port is specified to
-	// redirect.
-	RangeProtoSpecified bool
+	// Addr indicates address used to redirect.
+	Addr tcpip.Address
 
-	// MinIP indicates address used to redirect.
-	MinIP tcpip.Address
-
-	// MaxIP indicates address used to redirect.
-	MaxIP tcpip.Address
-
-	// MinPort indicates port used to redirect.
-	MinPort uint16
-
-	// MaxPort indicates port used to redirect.
-	MaxPort uint16
+	// Port indicates port used to redirect.
+	Port uint16
 
 	// NetworkProtocol is the network protocol the target is used with.
 	NetworkProtocol tcpip.NetworkProtocolNumber
@@ -180,11 +168,9 @@ func (rt RedirectTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, gso
 	// to primary address of the incoming interface in Prerouting.
 	switch hook {
 	case Output:
-		rt.MinIP = tcpip.Address([]byte{127, 0, 0, 1})
-		rt.MaxIP = tcpip.Address([]byte{127, 0, 0, 1})
+		rt.Addr = tcpip.Address([]byte{127, 0, 0, 1})
 	case Prerouting:
-		rt.MinIP = address
-		rt.MaxIP = address
+		rt.Addr = address
 	default:
 		panic("redirect target is supported only on output and prerouting hooks")
 	}
@@ -195,7 +181,7 @@ func (rt RedirectTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, gso
 	switch protocol := netHeader.TransportProtocol(); protocol {
 	case header.UDPProtocolNumber:
 		udpHeader := header.UDP(pkt.TransportHeader().View())
-		udpHeader.SetDestinationPort(rt.MinPort)
+		udpHeader.SetDestinationPort(rt.Port)
 
 		// Calculate UDP checksum and set it.
 		if hook == Output {
@@ -213,7 +199,7 @@ func (rt RedirectTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, gso
 			}
 		}
 		// Change destination address.
-		netHeader.SetDestinationAddress(rt.MinIP)
+		netHeader.SetDestinationAddress(rt.Addr)
 		netHeader.SetChecksum(0)
 		netHeader.SetChecksum(^netHeader.CalculateChecksum())
 		pkt.NatDone = true