1 files changed, 65 insertions, 50 deletions
diff --git a/pkg/tcpip/stack/iptables_targets.go b/pkg/tcpip/stack/iptables_targets.go
index 8be61f4b1..36cc6275d 100644
--- a/pkg/tcpip/stack/iptables_targets.go
+++ b/pkg/tcpip/stack/iptables_targets.go
@@ -24,7 +24,7 @@ import (
 type AcceptTarget struct{}
 
 // Action implements Target.Action.
-func (AcceptTarget) Action(packet PacketBuffer) (RuleVerdict, int) {
+func (AcceptTarget) Action(*PacketBuffer, *ConnTrackTable, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
 	return RuleAccept, 0
 }
 
@@ -32,7 +32,7 @@ func (AcceptTarget) Action(packet PacketBuffer) (RuleVerdict, int) {
 type DropTarget struct{}
 
 // Action implements Target.Action.
-func (DropTarget) Action(packet PacketBuffer) (RuleVerdict, int) {
+func (DropTarget) Action(*PacketBuffer, *ConnTrackTable, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
 	return RuleDrop, 0
 }
 
@@ -41,7 +41,7 @@ func (DropTarget) Action(packet PacketBuffer) (RuleVerdict, int) {
 type ErrorTarget struct{}
 
 // Action implements Target.Action.
-func (ErrorTarget) Action(packet PacketBuffer) (RuleVerdict, int) {
+func (ErrorTarget) Action(*PacketBuffer, *ConnTrackTable, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
 	log.Debugf("ErrorTarget triggered.")
 	return RuleDrop, 0
 }
@@ -52,7 +52,7 @@ type UserChainTarget struct {
 }
 
 // Action implements Target.Action.
-func (UserChainTarget) Action(PacketBuffer) (RuleVerdict, int) {
+func (UserChainTarget) Action(*PacketBuffer, *ConnTrackTable, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
 	panic("UserChainTarget should never be called.")
 }
 
@@ -61,7 +61,7 @@ func (UserChainTarget) Action(PacketBuffer) (RuleVerdict, int) {
 type ReturnTarget struct{}
 
 // Action implements Target.Action.
-func (ReturnTarget) Action(PacketBuffer) (RuleVerdict, int) {
+func (ReturnTarget) Action(*PacketBuffer, *ConnTrackTable, Hook, *GSO, *Route, tcpip.Address) (RuleVerdict, int) {
 	return RuleReturn, 0
 }
 
@@ -75,16 +75,16 @@ type RedirectTarget struct {
 	// redirect.
 	RangeProtoSpecified bool
 
-	// Min address used to redirect.
+	// MinIP indicates address used to redirect.
 	MinIP tcpip.Address
 
-	// Max address used to redirect.
+	// MaxIP indicates address used to redirect.
 	MaxIP tcpip.Address
 
-	// Min port used to redirect.
+	// MinPort indicates port used to redirect.
 	MinPort uint16
 
-	// Max port used to redirect.
+	// MaxPort indicates port used to redirect.
 	MaxPort uint16
 }
 
@@ -92,61 +92,76 @@ type RedirectTarget struct {
 // TODO(gvisor.dev/issue/170): Parse headers without copying. The current
 // implementation only works for PREROUTING and calls pkt.Clone(), neither
 // of which should be the case.
-func (rt RedirectTarget) Action(pkt PacketBuffer) (RuleVerdict, int) {
-	newPkt := pkt.Clone()
+func (rt RedirectTarget) Action(pkt *PacketBuffer, ct *ConnTrackTable, hook Hook, gso *GSO, r *Route, address tcpip.Address) (RuleVerdict, int) {
+	// Packet is already manipulated.
+	if pkt.NatDone {
+		return RuleAccept, 0
+	}
 
 	// Set network header.
-	headerView, ok := newPkt.Data.PullUp(header.IPv4MinimumSize)
-	if !ok {
-		return RuleDrop, 0
+	if hook == Prerouting {
+		parseHeaders(pkt)
 	}
-	netHeader := header.IPv4(headerView)
-	newPkt.NetworkHeader = headerView
 
-	hlen := int(netHeader.HeaderLength())
-	tlen := int(netHeader.TotalLength())
-	newPkt.Data.TrimFront(hlen)
-	newPkt.Data.CapLength(tlen - hlen)
+	// Drop the packet if network and transport header are not set.
+	if pkt.NetworkHeader == nil || pkt.TransportHeader == nil {
+		return RuleDrop, 0
+	}
 
-	// TODO(gvisor.dev/issue/170): Change destination address to
-	// loopback or interface address on which the packet was
-	// received.
+	// Change the address to localhost (127.0.0.1) in Output and
+	// 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})
+	case Prerouting:
+		rt.MinIP = address
+		rt.MaxIP = address
+	default:
+		panic("redirect target is supported only on output and prerouting hooks")
+	}
 
 	// TODO(gvisor.dev/issue/170): Check Flags in RedirectTarget if
 	// we need to change dest address (for OUTPUT chain) or ports.
+	netHeader := header.IPv4(pkt.NetworkHeader)
 	switch protocol := netHeader.TransportProtocol(); protocol {
 	case header.UDPProtocolNumber:
-		var udpHeader header.UDP
-		if newPkt.TransportHeader != nil {
-			udpHeader = header.UDP(newPkt.TransportHeader)
-		} else {
-			if pkt.Data.Size() < header.UDPMinimumSize {
-				return RuleDrop, 0
-			}
-			hdr, ok := newPkt.Data.PullUp(header.UDPMinimumSize)
-			if !ok {
-				return RuleDrop, 0
+		udpHeader := header.UDP(pkt.TransportHeader)
+		udpHeader.SetDestinationPort(rt.MinPort)
+
+		// Calculate UDP checksum and set it.
+		if hook == Output {
+			udpHeader.SetChecksum(0)
+			hdr := &pkt.Header
+			length := uint16(pkt.Data.Size()+hdr.UsedLength()) - uint16(netHeader.HeaderLength())
+
+			// Only calculate the checksum if offloading isn't supported.
+			if r.Capabilities()&CapabilityTXChecksumOffload == 0 {
+				xsum := r.PseudoHeaderChecksum(protocol, length)
+				for _, v := range pkt.Data.Views() {
+					xsum = header.Checksum(v, xsum)
+				}
+				udpHeader.SetChecksum(0)
+				udpHeader.SetChecksum(^udpHeader.CalculateChecksum(xsum))
 			}
-			udpHeader = header.UDP(hdr)
 		}
-		udpHeader.SetDestinationPort(rt.MinPort)
+		// Change destination address.
+		netHeader.SetDestinationAddress(rt.MinIP)
+		netHeader.SetChecksum(0)
+		netHeader.SetChecksum(^netHeader.CalculateChecksum())
+		pkt.NatDone = true
 	case header.TCPProtocolNumber:
-		var tcpHeader header.TCP
-		if newPkt.TransportHeader != nil {
-			tcpHeader = header.TCP(newPkt.TransportHeader)
-		} else {
-			if pkt.Data.Size() < header.TCPMinimumSize {
-				return RuleDrop, 0
-			}
-			hdr, ok := newPkt.Data.PullUp(header.TCPMinimumSize)
-			if !ok {
-				return RuleDrop, 0
-			}
-			tcpHeader = header.TCP(hdr)
+		if ct == nil {
+			return RuleAccept, 0
+		}
+
+		// Set up conection for matching NAT rule.
+		// Only the first packet of the connection comes here.
+		// Other packets will be manipulated in connection tracking.
+		if conn, _ := ct.connTrackForPacket(pkt, hook, true); conn != nil {
+			ct.SetNatInfo(pkt, rt, hook)
+			ct.HandlePacket(pkt, hook, gso, r)
 		}
-		// TODO(gvisor.dev/issue/170): Need to recompute checksum
-		// and implement nat connection tracking to support TCP.
-		tcpHeader.SetDestinationPort(rt.MinPort)
 	default:
 		return RuleDrop, 0
 	}