Pass AddressableEndpoint to IPTables

...instead of an address.

This allows a later change to more precisely select an address
based on the NAT type (source vs. destination NAT).

PiperOrigin-RevId: 398559901

5 files changed, 28 insertions, 26 deletions

diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index e4c08c016..dda473e48 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -841,7 +841,7 @@ func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 
 		// Loopback traffic skips the prerouting chain.
 		inNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-		if ok := e.protocol.stack.IPTables().CheckPrerouting(pkt, e.MainAddress().Address, inNicName); !ok {
+		if ok := e.protocol.stack.IPTables().CheckPrerouting(pkt, e, inNicName); !ok {
 			// iptables is telling us to drop the packet.
 			stats.IPTablesPreroutingDropped.Increment()
 			return
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index 877988aa7..e2d2cf907 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -1100,7 +1100,7 @@ func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 
 		// Loopback traffic skips the prerouting chain.
 		inNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-		if ok := e.protocol.stack.IPTables().CheckPrerouting(pkt, e.MainAddress().Address, inNicName); !ok {
+		if ok := e.protocol.stack.IPTables().CheckPrerouting(pkt, e, inNicName); !ok {
 			// iptables is telling us to drop the packet.
 			stats.IPTablesPreroutingDropped.Increment()
 			return
diff --git a/pkg/tcpip/stack/iptables.go b/pkg/tcpip/stack/iptables.go
index 3c33589ad..74c9075b4 100644
--- a/pkg/tcpip/stack/iptables.go
+++ b/pkg/tcpip/stack/iptables.go
@@ -270,8 +270,8 @@ const (
 // must be dropped if false is returned.
 //
 // Precondition: The packet's network and transport header must be set.
-func (it *IPTables) CheckPrerouting(pkt *PacketBuffer, preroutingAddr tcpip.Address, inNicName string) bool {
-	return it.check(Prerouting, pkt, nil /* route */, preroutingAddr, inNicName, "" /* outNicName */)
+func (it *IPTables) CheckPrerouting(pkt *PacketBuffer, addressEP AddressableEndpoint, inNicName string) bool {
+	return it.check(Prerouting, pkt, nil /* route */, addressEP, inNicName, "" /* outNicName */)
 }
 
 // CheckInput performs the input hook on the packet.
@@ -281,7 +281,7 @@ func (it *IPTables) CheckPrerouting(pkt *PacketBuffer, preroutingAddr tcpip.Addr
 //
 // Precondition: The packet's network and transport header must be set.
 func (it *IPTables) CheckInput(pkt *PacketBuffer, inNicName string) bool {
-	return it.check(Input, pkt, nil /* route */, "" /* preroutingAddr */, inNicName, "" /* outNicName */)
+	return it.check(Input, pkt, nil /* route */, nil /* addressEP */, inNicName, "" /* outNicName */)
 }
 
 // CheckForward performs the forward hook on the packet.
@@ -291,7 +291,7 @@ func (it *IPTables) CheckInput(pkt *PacketBuffer, inNicName string) bool {
 //
 // Precondition: The packet's network and transport header must be set.
 func (it *IPTables) CheckForward(pkt *PacketBuffer, inNicName, outNicName string) bool {
-	return it.check(Forward, pkt, nil /* route */, "" /* preroutingAddr */, inNicName, outNicName)
+	return it.check(Forward, pkt, nil /* route */, nil /* addressEP */, inNicName, outNicName)
 }
 
 // CheckOutput performs the output hook on the packet.
@@ -301,7 +301,7 @@ func (it *IPTables) CheckForward(pkt *PacketBuffer, inNicName, outNicName string
 //
 // Precondition: The packet's network and transport header must be set.
 func (it *IPTables) CheckOutput(pkt *PacketBuffer, r *Route, outNicName string) bool {
-	return it.check(Output, pkt, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName)
+	return it.check(Output, pkt, r, nil /* addressEP */, "" /* inNicName */, outNicName)
 }
 
 // CheckPostrouting performs the postrouting hook on the packet.
@@ -311,7 +311,7 @@ func (it *IPTables) CheckOutput(pkt *PacketBuffer, r *Route, outNicName string)
 //
 // Precondition: The packet's network and transport header must be set.
 func (it *IPTables) CheckPostrouting(pkt *PacketBuffer, r *Route, outNicName string) bool {
-	return it.check(Postrouting, pkt, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName)
+	return it.check(Postrouting, pkt, r, nil /* addressEP */, "" /* inNicName */, outNicName)
 }
 
 // check runs pkt through the rules for hook. It returns true when the packet
@@ -319,7 +319,7 @@ func (it *IPTables) CheckPostrouting(pkt *PacketBuffer, r *Route, outNicName str
 // dropped.
 //
 // Precondition: The packet's network and transport header must be set.
-func (it *IPTables) check(hook Hook, pkt *PacketBuffer, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) bool {
+func (it *IPTables) check(hook Hook, pkt *PacketBuffer, r *Route, addressEP AddressableEndpoint, inNicName, outNicName string) bool {
 	if pkt.NetworkProtocolNumber != header.IPv4ProtocolNumber && pkt.NetworkProtocolNumber != header.IPv6ProtocolNumber {
 		return true
 	}
@@ -350,7 +350,7 @@ func (it *IPTables) check(hook Hook, pkt *PacketBuffer, r *Route, preroutingAddr
 			table = it.v4Tables[tableID]
 		}
 		ruleIdx := table.BuiltinChains[hook]
-		switch verdict := it.checkChain(hook, pkt, table, ruleIdx, r, preroutingAddr, inNicName, outNicName); verdict {
+		switch verdict := it.checkChain(hook, pkt, table, ruleIdx, r, addressEP, inNicName, outNicName); verdict {
 		// If the table returns Accept, move on to the next table.
 		case chainAccept:
 			continue
@@ -361,7 +361,7 @@ func (it *IPTables) check(hook Hook, pkt *PacketBuffer, r *Route, preroutingAddr
 			// Any Return from a built-in chain means we have to
 			// call the underflow.
 			underflow := table.Rules[table.Underflows[hook]]
-			switch v, _ := underflow.Target.Action(pkt, &it.connections, hook, r, preroutingAddr); v {
+			switch v, _ := underflow.Target.Action(pkt, &it.connections, hook, r, addressEP); v {
 			case RuleAccept:
 				continue
 			case RuleDrop:
@@ -453,7 +453,7 @@ func (it *IPTables) CheckPostroutingPackets(pkts PacketBufferList, r *Route, out
 func (it *IPTables) checkPackets(hook Hook, pkts PacketBufferList, r *Route, outNicName string) (drop map[*PacketBuffer]struct{}, natPkts map[*PacketBuffer]struct{}) {
 	for pkt := pkts.Front(); pkt != nil; pkt = pkt.Next() {
 		if !pkt.NatDone {
-			if ok := it.check(hook, pkt, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
+			if ok := it.check(hook, pkt, r, nil /* addressEP */, "" /* inNicName */, outNicName); !ok {
 				if drop == nil {
 					drop = make(map[*PacketBuffer]struct{})
 				}
@@ -473,11 +473,11 @@ func (it *IPTables) checkPackets(hook Hook, pkts PacketBufferList, r *Route, out
 // Preconditions:
 // * pkt is a IPv4 packet of at least length header.IPv4MinimumSize.
 // * pkt.NetworkHeader is not nil.
-func (it *IPTables) checkChain(hook Hook, pkt *PacketBuffer, table Table, ruleIdx int, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) chainVerdict {
+func (it *IPTables) checkChain(hook Hook, pkt *PacketBuffer, table Table, ruleIdx int, r *Route, addressEP AddressableEndpoint, inNicName, outNicName string) chainVerdict {
 	// Start from ruleIdx and walk the list of rules until a rule gives us
 	// a verdict.
 	for ruleIdx < len(table.Rules) {
-		switch verdict, jumpTo := it.checkRule(hook, pkt, table, ruleIdx, r, preroutingAddr, inNicName, outNicName); verdict {
+		switch verdict, jumpTo := it.checkRule(hook, pkt, table, ruleIdx, r, addressEP, inNicName, outNicName); verdict {
 		case RuleAccept:
 			return chainAccept
 
@@ -494,7 +494,7 @@ func (it *IPTables) checkChain(hook Hook, pkt *PacketBuffer, table Table, ruleId
 				ruleIdx++
 				continue
 			}
-			switch verdict := it.checkChain(hook, pkt, table, jumpTo, r, preroutingAddr, inNicName, outNicName); verdict {
+			switch verdict := it.checkChain(hook, pkt, table, jumpTo, r, addressEP, inNicName, outNicName); verdict {
 			case chainAccept:
 				return chainAccept
 			case chainDrop:
@@ -520,7 +520,7 @@ func (it *IPTables) checkChain(hook Hook, pkt *PacketBuffer, table Table, ruleId
 // Preconditions:
 // * pkt is a IPv4 packet of at least length header.IPv4MinimumSize.
 // * pkt.NetworkHeader is not nil.
-func (it *IPTables) checkRule(hook Hook, pkt *PacketBuffer, table Table, ruleIdx int, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) (RuleVerdict, int) {
+func (it *IPTables) checkRule(hook Hook, pkt *PacketBuffer, table Table, ruleIdx int, r *Route, addressEP AddressableEndpoint, inNicName, outNicName string) (RuleVerdict, int) {
 	rule := table.Rules[ruleIdx]
 
 	// Check whether the packet matches the IP header filter.
@@ -543,7 +543,7 @@ func (it *IPTables) checkRule(hook Hook, pkt *PacketBuffer, table Table, ruleIdx
 	}
 
 	// All the matchers matched, so run the target.
-	return rule.Target.Action(pkt, &it.connections, hook, r, preroutingAddr)
+	return rule.Target.Action(pkt, &it.connections, hook, r, addressEP)
 }
 
 // OriginalDst returns the original destination of redirected connections. It
diff --git a/pkg/tcpip/stack/iptables_targets.go b/pkg/tcpip/stack/iptables_targets.go
index de5997e9e..e8806ebdb 100644
--- a/pkg/tcpip/stack/iptables_targets.go
+++ b/pkg/tcpip/stack/iptables_targets.go
@@ -29,7 +29,7 @@ type AcceptTarget struct {
 }
 
 // Action implements Target.Action.
-func (*AcceptTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*AcceptTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, AddressableEndpoint) (RuleVerdict, int) {
 	return RuleAccept, 0
 }
 
@@ -40,7 +40,7 @@ type DropTarget struct {
 }
 
 // Action implements Target.Action.
-func (*DropTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*DropTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, AddressableEndpoint) (RuleVerdict, int) {
 	return RuleDrop, 0
 }
 
@@ -52,7 +52,7 @@ type ErrorTarget struct {
 }
 
 // Action implements Target.Action.
-func (*ErrorTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*ErrorTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, AddressableEndpoint) (RuleVerdict, int) {
 	log.Debugf("ErrorTarget triggered.")
 	return RuleDrop, 0
 }
@@ -67,7 +67,7 @@ type UserChainTarget struct {
 }
 
 // Action implements Target.Action.
-func (*UserChainTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*UserChainTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, AddressableEndpoint) (RuleVerdict, int) {
 	panic("UserChainTarget should never be called.")
 }
 
@@ -79,7 +79,7 @@ type ReturnTarget struct {
 }
 
 // Action implements Target.Action.
-func (*ReturnTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int) {
+func (*ReturnTarget) Action(*PacketBuffer, *ConnTrack, Hook, *Route, AddressableEndpoint) (RuleVerdict, int) {
 	return RuleReturn, 0
 }
 
@@ -97,7 +97,7 @@ type RedirectTarget struct {
 }
 
 // Action implements Target.Action.
-func (rt *RedirectTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, r *Route, address tcpip.Address) (RuleVerdict, int) {
+func (rt *RedirectTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, r *Route, addressEP AddressableEndpoint) (RuleVerdict, int) {
 	// Sanity check.
 	if rt.NetworkProtocol != pkt.NetworkProtocolNumber {
 		panic(fmt.Sprintf(
@@ -117,6 +117,7 @@ func (rt *RedirectTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, r
 
 	// Change the address to loopback (127.0.0.1 or ::1) in Output and to
 	// the primary address of the incoming interface in Prerouting.
+	var address tcpip.Address
 	switch hook {
 	case Output:
 		if pkt.NetworkProtocolNumber == header.IPv4ProtocolNumber {
@@ -125,7 +126,8 @@ func (rt *RedirectTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, r
 			address = header.IPv6Loopback
 		}
 	case Prerouting:
-		// No-op, as address is already set correctly.
+		// addressEP is expected to be set for the prerouting hook.
+		address = addressEP.MainAddress().Address
 	default:
 		panic("redirect target is supported only on output and prerouting hooks")
 	}
@@ -180,7 +182,7 @@ type SNATTarget struct {
 }
 
 // Action implements Target.Action.
-func (st *SNATTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, r *Route, address tcpip.Address) (RuleVerdict, int) {
+func (st *SNATTarget) Action(pkt *PacketBuffer, ct *ConnTrack, hook Hook, r *Route, _ AddressableEndpoint) (RuleVerdict, int) {
 	// Sanity check.
 	if st.NetworkProtocol != pkt.NetworkProtocolNumber {
 		panic(fmt.Sprintf(
diff --git a/pkg/tcpip/stack/iptables_types.go b/pkg/tcpip/stack/iptables_types.go
index 66e5f22ac..976194124 100644
--- a/pkg/tcpip/stack/iptables_types.go
+++ b/pkg/tcpip/stack/iptables_types.go
@@ -352,5 +352,5 @@ type Target interface {
 	// Action takes an action on the packet and returns a verdict on how
 	// traversal should (or should not) continue. If the return value is
 	// Jump, it also returns the index of the rule to jump to.
-	Action(*PacketBuffer, *ConnTrack, Hook, *Route, tcpip.Address) (RuleVerdict, int)
+	Action(*PacketBuffer, *ConnTrack, Hook, *Route, AddressableEndpoint) (RuleVerdict, int)
 }