Introduce method per iptables hook

...to make it clear what arguments are needed per hook.

PiperOrigin-RevId: 398538776

3 files changed, 92 insertions, 26 deletions

diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index 25f5a52e3..e4c08c016 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -426,7 +426,7 @@ func (e *endpoint) WritePacket(r *stack.Route, params stack.NetworkHeaderParams,
 	// iptables filtering. All packets that reach here are locally
 	// generated.
 	outNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-	if ok := e.protocol.stack.IPTables().Check(stack.Output, pkt, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
+	if ok := e.protocol.stack.IPTables().CheckOutput(pkt, r, outNicName); !ok {
 		// iptables is telling us to drop the packet.
 		e.stats.ip.IPTablesOutputDropped.Increment()
 		return nil
@@ -466,7 +466,7 @@ func (e *endpoint) writePacket(r *stack.Route, pkt *stack.PacketBuffer, headerIn
 	// Postrouting NAT can only change the source address, and does not alter the
 	// route or outgoing interface of the packet.
 	outNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-	if ok := e.protocol.stack.IPTables().Check(stack.Postrouting, pkt, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
+	if ok := e.protocol.stack.IPTables().CheckPostrouting(pkt, r, outNicName); !ok {
 		// iptables is telling us to drop the packet.
 		e.stats.ip.IPTablesPostroutingDropped.Increment()
 		return nil
@@ -549,7 +549,7 @@ func (e *endpoint) WritePackets(r *stack.Route, pkts stack.PacketBufferList, par
 	outNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
 	// iptables filtering. All packets that reach here are locally
 	// generated.
-	outputDropped, natPkts := e.protocol.stack.IPTables().CheckPackets(stack.Output, pkts, r, "" /* inNicName */, outNicName)
+	outputDropped, natPkts := e.protocol.stack.IPTables().CheckOutputPackets(pkts, r, outNicName)
 	stats.IPTablesOutputDropped.IncrementBy(uint64(len(outputDropped)))
 	for pkt := range outputDropped {
 		pkts.Remove(pkt)
@@ -576,7 +576,7 @@ func (e *endpoint) WritePackets(r *stack.Route, pkts stack.PacketBufferList, par
 	// We ignore the list of NAT-ed packets here because Postrouting NAT can only
 	// change the source address, and does not alter the route or outgoing
 	// interface of the packet.
-	postroutingDropped, _ := e.protocol.stack.IPTables().CheckPackets(stack.Postrouting, pkts, r, "" /* inNicName */, outNicName)
+	postroutingDropped, _ := e.protocol.stack.IPTables().CheckPostroutingPackets(pkts, r, outNicName)
 	stats.IPTablesPostroutingDropped.IncrementBy(uint64(len(postroutingDropped)))
 	for pkt := range postroutingDropped {
 		pkts.Remove(pkt)
@@ -717,7 +717,7 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) ip.ForwardingError {
 	if ep := e.protocol.findEndpointWithAddress(dstAddr); ep != nil {
 		inNicName := stk.FindNICNameFromID(e.nic.ID())
 		outNicName := stk.FindNICNameFromID(ep.nic.ID())
-		if ok := stk.IPTables().Check(stack.Forward, pkt, nil, "" /* preroutingAddr */, inNicName, outNicName); !ok {
+		if ok := stk.IPTables().CheckForward(pkt, inNicName, outNicName); !ok {
 			// iptables is telling us to drop the packet.
 			e.stats.ip.IPTablesForwardDropped.Increment()
 			return nil
@@ -744,7 +744,7 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) ip.ForwardingError {
 
 	inNicName := stk.FindNICNameFromID(e.nic.ID())
 	outNicName := stk.FindNICNameFromID(r.NICID())
-	if ok := stk.IPTables().Check(stack.Forward, pkt, nil, "" /* preroutingAddr */, inNicName, outNicName); !ok {
+	if ok := stk.IPTables().CheckForward(pkt, inNicName, outNicName); !ok {
 		// iptables is telling us to drop the packet.
 		e.stats.ip.IPTablesForwardDropped.Increment()
 		return nil
@@ -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().Check(stack.Prerouting, pkt, nil, e.MainAddress().Address, inNicName, "" /* outNicName */); !ok {
+		if ok := e.protocol.stack.IPTables().CheckPrerouting(pkt, e.MainAddress().Address, inNicName); !ok {
 			// iptables is telling us to drop the packet.
 			stats.IPTablesPreroutingDropped.Increment()
 			return
@@ -940,7 +940,7 @@ func (e *endpoint) handleValidatedPacket(h header.IPv4, pkt *stack.PacketBuffer,
 
 	// iptables filtering. All packets that reach here are intended for
 	// this machine and will not be forwarded.
-	if ok := e.protocol.stack.IPTables().Check(stack.Input, pkt, nil, "" /* preroutingAddr */, inNICName, "" /* outNicName */); !ok {
+	if ok := e.protocol.stack.IPTables().CheckInput(pkt, inNICName); !ok {
 		// iptables is telling us to drop the packet.
 		stats.ip.IPTablesInputDropped.Increment()
 		return
diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go
index dab99d00d..877988aa7 100644
--- a/pkg/tcpip/network/ipv6/ipv6.go
+++ b/pkg/tcpip/network/ipv6/ipv6.go
@@ -748,7 +748,7 @@ func (e *endpoint) WritePacket(r *stack.Route, params stack.NetworkHeaderParams,
 	// iptables filtering. All packets that reach here are locally
 	// generated.
 	outNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-	if ok := e.protocol.stack.IPTables().Check(stack.Output, pkt, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
+	if ok := e.protocol.stack.IPTables().CheckOutput(pkt, r, outNicName); !ok {
 		// iptables is telling us to drop the packet.
 		e.stats.ip.IPTablesOutputDropped.Increment()
 		return nil
@@ -788,7 +788,7 @@ func (e *endpoint) writePacket(r *stack.Route, pkt *stack.PacketBuffer, protocol
 	// Postrouting NAT can only change the source address, and does not alter the
 	// route or outgoing interface of the packet.
 	outNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-	if ok := e.protocol.stack.IPTables().Check(stack.Postrouting, pkt, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
+	if ok := e.protocol.stack.IPTables().CheckPostrouting(pkt, r, outNicName); !ok {
 		// iptables is telling us to drop the packet.
 		e.stats.ip.IPTablesPostroutingDropped.Increment()
 		return nil
@@ -871,7 +871,7 @@ func (e *endpoint) WritePackets(r *stack.Route, pkts stack.PacketBufferList, par
 	// iptables filtering. All packets that reach here are locally
 	// generated.
 	outNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-	outputDropped, natPkts := e.protocol.stack.IPTables().CheckPackets(stack.Output, pkts, r, "" /* inNicName */, outNicName)
+	outputDropped, natPkts := e.protocol.stack.IPTables().CheckOutputPackets(pkts, r, outNicName)
 	stats.IPTablesOutputDropped.IncrementBy(uint64(len(outputDropped)))
 	for pkt := range outputDropped {
 		pkts.Remove(pkt)
@@ -897,7 +897,7 @@ func (e *endpoint) WritePackets(r *stack.Route, pkts stack.PacketBufferList, par
 	// We ignore the list of NAT-ed packets here because Postrouting NAT can only
 	// change the source address, and does not alter the route or outgoing
 	// interface of the packet.
-	postroutingDropped, _ := e.protocol.stack.IPTables().CheckPackets(stack.Postrouting, pkts, r, "" /* inNicName */, outNicName)
+	postroutingDropped, _ := e.protocol.stack.IPTables().CheckPostroutingPackets(pkts, r, outNicName)
 	stats.IPTablesPostroutingDropped.IncrementBy(uint64(len(postroutingDropped)))
 	for pkt := range postroutingDropped {
 		pkts.Remove(pkt)
@@ -984,7 +984,7 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) ip.ForwardingError {
 	if ep := e.protocol.findEndpointWithAddress(dstAddr); ep != nil {
 		inNicName := stk.FindNICNameFromID(e.nic.ID())
 		outNicName := stk.FindNICNameFromID(ep.nic.ID())
-		if ok := stk.IPTables().Check(stack.Forward, pkt, nil, "" /* preroutingAddr */, inNicName, outNicName); !ok {
+		if ok := stk.IPTables().CheckForward(pkt, inNicName, outNicName); !ok {
 			// iptables is telling us to drop the packet.
 			e.stats.ip.IPTablesForwardDropped.Increment()
 			return nil
@@ -1015,7 +1015,7 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) ip.ForwardingError {
 
 	inNicName := stk.FindNICNameFromID(e.nic.ID())
 	outNicName := stk.FindNICNameFromID(r.NICID())
-	if ok := stk.IPTables().Check(stack.Forward, pkt, nil, "" /* preroutingAddr */, inNicName, outNicName); !ok {
+	if ok := stk.IPTables().CheckForward(pkt, inNicName, outNicName); !ok {
 		// iptables is telling us to drop the packet.
 		e.stats.ip.IPTablesForwardDropped.Increment()
 		return nil
@@ -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().Check(stack.Prerouting, pkt, nil, e.MainAddress().Address, inNicName, "" /* outNicName */); !ok {
+		if ok := e.protocol.stack.IPTables().CheckPrerouting(pkt, e.MainAddress().Address, inNicName); !ok {
 			// iptables is telling us to drop the packet.
 			stats.IPTablesPreroutingDropped.Increment()
 			return
@@ -1183,7 +1183,7 @@ func (e *endpoint) handleValidatedPacket(h header.IPv6, pkt *stack.PacketBuffer,
 
 	// iptables filtering. All packets that reach here are intended for
 	// this machine and need not be forwarded.
-	if ok := e.protocol.stack.IPTables().Check(stack.Input, pkt, nil, "" /* preroutingAddr */, inNICName, "" /* outNicName */); !ok {
+	if ok := e.protocol.stack.IPTables().CheckInput(pkt, inNICName); !ok {
 		// iptables is telling us to drop the packet.
 		stats.IPTablesInputDropped.Increment()
 		return
diff --git a/pkg/tcpip/stack/iptables.go b/pkg/tcpip/stack/iptables.go
index 3617b6dd0..3c33589ad 100644
--- a/pkg/tcpip/stack/iptables.go
+++ b/pkg/tcpip/stack/iptables.go
@@ -264,12 +264,62 @@ const (
 	chainReturn
 )
 
-// Check runs pkt through the rules for hook. It returns true when the packet
+// CheckPrerouting performs the prerouting hook on the packet.
+//
+// Returns true iff the packet may continue traversing the stack; the packet
+// 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 */)
+}
+
+// CheckInput performs the input hook on the packet.
+//
+// Returns true iff the packet may continue traversing the stack; the packet
+// must be dropped if false is returned.
+//
+// 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 */)
+}
+
+// CheckForward performs the forward hook on the packet.
+//
+// Returns true iff the packet may continue traversing the stack; the packet
+// must be dropped if false is returned.
+//
+// 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)
+}
+
+// CheckOutput performs the output hook on the packet.
+//
+// Returns true iff the packet may continue traversing the stack; the packet
+// must be dropped if false is returned.
+//
+// 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)
+}
+
+// CheckPostrouting performs the postrouting hook on the packet.
+//
+// Returns true iff the packet may continue traversing the stack; the packet
+// must be dropped if false is returned.
+//
+// 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)
+}
+
+// check runs pkt through the rules for hook. It returns true when the packet
 // should continue traversing the network stack and false when it should be
 // dropped.
 //
-// Precondition: pkt.NetworkHeader is set.
-func (it *IPTables) Check(hook Hook, pkt *PacketBuffer, r *Route, preroutingAddr tcpip.Address, inNicName, outNicName string) bool {
+// 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 {
 	if pkt.NetworkProtocolNumber != header.IPv4ProtocolNumber && pkt.NetworkProtocolNumber != header.IPv6ProtocolNumber {
 		return true
 	}
@@ -375,19 +425,35 @@ func (it *IPTables) startReaper(interval time.Duration) {
 	}()
 }
 
-// CheckPackets runs pkts through the rules for hook and returns a map of packets that
-// should not go forward.
+// CheckOutputPackets performs the output hook on the packets.
 //
-// Preconditions:
-// * pkt is a IPv4 packet of at least length header.IPv4MinimumSize.
-// * pkt.NetworkHeader is not nil.
+// Returns a map of packets that must be dropped.
+//
+// Precondition:  The packets' network and transport header must be set.
+func (it *IPTables) CheckOutputPackets(pkts PacketBufferList, r *Route, outNicName string) (drop map[*PacketBuffer]struct{}, natPkts map[*PacketBuffer]struct{}) {
+	return it.checkPackets(Output, pkts, r, outNicName)
+}
+
+// CheckPostroutingPackets performs the postrouting hook on the packets.
+//
+// Returns a map of packets that must be dropped.
+//
+// Precondition:  The packets' network and transport header must be set.
+func (it *IPTables) CheckPostroutingPackets(pkts PacketBufferList, r *Route, outNicName string) (drop map[*PacketBuffer]struct{}, natPkts map[*PacketBuffer]struct{}) {
+	return it.checkPackets(Postrouting, pkts, r, outNicName)
+}
+
+// checkPackets runs pkts through the rules for hook and returns a map of
+// packets that should not go forward.
 //
 // NOTE: unlike the Check API the returned map contains packets that should be
 // dropped.
-func (it *IPTables) CheckPackets(hook Hook, pkts PacketBufferList, r *Route, inNicName, outNicName string) (drop map[*PacketBuffer]struct{}, natPkts map[*PacketBuffer]struct{}) {
+//
+// Precondition:  The packets' network and transport header must be set.
+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, "", inNicName, outNicName); !ok {
+			if ok := it.check(hook, pkt, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
 				if drop == nil {
 					drop = make(map[*PacketBuffer]struct{})
 				}