iptables: support matching the input interface name

We have support for the output interface name, but not for the input
interface name.
This change adds the support for the input interface name, and adds the
test cases for it.

Fixes #5300

PiperOrigin-RevId: 353179389

2 files changed, 9 insertions, 7 deletions

diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go
index f295a9192..2ccfa0822 100644
--- a/pkg/tcpip/network/ipv4/ipv4.go
+++ b/pkg/tcpip/network/ipv4/ipv4.go
@@ -321,8 +321,8 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.Netw
 
 	// iptables filtering. All packets that reach here are locally
 	// generated.
-	nicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
-	if ok := e.protocol.stack.IPTables().Check(stack.Output, pkt, gso, r, "", nicName); !ok {
+	outNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
+	if ok := e.protocol.stack.IPTables().Check(stack.Output, pkt, gso, r, "" /* preroutingAddr */, "" /* inNicName */, outNicName); !ok {
 		// iptables is telling us to drop the packet.
 		e.stats.ip.IPTablesOutputDropped.Increment()
 		return nil
@@ -436,10 +436,10 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe
 		}
 	}
 
-	nicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
+	outNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
 	// iptables filtering. All packets that reach here are locally
 	// generated.
-	dropped, natPkts := e.protocol.stack.IPTables().CheckPackets(stack.Output, pkts, gso, r, nicName)
+	dropped, natPkts := e.protocol.stack.IPTables().CheckPackets(stack.Output, pkts, gso, r, "", outNicName)
 	if len(dropped) == 0 && len(natPkts) == 0 {
 		// Fast path: If no packets are to be dropped then we can just invoke the
 		// faster WritePackets API directly.
@@ -611,7 +611,8 @@ func (e *endpoint) HandlePacket(pkt *stack.PacketBuffer) {
 
 	// Loopback traffic skips the prerouting chain.
 	if !e.nic.IsLoopback() {
-		if ok := e.protocol.stack.IPTables().Check(stack.Prerouting, pkt, nil, nil, e.MainAddress().Address, ""); !ok {
+		inNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
+		if ok := e.protocol.stack.IPTables().Check(stack.Prerouting, pkt, nil, nil, e.MainAddress().Address, inNicName, "" /* outNicName */); !ok {
 			// iptables is telling us to drop the packet.
 			stats.IPTablesPreroutingDropped.Increment()
 			return
@@ -698,7 +699,8 @@ func (e *endpoint) handlePacket(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, nil, "", ""); !ok {
+	inNicName := e.protocol.stack.FindNICNameFromID(e.nic.ID())
+	if ok := e.protocol.stack.IPTables().Check(stack.Input, pkt, nil, nil, "" /* preroutingAddr */, inNicName, "" /* outNicName */); !ok {
 		// iptables is telling us to drop the packet.
 		stats.ip.IPTablesInputDropped.Increment()
 		return
diff --git a/pkg/tcpip/network/ipv4/ipv4_test.go b/pkg/tcpip/network/ipv4/ipv4_test.go
index af6f22598..dac7cbfd4 100644
--- a/pkg/tcpip/network/ipv4/ipv4_test.go
+++ b/pkg/tcpip/network/ipv4/ipv4_test.go
@@ -2656,7 +2656,7 @@ func (*limitedMatcher) Name() string {
 }
 
 // Match implements Matcher.Match.
-func (lm *limitedMatcher) Match(stack.Hook, *stack.PacketBuffer, string) (bool, bool) {
+func (lm *limitedMatcher) Match(stack.Hook, *stack.PacketBuffer, string, string) (bool, bool) {
 	if lm.limit == 0 {
 		return true, false
 	}