Implement IP_TTL.

Also change the default TTL to 64 to match Linux.

PiperOrigin-RevId: 273430341

3 files changed, 7 insertions, 3 deletions

diff --git a/pkg/tcpip/stack/route.go b/pkg/tcpip/stack/route.go
index 0b09e6517..22db619a1 100644
--- a/pkg/tcpip/stack/route.go
+++ b/pkg/tcpip/stack/route.go
@@ -154,11 +154,15 @@ func (r *Route) IsResolutionRequired() bool {
 }
 
 // WritePacket writes the packet through the given route.
-func (r *Route) WritePacket(gso *GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, ttl uint8) *tcpip.Error {
+func (r *Route) WritePacket(gso *GSO, hdr buffer.Prependable, payload buffer.VectorisedView, protocol tcpip.TransportProtocolNumber, ttl uint8, useDefaultTTL bool) *tcpip.Error {
 	if !r.ref.isValidForOutgoing() {
 		return tcpip.ErrInvalidEndpointState
 	}
 
+	if useDefaultTTL {
+		ttl = r.DefaultTTL()
+	}
+
 	err := r.ref.ep.WritePacket(r, gso, hdr, payload, protocol, ttl, r.loop)
 	if err != nil {
 		r.Stats().IP.OutgoingPacketErrors.Increment()
diff --git a/pkg/tcpip/stack/stack_test.go b/pkg/tcpip/stack/stack_test.go
index a2e0a6e7b..8f063038b 100644
--- a/pkg/tcpip/stack/stack_test.go
+++ b/pkg/tcpip/stack/stack_test.go
@@ -310,7 +310,7 @@ func sendTo(s *stack.Stack, addr tcpip.Address, payload buffer.View) *tcpip.Erro
 
 func send(r stack.Route, payload buffer.View) *tcpip.Error {
 	hdr := buffer.NewPrependable(int(r.MaxHeaderLength()))
-	return r.WritePacket(nil /* gso */, hdr, payload.ToVectorisedView(), fakeTransNumber, 123)
+	return r.WritePacket(nil /* gso */, hdr, payload.ToVectorisedView(), fakeTransNumber, 123 /* ttl */, false /* useDefaultTTL */)
 }
 
 func testSendTo(t *testing.T, s *stack.Stack, addr tcpip.Address, ep *channel.Endpoint, payload buffer.View) {
diff --git a/pkg/tcpip/stack/transport_test.go b/pkg/tcpip/stack/transport_test.go
index 842a16277..db290c404 100644
--- a/pkg/tcpip/stack/transport_test.go
+++ b/pkg/tcpip/stack/transport_test.go
@@ -75,7 +75,7 @@ func (f *fakeTransportEndpoint) Write(p tcpip.Payloader, opts tcpip.WriteOptions
 	if err != nil {
 		return 0, nil, err
 	}
-	if err := f.route.WritePacket(nil /* gso */, hdr, buffer.View(v).ToVectorisedView(), fakeTransNumber, 123); err != nil {
+	if err := f.route.WritePacket(nil /* gso */, hdr, buffer.View(v).ToVectorisedView(), fakeTransNumber, 123 /* ttl */, false /* useDefaultTTL */); err != nil {
 		return 0, nil, err
 	}