Don't include link header when forwarding packets

Before this change, if a link header was included in an incoming packet
that is forwarded, the packet that gets sent out will take the original
packet and add a link header to it while keeping the old link header.
This would make the sent packet look like:

   OUTGOING LINK HDR | INCOMING LINK HDR | NETWORK HDR | ...

Obviously this is incorrect as we should drop the incoming link header
and only include the outgoing link header. This change fixes this bug.

Test: integration_test.TestForwarding
PiperOrigin-RevId: 337571447

3 files changed, 12 insertions, 9 deletions

diff --git a/pkg/tcpip/tests/integration/BUILD b/pkg/tcpip/tests/integration/BUILD
index a4f141253..34aab32d0 100644
--- a/pkg/tcpip/tests/integration/BUILD
+++ b/pkg/tcpip/tests/integration/BUILD
@@ -16,6 +16,7 @@ go_test(
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
         "//pkg/tcpip/link/channel",
+        "//pkg/tcpip/link/ethernet",
         "//pkg/tcpip/link/loopback",
         "//pkg/tcpip/link/pipe",
         "//pkg/tcpip/network/arp",
diff --git a/pkg/tcpip/tests/integration/forward_test.go b/pkg/tcpip/tests/integration/forward_test.go
index ffd38ee1a..0dcef7b04 100644
--- a/pkg/tcpip/tests/integration/forward_test.go
+++ b/pkg/tcpip/tests/integration/forward_test.go
@@ -21,6 +21,7 @@ import (
 	"github.com/google/go-cmp/cmp"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
+	"gvisor.dev/gvisor/pkg/tcpip/link/ethernet"
 	"gvisor.dev/gvisor/pkg/tcpip/link/pipe"
 	"gvisor.dev/gvisor/pkg/tcpip/network/arp"
 	"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
@@ -178,19 +179,19 @@ func TestForwarding(t *testing.T) {
 			routerStack := stack.New(stackOpts)
 			host2Stack := stack.New(stackOpts)
 
-			host1NIC, routerNIC1 := pipe.New(host1NICLinkAddr, routerNIC1LinkAddr, stack.CapabilityResolutionRequired)
-			routerNIC2, host2NIC := pipe.New(routerNIC2LinkAddr, host2NICLinkAddr, stack.CapabilityResolutionRequired)
+			host1NIC, routerNIC1 := pipe.New(host1NICLinkAddr, routerNIC1LinkAddr)
+			routerNIC2, host2NIC := pipe.New(routerNIC2LinkAddr, host2NICLinkAddr)
 
-			if err := host1Stack.CreateNIC(host1NICID, host1NIC); err != nil {
+			if err := host1Stack.CreateNIC(host1NICID, ethernet.New(host1NIC)); err != nil {
 				t.Fatalf("host1Stack.CreateNIC(%d, _): %s", host1NICID, err)
 			}
-			if err := routerStack.CreateNIC(routerNICID1, routerNIC1); err != nil {
+			if err := routerStack.CreateNIC(routerNICID1, ethernet.New(routerNIC1)); err != nil {
 				t.Fatalf("routerStack.CreateNIC(%d, _): %s", routerNICID1, err)
 			}
-			if err := routerStack.CreateNIC(routerNICID2, routerNIC2); err != nil {
+			if err := routerStack.CreateNIC(routerNICID2, ethernet.New(routerNIC2)); err != nil {
 				t.Fatalf("routerStack.CreateNIC(%d, _): %s", routerNICID2, err)
 			}
-			if err := host2Stack.CreateNIC(host2NICID, host2NIC); err != nil {
+			if err := host2Stack.CreateNIC(host2NICID, ethernet.New(host2NIC)); err != nil {
 				t.Fatalf("host2Stack.CreateNIC(%d, _): %s", host2NICID, err)
 			}
 
diff --git a/pkg/tcpip/tests/integration/link_resolution_test.go b/pkg/tcpip/tests/integration/link_resolution_test.go
index bf3a6f6ee..6ddcda70c 100644
--- a/pkg/tcpip/tests/integration/link_resolution_test.go
+++ b/pkg/tcpip/tests/integration/link_resolution_test.go
@@ -22,6 +22,7 @@ import (
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/link/ethernet"
 	"gvisor.dev/gvisor/pkg/tcpip/link/pipe"
 	"gvisor.dev/gvisor/pkg/tcpip/network/arp"
 	"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
@@ -126,12 +127,12 @@ func TestPing(t *testing.T) {
 			host1Stack := stack.New(stackOpts)
 			host2Stack := stack.New(stackOpts)
 
-			host1NIC, host2NIC := pipe.New(host1NICLinkAddr, host2NICLinkAddr, stack.CapabilityResolutionRequired)
+			host1NIC, host2NIC := pipe.New(host1NICLinkAddr, host2NICLinkAddr)
 
-			if err := host1Stack.CreateNIC(host1NICID, host1NIC); err != nil {
+			if err := host1Stack.CreateNIC(host1NICID, ethernet.New(host1NIC)); err != nil {
 				t.Fatalf("host1Stack.CreateNIC(%d, _): %s", host1NICID, err)
 			}
-			if err := host2Stack.CreateNIC(host2NICID, host2NIC); err != nil {
+			if err := host2Stack.CreateNIC(host2NICID, ethernet.New(host2NIC)); err != nil {
 				t.Fatalf("host2Stack.CreateNIC(%d, _): %s", host2NICID, err)
 			}