sentry: Add simple SIOCGIFFLAGS support (IFF_RUNNING and IFF_PROMIS).

Establishes a way of communicating interface flags between netstack and
epsocket. More flags can be added over time.

PiperOrigin-RevId: 197616669
Change-Id: I230448c5fb5b7d2e8d69b41a451eb4e1096a0e30

2 files changed, 10 insertions, 0 deletions

diff --git a/pkg/tcpip/link/waitable/waitable.go b/pkg/tcpip/link/waitable/waitable.go
index 2c6e73f22..91aed7a12 100644
--- a/pkg/tcpip/link/waitable/waitable.go
+++ b/pkg/tcpip/link/waitable/waitable.go
@@ -58,6 +58,11 @@ func (e *Endpoint) Attach(dispatcher stack.NetworkDispatcher) {
 	e.lower.Attach(e)
 }
 
+// IsAttached implements stack.LinkEndpoint.IsAttached.
+func (e *Endpoint) IsAttached() bool {
+	return e.dispatcher != nil
+}
+
 // MTU implements stack.LinkEndpoint.MTU. It just forwards the request to the
 // lower endpoint.
 func (e *Endpoint) MTU() uint32 {
diff --git a/pkg/tcpip/link/waitable/waitable_test.go b/pkg/tcpip/link/waitable/waitable_test.go
index cb433dc19..188049322 100644
--- a/pkg/tcpip/link/waitable/waitable_test.go
+++ b/pkg/tcpip/link/waitable/waitable_test.go
@@ -34,6 +34,11 @@ func (e *countedEndpoint) Attach(dispatcher stack.NetworkDispatcher) {
 	e.dispatcher = dispatcher
 }
 
+// IsAttached implements stack.LinkEndpoint.IsAttached.
+func (e *countedEndpoint) IsAttached() bool {
+	return e.dispatcher != nil
+}
+
 func (e *countedEndpoint) MTU() uint32 {
 	return e.mtu
 }