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

7 files changed, 42 insertions, 3 deletions

diff --git a/pkg/tcpip/link/channel/channel.go b/pkg/tcpip/link/channel/channel.go
index cebc34553..3f5440cc1 100644
--- a/pkg/tcpip/link/channel/channel.go
+++ b/pkg/tcpip/link/channel/channel.go
@@ -67,6 +67,11 @@ func (e *Endpoint) Attach(dispatcher stack.NetworkDispatcher) {
 	e.dispatcher = dispatcher
 }
 
+// IsAttached implements stack.LinkEndpoint.IsAttached.
+func (e *Endpoint) IsAttached() bool {
+	return e.dispatcher != nil
+}
+
 // MTU implements stack.LinkEndpoint.MTU. It returns the value initialized
 // during construction.
 func (e *Endpoint) MTU() uint32 {
diff --git a/pkg/tcpip/link/fdbased/endpoint.go b/pkg/tcpip/link/fdbased/endpoint.go
index da74cd644..668514454 100644
--- a/pkg/tcpip/link/fdbased/endpoint.go
+++ b/pkg/tcpip/link/fdbased/endpoint.go
@@ -45,9 +45,10 @@ type endpoint struct {
 	// its end of the communication pipe.
 	closed func(*tcpip.Error)
 
-	vv     *buffer.VectorisedView
-	iovecs []syscall.Iovec
-	views  []buffer.View
+	vv       *buffer.VectorisedView
+	iovecs   []syscall.Iovec
+	views    []buffer.View
+	attached bool
 }
 
 // Options specify the details about the fd-based endpoint to be created.
@@ -96,9 +97,15 @@ func New(opts *Options) tcpip.LinkEndpointID {
 // Attach launches the goroutine that reads packets from the file descriptor and
 // dispatches them via the provided dispatcher.
 func (e *endpoint) Attach(dispatcher stack.NetworkDispatcher) {
+	e.attached = true
 	go e.dispatchLoop(dispatcher) // S/R-FIXME
 }
 
+// IsAttached implements stack.LinkEndpoint.IsAttached.
+func (e *endpoint) IsAttached() bool {
+	return e.attached
+}
+
 // MTU implements stack.LinkEndpoint.MTU. It returns the value initialized
 // during construction.
 func (e *endpoint) MTU() uint32 {
diff --git a/pkg/tcpip/link/loopback/loopback.go b/pkg/tcpip/link/loopback/loopback.go
index 1a9cd09d7..f38847949 100644
--- a/pkg/tcpip/link/loopback/loopback.go
+++ b/pkg/tcpip/link/loopback/loopback.go
@@ -32,6 +32,11 @@ func (e *endpoint) Attach(dispatcher stack.NetworkDispatcher) {
 	e.dispatcher = dispatcher
 }
 
+// IsAttached implements stack.LinkEndpoint.IsAttached.
+func (e *endpoint) IsAttached() bool {
+	return e.dispatcher != nil
+}
+
 // MTU implements stack.LinkEndpoint.MTU. It returns a constant that matches the
 // linux loopback interface.
 func (*endpoint) MTU() uint32 {
diff --git a/pkg/tcpip/link/sharedmem/sharedmem.go b/pkg/tcpip/link/sharedmem/sharedmem.go
index 2c0f1b294..5369ebc68 100644
--- a/pkg/tcpip/link/sharedmem/sharedmem.go
+++ b/pkg/tcpip/link/sharedmem/sharedmem.go
@@ -137,6 +137,13 @@ func (e *endpoint) Attach(dispatcher stack.NetworkDispatcher) {
 	e.mu.Unlock()
 }
 
+// IsAttached implements stack.LinkEndpoint.IsAttached.
+func (e *endpoint) IsAttached() bool {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	return e.workerStarted
+}
+
 // MTU implements stack.LinkEndpoint.MTU. It returns the value initialized
 // during construction.
 func (e *endpoint) MTU() uint32 {
diff --git a/pkg/tcpip/link/sniffer/sniffer.go b/pkg/tcpip/link/sniffer/sniffer.go
index 72d9a0f1c..3a40081c0 100644
--- a/pkg/tcpip/link/sniffer/sniffer.go
+++ b/pkg/tcpip/link/sniffer/sniffer.go
@@ -143,6 +143,11 @@ 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.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
 }