Track and export socket state.

This is necessary for implementing network diagnostic interfaces like
/proc/net/{tcp,udp,unix} and sock_diag(7).

For pass-through endpoints such as hostinet, we obtain the socket
state from the backend. For netstack, we add explicit tracking of TCP
states.

PiperOrigin-RevId: 251934850

2 files changed, 7 insertions, 0 deletions

diff --git a/pkg/tcpip/transport/icmp/BUILD b/pkg/tcpip/transport/icmp/BUILD
index 9aa6f3978..84a2b53b7 100644
--- a/pkg/tcpip/transport/icmp/BUILD
+++ b/pkg/tcpip/transport/icmp/BUILD
@@ -33,6 +33,7 @@ go_library(
         "//pkg/tcpip/header",
         "//pkg/tcpip/stack",
         "//pkg/tcpip/transport/raw",
+        "//pkg/tcpip/transport/tcp",
         "//pkg/waiter",
     ],
 )
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index e2b90ef10..b8005093a 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -708,3 +708,9 @@ func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, vv
 // HandleControlPacket implements stack.TransportEndpoint.HandleControlPacket.
 func (e *endpoint) HandleControlPacket(id stack.TransportEndpointID, typ stack.ControlType, extra uint32, vv buffer.VectorisedView) {
 }
+
+// State implements tcpip.Endpoint.State. The ICMP endpoint currently doesn't
+// expose internal socket state.
+func (e *endpoint) State() uint32 {
+	return 0
+}