recv() on a closed TCP socket returns ENOTCONN

From RFC 793 s3.9 p58 Event Processing:

If RECEIVE Call arrives in CLOSED state and the user has access to such a
connection, the return should be "error: connection does not exist"

Fixes #1598

PiperOrigin-RevId: 293494287

1 files changed, 4 insertions, 0 deletions

diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index 0fa141d58..d29d9a704 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -1124,6 +1124,10 @@ type ReadErrors struct {
 	// InvalidEndpointState is the number of times we found the endpoint state
 	// to be unexpected.
 	InvalidEndpointState StatCounter
+
+	// NotConnected is the number of times we tried to read but found that the
+	// endpoint was not connected.
+	NotConnected StatCounter
 }
 
 // WriteErrors collects packet write errors from an endpoint write call.