Explicitely close files for recvfd client *after* they don't matter. (n…

…etworkservicemesh#548)

Previous we were allowing the recvfd files to be closed by their
finalizer and the GC.

This sometimes led to premature closing of files leading to errors like:

networkservicemesh/cmd-forwarder-vppagent#187

'Delete' case.  This fixes that by closing the files only after the
ctx has is Done.

Signed-off-by: Ed Warnicke <hagbard@gmail.com>
Signed-off-by: Sergey Ershov <sergey.ershov@xored.com>

pkg/networkservice/common/mechanisms/recvfd/client.go

@@ -30,6 +30,7 @@ import (
 	"github.com/edwarnicke/grpcfd"
 
 	"github.com/networkservicemesh/sdk/pkg/networkservice/core/next"
+	"github.com/networkservicemesh/sdk/pkg/networkservice/core/trace"
 )
 
 type recvFDClient struct {
@@ -82,6 +83,14 @@ func (r *recvFDClient) Close(ctx context.Context, conn *networkservice.Connectio
 		inodeURLbyFilename: make(map[string]*url.URL),
 	})
 
+	go func(fileMap *perConnectionFileMap, conn *networkservice.Connection) {
+		<-ctx.Done()
+		for _, file := range fileMap.filesByInodeURL {
+			trace.Log(ctx).Infof("Closing file %q related to closed connection %s", file.Name(), conn.GetId())
+			_ = file.Close()
+		}
+	}(fileMap, conn)
+
 	// Whatever happens, clean up the fileMap
 	defer r.fileMaps.Delete(conn.GetId())