Add transport.BoundSocketFD interface.

This is beneficial for 2 reasons:
- transport package should not depend on lisafs, which is a user of that
  package.
- This allows users other than lisafs client to use transport.HostBoundEndpoint.

PiperOrigin-RevId: 475326947

pkg/lisafs/client_file.go

@@ -573,7 +573,8 @@ func (f *ClientFD) RemoveXattr(ctx context.Context, name string) error {
 	return err
 }
 
-// ClientBoundSocketFD corresponds to a bound socket on the server.
+// ClientBoundSocketFD corresponds to a bound socket on the server. It
+// implements transport.BoundSocketFD.
 //
 // All fields are immutable.
 type ClientBoundSocketFD struct {
@@ -587,19 +588,18 @@ type ClientBoundSocketFD struct {
 	client *Client
 }
 
-// Close closes the host and gofer-backed FDs associated to this bound socket.
+// Close implements transport.BoundSocketFD.Close.
 func (f *ClientBoundSocketFD) Close(ctx context.Context) {
 	_ = unix.Close(int(f.notificationFD))
 	f.client.CloseFD(ctx, f.fd, true /* flush */)
 }
 
-// NotificationFD is a host FD that can be used to notify when new clients
-// connect to the socket.
+// NotificationFD implements transport.BoundSocketFD.NotificationFD.
 func (f *ClientBoundSocketFD) NotificationFD() int32 {
 	return f.notificationFD
 }
 
-// Listen makes a Listen RPC.
+// Listen implements transport.BoundSocketFD.Listen.
 func (f *ClientBoundSocketFD) Listen(ctx context.Context, backlog int32) error {
 	req := ListenReq{
 		FD:      f.fd,
@@ -612,7 +612,7 @@ func (f *ClientBoundSocketFD) Listen(ctx context.Context, backlog int32) error {
 	return err
 }
 
-// Accept makes an Accept RPC.
+// Accept implements transport.BoundSocketFD.Accept.
 func (f *ClientBoundSocketFD) Accept(ctx context.Context) (int, error) {
 	req := AcceptReq{
 		FD: f.fd,

pkg/sentry/socket/unix/transport/BUILD

@@ -99,7 +99,6 @@ go_library(
         "//pkg/errors/linuxerr",
         "//pkg/fdnotifier",
         "//pkg/ilist",
-        "//pkg/lisafs",
         "//pkg/log",
         "//pkg/refs",
         "//pkg/refsvfs2",

pkg/sentry/socket/unix/transport/connectioned.go

@@ -21,7 +21,6 @@ import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/fdnotifier"
-	"gvisor.dev/gvisor/pkg/lisafs"
 	"gvisor.dev/gvisor/pkg/sentry/uniqueid"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/tcpip"
@@ -120,7 +119,7 @@ type connectionedEndpoint struct {
 	// that may listen and accept incoming connections.
 	//
 	// boundSocketFD is protected by baseEndpoint.mu.
-	boundSocketFD *lisafs.ClientBoundSocketFD
+	boundSocketFD BoundSocketFD
 }
 
 var (
@@ -604,7 +603,7 @@ func (e *connectionedEndpoint) OnSetSendBufferSize(v int64) (newSz int64) {
 func (e *connectionedEndpoint) WakeupWriters() {}
 
 // SetBoundSocketFD implement HostBountEndpoint.SetBoundSocketFD.
-func (e *connectionedEndpoint) SetBoundSocketFD(bsFD *lisafs.ClientBoundSocketFD) {
+func (e *connectionedEndpoint) SetBoundSocketFD(bsFD BoundSocketFD) {
 	e.Lock()
 	defer e.Unlock()
 	if e.boundSocketFD != nil {

pkg/sentry/socket/unix/transport/unix.go

@@ -18,7 +18,6 @@ package transport
 import (
 	"gvisor.dev/gvisor/pkg/abi/linux"
 	"gvisor.dev/gvisor/pkg/context"
-	"gvisor.dev/gvisor/pkg/lisafs"
 	"gvisor.dev/gvisor/pkg/log"
 	"gvisor.dev/gvisor/pkg/syserr"
 	"gvisor.dev/gvisor/pkg/tcpip"
@@ -269,9 +268,26 @@ type BoundEndpoint interface {
 // on the host.
 type HostBoundEndpoint interface {
 	// SetBoundSocketFD will be called on supporting endpoints after
-	// binding a socket on the host filesystem. Implementations should use
-	// delegate Listen and Accept calls to the ClientBoundSocketFD.
-	SetBoundSocketFD(*lisafs.ClientBoundSocketFD)
+	// binding a socket on the host filesystem. Implementations should
+	// delegate Listen and Accept calls to the BoundSocketFD.
+	SetBoundSocketFD(bsFD BoundSocketFD)
+}
+
+// BoundSocketFD is an interface that wraps a socket FD that was bind(2)-ed.
+// It allows to listen and accept on that socket.
+type BoundSocketFD interface {
+	// Close closes the socket FD.
+	Close(ctx context.Context)
+
+	// NotificationFD is a host FD that can be used to notify when new clients
+	// connect to the socket.
+	NotificationFD() int32
+
+	// Listen is analogous to listen(2).
+	Listen(ctx context.Context, backlog int32) error
+
+	// Accept is analogous to accept(2).
+	Accept(ctx context.Context) (int, error)
 }
 
 // message represents a message passed over a Unix domain socket.