Add BoundEndpointAt filesystem operation.

BoundEndpointAt() is needed to support Unix sockets bound at a
file path, corresponding to BoundEndpoint() in VFS1.

Updates #1476.

PiperOrigin-RevId: 303258251

8 files changed, 45 insertions, 0 deletions

diff --git a/pkg/sentry/fsimpl/ext/BUILD b/pkg/sentry/fsimpl/ext/BUILD
index 6f78f478f..d83d75b3d 100644
--- a/pkg/sentry/fsimpl/ext/BUILD
+++ b/pkg/sentry/fsimpl/ext/BUILD
@@ -45,6 +45,7 @@ go_library(
         "//pkg/sentry/fsimpl/ext/disklayout",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/memmap",
+        "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/syscalls/linux",
         "//pkg/sentry/vfs",
         "//pkg/sync",
diff --git a/pkg/sentry/fsimpl/ext/filesystem.go b/pkg/sentry/fsimpl/ext/filesystem.go
index 8497be615..48eaccdbc 100644
--- a/pkg/sentry/fsimpl/ext/filesystem.go
+++ b/pkg/sentry/fsimpl/ext/filesystem.go
@@ -23,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/sentry/fsimpl/ext/disklayout"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/sync"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -463,6 +464,17 @@ func (fs *filesystem) UnlinkAt(ctx context.Context, rp *vfs.ResolvingPath) error
 	return syserror.EROFS
 }
 
+// BoundEndpointAt implements FilesystemImpl.BoundEndpointAt.
+func (fs *filesystem) BoundEndpointAt(ctx context.Context, rp *vfs.ResolvingPath) (transport.BoundEndpoint, error) {
+	_, _, err := fs.walk(rp, false)
+	if err != nil {
+		return nil, err
+	}
+
+	// TODO(b/134676337): Support sockets.
+	return nil, syserror.ECONNREFUSED
+}
+
 // ListxattrAt implements vfs.FilesystemImpl.ListxattrAt.
 func (fs *filesystem) ListxattrAt(ctx context.Context, rp *vfs.ResolvingPath) ([]string, error) {
 	_, _, err := fs.walk(rp, false)
diff --git a/pkg/sentry/fsimpl/gofer/BUILD b/pkg/sentry/fsimpl/gofer/BUILD
index 4ba76a1e8..d15a36709 100644
--- a/pkg/sentry/fsimpl/gofer/BUILD
+++ b/pkg/sentry/fsimpl/gofer/BUILD
@@ -46,6 +46,7 @@ go_library(
         "//pkg/sentry/memmap",
         "//pkg/sentry/pgalloc",
         "//pkg/sentry/platform",
+        "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/usage",
         "//pkg/sentry/vfs",
         "//pkg/syserror",
diff --git a/pkg/sentry/fsimpl/gofer/filesystem.go b/pkg/sentry/fsimpl/gofer/filesystem.go
index 1e43df9ec..269624362 100644
--- a/pkg/sentry/fsimpl/gofer/filesystem.go
+++ b/pkg/sentry/fsimpl/gofer/filesystem.go
@@ -22,6 +22,7 @@ import (
 	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/p9"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
@@ -1059,6 +1060,13 @@ func (fs *filesystem) UnlinkAt(ctx context.Context, rp *vfs.ResolvingPath) error
 	return fs.unlinkAt(ctx, rp, false /* dir */)
 }
 
+// BoundEndpointAt implements FilesystemImpl.BoundEndpointAt.
+//
+// TODO(gvisor.dev/issue/1476): Implement BoundEndpointAt.
+func (fs *filesystem) BoundEndpointAt(ctx context.Context, rp *vfs.ResolvingPath) (transport.BoundEndpoint, error) {
+	return nil, syserror.ECONNREFUSED
+}
+
 // ListxattrAt implements vfs.FilesystemImpl.ListxattrAt.
 func (fs *filesystem) ListxattrAt(ctx context.Context, rp *vfs.ResolvingPath) ([]string, error) {
 	var ds *[]*dentry
diff --git a/pkg/sentry/fsimpl/kernfs/BUILD b/pkg/sentry/fsimpl/kernfs/BUILD
index e73f1f857..b3d6299d0 100644
--- a/pkg/sentry/fsimpl/kernfs/BUILD
+++ b/pkg/sentry/fsimpl/kernfs/BUILD
@@ -35,6 +35,7 @@ go_library(
         "//pkg/refs",
         "//pkg/sentry/kernel/auth",
         "//pkg/sentry/memmap",
+        "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/vfs",
         "//pkg/sync",
         "//pkg/syserror",
diff --git a/pkg/sentry/fsimpl/kernfs/filesystem.go b/pkg/sentry/fsimpl/kernfs/filesystem.go
index 31da8b511..a429fa23d 100644
--- a/pkg/sentry/fsimpl/kernfs/filesystem.go
+++ b/pkg/sentry/fsimpl/kernfs/filesystem.go
@@ -23,6 +23,7 @@ import (
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
@@ -728,6 +729,18 @@ func (fs *Filesystem) UnlinkAt(ctx context.Context, rp *vfs.ResolvingPath) error
 	return nil
 }
 
+// BoundEndpointAt implements FilesystemImpl.BoundEndpointAt.
+func (fs *Filesystem) BoundEndpointAt(ctx context.Context, rp *vfs.ResolvingPath) (transport.BoundEndpoint, error) {
+	fs.mu.RLock()
+	_, _, err := fs.walkExistingLocked(ctx, rp)
+	fs.mu.RUnlock()
+	fs.processDeferredDecRefs()
+	if err != nil {
+		return nil, err
+	}
+	return nil, syserror.ECONNREFUSED
+}
+
 // ListxattrAt implements vfs.FilesystemImpl.ListxattrAt.
 func (fs *Filesystem) ListxattrAt(ctx context.Context, rp *vfs.ResolvingPath) ([]string, error) {
 	fs.mu.RLock()
diff --git a/pkg/sentry/fsimpl/tmpfs/BUILD b/pkg/sentry/fsimpl/tmpfs/BUILD
index 57abd5583..6ea35affb 100644
--- a/pkg/sentry/fsimpl/tmpfs/BUILD
+++ b/pkg/sentry/fsimpl/tmpfs/BUILD
@@ -46,6 +46,7 @@ go_library(
         "//pkg/sentry/memmap",
         "//pkg/sentry/pgalloc",
         "//pkg/sentry/platform",
+        "//pkg/sentry/socket/unix/transport",
         "//pkg/sentry/usage",
         "//pkg/sentry/vfs",
         "//pkg/sentry/vfs/lock",
diff --git a/pkg/sentry/fsimpl/tmpfs/filesystem.go b/pkg/sentry/fsimpl/tmpfs/filesystem.go
index 12cc64385..e678ecc37 100644
--- a/pkg/sentry/fsimpl/tmpfs/filesystem.go
+++ b/pkg/sentry/fsimpl/tmpfs/filesystem.go
@@ -21,6 +21,7 @@ import (
 	"gvisor.dev/gvisor/pkg/context"
 	"gvisor.dev/gvisor/pkg/fspath"
 	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
 	"gvisor.dev/gvisor/pkg/sentry/vfs"
 	"gvisor.dev/gvisor/pkg/syserror"
 )
@@ -656,6 +657,13 @@ func (fs *filesystem) UnlinkAt(ctx context.Context, rp *vfs.ResolvingPath) error
 	return nil
 }
 
+// BoundEndpointAt implements FilesystemImpl.BoundEndpointAt.
+//
+// TODO(gvisor.dev/issue/1476): Implement BoundEndpointAt.
+func (fs *filesystem) BoundEndpointAt(ctx context.Context, rp *vfs.ResolvingPath) (transport.BoundEndpoint, error) {
+	return nil, syserror.ECONNREFUSED
+}
+
 // ListxattrAt implements vfs.FilesystemImpl.ListxattrAt.
 func (fs *filesystem) ListxattrAt(ctx context.Context, rp *vfs.ResolvingPath) ([]string, error) {
 	fs.mu.RLock()