Hide /dev/net/tun when using hostinet.

/dev/net/tun does not currently work with hostinet. This has caused some
program starts failing because it thinks the feature exists.

PiperOrigin-RevId: 297876196

3 files changed, 13 insertions, 2 deletions

diff --git a/pkg/sentry/fs/dev/BUILD b/pkg/sentry/fs/dev/BUILD
index 9b6bb26d0..9379a4d7b 100644
--- a/pkg/sentry/fs/dev/BUILD
+++ b/pkg/sentry/fs/dev/BUILD
@@ -26,6 +26,7 @@ go_library(
         "//pkg/sentry/fs/fsutil",
         "//pkg/sentry/fs/ramfs",
         "//pkg/sentry/fs/tmpfs",
+        "//pkg/sentry/inet",
         "//pkg/sentry/kernel",
         "//pkg/sentry/memmap",
         "//pkg/sentry/mm",
diff --git a/pkg/sentry/fs/dev/dev.go b/pkg/sentry/fs/dev/dev.go
index 7e66c29b0..acbd401a0 100644
--- a/pkg/sentry/fs/dev/dev.go
+++ b/pkg/sentry/fs/dev/dev.go
@@ -22,6 +22,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/ramfs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/tmpfs"
+	"gvisor.dev/gvisor/pkg/sentry/inet"
 	"gvisor.dev/gvisor/pkg/usermem"
 )
 
@@ -124,10 +125,12 @@ func New(ctx context.Context, msrc *fs.MountSource) *fs.Inode {
 		"ptmx": newSymlink(ctx, "pts/ptmx", msrc),
 
 		"tty": newCharacterDevice(ctx, newTTYDevice(ctx, fs.RootOwner, 0666), msrc, ttyDevMajor, ttyDevMinor),
+	}
 
-		"net": newDirectory(ctx, map[string]*fs.Inode{
+	if isNetTunSupported(inet.StackFromContext(ctx)) {
+		contents["net"] = newDirectory(ctx, map[string]*fs.Inode{
 			"tun": newCharacterDevice(ctx, newNetTunDevice(ctx, fs.RootOwner, 0666), msrc, netTunDevMajor, netTunDevMinor),
-		}, msrc),
+		}, msrc)
 	}
 
 	iops := ramfs.NewDir(ctx, contents, fs.RootOwner, fs.FilePermsFromMode(0555))
diff --git a/pkg/sentry/fs/dev/net_tun.go b/pkg/sentry/fs/dev/net_tun.go
index 755644488..dc7ad075a 100644
--- a/pkg/sentry/fs/dev/net_tun.go
+++ b/pkg/sentry/fs/dev/net_tun.go
@@ -20,6 +20,7 @@ import (
 	"gvisor.dev/gvisor/pkg/sentry/arch"
 	"gvisor.dev/gvisor/pkg/sentry/fs"
 	"gvisor.dev/gvisor/pkg/sentry/fs/fsutil"
+	"gvisor.dev/gvisor/pkg/sentry/inet"
 	"gvisor.dev/gvisor/pkg/sentry/kernel"
 	"gvisor.dev/gvisor/pkg/sentry/socket/netstack"
 	"gvisor.dev/gvisor/pkg/syserror"
@@ -168,3 +169,9 @@ func (fops *netTunFileOperations) EventRegister(e *waiter.Entry, mask waiter.Eve
 func (fops *netTunFileOperations) EventUnregister(e *waiter.Entry) {
 	fops.device.EventUnregister(e)
 }
+
+// isNetTunSupported returns whether /dev/net/tun device is supported for s.
+func isNetTunSupported(s inet.Stack) bool {
+	_, ok := s.(*netstack.Stack)
+	return ok
+}