2 files changed, 115 insertions, 0 deletions
diff --git a/pkg/sentry/fsimpl/sockfs/BUILD b/pkg/sentry/fsimpl/sockfs/BUILD
new file mode 100644
index 000000000..52084ddb5
--- /dev/null
+++ b/pkg/sentry/fsimpl/sockfs/BUILD
@@ -0,0 +1,17 @@
+load("//tools:defs.bzl", "go_library")
+
+licenses(["notice"])
+
+go_library(
+    name = "sockfs",
+    srcs = ["sockfs.go"],
+    visibility = ["//pkg/sentry:internal"],
+    deps = [
+        "//pkg/abi/linux",
+        "//pkg/context",
+        "//pkg/sentry/fsimpl/kernfs",
+        "//pkg/sentry/kernel/auth",
+        "//pkg/sentry/vfs",
+        "//pkg/syserror",
+    ],
+)
diff --git a/pkg/sentry/fsimpl/sockfs/sockfs.go b/pkg/sentry/fsimpl/sockfs/sockfs.go
new file mode 100644
index 000000000..5ce50625b
--- /dev/null
+++ b/pkg/sentry/fsimpl/sockfs/sockfs.go
@@ -0,0 +1,98 @@
+// Copyright 2020 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package sockfs provides a filesystem implementation for anonymous sockets.
+package sockfs
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/fsimpl/kernfs"
+	"gvisor.dev/gvisor/pkg/sentry/kernel/auth"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+// filesystemType implements vfs.FilesystemType.
+type filesystemType struct{}
+
+// GetFilesystem implements FilesystemType.GetFilesystem.
+func (fsType filesystemType) GetFilesystem(_ context.Context, vfsObj *vfs.VirtualFilesystem, _ *auth.Credentials, _ string, _ vfs.GetFilesystemOptions) (*vfs.Filesystem, *vfs.Dentry, error) {
+	panic("sockfs.filesystemType.GetFilesystem should never be called")
+}
+
+// Name implements FilesystemType.Name.
+//
+// Note that registering sockfs is unnecessary, except for the fact that it
+// will not show up under /proc/filesystems as a result. This is a very minor
+// discrepancy from Linux.
+func (filesystemType) Name() string {
+	return "sockfs"
+}
+
+// filesystem implements vfs.FilesystemImpl.
+type filesystem struct {
+	kernfs.Filesystem
+}
+
+// NewFilesystem sets up and returns a new sockfs filesystem.
+//
+// Note that there should only ever be one instance of sockfs.Filesystem,
+// backing a global socket mount.
+func NewFilesystem(vfsObj *vfs.VirtualFilesystem) *vfs.Filesystem {
+	fs := &filesystem{}
+	fs.Init(vfsObj, filesystemType{})
+	return fs.VFSFilesystem()
+}
+
+// inode implements kernfs.Inode.
+//
+// TODO(gvisor.dev/issue/1476): Add device numbers to this inode (which are
+// not included in InodeAttrs) to store the numbers of the appropriate
+// socket device. Override InodeAttrs.Stat() accordingly.
+type inode struct {
+	kernfs.InodeNotDirectory
+	kernfs.InodeNotSymlink
+	kernfs.InodeAttrs
+	kernfs.InodeNoopRefCount
+}
+
+// Open implements kernfs.Inode.Open.
+func (i *inode) Open(ctx context.Context, rp *vfs.ResolvingPath, vfsd *vfs.Dentry, opts vfs.OpenOptions) (*vfs.FileDescription, error) {
+	return nil, syserror.ENXIO
+}
+
+// InitSocket initializes a socket FileDescription, with a corresponding
+// Dentry in mnt.
+//
+// fd should be the FileDescription associated with socketImpl, i.e. its first
+// field. mnt should be the global socket mount, Kernel.socketMount.
+func InitSocket(socketImpl vfs.FileDescriptionImpl, fd *vfs.FileDescription, mnt *vfs.Mount, creds *auth.Credentials) error {
+	fsimpl := mnt.Filesystem().Impl()
+	fs := fsimpl.(*kernfs.Filesystem)
+
+	// File mode matches net/socket.c:sock_alloc.
+	filemode := linux.FileMode(linux.S_IFSOCK | 0600)
+	i := &inode{}
+	i.Init(creds, fs.NextIno(), filemode)
+
+	d := &kernfs.Dentry{}
+	d.Init(i)
+
+	opts := &vfs.FileDescriptionOptions{UseDentryMetadata: true}
+	if err := fd.Init(socketImpl, linux.O_RDWR, mnt, d.VFSDentry(), opts); err != nil {
+		return err
+	}
+	return nil
+}