1 files changed, 131 insertions, 0 deletions
diff --git a/pkg/sentry/socket/control/control_vfs2.go b/pkg/sentry/socket/control/control_vfs2.go
new file mode 100644
index 000000000..fd08179be
--- /dev/null
+++ b/pkg/sentry/socket/control/control_vfs2.go
@@ -0,0 +1,131 @@
+// 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 control
+
+import (
+	"gvisor.dev/gvisor/pkg/abi/linux"
+	"gvisor.dev/gvisor/pkg/context"
+	"gvisor.dev/gvisor/pkg/sentry/kernel"
+	"gvisor.dev/gvisor/pkg/sentry/socket/unix/transport"
+	"gvisor.dev/gvisor/pkg/sentry/vfs"
+	"gvisor.dev/gvisor/pkg/syserror"
+)
+
+// SCMRightsVFS2 represents a SCM_RIGHTS socket control message.
+type SCMRightsVFS2 interface {
+	transport.RightsControlMessage
+
+	// Files returns up to max RightsFiles.
+	//
+	// Returned files are consumed and ownership is transferred to the caller.
+	// Subsequent calls to Files will return the next files.
+	Files(ctx context.Context, max int) (rf RightsFilesVFS2, truncated bool)
+}
+
+// RightsFiles represents a SCM_RIGHTS socket control message. A reference is
+// maintained for each vfs.FileDescription and is release either when an FD is created or
+// when the Release method is called.
+type RightsFilesVFS2 []*vfs.FileDescription
+
+// NewSCMRightsVFS2 creates a new SCM_RIGHTS socket control message
+// representation using local sentry FDs.
+func NewSCMRightsVFS2(t *kernel.Task, fds []int32) (SCMRightsVFS2, error) {
+	files := make(RightsFilesVFS2, 0, len(fds))
+	for _, fd := range fds {
+		file := t.GetFileVFS2(fd)
+		if file == nil {
+			files.Release()
+			return nil, syserror.EBADF
+		}
+		files = append(files, file)
+	}
+	return &files, nil
+}
+
+// Files implements SCMRights.Files.
+func (fs *RightsFilesVFS2) Files(ctx context.Context, max int) (RightsFilesVFS2, bool) {
+	n := max
+	var trunc bool
+	if l := len(*fs); n > l {
+		n = l
+	} else if n < l {
+		trunc = true
+	}
+	rf := (*fs)[:n]
+	*fs = (*fs)[n:]
+	return rf, trunc
+}
+
+// Clone implements transport.RightsControlMessage.Clone.
+func (fs *RightsFilesVFS2) Clone() transport.RightsControlMessage {
+	nfs := append(RightsFilesVFS2(nil), *fs...)
+	for _, nf := range nfs {
+		nf.IncRef()
+	}
+	return &nfs
+}
+
+// Release implements transport.RightsControlMessage.Release.
+func (fs *RightsFilesVFS2) Release() {
+	for _, f := range *fs {
+		f.DecRef()
+	}
+	*fs = nil
+}
+
+// rightsFDsVFS2 gets up to the specified maximum number of FDs.
+func rightsFDsVFS2(t *kernel.Task, rights SCMRightsVFS2, cloexec bool, max int) ([]int32, bool) {
+	files, trunc := rights.Files(t, max)
+	fds := make([]int32, 0, len(files))
+	for i := 0; i < max && len(files) > 0; i++ {
+		fd, err := t.NewFDFromVFS2(0, files[0], kernel.FDFlags{
+			CloseOnExec: cloexec,
+		})
+		files[0].DecRef()
+		files = files[1:]
+		if err != nil {
+			t.Warningf("Error inserting FD: %v", err)
+			// This is what Linux does.
+			break
+		}
+
+		fds = append(fds, int32(fd))
+	}
+	return fds, trunc
+}
+
+// PackRightsVFS2 packs as many FDs as will fit into the unused capacity of buf.
+func PackRightsVFS2(t *kernel.Task, rights SCMRightsVFS2, cloexec bool, buf []byte, flags int) ([]byte, int) {
+	maxFDs := (cap(buf) - len(buf) - linux.SizeOfControlMessageHeader) / 4
+	// Linux does not return any FDs if none fit.
+	if maxFDs <= 0 {
+		flags |= linux.MSG_CTRUNC
+		return buf, flags
+	}
+	fds, trunc := rightsFDsVFS2(t, rights, cloexec, maxFDs)
+	if trunc {
+		flags |= linux.MSG_CTRUNC
+	}
+	align := t.Arch().Width()
+	return putCmsg(buf, flags, linux.SCM_RIGHTS, align, fds)
+}
+
+// NewVFS2 creates default control messages if needed.
+func NewVFS2(t *kernel.Task, socketOrEndpoint interface{}, rights SCMRightsVFS2) transport.ControlMessages {
+	return transport.ControlMessages{
+		Credentials: makeCreds(t, socketOrEndpoint),
+		Rights:      rights,
+	}
+}