Check in gVisor.

PiperOrigin-RevId: 194583126
Change-Id: Ica1d8821a90f74e7e745962d71801c598c652463

1 files changed, 134 insertions, 0 deletions

diff --git a/runsc/cmd/gofer.go b/runsc/cmd/gofer.go
new file mode 100644
index 000000000..844e16dbf
--- /dev/null
+++ b/runsc/cmd/gofer.go
@@ -0,0 +1,134 @@
+// Copyright 2018 Google Inc.
+//
+// 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 cmd
+
+import (
+	"sync"
+
+	"context"
+	"flag"
+	"github.com/google/subcommands"
+	"gvisor.googlesource.com/gvisor/pkg/log"
+	"gvisor.googlesource.com/gvisor/pkg/p9"
+	"gvisor.googlesource.com/gvisor/pkg/unet"
+	"gvisor.googlesource.com/gvisor/runsc/fsgofer"
+	"gvisor.googlesource.com/gvisor/runsc/specutils"
+)
+
+// Gofer implements subcommands.Command for the "gofer" command, which starts a
+// filesystem gofer.  This command should not be called directly.
+type Gofer struct {
+	bundleDir string
+	ioFDs     intFlags
+}
+
+// Name implements subcommands.Command.
+func (*Gofer) Name() string {
+	return "gofer"
+}
+
+// Synopsis implements subcommands.Command.
+func (*Gofer) Synopsis() string {
+	return "launch a gofer process that server files over 9P protocol (internal use only)"
+}
+
+// Usage implements subcommands.Command.
+func (*Gofer) Usage() string {
+	return `gofer [flags]`
+}
+
+// SetFlags implements subcommands.Command.
+func (g *Gofer) SetFlags(f *flag.FlagSet) {
+	f.StringVar(&g.bundleDir, "bundle", "", "path to the root of the bundle directory, defaults to the current directory")
+	f.Var(&g.ioFDs, "io-fds", "list of FDs to connect 9P servers. They must follow this order: root first, then mounts as defined in the spec")
+}
+
+// Execute implements subcommands.Command.
+func (g *Gofer) Execute(_ context.Context, f *flag.FlagSet, args ...interface{}) subcommands.ExitStatus {
+	if g.bundleDir == "" || len(g.ioFDs) < 1 {
+		f.Usage()
+		return subcommands.ExitUsageError
+	}
+
+	spec, err := specutils.ReadSpec(g.bundleDir)
+	if err != nil {
+		Fatalf("error reading spec: %v", err)
+	}
+	specutils.LogSpec(spec)
+
+	// Start with root mount, then add any other addition mount as needed.
+	ats := make([]p9.Attacher, 0, len(spec.Mounts)+1)
+	p := absPath(g.bundleDir, spec.Root.Path)
+	ats = append(ats, fsgofer.NewAttachPoint(p, fsgofer.Config{
+		ROMount: spec.Root.Readonly,
+		// Docker uses overlay2 by default for the root mount, and overlay2 does a copy-up when
+		// each file is opened as writable. Thus, we open files lazily to avoid copy-up.
+		LazyOpenForWrite: true,
+	}))
+	log.Infof("Serving %q mapped to %q on FD %d", "/", p, g.ioFDs[0])
+
+	mountIdx := 1 // first one is the root
+	for _, m := range spec.Mounts {
+		if specutils.Is9PMount(m) {
+			p = absPath(g.bundleDir, m.Source)
+			ats = append(ats, fsgofer.NewAttachPoint(p, fsgofer.Config{
+				ROMount:          isReadonlyMount(m.Options),
+				LazyOpenForWrite: false,
+			}))
+
+			if mountIdx >= len(g.ioFDs) {
+				Fatalf("No FD found for mount. Did you forget --io-fd? mount: %d, %v", len(g.ioFDs), m)
+			}
+			log.Infof("Serving %q mapped to %q on FD %d", m.Destination, p, g.ioFDs[mountIdx])
+			mountIdx++
+		}
+	}
+	if mountIdx != len(g.ioFDs) {
+		Fatalf("Too many FDs passed for mounts. mounts: %d, FDs: %d", mountIdx, len(g.ioFDs))
+	}
+
+	runServers(ats, g.ioFDs)
+	return subcommands.ExitSuccess
+}
+
+func runServers(ats []p9.Attacher, ioFDs []int) {
+	// Run the loops and wait for all to exit.
+	var wg sync.WaitGroup
+	for i, ioFD := range ioFDs {
+		wg.Add(1)
+		go func(ioFD int, at p9.Attacher) {
+			socket, err := unet.NewSocket(ioFD)
+			if err != nil {
+				Fatalf("err creating server on FD %d: %v", ioFD, err)
+			}
+			s := p9.NewServer(at)
+			if err := s.Handle(socket); err != nil {
+				Fatalf("P9 server returned error. Gofer is shutting down. FD: %d, err: %v", ioFD, err)
+			}
+			wg.Done()
+		}(ioFD, ats[i])
+	}
+	wg.Wait()
+	log.Infof("All 9P servers exited.")
+}
+
+func isReadonlyMount(opts []string) bool {
+	for _, o := range opts {
+		if o == "ro" {
+			return true
+		}
+	}
+	return false
+}