Fix documentation, clean up seccomp filter installation, rename helpers.

Filter installation has been streamlined and functions renamed. 
Documentation has been fixed to be standards compliant, and missing 
documentation added. gofmt has also been applied to modified files.

pkg/fd/fd.go

@@ -17,12 +17,12 @@ package fd
 
 import (
 	"fmt"
+	"gvisor.dev/gvisor/pkg/unet"
 	"io"
 	"os"
 	"runtime"
 	"sync/atomic"
 	"syscall"
-	"gvisor.dev/gvisor/pkg/unet"
 )
 
 // ReadWriter implements io.ReadWriter, io.ReaderAt, and io.WriterAt for fd. It
@@ -186,8 +186,8 @@ func OpenAt(dir *FD, path string, flags int, mode uint32) (*FD, error) {
 	return New(f), nil
 }
 
-// OpenUnix Open a Unix Domain Socket and return the file descriptor for it.
-func OpenUnix(path string) (*FD, error) {
+// DialUnix connects to a Unix Domain Socket and return the file descriptor.
+func DialUnix(path string) (*FD, error) {
 	socket, err := unet.Connect(path, false)
 	return New(socket.FD()), err
 }

runsc/boot/config.go

@@ -138,7 +138,7 @@ type Config struct {
 	// Overlay is whether to wrap the root filesystem in an overlay.
 	Overlay bool
 
-	// fsGoferHostUDSAllowed enables the gofer to mount a host UDS
+	// FSGoferHostUDSAllowed enables the gofer to mount a host UDS.
 	FSGoferHostUDSAllowed bool
 
 	// Network indicates what type of network to use.

runsc/cmd/gofer.go

@@ -204,13 +204,11 @@ func (g *Gofer) Execute(_ context.Context, f *flag.FlagSet, args ...interface{})
 	}
 
 	if g.hostUDSAllowed {
-		if err := filter.InstallUDS(); err != nil {
-			Fatalf("installing UDS seccomp filters: %v", err)
-		}
-	} else {
-		if err := filter.Install(); err != nil {
-			Fatalf("installing seccomp filters: %v", err)
-		}
+		filter.InstallUDSFilters()
+	}
+
+	if err := filter.Install(); err != nil {
+		Fatalf("installing seccomp filters: %v", err)
 	}
 
 	runServers(ats, g.ioFDs)

runsc/fsgofer/filter/filter.go

@@ -23,23 +23,16 @@ import (
 
 // Install installs seccomp filters.
 func Install() error {
-	s := allowedSyscalls
-
 	// Set of additional filters used by -race and -msan. Returns empty
 	// when not enabled.
-	s.Merge(instrumentationFilters())
+	allowedSyscalls.Merge(instrumentationFilters())
 
-	return seccomp.Install(s)
+	return seccomp.Install(allowedSyscalls)
 }
 
-// InstallUDS installs the standard Gofer seccomp filters along with filters
-// allowing the gofer to connect to a host UDS.
-func InstallUDS() error {
-	// Use the base syscall
-	s := allowedSyscalls
-
+// InstallUDSFilters installs the seccomp filters required to let the gofer connect
+// to a host UDS.
+func InstallUDSFilters() {
 	// Add additional filters required for connecting to the host's sockets.
-	s.Merge(udsSyscalls)
-
-	return seccomp.Install(s)
+	allowedSyscalls.Merge(udsSyscalls)
 }

runsc/fsgofer/fsgofer.go

@@ -21,6 +21,7 @@
 package fsgofer
 
 import (
+	"errors"
 	"fmt"
 	"io"
 	"math"
@@ -86,7 +87,7 @@ type Config struct {
 	// PanicOnWrite panics on attempts to write to RO mounts.
 	PanicOnWrite bool
 
-	// HostUDS prevents
+	// HostUDSAllowed signals whether the gofer can mount a host's UDS.
 	HostUDSAllowed bool
 }
 
@@ -131,23 +132,23 @@ func (a *attachPoint) Attach() (p9.File, error) {
 		return nil, fmt.Errorf("stat file %q, err: %v", a.prefix, err)
 	}
 
-	// Acquire the attach point lock
+	// Acquire the attach point lock.
 	a.attachedMu.Lock()
 	defer a.attachedMu.Unlock()
 
-	// Hold the file descriptor we are converting into a p9.File
+	// Hold the file descriptor we are converting into a p9.File.
 	var f *fd.FD
 
-	// Apply the S_IFMT bitmask so we can detect file type appropriately
-	switch fmtStat := stat.Mode & syscall.S_IFMT; {
-	case fmtStat == syscall.S_IFSOCK:
-		// Check to see if the CLI option has been set to allow the UDS mount
+	// Apply the S_IFMT bitmask so we can detect file type appropriately.
+	switch fmtStat := stat.Mode & syscall.S_IFMT; fmtStat {
+	case syscall.S_IFSOCK:
+		// Check to see if the CLI option has been set to allow the UDS mount.
 		if !a.conf.HostUDSAllowed {
-			return nil, fmt.Errorf("host UDS support is disabled")
+			return nil, errors.New("host UDS support is disabled")
 		}
 
 		// Attempt to open a connection. Bubble up the failures.
-		f, err = fd.OpenUnix(a.prefix)
+		f, err = fd.DialUnix(a.prefix)
 		if err != nil {
 			return nil, err
 		}
@@ -1058,7 +1059,7 @@ func (l *localFile) Flush() error {
 
 // Connect implements p9.File.
 func (l *localFile) Connect(p9.ConnectFlags) (*fd.FD, error) {
-	return fd.OpenUnix(l.hostPath)
+	return fd.DialUnix(l.hostPath)
 }
 
 // Close implements p9.File.