TUN-8861: Add session limiter to UDP session manager

## Summary
In order to make cloudflared behavior more predictable and
prevent an exhaustion of resources, we have decided to add
session limits that can be configured by the user. This first
commit introduces the session limiter and adds it to the UDP
handling path. For now the limiter is set to run only in
unlimited mode.

vendor/golang.org/x/tools/go/internal/packagesdriver/sizes.go

@@ -13,6 +13,7 @@ import (
 	"golang.org/x/tools/internal/gocommand"
 )
 
+// TODO(adonovan): move back into go/packages.
 func GetSizesForArgsGolist(ctx context.Context, inv gocommand.Invocation, gocmdRunner *gocommand.Runner) (string, string, error) {
 	inv.Verb = "list"
 	inv.Args = []string{"-f", "{{context.GOARCH}} {{context.Compiler}}", "--", "unsafe"}

vendor/golang.org/x/tools/go/packages/doc.go

@@ -198,14 +198,6 @@ Instead, ssadump no longer requests the runtime package,
 but seeks it among the dependencies of the user-specified packages,
 and emits an error if it is not found.
 
-Overlays: The Overlay field in the Config allows providing alternate contents
-for Go source files, by providing a mapping from file path to contents.
-go/packages will pull in new imports added in overlay files when go/packages
-is run in LoadImports mode or greater.
-Overlay support for the go list driver isn't complete yet: if the file doesn't
-exist on disk, it will only be recognized in an overlay if it is a non-test file
-and the package would be reported even without the overlay.
-
 Questions & Tasks
 
 - Add GOARCH/GOOS?

vendor/golang.org/x/tools/go/packages/external.go

@@ -34,8 +34,8 @@ type DriverRequest struct {
 	// Tests specifies whether the patterns should also return test packages.
 	Tests bool `json:"tests"`
 
-	// Overlay maps file paths (relative to the driver's working directory) to the byte contents
-	// of overlay files.
+	// Overlay maps file paths (relative to the driver's working directory)
+	// to the contents of overlay files (see Config.Overlay).
 	Overlay map[string][]byte `json:"overlay"`
 }
 
@@ -119,7 +119,19 @@ func findExternalDriver(cfg *Config) driver {
 		stderr := new(bytes.Buffer)
 		cmd := exec.CommandContext(cfg.Context, tool, words...)
 		cmd.Dir = cfg.Dir
-		cmd.Env = cfg.Env
+		// The cwd gets resolved to the real path. On Darwin, where
+		// /tmp is a symlink, this breaks anything that expects the
+		// working directory to keep the original path, including the
+		// go command when dealing with modules.
+		//
+		// os.Getwd stdlib has a special feature where if the
+		// cwd and the PWD are the same node then it trusts
+		// the PWD, so by setting it in the env for the child
+		// process we fix up all the paths returned by the go
+		// command.
+		//
+		// (See similar trick in Invocation.run in ../../internal/gocommand/invoke.go)
+		cmd.Env = append(slicesClip(cfg.Env), "PWD="+cfg.Dir)
 		cmd.Stdin = bytes.NewReader(req)
 		cmd.Stdout = buf
 		cmd.Stderr = stderr
@@ -138,3 +150,7 @@ func findExternalDriver(cfg *Config) driver {
 		return &response, nil
 	}
 }
+
+// slicesClip removes unused capacity from the slice, returning s[:len(s):len(s)].
+// TODO(adonovan): use go1.21 slices.Clip.
+func slicesClip[S ~[]E, E any](s S) S { return s[:len(s):len(s)] }

vendor/golang.org/x/tools/go/packages/golist.go

@@ -841,6 +841,7 @@ func (state *golistState) cfgInvocation() gocommand.Invocation {
 		Env:        cfg.Env,
 		Logf:       cfg.Logf,
 		WorkingDir: cfg.Dir,
+		Overlay:    cfg.goListOverlayFile,
 	}
 }
 
@@ -849,26 +850,6 @@ func (state *golistState) invokeGo(verb string, args ...string) (*bytes.Buffer,
 	cfg := state.cfg
 
 	inv := state.cfgInvocation()
-
-	// For Go versions 1.16 and above, `go list` accepts overlays directly via
-	// the -overlay flag. Set it, if it's available.
-	//
-	// The check for "list" is not necessarily required, but we should avoid
-	// getting the go version if possible.
-	if verb == "list" {
-		goVersion, err := state.getGoVersion()
-		if err != nil {
-			return nil, err
-		}
-		if goVersion >= 16 {
-			filename, cleanup, err := state.writeOverlays()
-			if err != nil {
-				return nil, err
-			}
-			defer cleanup()
-			inv.Overlay = filename
-		}
-	}
 	inv.Verb = verb
 	inv.Args = args
 	gocmdRunner := cfg.gocmdRunner
@@ -1015,67 +996,6 @@ func (state *golistState) invokeGo(verb string, args ...string) (*bytes.Buffer,
 	return stdout, nil
 }
 
-// OverlayJSON is the format overlay files are expected to be in.
-// The Replace map maps from overlaid paths to replacement paths:
-// the Go command will forward all reads trying to open
-// each overlaid path to its replacement path, or consider the overlaid
-// path not to exist if the replacement path is empty.
-//
-// From golang/go#39958.
-type OverlayJSON struct {
-	Replace map[string]string `json:"replace,omitempty"`
-}
-
-// writeOverlays writes out files for go list's -overlay flag, as described
-// above.
-func (state *golistState) writeOverlays() (filename string, cleanup func(), err error) {
-	// Do nothing if there are no overlays in the config.
-	if len(state.cfg.Overlay) == 0 {
-		return "", func() {}, nil
-	}
-	dir, err := os.MkdirTemp("", "gopackages-*")
-	if err != nil {
-		return "", nil, err
-	}
-	// The caller must clean up this directory, unless this function returns an
-	// error.
-	cleanup = func() {
-		os.RemoveAll(dir)
-	}
-	defer func() {
-		if err != nil {
-			cleanup()
-		}
-	}()
-	overlays := map[string]string{}
-	for k, v := range state.cfg.Overlay {
-		// Create a unique filename for the overlaid files, to avoid
-		// creating nested directories.
-		noSeparator := strings.Join(strings.Split(filepath.ToSlash(k), "/"), "")
-		f, err := os.CreateTemp(dir, fmt.Sprintf("*-%s", noSeparator))
-		if err != nil {
-			return "", func() {}, err
-		}
-		if _, err := f.Write(v); err != nil {
-			return "", func() {}, err
-		}
-		if err := f.Close(); err != nil {
-			return "", func() {}, err
-		}
-		overlays[k] = f.Name()
-	}
-	b, err := json.Marshal(OverlayJSON{Replace: overlays})
-	if err != nil {
-		return "", func() {}, err
-	}
-	// Write out the overlay file that contains the filepath mappings.
-	filename = filepath.Join(dir, "overlay.json")
-	if err := os.WriteFile(filename, b, 0665); err != nil {
-		return "", func() {}, err
-	}
-	return filename, cleanup, nil
-}
-
 func containsGoFile(s []string) bool {
 	for _, f := range s {
 		if strings.HasSuffix(f, ".go") {

vendor/golang.org/x/tools/go/packages/packages.go

@@ -37,10 +37,20 @@ import (
 // A LoadMode controls the amount of detail to return when loading.
 // The bits below can be combined to specify which fields should be
 // filled in the result packages.
+//
 // The zero value is a special case, equivalent to combining
 // the NeedName, NeedFiles, and NeedCompiledGoFiles bits.
+//
 // ID and Errors (if present) will always be filled.
-// Load may return more information than requested.
+// [Load] may return more information than requested.
+//
+// Unfortunately there are a number of open bugs related to
+// interactions among the LoadMode bits:
+// - https://github.com/golang/go/issues/48226
+// - https://github.com/golang/go/issues/56633
+// - https://github.com/golang/go/issues/56677
+// - https://github.com/golang/go/issues/58726
+// - https://github.com/golang/go/issues/63517
 type LoadMode int
 
 const (
@@ -123,7 +133,14 @@ const (
 
 // A Config specifies details about how packages should be loaded.
 // The zero value is a valid configuration.
+//
 // Calls to Load do not modify this struct.
+//
+// TODO(adonovan): #67702: this is currently false: in fact,
+// calls to [Load] do not modify the public fields of this struct, but
+// may modify hidden fields, so concurrent calls to [Load] must not
+// use the same Config. But perhaps we should reestablish the
+// documented invariant.
 type Config struct {
 	// Mode controls the level of information returned for each package.
 	Mode LoadMode
@@ -199,13 +216,23 @@ type Config struct {
 	// setting Tests may have no effect.
 	Tests bool
 
-	// Overlay provides a mapping of absolute file paths to file contents.
-	// If the file with the given path already exists, the parser will use the
-	// alternative file contents provided by the map.
+	// Overlay is a mapping from absolute file paths to file contents.
 	//
-	// Overlays provide incomplete support for when a given file doesn't
-	// already exist on disk. See the package doc above for more details.
+	// For each map entry, [Load] uses the alternative file
+	// contents provided by the overlay mapping instead of reading
+	// from the file system. This mechanism can be used to enable
+	// editor-integrated tools to correctly analyze the contents
+	// of modified but unsaved buffers, for example.
+	//
+	// The overlay mapping is passed to the build system's driver
+	// (see "The driver protocol") so that it too can report
+	// consistent package metadata about unsaved files. However,
+	// drivers may vary in their level of support for overlays.
 	Overlay map[string][]byte
+
+	// goListOverlayFile is the JSON file that encodes the Overlay
+	// mapping, used by 'go list -overlay=...'
+	goListOverlayFile string
 }
 
 // Load loads and returns the Go packages named by the given patterns.
@@ -213,6 +240,20 @@ type Config struct {
 // Config specifies loading options;
 // nil behaves the same as an empty Config.
 //
+// The [Config.Mode] field is a set of bits that determine what kinds
+// of information should be computed and returned. Modes that require
+// more information tend to be slower. See [LoadMode] for details
+// and important caveats. Its zero value is equivalent to
+// NeedName | NeedFiles | NeedCompiledGoFiles.
+//
+// Each call to Load returns a new set of [Package] instances.
+// The Packages and their Imports form a directed acyclic graph.
+//
+// If the [NeedTypes] mode flag was set, each call to Load uses a new
+// [types.Importer], so [types.Object] and [types.Type] values from
+// different calls to Load must not be mixed as they will have
+// inconsistent notions of type identity.
+//
 // If any of the patterns was invalid as defined by the
 // underlying build system, Load returns an error.
 // It may return an empty list of packages without an error,
@@ -286,6 +327,17 @@ func defaultDriver(cfg *Config, patterns ...string) (*DriverResponse, bool, erro
 		// (fall through)
 	}
 
+	// go list fallback
+	//
+	// Write overlays once, as there are many calls
+	// to 'go list' (one per chunk plus others too).
+	overlay, cleanupOverlay, err := gocommand.WriteOverlays(cfg.Overlay)
+	if err != nil {
+		return nil, false, err
+	}
+	defer cleanupOverlay()
+	cfg.goListOverlayFile = overlay
+
 	response, err := callDriverOnChunks(goListDriver, cfg, chunks)
 	if err != nil {
 		return nil, false, err
@@ -365,6 +417,9 @@ func mergeResponses(responses ...*DriverResponse) *DriverResponse {
 }
 
 // A Package describes a loaded Go package.
+//
+// It also defines part of the JSON schema of [DriverResponse].
+// See the package documentation for an overview.
 type Package struct {
 	// ID is a unique identifier for a package,
 	// in a syntax provided by the underlying build system.
@@ -423,6 +478,13 @@ type Package struct {
 	// to corresponding loaded Packages.
 	Imports map[string]*Package
 
+	// Module is the module information for the package if it exists.
+	//
+	// Note: it may be missing for std and cmd; see Go issue #65816.
+	Module *Module
+
+	// -- The following fields are not part of the driver JSON schema. --
+
 	// Types provides type information for the package.
 	// The NeedTypes LoadMode bit sets this field for packages matching the
 	// patterns; type information for dependencies may be missing or incomplete,
@@ -431,15 +493,15 @@ type Package struct {
 	// Each call to [Load] returns a consistent set of type
 	// symbols, as defined by the comment at [types.Identical].
 	// Avoid mixing type information from two or more calls to [Load].
-	Types *types.Package
+	Types *types.Package `json:"-"`
 
 	// Fset provides position information for Types, TypesInfo, and Syntax.
 	// It is set only when Types is set.
-	Fset *token.FileSet
+	Fset *token.FileSet `json:"-"`
 
 	// IllTyped indicates whether the package or any dependency contains errors.
 	// It is set only when Types is set.
-	IllTyped bool
+	IllTyped bool `json:"-"`
 
 	// Syntax is the package's syntax trees, for the files listed in CompiledGoFiles.
 	//
@@ -449,26 +511,28 @@ type Package struct {
 	//
 	// Syntax is kept in the same order as CompiledGoFiles, with the caveat that nils are
 	// removed.  If parsing returned nil, Syntax may be shorter than CompiledGoFiles.
-	Syntax []*ast.File
+	Syntax []*ast.File `json:"-"`
 
 	// TypesInfo provides type information about the package's syntax trees.
 	// It is set only when Syntax is set.
-	TypesInfo *types.Info
+	TypesInfo *types.Info `json:"-"`
 
 	// TypesSizes provides the effective size function for types in TypesInfo.
-	TypesSizes types.Sizes
+	TypesSizes types.Sizes `json:"-"`
+
+	// -- internal --
 
 	// forTest is the package under test, if any.
 	forTest string
 
 	// depsErrors is the DepsErrors field from the go list response, if any.
 	depsErrors []*packagesinternal.PackageError
-
-	// module is the module information for the package if it exists.
-	Module *Module
 }
 
 // Module provides module information for a package.
+//
+// It also defines part of the JSON schema of [DriverResponse].
+// See the package documentation for an overview.
 type Module struct {
 	Path      string       // module path
 	Version   string       // module version
@@ -601,6 +665,7 @@ func (p *Package) UnmarshalJSON(b []byte) error {
 		OtherFiles:      flat.OtherFiles,
 		EmbedFiles:      flat.EmbedFiles,
 		EmbedPatterns:   flat.EmbedPatterns,
+		IgnoredFiles:    flat.IgnoredFiles,
 		ExportFile:      flat.ExportFile,
 	}
 	if len(flat.Imports) > 0 {

vendor/golang.org/x/tools/internal/gocommand/invoke.go

@@ -8,12 +8,14 @@ package gocommand
 import (
 	"bytes"
 	"context"
+	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
 	"log"
 	"os"
 	"os/exec"
+	"path/filepath"
 	"reflect"
 	"regexp"
 	"runtime"
@@ -167,7 +169,9 @@ type Invocation struct {
 	// TODO(rfindley): remove, in favor of Args.
 	ModFile string
 
-	// If Overlay is set, the go command is invoked with -overlay=Overlay.
+	// Overlay is the name of the JSON overlay file that describes
+	// unsaved editor buffers; see [WriteOverlays].
+	// If set, the go command is invoked with -overlay=Overlay.
 	// TODO(rfindley): remove, in favor of Args.
 	Overlay string
 
@@ -255,12 +259,15 @@ func (i *Invocation) run(ctx context.Context, stdout, stderr io.Writer) error {
 		waitDelay.Set(reflect.ValueOf(30 * time.Second))
 	}
 
-	// On darwin the cwd gets resolved to the real path, which breaks anything that
-	// expects the working directory to keep the original path, including the
+	// The cwd gets resolved to the real path. On Darwin, where
+	// /tmp is a symlink, this breaks anything that expects the
+	// working directory to keep the original path, including the
 	// go command when dealing with modules.
-	// The Go stdlib has a special feature where if the cwd and the PWD are the
-	// same node then it trusts the PWD, so by setting it in the env for the child
-	// process we fix up all the paths returned by the go command.
+	//
+	// os.Getwd has a special feature where if the cwd and the PWD
+	// are the same node then it trusts the PWD, so by setting it
+	// in the env for the child process we fix up all the paths
+	// returned by the go command.
 	if !i.CleanEnv {
 		cmd.Env = os.Environ()
 	}
@@ -351,6 +358,7 @@ func runCmdContext(ctx context.Context, cmd *exec.Cmd) (err error) {
 		}
 	}
 
+	startTime := time.Now()
 	err = cmd.Start()
 	if stdoutW != nil {
 		// The child process has inherited the pipe file,
@@ -377,7 +385,7 @@ func runCmdContext(ctx context.Context, cmd *exec.Cmd) (err error) {
 		case err := <-resChan:
 			return err
 		case <-timer.C:
-			HandleHangingGoCommand(cmd.Process)
+			HandleHangingGoCommand(startTime, cmd)
 		case <-ctx.Done():
 		}
 	} else {
@@ -411,7 +419,7 @@ func runCmdContext(ctx context.Context, cmd *exec.Cmd) (err error) {
 	return <-resChan
 }
 
-func HandleHangingGoCommand(proc *os.Process) {
+func HandleHangingGoCommand(start time.Time, cmd *exec.Cmd) {
 	switch runtime.GOOS {
 	case "linux", "darwin", "freebsd", "netbsd":
 		fmt.Fprintln(os.Stderr, `DETECTED A HANGING GO COMMAND
@@ -444,7 +452,7 @@ See golang/go#54461 for more details.`)
 			panic(fmt.Sprintf("running %s: %v", listFiles, err))
 		}
 	}
-	panic(fmt.Sprintf("detected hanging go command (pid %d): see golang/go#54461 for more details", proc.Pid))
+	panic(fmt.Sprintf("detected hanging go command (golang/go#54461); waited %s\n\tcommand:%s\n\tpid:%d", time.Since(start), cmd, cmd.Process.Pid))
 }
 
 func cmdDebugStr(cmd *exec.Cmd) string {
@@ -468,3 +476,73 @@ func cmdDebugStr(cmd *exec.Cmd) string {
 	}
 	return fmt.Sprintf("GOROOT=%v GOPATH=%v GO111MODULE=%v GOPROXY=%v PWD=%v %v", env["GOROOT"], env["GOPATH"], env["GO111MODULE"], env["GOPROXY"], env["PWD"], strings.Join(args, " "))
 }
+
+// WriteOverlays writes each value in the overlay (see the Overlay
+// field of go/packages.Config) to a temporary file and returns the name
+// of a JSON file describing the mapping that is suitable for the "go
+// list -overlay" flag.
+//
+// On success, the caller must call the cleanup function exactly once
+// when the files are no longer needed.
+func WriteOverlays(overlay map[string][]byte) (filename string, cleanup func(), err error) {
+	// Do nothing if there are no overlays in the config.
+	if len(overlay) == 0 {
+		return "", func() {}, nil
+	}
+
+	dir, err := os.MkdirTemp("", "gocommand-*")
+	if err != nil {
+		return "", nil, err
+	}
+
+	// The caller must clean up this directory,
+	// unless this function returns an error.
+	// (The cleanup operand of each return
+	// statement below is ignored.)
+	defer func() {
+		cleanup = func() {
+			os.RemoveAll(dir)
+		}
+		if err != nil {
+			cleanup()
+			cleanup = nil
+		}
+	}()
+
+	// Write each map entry to a temporary file.
+	overlays := make(map[string]string)
+	for k, v := range overlay {
+		// Use a unique basename for each file (001-foo.go),
+		// to avoid creating nested directories.
+		base := fmt.Sprintf("%d-%s.go", 1+len(overlays), filepath.Base(k))
+		filename := filepath.Join(dir, base)
+		err := os.WriteFile(filename, v, 0666)
+		if err != nil {
+			return "", nil, err
+		}
+		overlays[k] = filename
+	}
+
+	// Write the JSON overlay file that maps logical file names to temp files.
+	//
+	// OverlayJSON is the format overlay files are expected to be in.
+	// The Replace map maps from overlaid paths to replacement paths:
+	// the Go command will forward all reads trying to open
+	// each overlaid path to its replacement path, or consider the overlaid
+	// path not to exist if the replacement path is empty.
+	//
+	// From golang/go#39958.
+	type OverlayJSON struct {
+		Replace map[string]string `json:"replace,omitempty"`
+	}
+	b, err := json.Marshal(OverlayJSON{Replace: overlays})
+	if err != nil {
+		return "", nil, err
+	}
+	filename = filepath.Join(dir, "overlay.json")
+	if err := os.WriteFile(filename, b, 0666); err != nil {
+		return "", nil, err
+	}
+
+	return filename, nil, nil
+}

vendor/golang.org/x/tools/internal/imports/fix.go

@@ -104,7 +104,10 @@ type packageInfo struct {
 
 // parseOtherFiles parses all the Go files in srcDir except filename, including
 // test files if filename looks like a test.
-func parseOtherFiles(fset *token.FileSet, srcDir, filename string) []*ast.File {
+//
+// It returns an error only if ctx is cancelled. Files with parse errors are
+// ignored.
+func parseOtherFiles(ctx context.Context, fset *token.FileSet, srcDir, filename string) ([]*ast.File, error) {
 	// This could use go/packages but it doesn't buy much, and it fails
 	// with https://golang.org/issue/26296 in LoadFiles mode in some cases.
 	considerTests := strings.HasSuffix(filename, "_test.go")
@@ -112,11 +115,14 @@ func parseOtherFiles(fset *token.FileSet, srcDir, filename string) []*ast.File {
 	fileBase := filepath.Base(filename)
 	packageFileInfos, err := os.ReadDir(srcDir)
 	if err != nil {
-		return nil
+		return nil, ctx.Err()
 	}
 
 	var files []*ast.File
 	for _, fi := range packageFileInfos {
+		if ctx.Err() != nil {
+			return nil, ctx.Err()
+		}
 		if fi.Name() == fileBase || !strings.HasSuffix(fi.Name(), ".go") {
 			continue
 		}
@@ -132,7 +138,7 @@ func parseOtherFiles(fset *token.FileSet, srcDir, filename string) []*ast.File {
 		files = append(files, f)
 	}
 
-	return files
+	return files, ctx.Err()
 }
 
 // addGlobals puts the names of package vars into the provided map.
@@ -557,12 +563,7 @@ func (p *pass) addCandidate(imp *ImportInfo, pkg *packageInfo) {
 
 // fixImports adds and removes imports from f so that all its references are
 // satisfied and there are no unused imports.
-//
-// This is declared as a variable rather than a function so goimports can
-// easily be extended by adding a file with an init function.
-var fixImports = fixImportsDefault
-
-func fixImportsDefault(fset *token.FileSet, f *ast.File, filename string, env *ProcessEnv) error {
+func fixImports(fset *token.FileSet, f *ast.File, filename string, env *ProcessEnv) error {
 	fixes, err := getFixes(context.Background(), fset, f, filename, env)
 	if err != nil {
 		return err
@@ -592,7 +593,10 @@ func getFixes(ctx context.Context, fset *token.FileSet, f *ast.File, filename st
 		return fixes, nil
 	}
 
-	otherFiles := parseOtherFiles(fset, srcDir, filename)
+	otherFiles, err := parseOtherFiles(ctx, fset, srcDir, filename)
+	if err != nil {
+		return nil, err
+	}
 
 	// Second pass: add information from other files in the same package,
 	// like their package vars and imports.
@@ -1192,7 +1196,7 @@ func addExternalCandidates(ctx context.Context, pass *pass, refs references, fil
 	if err != nil {
 		return err
 	}
-	if err = resolver.scan(context.Background(), callback); err != nil {
+	if err = resolver.scan(ctx, callback); err != nil {
 		return err
 	}
 
@@ -1203,7 +1207,7 @@ func addExternalCandidates(ctx context.Context, pass *pass, refs references, fil
 	}
 	results := make(chan result, len(refs))
 
-	ctx, cancel := context.WithCancel(context.TODO())
+	ctx, cancel := context.WithCancel(ctx)
 	var wg sync.WaitGroup
 	defer func() {
 		cancel()

vendor/golang.org/x/tools/internal/versions/types_go122.go

@@ -12,7 +12,7 @@ import (
 	"go/types"
 )
 
-// FileVersions returns a file's Go version.
+// FileVersion returns a file's Go version.
 // The reported version is an unknown Future version if a
 // version cannot be determined.
 func FileVersion(info *types.Info, file *ast.File) string {