diff --git a/cmd/tailscaled/depaware.txt b/cmd/tailscaled/depaware.txt
index 5ecec59dd..2e18d1f9b 100644
--- a/cmd/tailscaled/depaware.txt
+++ b/cmd/tailscaled/depaware.txt
@@ -353,6 +353,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
hash/fnv from gvisor.dev/gvisor/pkg/tcpip/network/ipv6+
hash/maphash from go4.org/mem
html from net/http/pprof+
+ html/template from tailscale.com/tsweb
io from bufio+
io/fs from crypto/rand+
io/ioutil from github.com/aws/aws-sdk-go-v2/aws/protocol/query+
@@ -391,6 +392,8 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
sync/atomic from context+
syscall from crypto/rand+
text/tabwriter from runtime/pprof
+ text/template from html/template
+ text/template/parse from html/template+
time from compress/gzip+
unicode from bytes+
unicode/utf16 from crypto/x509+
diff --git a/tsweb/debug.go b/tsweb/debug.go
index 54fd188cb..39a3bb25c 100644
--- a/tsweb/debug.go
+++ b/tsweb/debug.go
@@ -6,14 +6,20 @@ package tsweb
import (
"expvar"
+ "flag"
"fmt"
"html"
+ "html/template"
"io"
+ "log"
"net/http"
"net/http/pprof"
"net/url"
"os"
"runtime"
+ "sort"
+ "strings"
+ "sync"
"tailscale.com/version"
)
@@ -33,6 +39,9 @@ type DebugHandler struct {
kvs []func(io.Writer) // output one ... each, see KV()
urls []string // one ... block with link each
sections []func(io.Writer, *http.Request) // invoked in registration order prior to outputting
+ flagmu sync.Mutex // flagmu protects access to flagset and flagc
+ flagset *flag.FlagSet // runtime-modifiable flags, may be nil
+ flagc chan map[string]interface{} // DebugHandler sends new flag values on flagc when the flags have been modified
}
// Debugger returns the DebugHandler registered on mux at /debug/,
@@ -139,3 +148,161 @@ func gcHandler(w http.ResponseWriter, r *http.Request) {
runtime.GC()
w.Write([]byte("Done.\n"))
}
+
+// FlagSet returns a FlagSet that can be used to add runtime-modifiable flags to d.
+// Calling code should add flags to fs, but not retain the values directly.
+// Modifications to fs will be delivered via c.
+// Maps sent to c will be keyed on the flag name, and contain the new value.
+// Only modified values will be sent on c.
+//
+// Sample usage:
+// flagset, flagc := debug.FlagSet()
+// flagset.Int("max", 0, "maximum number of bars")
+// flagset.String("s", "qux", "default name for new foos")
+// go func() {
+// for change := range flagc {
+// // TODO: handle change, which will contain values for keys "max" and/or "s"
+// }
+// }()
+func (d *DebugHandler) FlagSet() (fs *flag.FlagSet, c chan map[string]interface{}) {
+ d.flagmu.Lock()
+ defer d.flagmu.Unlock()
+ if d.flagset == nil {
+ d.flagset = flag.NewFlagSet("debug", flag.ContinueOnError)
+ d.flagc = make(chan map[string]interface{})
+ d.Handle("flags", "Runtime flags", http.HandlerFunc(d.handleFlags))
+ }
+ return d.flagset, d.flagc
+}
+
+type copiedFlag struct {
+ Name string
+ Value string
+ Usage string
+}
+
+func copyFlags(fs *flag.FlagSet) []copiedFlag {
+ var all []copiedFlag
+ fs.VisitAll(func(f *flag.Flag) {
+ all = append(all, copiedFlag{Name: f.Name, Value: f.Value.String(), Usage: f.Usage})
+ })
+ return all
+}
+
+func (d *DebugHandler) handleFlags(w http.ResponseWriter, r *http.Request) {
+ d.flagmu.Lock()
+ defer d.flagmu.Unlock()
+
+ var userError string
+ var modified string
+ if r.Method == http.MethodPost {
+ err := r.ParseForm()
+ if err != nil {
+ http.Error(w, err.Error(), http.StatusBadRequest)
+ return
+ }
+ // Make a copy of existing values, in case we need to roll back.
+ all := copyFlags(d.flagset)
+ // Set inbound values.
+ changed := make(map[string][2]string)
+ rollback := false
+ for k, v := range r.PostForm {
+ if len(v) != 1 {
+ userError = fmt.Sprintf("multiple values for name %q: %q", k, v)
+ rollback = true
+ break
+ }
+ f := d.flagset.Lookup(k)
+ if f == nil {
+ userError = fmt.Sprintf("unknown name %q", k)
+ rollback = true
+ break
+ }
+ prev := f.Value.String()
+ new := strings.TrimSpace(v[0])
+ if prev == new {
+ continue
+ }
+ err := d.flagset.Set(k, new)
+ if err != nil {
+ userError = fmt.Sprintf("parsing value %q for name %q: %v", new, k, err)
+ rollback = true
+ break
+ }
+ changed[k] = [2]string{prev, new}
+ }
+ if rollback {
+ for _, f := range all {
+ d.flagset.Set(f.Name, f.Value)
+ }
+ } else {
+ // Generate description of modifications.
+ var names []string
+ for k := range changed {
+ names = append(names, k)
+ }
+ sort.Strings(names)
+ buf := new(strings.Builder)
+ for i, k := range names {
+ if i != 0 {
+ buf.WriteString("; ")
+ }
+ pn := changed[k]
+ fmt.Fprintf(buf, "%q: %v → %v", k, pn[0], pn[1])
+ }
+ modified = buf.String()
+ vals := make(map[string]interface{})
+ for _, k := range names {
+ vals[k] = d.flagset.Lookup(k).Value.(flag.Getter).Get()
+ }
+
+ d.flagc <- vals
+ // TODO: post modifications to Slack, along with attribution
+ }
+ }
+
+ dot := &struct {
+ Error string
+ Modified string
+ Flags []copiedFlag
+ }{
+ Error: userError,
+ Modified: modified,
+ Flags: copyFlags(d.flagset),
+ }
+ err := flagsTemplate.Execute(w, dot)
+ if err != nil {
+ log.Print(err)
+ }
+}
+
+var (
+ flagsTemplate = template.Must(template.New("flags").Parse(`
+
+