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cmd/tailscale/cli: add bind-address and bind-port flags to netcheck command (#18621)

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Add more explicit `--bind-address` and `--bind-port` flags to the `tailscale netcheck` CLI to give users control over UDP probes' source IP and UDP port.

This was already supported in a less documented manner via the` TS_DEBUG_NETCHECK_UDP_BIND` environment variable. The environment variable reference is preserved and used as a fallback value in the absence of these new CLI flags.

Updates tailscale/corp#36833

Signed-off-by: Amal Bansode <amal@tailscale.com>
This commit is contained in:
Amal Bansode
2026-02-19 11:39:16 -08:00
committed by GitHub
parent 9e31a68547
commit c38d1badba
2 changed files with 184 additions and 11 deletions
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87
cmd/tailscale/cli/netcheck.go
View File

@@ -10,7 +10,9 @@
"fmt"
"io"
"log"
"math"
"net/http"
"net/netip"
"sort"
"strings"
"time"
@@ -26,6 +28,7 @@
"tailscale.com/tailcfg"
"tailscale.com/types/logger"
"tailscale.com/util/eventbus"
"tailscale.com/util/set"
// The "netcheck" command also wants the portmapper linked.
//
@@ -41,19 +44,25 @@
ShortUsage: "tailscale netcheck",
ShortHelp: "Print an analysis of local network conditions",
Exec: runNetcheck,
FlagSet: (func() *flag.FlagSet {
fs := newFlagSet("netcheck")
fs.StringVar(&netcheckArgs.format, "format", "", `output format; empty (for human-readable), "json" or "json-line"`)
fs.DurationVar(&netcheckArgs.every, "every", 0, "if non-zero, do an incremental report with the given frequency")
fs.BoolVar(&netcheckArgs.verbose, "verbose", false, "verbose logs")
return fs
})(),
FlagSet: netcheckFlagSet,
}
var netcheckFlagSet = func() *flag.FlagSet {
fs := newFlagSet("netcheck")
fs.StringVar(&netcheckArgs.format, "format", "", `output format; empty (for human-readable), "json" or "json-line"`)
fs.DurationVar(&netcheckArgs.every, "every", 0, "if non-zero, do an incremental report with the given frequency")
fs.BoolVar(&netcheckArgs.verbose, "verbose", false, "verbose logs")
fs.StringVar(&netcheckArgs.bindAddress, "bind-address", "", "send and receive connectivity probes using this locally bound IP address; default: OS-assigned")
fs.IntVar(&netcheckArgs.bindPort, "bind-port", 0, "send and receive connectivity probes using this UDP port; default: OS-assigned")
return fs
}()
var netcheckArgs struct {
format string
every time.Duration
verbose bool
format string
every time.Duration
verbose bool
bindAddress string
bindPort int
}
func runNetcheck(ctx context.Context, args []string) error {
@@ -73,6 +82,11 @@ func runNetcheck(ctx context.Context, args []string) error {
defer pm.Close()
}
flagsProvided := set.Set[string]{}
netcheckFlagSet.Visit(func(f *flag.Flag) {
flagsProvided.Add(f.Name)
})
c := &netcheck.Client{
NetMon: netMon,
PortMapper: pm,
@@ -89,7 +103,17 @@ func runNetcheck(ctx context.Context, args []string) error {
fmt.Fprintln(Stderr, "# Warning: this JSON format is not yet considered a stable interface")
}
if err := c.Standalone(ctx, envknob.String("TS_DEBUG_NETCHECK_UDP_BIND")); err != nil {
bind, err := createNetcheckBindString(
netcheckArgs.bindAddress,
flagsProvided.Contains("bind-address"),
netcheckArgs.bindPort,
flagsProvided.Contains("bind-port"),
envknob.String("TS_DEBUG_NETCHECK_UDP_BIND"))
if err != nil {
return err
}
if err := c.Standalone(ctx, bind); err != nil {
fmt.Fprintln(Stderr, "netcheck: UDP test failure:", err)
}
@@ -265,3 +289,44 @@ func prodDERPMap(ctx context.Context, httpc *http.Client) (*tailcfg.DERPMap, err
}
return &derpMap, nil
}
// createNetcheckBindString determines the netcheck socket bind "address:port" string based
// on the CLI args and environment variable values used to invoke the netcheck CLI.
// Arguments cliAddressIsSet and cliPortIsSet explicitly indicate whether the
// corresponding cliAddress and cliPort were set in CLI args, instead of relying
// on in-band sentinel values.
func createNetcheckBindString(cliAddress string, cliAddressIsSet bool, cliPort int, cliPortIsSet bool, envBind string) (string, error) {
// Default to port number 0 but overwrite with a valid CLI value, if set.
var port uint16 = 0
if cliPortIsSet {
// 0 is valid, results in OS picking port.
if cliPort >= 0 && cliPort <= math.MaxUint16 {
port = uint16(cliPort)
} else {
return "", fmt.Errorf("invalid bind port number: %d", cliPort)
}
}
// Use CLI address, if set.
if cliAddressIsSet {
addr, err := netip.ParseAddr(cliAddress)
if err != nil {
return "", fmt.Errorf("invalid bind address: %q", cliAddress)
}
return netip.AddrPortFrom(addr, port).String(), nil
} else {
// No CLI address set, but port is set.
if cliPortIsSet {
return fmt.Sprintf(":%d", port), nil
}
}
// Fall back to the environment variable.
// Intentionally skipping input validation here to avoid breaking legacy usage method.
if envBind != "" {
return envBind, nil
}
// OS picks both address and port.
return ":0", nil
}

108
cmd/tailscale/cli/netcheck_test.go Normal file
View File

@@ -0,0 +1,108 @@
// Copyright (c) Tailscale Inc & contributors
// SPDX-License-Identifier: BSD-3-Clause
package cli
import (
"testing"
)
func TestCreateBindStr(t *testing.T) {
// Test all combinations of CLI arg address, CLI arg port, and env var string
// as inputs to create netcheck bind string.
tests := []struct {
name string
cliAddress string
cliAddressIsSet bool
cliPort int
cliPortIsSet bool
envBind string
want string
wantError string
}{
{
name: "noAddr-noPort-noEnv",
want: ":0",
},
{
name: "yesAddrv4-noPort-noEnv",
cliAddress: "100.123.123.123",
cliAddressIsSet: true,
want: "100.123.123.123:0",
},
{
name: "yesAddrv6-noPort-noEnv",
cliAddress: "dead::beef",
cliAddressIsSet: true,
want: "[dead::beef]:0",
},
{
name: "yesAddr-yesPort-noEnv",
cliAddress: "100.123.123.123",
cliAddressIsSet: true,
cliPort: 456,
cliPortIsSet: true,
want: "100.123.123.123:456",
},
{
name: "yesAddr-yesPort-yesEnv",
cliAddress: "100.123.123.123",
cliAddressIsSet: true,
cliPort: 456,
cliPortIsSet: true,
envBind: "55.55.55.55:789",
want: "100.123.123.123:456",
},
{
name: "noAddr-yesPort-noEnv",
cliPort: 456,
cliPortIsSet: true,
want: ":456",
},
{
name: "noAddr-yesPort-yesEnv",
cliPort: 456,
cliPortIsSet: true,
envBind: "55.55.55.55:789",
want: ":456",
},
{
name: "noAddr-noPort-yesEnv",
envBind: "55.55.55.55:789",
want: "55.55.55.55:789",
},
{
name: "badAddr-noPort-noEnv-1",
cliAddress: "678.678.678.678",
cliAddressIsSet: true,
wantError: `invalid bind address: "678.678.678.678"`,
},
{
name: "badAddr-noPort-noEnv-2",
cliAddress: "lorem ipsum",
cliAddressIsSet: true,
wantError: `invalid bind address: "lorem ipsum"`,
},
{
name: "noAddr-badPort-noEnv",
cliPort: -1,
cliPortIsSet: true,
wantError: "invalid bind port number: -1",
},
}
for _, tt := range tests {
t.Run(tt.name, func(t *testing.T) {
got, gotErr := createNetcheckBindString(tt.cliAddress, tt.cliAddressIsSet, tt.cliPort, tt.cliPortIsSet, tt.envBind)
var gotErrStr string
if gotErr != nil {
gotErrStr = gotErr.Error()
}
if gotErrStr != tt.wantError {
t.Errorf("got error %q; want error %q", gotErrStr, tt.wantError)
}
if got != tt.want {
t.Errorf("got result %q; want result %q", got, tt.want)
}
})
}
}