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cmd/tailscale: warn subnet route users if IP forwarding is off. #320

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Signed-off-by: David Anderson <danderson@tailscale.com>
This commit is contained in:
David Anderson 2020-05-11 06:07:48 +00:00
parent ad1cfe8bbe
commit 8b0be7475b
1 changed files with 25 additions and 0 deletions
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25
cmd/tailscale/tailscale.go
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@ -7,14 +7,17 @@
package main // import "tailscale.com/cmd/tailscale"
import (
"bytes"
"context"
"flag"
"fmt"
"io/ioutil"
"log"
"net"
"os"
"os/signal"
"runtime"
"strconv"
"strings"
"syscall"
@ -128,6 +131,27 @@ func parseIPOrCIDR(s string) (wgcfg.CIDR, bool) {
}
}
// checkIPForwarding prints warnings on linux if IP forwarding is not
// enabled, or if we were unable to verify the state of IP forwarding.
func checkIPForwarding() {
if runtime.GOOS != "linux" {
return
}
bs, err := ioutil.ReadFile("/proc/sys/net/ipv4/ip_forward")
if err != nil {
fmt.Printf("Warning: couldn't check if IP forwarding is enabled (%v). IP forwarding must be enabled for subnet routes to work.", err)
return
}
on, err := strconv.ParseBool(string(bytes.TrimSpace(bs)))
if err != nil {
fmt.Printf("Warning: couldn't check if IP forwarding is enabled (%v). IP forwarding must be enabled for subnet routes to work.", err)
return
}
if !on {
fmt.Printf("Warning: IP forwarding is disabled, subnet routes will not work.")
}
}
func runUp(ctx context.Context, args []string) error {
if len(args) > 0 {
log.Fatalf("too many non-flag arguments: %q", args)
@ -135,6 +159,7 @@ func runUp(ctx context.Context, args []string) error {
var routes []wgcfg.CIDR
if upArgs.advertiseRoutes != "" {
checkIPForwarding()
advroutes := strings.Split(upArgs.advertiseRoutes, ",")
for _, s := range advroutes {
cidr, ok := parseIPOrCIDR(s)