TheArchive/tailscale
1
0
Fork 0
mirror of https://github.com/tailscale/tailscale.git synced 2025-08-20 01:47:33 +00:00
Code Issues Packages Projects Releases Wiki Activity

cmd/natc: add a flag to use specific DNS servers

Browse Source 
If natc is running on a host with tailscale using `--accept-dns=true`
then a DNS loop can occur. Provide a flag for some specific DNS
upstreams for natc to use instead, to overcome such situations.

Updates #14667

Signed-off-by: James Tucker <james@tailscale.com>
This commit is contained in:
James Tucker
2025-06-16 10:27:00 -07:00
committed by James Tucker
parent 735f15cb49
commit 86985228bc
2 changed files with 225 additions and 2 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
cmd/natc/natc.go
View File

@@ -54,6 +54,7 @@ func main() {
hostname = fs.String("hostname", "", "Hostname to register the service under")
siteID = fs.Uint("site-id", 1, "an integer site ID to use for the ULA prefix which allows for multiple proxies to act in a HA configuration")
v4PfxStr = fs.String("v4-pfx", "100.64.1.0/24", "comma-separated list of IPv4 prefixes to advertise")
dnsServers = fs.String("dns-servers", "", "comma separated list of upstream DNS to use, including host and port (use system if empty)")
verboseTSNet = fs.Bool("verbose-tsnet", false, "enable verbose logging in tsnet")
printULA = fs.Bool("print-ula", false, "print the ULA prefix and exit")
ignoreDstPfxStr = fs.String("ignore-destinations", "", "comma-separated list of prefixes to ignore")
@@ -78,7 +79,7 @@ func main() {
}
var ignoreDstTable *bart.Table[bool]
for _, s := range strings.Split(*ignoreDstPfxStr, ",") {
for s := range strings.SplitSeq(*ignoreDstPfxStr, ",") {
s := strings.TrimSpace(s)
if s == "" {
continue
@@ -185,11 +186,37 @@ func main() {
ipPool: ipp,
routes: routes,
dnsAddr: dnsAddr,
resolver: net.DefaultResolver,
resolver: getResolver(*dnsServers),
}
c.run(ctx, lc)
}
// getResolver parses serverFlag and returns either the default resolver, or a
// resolver that uses the provided comma-separated DNS server AddrPort's, or
// panics.
func getResolver(serverFlag string) lookupNetIPer {
if serverFlag == "" {
return net.DefaultResolver
}
var addrs []string
for s := range strings.SplitSeq(serverFlag, ",") {
s = strings.TrimSpace(s)
addr, err := netip.ParseAddrPort(s)
if err != nil {
log.Fatalf("dns server provided: %q does not parse: %v", s, err)
}
addrs = append(addrs, addr.String())
}
return &net.Resolver{
PreferGo: true,
Dial: func(ctx context.Context, network string, address string) (net.Conn, error) {
var dialer net.Dialer
// TODO(raggi): perhaps something other than random?
return dialer.DialContext(ctx, network, addrs[rand.N(len(addrs))])
},
}
}
func calculateAddresses(prefixes []netip.Prefix) (*netipx.IPSet, netip.Addr, *netipx.IPSet) {
var ipsb netipx.IPSetBuilder
for _, p := range prefixes {