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fix: run (Linux): rewrite child UDP/53 to <gateway>:53 in the daemon as belt-... #789

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fix: run (Linux): rewrite child UDP/53 to <gateway>:53 in the daemon as belt-... #789

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13 changes: 12 additions & 1 deletion cmd/clawpatrol/daemon_session_linux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -193,6 +193,17 @@ func newRunUDPProtocolHandler(s *stack.Stack, handler udp.ForwarderHandler) func
}
}

type udpDNSGateway interface {
udpDNSGatewayAddr() netip.Addr
}

func udpDialAddr(transport daemonTransport, dstIP string, dstPort uint16) string {
if gateway, ok := transport.(udpDNSGateway); ok && dstPort == 53 {
dstIP = gateway.udpDNSGatewayAddr().String()
}
return net.JoinHostPort(dstIP, strconv.Itoa(int(dstPort)))
}

func newTransportUDPProtocolHandler(ctx context.Context, s *stack.Stack, transport daemonTransport, idleTimeout time.Duration, slots chan struct{}) func(stack.TransportEndpointID, *stack.PacketBuffer) bool {
return newRunUDPProtocolHandler(s, func(req *udp.ForwarderRequest) bool {
select {
Expand All @@ -214,7 +225,7 @@ func newTransportUDPProtocolHandler(ctx context.Context, s *stack.Stack, transpo
return true
}
local := gonet.NewUDPConn(&wq, ep)
dstAddr := net.JoinHostPort(id.LocalAddress.String(), strconv.Itoa(int(id.LocalPort)))
dstAddr := udpDialAddr(transport, id.LocalAddress.String(), id.LocalPort)
go func() {
dialCtx, cancel := context.WithTimeout(ctx, transportDialTimeout)
defer cancel()
Expand Down
17 changes: 17 additions & 0 deletions cmd/clawpatrol/daemon_session_linux_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -149,6 +149,23 @@ func TestRunUDPProtocolHandlerFlowLimitRejectionDoesNotClonePacket(t *testing.T)
}
}

func TestUDPDialAddrRewritesTSnetDNS(t *testing.T) {
tsnet := &tsnetTransport{gatewayAddr: netip.MustParseAddr("100.64.0.1")}
if got, want := udpDialAddr(tsnet, "8.8.8.8", 53), "100.64.0.1:53"; got != want {
t.Fatalf("udpDialAddr(tsnet DNS) = %q, want %q", got, want)
}
if got, want := udpDialAddr(tsnet, "8.8.8.8", 443), "8.8.8.8:443"; got != want {
t.Fatalf("udpDialAddr(tsnet non-DNS) = %q, want %q", got, want)
}
plain := &fakeTransport{}
if got, want := udpDialAddr(plain, "8.8.8.8", 53), "8.8.8.8:53"; got != want {
t.Fatalf("udpDialAddr(non-tsnet DNS) = %q, want %q", got, want)
}
if got, want := udpDialAddr(plain, "2001:db8::53", 53), "[2001:db8::53]:53"; got != want {
t.Fatalf("udpDialAddr(non-tsnet IPv6 DNS) = %q, want %q", got, want)
}
}

// pump copies outbound packets from src's channel endpoint into dst's
// inbound path until ctx is done.
func pump(ctx context.Context, src, dst *channel.Endpoint) {
Expand Down
10 changes: 6 additions & 4 deletions cmd/clawpatrol/daemon_transport_tsnet_linux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -26,16 +26,18 @@ import (
type tsnetTransport struct {
s *tsnet.Server
localAddr netip.Addr
gatewayAddr netip.Addr
bootWarning string
}

func (t *tsnetTransport) Dial(ctx context.Context, network, addr string) (net.Conn, error) {
return t.s.Dial(ctx, network, addr)
}

func (t *tsnetTransport) LocalAddr() netip.Addr { return t.localAddr }
func (t *tsnetTransport) BootWarning() string { return t.bootWarning }
func (t *tsnetTransport) Close() error { return t.s.Close() }
func (t *tsnetTransport) LocalAddr() netip.Addr { return t.localAddr }
func (t *tsnetTransport) udpDNSGatewayAddr() netip.Addr { return t.gatewayAddr }
func (t *tsnetTransport) BootWarning() string { return t.bootWarning }
func (t *tsnetTransport) Close() error { return t.s.Close() }

// startTsnetTransport reads persisted join state (auth-key, control-url,
// gateway-ip), starts a tsnet.Server, waits for it to come up, points
Expand Down Expand Up @@ -126,7 +128,7 @@ func startTsnetTransport() (daemonTransport, error) {
// daemon restart.
daemonRegisterTsnetPeer(s, tsIP)

return &tsnetTransport{s: s, localAddr: tsIP, bootWarning: bootWarning}, nil
return &tsnetTransport{s: s, localAddr: tsIP, gatewayAddr: gwIP, bootWarning: bootWarning}, nil
}

// daemonRegisterTsnetPeer POSTs this daemon's tsnet IP to the
Expand Down
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