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proxy controlplane so netcheck can get derpmap

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Change-Id: Iecef62dc6f3904f588597e3134429b1521e9fe10
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2024-07-26 10:22:23 -07:00
parent c0581779ed
commit 8070c8d1d5
1 changed files with 52 additions and 10 deletions
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62
natlab/natlabd/natlabd.go
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@ -190,6 +190,7 @@ func (s *Server) acceptTCP(r *tcp.ForwarderRequest) {
log.Printf("AcceptTCP: %v", stringifyTEI(reqDetails))
clientRemoteIP := netaddrIPFromNetstackIP(reqDetails.RemoteAddress)
destIP := netaddrIPFromNetstackIP(reqDetails.LocalAddress)
if !clientRemoteIP.IsValid() {
r.Complete(true) // sends a RST
return
@ -202,17 +203,40 @@ func (s *Server) acceptTCP(r *tcp.ForwarderRequest) {
r.Complete(true) // sends a RST
return
}
r.Complete(false)
ep.SocketOptions().SetKeepAlive(true)
tc := gonet.NewTCPConn(&wq, ep)
io.WriteString(tc, "Hello from Go\nGoodbye.\n")
tc.Close()
if reqDetails.LocalPort == 123 {
r.Complete(false)
tc := gonet.NewTCPConn(&wq, ep)
io.WriteString(tc, "Hello from Go\nGoodbye.\n")
tc.Close()
return
}
if destIP == fakeControlplaneIP {
c, err := net.Dial("tcp", "controlplane.tailscale.com:"+strconv.Itoa(int(reqDetails.LocalPort)))
if err != nil {
r.Complete(true)
log.Printf("Dial controlplane: %v", err)
return
}
defer c.Close()
tc := gonet.NewTCPConn(&wq, ep)
defer tc.Close()
r.Complete(false)
errc := make(chan error, 2)
go func() { _, err := io.Copy(tc, c); errc <- err }()
go func() { _, err := io.Copy(c, tc); errc <- err }()
<-errc
}
}
var gwMAC = net.HardwareAddr{0x52, 0x54, 0x00, 0x01, 0x01, 0x01}
var fakeDNSIP = netip.AddrFrom4([4]byte{4, 11, 4, 11})
var (
fakeDNSIP = netip.AddrFrom4([4]byte{4, 11, 4, 11})
fakeControlplaneIP = netip.AddrFrom4([4]byte{52, 52, 0, 1})
)
var gwIP = netip.AddrFrom4([4]byte{192, 168, 1, 1})
@ -265,8 +289,11 @@ func (s *Server) HWAddr(mac MAC) net.HardwareAddr {
// IPv4ForDNS returns the IP address for the given DNS query name (for IPv4 A
// queries only).
func (s *Server) IPv4ForDNS(qname string) (netip.Addr, bool) {
if qname == "dns" {
switch qname {
case "dns":
return fakeDNSIP, true
case "controlplane.tailscale.com":
return fakeControlplaneIP, true
}
return netip.Addr{}, false
}
@ -360,8 +387,7 @@ func (s *Server) serveConn(uc net.Conn) {
continue
}
if isTCPTo123(packet) {
log.Printf("Injecting TCP to 123")
if shouldInterceptTCP(packet) {
ipp := packet.Layer(layers.LayerTypeIPv4).(*layers.IPv4)
pktCopy := make([]byte, 0, len(ipp.Contents)+len(ipp.Payload))
pktCopy = append(pktCopy, ipp.Contents...)
@ -504,9 +530,25 @@ func isMDNSQuery(pkt gopacket.Packet) bool {
return ok && udp.SrcPort == 5353 && udp.DstPort == 5353
}
func isTCPTo123(pkt gopacket.Packet) bool {
func shouldInterceptTCP(pkt gopacket.Packet) bool {
tcp, ok := pkt.Layer(layers.LayerTypeTCP).(*layers.TCP)
return ok && tcp.DstPort == 123
if !ok {
return false
}
ipv4, ok := pkt.Layer(layers.LayerTypeIPv4).(*layers.IPv4)
if !ok {
return false
}
if tcp.DstPort == 123 {
return true
}
if tcp.DstPort == 80 || tcp.DstPort == 443 {
dstIP, _ := netip.AddrFromSlice(ipv4.DstIP.To4())
if dstIP == fakeControlplaneIP {
return true
}
}
return false
}
// isDNSRequest reports whether pkt is a DNS request to the fake DNS server.