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net/tstun: handle exit nodes in NAT configs

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In the case where the exit node requires SNAT, we would SNAT all traffic not just the
traffic meant to go through the exit node. This was a result of the default route being
added to the routing table which would match basically everything.

In this case, we need to account for all peers in the routing table not just the ones
that require NAT.

Fix and add a test.

Updates tailscale/corp#8020

Signed-off-by: Maisem Ali <maisem@tailscale.com>
This commit is contained in:
Maisem Ali 2023-05-02 12:12:44 -07:00 committed by Maisem Ali
parent bcf7b63d7e
commit 3ae7140690
2 changed files with 74 additions and 33 deletions
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26
net/tstun/wrap.go
View File

@ -20,6 +20,7 @@
"github.com/tailscale/wireguard-go/device"
"github.com/tailscale/wireguard-go/tun"
"go4.org/mem"
"golang.org/x/exp/slices"
"gvisor.dev/gvisor/pkg/tcpip/stack"
"tailscale.com/disco"
"tailscale.com/net/connstats"
@ -590,16 +591,33 @@ func natConfigFromWGConfig(wcfg *wgcfg.Config) *natV4Config {
dstMasqAddrs map[key.NodePublic]netip.Addr
listenAddrs map[netip.Addr]struct{}
)
// When using an exit node that requires masquerading, we need to
// fill out the routing table with all peers not just the ones that
// require masquerading.
exitNodeRequiresMasq := false // true if using an exit node and it requires masquerading
for _, p := range wcfg.Peers {
isExitNode := slices.Contains(p.AllowedIPs, tsaddr.AllIPv4()) || slices.Contains(p.AllowedIPs, tsaddr.AllIPv6())
if isExitNode && p.V4MasqAddr != nil && p.V4MasqAddr.IsValid() {
exitNodeRequiresMasq = true
break
}
}
for i := range wcfg.Peers {
p := &wcfg.Peers[i]
if p.V4MasqAddr == nil || !p.V4MasqAddr.IsValid() {
var addrToUse netip.Addr
if p.V4MasqAddr != nil && p.V4MasqAddr.IsValid() {
addrToUse = *p.V4MasqAddr
mak.Set(&listenAddrs, addrToUse, struct{}{})
} else if exitNodeRequiresMasq {
addrToUse = nativeAddr
} else {
continue
}
rt.InsertOrReplace(p.PublicKey, p.AllowedIPs...)
mak.Set(&dstMasqAddrs, p.PublicKey, *p.V4MasqAddr)
mak.Set(&listenAddrs, *p.V4MasqAddr, struct{}{})
mak.Set(&dstMasqAddrs, p.PublicKey, addrToUse)
}
if len(listenAddrs) == 0 || len(dstMasqAddrs) == 0 {
if len(listenAddrs) == 0 && len(dstMasqAddrs) == 0 {
return nil
}
return &natV4Config{

81
net/tstun/wrap_test.go
View File

@ -602,13 +602,13 @@ func TestFilterDiscoLoop(t *testing.T) {
}
func TestNATCfg(t *testing.T) {
node := func(ip, eip netip.Addr, otherAllowedIPs ...netip.Prefix) wgcfg.Peer {
node := func(ip, masqIP netip.Addr, otherAllowedIPs ...netip.Prefix) wgcfg.Peer {
p := wgcfg.Peer{
PublicKey: key.NewNode().Public(),
AllowedIPs: []netip.Prefix{
netip.PrefixFrom(ip, ip.BitLen()),
},
V4MasqAddr: ptr.To(eip),
V4MasqAddr: ptr.To(masqIP),
}
p.AllowedIPs = append(p.AllowedIPs, otherAllowedIPs...)
return p
@ -619,13 +619,16 @@ func TestNATCfg(t *testing.T) {
selfNativeIP = netip.MustParseAddr("100.64.0.1")
selfEIP1 = netip.MustParseAddr("100.64.1.1")
selfEIP2 = netip.MustParseAddr("100.64.1.2")
selfAddrs = []netip.Prefix{netip.PrefixFrom(selfNativeIP, selfNativeIP.BitLen())}
peer1IP = netip.MustParseAddr("100.64.0.2")
peer2IP = netip.MustParseAddr("100.64.0.3")
subnet = netip.MustParseAddr("192.168.0.1")
subnet = netip.MustParsePrefix("192.168.0.0/24")
subnetIP = netip.MustParseAddr("192.168.0.1")
selfAddrs = []netip.Prefix{netip.PrefixFrom(selfNativeIP, selfNativeIP.BitLen())}
exitRoute = netip.MustParsePrefix("0.0.0.0/0")
publicIP = netip.MustParseAddr("8.8.8.8")
)
tests := []struct {
@ -638,9 +641,9 @@ func TestNATCfg(t *testing.T) {
name: "no-cfg",
wcfg: nil,
snatMap: map[netip.Addr]netip.Addr{
peer1IP: selfNativeIP,
peer2IP: selfNativeIP,
subnet: selfNativeIP,
peer1IP: selfNativeIP,
peer2IP: selfNativeIP,
subnetIP: selfNativeIP,
},
dnatMap: map[netip.Addr]netip.Addr{
selfNativeIP: selfNativeIP,
@ -658,15 +661,15 @@ func TestNATCfg(t *testing.T) {
},
},
snatMap: map[netip.Addr]netip.Addr{
peer1IP: selfNativeIP,
peer2IP: selfEIP1,
subnet: selfNativeIP,
peer1IP: selfNativeIP,
peer2IP: selfEIP1,
subnetIP: selfNativeIP,
},
dnatMap: map[netip.Addr]netip.Addr{
selfNativeIP: selfNativeIP,
selfEIP1: selfNativeIP,
selfEIP2: selfEIP2,
subnet: subnet,
subnetIP: subnetIP,
},
},
{
@ -679,15 +682,15 @@ func TestNATCfg(t *testing.T) {
},
},
snatMap: map[netip.Addr]netip.Addr{
peer1IP: selfEIP1,
peer2IP: selfEIP2,
subnet: selfNativeIP,
peer1IP: selfEIP1,
peer2IP: selfEIP2,
subnetIP: selfNativeIP,
},
dnatMap: map[netip.Addr]netip.Addr{
selfNativeIP: selfNativeIP,
selfEIP1: selfNativeIP,
selfEIP2: selfNativeIP,
subnet: subnet,
subnetIP: subnetIP,
},
},
{
@ -696,19 +699,19 @@ func TestNATCfg(t *testing.T) {
Addresses: selfAddrs,
Peers: []wgcfg.Peer{
node(peer1IP, selfEIP1),
node(peer2IP, selfEIP2, netip.MustParsePrefix("192.168.0.0/24")),
node(peer2IP, selfEIP2, subnet),
},
},
snatMap: map[netip.Addr]netip.Addr{
peer1IP: selfEIP1,
peer2IP: selfEIP2,
subnet: selfEIP2,
peer1IP: selfEIP1,
peer2IP: selfEIP2,
subnetIP: selfEIP2,
},
dnatMap: map[netip.Addr]netip.Addr{
selfNativeIP: selfNativeIP,
selfEIP1: selfNativeIP,
selfEIP2: selfNativeIP,
subnet: subnet,
subnetIP: subnetIP,
},
},
{
@ -717,19 +720,19 @@ func TestNATCfg(t *testing.T) {
Addresses: selfAddrs,
Peers: []wgcfg.Peer{
node(peer1IP, selfEIP1),
node(peer2IP, selfEIP2, netip.MustParsePrefix("0.0.0.0/0")),
node(peer2IP, selfEIP2, exitRoute),
},
},
snatMap: map[netip.Addr]netip.Addr{
peer1IP: selfEIP1,
peer2IP: selfEIP2,
netip.MustParseAddr("8.8.8.8"): selfEIP2,
peer1IP: selfEIP1,
peer2IP: selfEIP2,
publicIP: selfEIP2,
},
dnatMap: map[netip.Addr]netip.Addr{
selfNativeIP: selfNativeIP,
selfEIP1: selfNativeIP,
selfEIP2: selfNativeIP,
subnet: subnet,
subnetIP: subnetIP,
},
},
{
@ -742,15 +745,35 @@ func TestNATCfg(t *testing.T) {
},
},
snatMap: map[netip.Addr]netip.Addr{
peer1IP: selfNativeIP,
peer2IP: selfNativeIP,
subnet: selfNativeIP,
peer1IP: selfNativeIP,
peer2IP: selfNativeIP,
subnetIP: selfNativeIP,
},
dnatMap: map[netip.Addr]netip.Addr{
selfNativeIP: selfNativeIP,
selfEIP1: selfEIP1,
selfEIP2: selfEIP2,
subnet: subnet,
subnetIP: subnetIP,
},
},
{
name: "exit-node-require-nat-peer-doesnt",
wcfg: &wgcfg.Config{
Addresses: selfAddrs,
Peers: []wgcfg.Peer{
node(peer1IP, noIP),
node(peer2IP, selfEIP2, exitRoute),
},
},
snatMap: map[netip.Addr]netip.Addr{
peer1IP: selfNativeIP,
peer2IP: selfEIP2,
publicIP: selfEIP2,
},
dnatMap: map[netip.Addr]netip.Addr{
selfNativeIP: selfNativeIP,
selfEIP2: selfNativeIP,
subnetIP: subnetIP,
},
},
}