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net/interfaces: don't send over zt* interfaces

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Fixes #1208

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
This commit is contained in:
Brad Fitzpatrick 2021-01-26 15:14:59 -08:00 committed by Brad Fitzpatrick
parent 692a011b54
commit 35e10c78fc
1 changed files with 17 additions and 2 deletions
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19
net/interfaces/interfaces.go
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@ -10,6 +10,7 @@
"net"
"net/http"
"reflect"
"runtime"
"sort"
"strings"
@ -63,6 +64,18 @@ func maybeTailscaleInterfaceName(s string) bool {
func isUp(nif *net.Interface) bool { return nif.Flags&net.FlagUp != 0 }
func isLoopback(nif *net.Interface) bool { return nif.Flags&net.FlagLoopback != 0 }
func isProblematicInterface(nif *net.Interface) bool {
name := nif.Name
// Don't try to send disco/etc packets over zerotier; they effectively
// DoS each other by doing traffic amplification, both of them
// preferring/trying to use each other for transport. See:
// https://github.com/tailscale/tailscale/issues/1208
if strings.HasPrefix(name, "zt") || (runtime.GOOS == "windows" && strings.Contains(name, "ZeroTier")) {
return true
}
return false
}
// LocalAddresses returns the machine's IP addresses, separated by
// whether they're loopback addresses.
func LocalAddresses() (regular, loopback []string, err error) {
@ -73,8 +86,10 @@ func LocalAddresses() (regular, loopback []string, err error) {
}
for i := range ifaces {
iface := &ifaces[i]
if !isUp(iface) {
// Down interfaces don't count
if !isUp(iface) || isProblematicInterface(iface) {
// Skip down interfaces and ones that are
// problematic that we don't want to try to
// send Tailscale traffic over.
continue
}
ifcIsLoopback := isLoopback(iface)