wgengine/magicsock: add TS_DISCO_PONG_IPV4_DELAY knob to bias IPv6 paths

Fixes #6818

Change-Id: I71597a045c5b4117af69fba869cb616271c0dfe1
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
pull/6831/head
Brad Fitzpatrick 2 years ago committed by Brad Fitzpatrick
parent e36cdacf70
commit be10b529ec

@ -36,6 +36,7 @@ import (
"tailscale.com/derp"
"tailscale.com/derp/derphttp"
"tailscale.com/disco"
"tailscale.com/envknob"
"tailscale.com/health"
"tailscale.com/hostinfo"
"tailscale.com/ipn/ipnstate"
@ -1946,6 +1947,12 @@ const (
discoVerboseLog
)
// TS_DISCO_PONG_IPV4_DELAY, if set, is a time.Duration string that is how much
// fake latency to add before replying to disco pings. This can be used to bias
// peers towards using IPv6 when both IPv4 and IPv6 are available at similar
// speeds.
var debugIPv4DiscoPingPenalty = envknob.RegisterDuration("TS_DISCO_PONG_IPV4_DELAY")
// sendDiscoMessage sends discovery message m to dstDisco at dst.
//
// If dst is a DERP IP:port, then dstKey must be non-zero.
@ -1953,6 +1960,11 @@ const (
// The dstKey should only be non-zero if the dstDisco key
// unambiguously maps to exactly one peer.
func (c *Conn) sendDiscoMessage(dst netip.AddrPort, dstKey key.NodePublic, dstDisco key.DiscoPublic, m disco.Message, logLevel discoLogLevel) (sent bool, err error) {
isDERP := dst.Addr() == derpMagicIPAddr
if _, isPong := m.(*disco.Pong); isPong && !isDERP && dst.Addr().Is4() {
time.Sleep(debugIPv4DiscoPingPenalty())
}
c.mu.Lock()
if c.closed {
c.mu.Unlock()
@ -1968,7 +1980,6 @@ func (c *Conn) sendDiscoMessage(dst netip.AddrPort, dstKey key.NodePublic, dstDi
di := c.discoInfoLocked(dstDisco)
c.mu.Unlock()
isDERP := dst.Addr() == derpMagicIPAddr
if isDERP {
metricSendDiscoDERP.Add(1)
} else {

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