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wgengine/magicsock: skip an endpoint update at start-up

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At startup the client doesn't yet have the DERP map so can't do STUN
queries against DERP servers, so it only knows it local interface
addresses, not its STUN-mapped addresses.

We were reporting the interface-local addresses to control, getting
the DERP map, and then immediately reporting the full set of
updates. That was an extra HTTP request to control, but worse: it was
an extra broadcast from control out to all the peers in the network.

Now, skip the initial update if there are no stun results and we don't
have a DERP map.

More work remains optimizing start-up requests/map updates, but this
is a start.

Updates tailscale/corp#557
This commit is contained in:
Brad Fitzpatrick 2020-10-14 10:44:54 -07:00
parent 551e1e99e9
commit 105a820622
1 changed files with 24 additions and 2 deletions
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26
wgengine/magicsock/magicsock.go
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@ -437,7 +437,7 @@ func (c *Conn) updateEndpoints(why string) {
return
}
if c.setEndpoints(endpoints) {
if c.setEndpoints(endpoints, reasons) {
c.logEndpointChange(endpoints, reasons)
c.epFunc(endpoints)
}
@ -445,9 +445,31 @@ func (c *Conn) updateEndpoints(why string) {
// setEndpoints records the new endpoints, reporting whether they're changed.
// It takes ownership of the slice.
func (c *Conn) setEndpoints(endpoints []string) (changed bool) {
func (c *Conn) setEndpoints(endpoints []string, reasons map[string]string) (changed bool) {
anySTUN := false
for _, reason := range reasons {
if reason == "stun" {
anySTUN = true
}
}
c.mu.Lock()
defer c.mu.Unlock()
if !anySTUN && c.derpMap == nil && !inTest() {
// Don't bother storing or reporting this yet. We
// don't have a DERP map or any STUN entries, so we're
// just starting up. A DERP map should arrive shortly
// and then we'll have more interesting endpoints to
// report. This saves a map update.
// TODO(bradfitz): this optimization is currently
// skipped during the e2e tests because they depend
// too much on the exact sequence of updates. Fix the
// tests. But a protocol rewrite might happen first.
c.logf("magicsock: ignoring pre-DERP map, STUN-less endpoint update: %v", endpoints)
return false
}
if stringsEqual(endpoints, c.lastEndpoints) {
return false
}