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net/netcheck,wgengine/magicsock: align DERP frame receive time heuristics

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The netcheck package and the magicksock package coordinate via the
health package, but both sides have time based heuristics through
indirect dependencies. These were misaligned, so the implemented
heuristic aimed at reducing DERP moves while there is active traffic
were non-operational about 3/5ths of the time.

It is problematic to setup a good test for this integration presently,
so instead I added comment breadcrumbs along with the initial fix.

Updates #8603

Signed-off-by: James Tucker <james@tailscale.com>
This commit is contained in:
James Tucker
2024-04-05 12:12:18 -07:00
committed by James Tucker
parent 1fbaf26106
commit 6e334e64a1
4 changed files with 29 additions and 6 deletions
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7
net/netcheck/netcheck.go
View File

@@ -1388,10 +1388,11 @@ const (
// node is near region 1 @ 4ms and region 2 @ 5ms, region 1 getting
// 5ms slower would cause a flap).
preferredDERPAbsoluteDiff = 10 * time.Millisecond
// preferredDERPFrameTime is the time which, if a DERP frame has been
// PreferredDERPFrameTime is the time which, if a DERP frame has been
// received within that period, we treat that region as being present
// even without receiving a STUN response.
preferredDERPFrameTime = 2 * time.Second
// Note: must remain higher than the derp package frameReceiveRecordRate
PreferredDERPFrameTime = 8 * time.Second
)
// addReportHistoryAndSetPreferredDERP adds r to the set of recent Reports
@@ -1480,7 +1481,7 @@ func (c *Client) addReportHistoryAndSetPreferredDERP(rs *reportState, r *Report,
now := c.timeNow()
heardFromOldRegionRecently = lastHeard.After(rs.start)
heardFromOldRegionRecently = heardFromOldRegionRecently || lastHeard.After(now.Add(-preferredDERPFrameTime))
heardFromOldRegionRecently = heardFromOldRegionRecently || lastHeard.After(now.Add(-PreferredDERPFrameTime))
}
}

4
net/netcheck/netcheck_test.go
View File

@@ -410,7 +410,7 @@ func TestAddReportHistoryAndSetPreferredDERP(t *testing.T) {
},
opts: &GetReportOpts{
GetLastDERPActivity: mkLDAFunc(map[int]time.Time{
1: startTime.Add(2*time.Second + preferredDERPFrameTime/2), // within active window of step (3)
1: startTime.Add(2*time.Second + PreferredDERPFrameTime/2), // within active window of step (3)
}),
},
wantPrevLen: 3,
@@ -425,7 +425,7 @@ func TestAddReportHistoryAndSetPreferredDERP(t *testing.T) {
},
opts: &GetReportOpts{
GetLastDERPActivity: mkLDAFunc(map[int]time.Time{
1: startTime.Add(4*time.Second - preferredDERPFrameTime - 1), // not within active window of (3)
1: startTime.Add(4*time.Second - PreferredDERPFrameTime - 1), // not within active window of (3)
}),
},
wantPrevLen: 3,