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net/netcheck: don't mutate Client.TimeNow in AddReportHistoryForTest

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AddReportHistoryForTest temporarily swapped out Client.TimeNow without
holding any lock, racing with concurrent GetReport calls reading it
from ReSTUN goroutines during tests. Instead, pass the current time to
addReportHistoryAndSetPreferredDERP explicitly so the test helper never
needs to touch the field.

Fixes #20438

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Change-Id: I9c4f0a2f9427b5f1d3e8b06a49f0d2b71c3ee8a4
This commit is contained in:
Brad Fitzpatrick
2026-07-13 15:20:36 -07:00
committed by Brad Fitzpatrick
parent b803ba048c
commit 55b1a4de74
2 changed files with 5 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files
net/netcheck/netcheck.go
+3 -6
View File
@@ -1026,7 +1026,7 @@ func (c *Client) finishAndStoreReport(rs *reportState, dm *tailcfg.DERPMap) *Rep
report := rs.report.Clone()
rs.mu.Unlock()
c.addReportHistoryAndSetPreferredDERP(rs, report, dm.View())
c.addReportHistoryAndSetPreferredDERP(rs, report, dm.View(), c.timeNow())
c.logConciseReport(report, dm)
return report
@@ -1381,7 +1381,7 @@ func (c *Client) addReportAndPruneExpired(now time.Time, r *Report) {
// addReportHistoryAndSetPreferredDERP adds r to the set of recent Reports
// and mutates r.PreferredDERP to contain the best recent one.
func (c *Client) addReportHistoryAndSetPreferredDERP(rs *reportState, r *Report, dm tailcfg.DERPMapView) {
func (c *Client) addReportHistoryAndSetPreferredDERP(rs *reportState, r *Report, dm tailcfg.DERPMapView, now time.Time) {
c.mu.Lock()
defer c.mu.Unlock()
@@ -1392,7 +1392,6 @@ func (c *Client) addReportHistoryAndSetPreferredDERP(rs *reportState, r *Report,
// Add report to history, enforce retention window, then take the best (lowest)
// latency seen per region across what remains.
now := c.timeNow()
c.addReportAndPruneExpired(now, r)
bestRecent := c.bestRecentLatencyLocked()
@@ -1517,10 +1516,8 @@ func (c *Client) RecentRegionLatency() map[int]time.Duration {
// r.PreferredDERP from that history.
func (c *Client) AddReportHistoryForTest(dm *tailcfg.DERPMap, r *Report, now time.Time) {
testenv.AssertInTest()
defer func(prev func() time.Time) { c.TimeNow = prev }(c.TimeNow)
c.TimeNow = func() time.Time { return now }
rs := &reportState{c: c, start: now}
c.addReportHistoryAndSetPreferredDERP(rs, r, dm.View())
c.addReportHistoryAndSetPreferredDERP(rs, r, dm.View(), now)
}
func updateLatency(m map[int]time.Duration, regionID int, d time.Duration) {
net/netcheck/netcheck_test.go
+2 -2
View File
@@ -468,7 +468,7 @@ func TestAddReportHistoryAndSetPreferredDERP(t *testing.T) {
for _, s := range tt.steps {
fakeTime = fakeTime.Add(s.after)
rs.start = fakeTime.Add(-100 * time.Millisecond)
c.addReportHistoryAndSetPreferredDERP(rs, s.r, dm.View())
c.addReportHistoryAndSetPreferredDERP(rs, s.r, dm.View(), fakeTime)
}
lastReport := tt.steps[len(tt.steps)-1].r
if got, want := len(c.prev), tt.wantPrevLen; got != want {
@@ -522,7 +522,7 @@ func TestRecentReportsRetainFullNetcheck(t *testing.T) {
regions = allRegions
lastFull = now
}
c.addReportHistoryAndSetPreferredDERP(&reportState{c: c, start: now}, mkReport(regions), dm.View())
c.addReportHistoryAndSetPreferredDERP(&reportState{c: c, start: now}, mkReport(regions), dm.View(), now)
// Recent latency must always cover every region, which is only
// possible while a full report remains in c.prev.