TheArchive/tailscale
1
0
Fork 0
mirror of https://github.com/tailscale/tailscale.git synced 2025-08-12 05:37:32 +00:00
Code Issues Packages Projects Releases Wiki Activity

ipn/ipnlocal: improve testability of random node selection

Browse Source 
In order to test the sticky last suggestion code, a test was written for
LocalBackend.SuggestExitNode but it contains a random number generator
which makes writing comprehensive tests very difficult. This doesn't
change how the last suggestion works, but it adds some infrastructure to
make that easier in a later PR.

This adds func parameters for the two randomized parts: breaking ties
between DERP regions and breaking ties between nodes. This way tests can
validate the entire list of tied options, rather than expecting a
particular outcome given a particular random seed.

As a result of this, the global random number generator can be used
rather than seeding a local one each time.

In order to see the tied nodes for the location based (i.e. Mullvad)
case, pickWeighted needed to return a slice instead of a single
arbitrary option, so there is a small change in how that works.

Updates tailscale/corp#19681

Change-Id: I83c48a752abdec0f59c58ccfd8bfb3f3f17d0ea8
Signed-off-by: Adrian Dewhurst <adrian@tailscale.com>
This commit is contained in:
Adrian Dewhurst
2024-06-03 16:12:12 -04:00
committed by Adrian Dewhurst
parent d21c00205d
commit 3bf2bddbb5
2 changed files with 143 additions and 54 deletions
Download Patch File Download Diff File Expand all files Collapse all files

61
ipn/ipnlocal/local.go
View File

@@ -6420,9 +6420,8 @@ func (b *LocalBackend) SuggestExitNode() (response apitype.ExitNodeSuggestionRes
}
return last, err
}
seed := time.Now().UnixNano()
r := rand.New(rand.NewSource(seed))
res, err := suggestExitNode(lastReport, netMap, r)
res, err := suggestExitNode(lastReport, netMap, randomRegion, randomNode)
if err != nil {
last, err := lastSuggestedExitNode.asAPIType()
if err != nil {
@@ -6437,6 +6436,13 @@ func (b *LocalBackend) SuggestExitNode() (response apitype.ExitNodeSuggestionRes
return res, err
}
// selectRegionFunc returns a DERP region from the slice of candidate regions.
// The value is returned, not the slice index.
type selectRegionFunc func(views.Slice[int]) int
// selectNodeFunc returns a node from the slice of candidate nodes.
type selectNodeFunc func(nodes views.Slice[tailcfg.NodeView]) tailcfg.NodeView
// asAPIType formats a response with the last suggested exit node's ID and name.
// Returns error if there is no id or name.
// Used as a fallback before returning a nil response and error.
@@ -6449,8 +6455,8 @@ func (n lastSuggestedExitNode) asAPIType() (res apitype.ExitNodeSuggestionRespon
return res, ErrUnableToSuggestLastExitNode
}
func suggestExitNode(report *netcheck.Report, netMap *netmap.NetworkMap, r *rand.Rand) (res apitype.ExitNodeSuggestionResponse, err error) {
if report.PreferredDERP == 0 {
func suggestExitNode(report *netcheck.Report, netMap *netmap.NetworkMap, selectRegion selectRegionFunc, selectNode selectNodeFunc) (res apitype.ExitNodeSuggestionResponse, err error) {
if report.PreferredDERP == 0 || netMap == nil || netMap.DERPMap == nil {
return res, ErrNoPreferredDERP
}
var allowedCandidates set.Set[string]
@@ -6461,6 +6467,9 @@ func suggestExitNode(report *netcheck.Report, netMap *netmap.NetworkMap, r *rand
}
candidates := make([]tailcfg.NodeView, 0, len(netMap.Peers))
for _, peer := range netMap.Peers {
if !peer.Valid() {
continue
}
if allowedCandidates != nil && !allowedCandidates.Contains(string(peer.StableID())) {
continue
}
@@ -6484,7 +6493,10 @@ func suggestExitNode(report *netcheck.Report, netMap *netmap.NetworkMap, r *rand
}
candidatesByRegion := make(map[int][]tailcfg.NodeView, len(netMap.DERPMap.Regions))
var preferredDERP *tailcfg.DERPRegion = netMap.DERPMap.Regions[report.PreferredDERP]
preferredDERP, ok := netMap.DERPMap.Regions[report.PreferredDERP]
if !ok {
return res, ErrNoPreferredDERP
}
var minDistance float64 = math.MaxFloat64
type nodeDistance struct {
nv tailcfg.NodeView
@@ -6492,9 +6504,6 @@ func suggestExitNode(report *netcheck.Report, netMap *netmap.NetworkMap, r *rand
}
distances := make([]nodeDistance, 0, len(candidates))
for _, c := range candidates {
if !c.Valid() {
continue
}
if c.DERP() != "" {
ipp, err := netip.ParseAddrPort(c.DERP())
if err != nil {
@@ -6533,13 +6542,13 @@ func suggestExitNode(report *netcheck.Report, netMap *netmap.NetworkMap, r *rand
if len(candidatesByRegion) > 0 {
minRegion := minLatencyDERPRegion(xmaps.Keys(candidatesByRegion), report)
if minRegion == 0 {
minRegion = randomRegion(xmaps.Keys(candidatesByRegion), r)
minRegion = selectRegion(views.SliceOf(xmaps.Keys(candidatesByRegion)))
}
regionCandidates, ok := candidatesByRegion[minRegion]
if !ok {
return res, errors.New("no candidates in expected region: this is a bug")
}
chosen := randomNode(regionCandidates, r)
chosen := selectNode(views.SliceOf(regionCandidates))
res.ID = chosen.StableID()
res.Name = chosen.Name()
if hi := chosen.Hostinfo(); hi.Valid() {
@@ -6565,7 +6574,8 @@ func suggestExitNode(report *netcheck.Report, netMap *netmap.NetworkMap, r *rand
pickFrom = append(pickFrom, candidate.nv)
}
}
chosen := pickWeighted(pickFrom)
bestCandidates := pickWeighted(pickFrom)
chosen := selectNode(views.SliceOf(bestCandidates))
if !chosen.Valid() {
return res, errors.New("chosen candidate invalid: this is a bug")
}
@@ -6580,36 +6590,35 @@ func suggestExitNode(report *netcheck.Report, netMap *netmap.NetworkMap, r *rand
}
// pickWeighted chooses the node with highest priority given a list of mullvad nodes.
func pickWeighted(candidates []tailcfg.NodeView) tailcfg.NodeView {
func pickWeighted(candidates []tailcfg.NodeView) []tailcfg.NodeView {
maxWeight := 0
var best tailcfg.NodeView
best := make([]tailcfg.NodeView, 0, 1)
for _, c := range candidates {
hi := c.Hostinfo()
if !hi.Valid() {
continue
}
loc := hi.Location()
if loc == nil || loc.Priority <= maxWeight {
if loc == nil || loc.Priority < maxWeight {
continue
}
if maxWeight != loc.Priority {
best = best[:0]
}
maxWeight = loc.Priority
best = c
best = append(best, c)
}
return best
}
// randomNode chooses a node randomly given a list of nodes and a *rand.Rand.
func randomNode(nodes []tailcfg.NodeView, r *rand.Rand) tailcfg.NodeView {
return nodes[r.Intn(len(nodes))]
// randomRegion is a selectRegionFunc that selects a uniformly random region.
func randomRegion(regions views.Slice[int]) int {
return regions.At(rand.Intn(regions.Len()))
}
// randomRegion chooses a region randomly given a list of ints and a *rand.Rand
func randomRegion(regions []int, r *rand.Rand) int {
if testenv.InTest() {
regions = slices.Clone(regions)
slices.Sort(regions)
}
return regions[r.Intn(len(regions))]
// randomNode is a selectNodeFunc that returns a uniformly random node.
func randomNode(nodes views.Slice[tailcfg.NodeView]) tailcfg.NodeView {
return nodes.At(rand.Intn(nodes.Len()))
}
// minLatencyDERPRegion returns the region with the lowest latency value given the last netcheck report.