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flannel: protect knownSubnets map with mutex to fix data race #6

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Merged
phaus merged 1 commit into from
Sep 4, 2026
Merged

flannel: protect knownSubnets map with mutex to fix data race #6

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6 changes: 6 additions & 0 deletions flannel/discoverd/registry.go
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@ import (
"encoding/json"
"errors"
"reflect"
"sync"
"time"

"github.com/flynn/flynn/discoverd/client"
Expand Down Expand Up @@ -89,6 +90,9 @@ func (r *registry) UpdateSubnet(sn, data string, ttl uint64) (*subnet.Response,
return newResponse(net), nil
}

// knownSubnetsMu protects knownSubnets from concurrent access.
var knownSubnetsMu sync.Mutex

// knownSubnets is updated each time we receive a service metadata event so
// that we can calculate which subnets are new and should be returned from
// WatchSubnets
Expand All @@ -111,13 +115,15 @@ func (r *registry) WatchSubnets(since uint64, stop chan bool) (*subnet.Response,
return nil, err
}
subnets := make(map[string][]byte)
knownSubnetsMu.Lock()
for subnet, data := range net.Subnets {
if known, ok := knownSubnets[subnet]; ok && reflect.DeepEqual(known, data) {
continue
}
subnets[subnet] = []byte(*data)
}
knownSubnets = net.Subnets
knownSubnetsMu.Unlock()
if event.ServiceMeta.Index >= since {
return &subnet.Response{Subnets: subnets, Index: event.ServiceMeta.Index}, nil
}
Expand Down
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