daemon: Init k8s watchers after setting agent flags #18770
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The way our agent startup is structured can lead to a data race on the
EnableBPFMasquerade flag. In the main thread, we initialize k8s watchers
via goroutines which may end up using flag EnableBPFMasquerade. We then
update the value of that flag. So we can have a race between the main
thread and a k8s watcher goroutine. The full stack traces for the data
race are shown below.
Moving the k8s watcher initialization after the flags are fully updated
removes this data race.
WARNING: DATA RACE
Write at 0x000005803072 by main goroutine:
github.com/cilium/cilium/daemon/cmd.NewDaemon()
/go/src/github.com/cilium/cilium/daemon/cmd/daemon.go:710 +0x5587
github.com/cilium/cilium/daemon/cmd.runDaemon()
/go/src/github.com/cilium/cilium/daemon/cmd/daemon_main.go:1652 +0xa98
github.com/cilium/cilium/daemon/cmd.glob..func1()
/go/src/github.com/cilium/cilium/daemon/cmd/daemon_main.go:126 +0x494
github.com/spf13/cobra.(*Command).execute()
/go/src/github.com/cilium/cilium/vendor/github.com/spf13/cobra/command.go:860 +0xaf3
github.com/spf13/cobra.(*Command).ExecuteC()
/go/src/github.com/cilium/cilium/vendor/github.com/spf13/cobra/command.go:974 +0x5da
github.com/spf13/cobra.(*Command).Execute()
/go/src/github.com/cilium/cilium/vendor/github.com/spf13/cobra/command.go:902 +0x65
github.com/cilium/cilium/daemon/cmd.Execute()
/go/src/github.com/cilium/cilium/daemon/cmd/daemon_main.go:140 +0x4e
main.main()
/go/src/github.com/cilium/cilium/daemon/main.go:16 +0x24
runtime.main()
/usr/local/go/src/runtime/proc.go:255 +0x226
github.com/cilium/ebpf.init()
/go/src/github.com/cilium/cilium/vendor/github.com/cilium/ebpf/syscalls.go:220 +0x868
github.com/cilium/ebpf.init()
/go/src/github.com/cilium/cilium/vendor/github.com/cilium/ebpf/syscalls.go:188 +0x808
github.com/cilium/ebpf.init()
/go/src/github.com/cilium/cilium/vendor/github.com/cilium/ebpf/syscalls.go:166 +0x7a8
github.com/cilium/ebpf.init()
/go/src/github.com/cilium/cilium/vendor/github.com/cilium/ebpf/syscalls.go:148 +0x748
github.com/cilium/ebpf.init()
/go/src/github.com/cilium/cilium/vendor/github.com/cilium/ebpf/syscalls.go:108 +0x6e8
github.com/cilium/ebpf.init()
/go/src/github.com/cilium/cilium/vendor/github.com/cilium/ebpf/syscalls.go:92 +0x688
github.com/cilium/ebpf.init()
/go/src/github.com/cilium/cilium/vendor/github.com/cilium/ebpf/syscalls.go:76 +0x628
github.com/cilium/ebpf.init()
/go/src/github.com/cilium/cilium/vendor/github.com/cilium/ebpf/syscalls.go:59 +0x5c8
github.com/cilium/ebpf.init()
/go/src/github.com/cilium/cilium/vendor/github.com/cilium/ebpf/syscalls.go:41 +0x568
runtime.doInit()
/usr/local/go/src/runtime/proc.go:6498 +0x122
github.com/cilium/ebpf/internal/btf.init()
/go/src/github.com/cilium/cilium/vendor/github.com/cilium/ebpf/internal/btf/btf.go:820 +0x1bc
Previous read at 0x000005803072 by goroutine 179:
github.com/cilium/cilium/pkg/option.(*DaemonConfig).IptablesMasqueradingIPv4Enabled()
/go/src/github.com/cilium/cilium/pkg/option/config.go:2182 +0x17a9
github.com/cilium/cilium/pkg/option.(*DaemonConfig).IptablesMasqueradingEnabled()
/go/src/github.com/cilium/cilium/pkg/option/config.go:2194 +0x17dc
github.com/cilium/cilium/pkg/node/manager.(*Manager).NodeUpdated()
/go/src/github.com/cilium/cilium/pkg/node/manager/manager.go:414 +0x1778
github.com/cilium/cilium/pkg/k8s/watchers.(*K8sWatcher).ciliumNodeInit.func1()
/go/src/github.com/cilium/cilium/pkg/k8s/watchers/cilium_node.go:43 +0x374
k8s.io/client-go/tools/cache.ResourceEventHandlerFuncs.OnAdd()
/go/src/github.com/cilium/cilium/vendor/k8s.io/client-go/tools/cache/controller.go:231 +0x79
k8s.io/client-go/tools/cache.(*ResourceEventHandlerFuncs).OnAdd()
<autogenerated>:1 +0x33
github.com/cilium/cilium/pkg/k8s/informer.NewInformerWithStore.func1()
/go/src/github.com/cilium/cilium/pkg/k8s/informer/informer.go:108 +0x2d8
k8s.io/client-go/tools/cache.(*DeltaFIFO).Pop()
/go/src/github.com/cilium/cilium/vendor/k8s.io/client-go/tools/cache/delta_fifo.go:554 +0x8c9
k8s.io/client-go/tools/cache.(*controller).processLoop()
/go/src/github.com/cilium/cilium/vendor/k8s.io/client-go/tools/cache/controller.go:183 +0x61
k8s.io/client-go/tools/cache.(*controller).processLoop-fm()
/go/src/github.com/cilium/cilium/vendor/k8s.io/client-go/tools/cache/controller.go:181 +0x39
k8s.io/apimachinery/pkg/util/wait.BackoffUntil.func1()
/go/src/github.com/cilium/cilium/vendor/k8s.io/apimachinery/pkg/util/wait/wait.go:155 +0x81
k8s.io/apimachinery/pkg/util/wait.BackoffUntil()
/go/src/github.com/cilium/cilium/vendor/k8s.io/apimachinery/pkg/util/wait/wait.go:156 +0xce
k8s.io/apimachinery/pkg/util/wait.JitterUntil()
/go/src/github.com/cilium/cilium/vendor/k8s.io/apimachinery/pkg/util/wait/wait.go:133 +0x104
k8s.io/apimachinery/pkg/util/wait.Until()
/go/src/github.com/cilium/cilium/vendor/k8s.io/apimachinery/pkg/util/wait/wait.go:90 +0x616
k8s.io/client-go/tools/cache.(*controller).Run()
/go/src/github.com/cilium/cilium/vendor/k8s.io/client-go/tools/cache/controller.go:154 +0x5cd
github.com/cilium/cilium/pkg/k8s/watchers.(*K8sWatcher).ciliumNodeInit·dwrap·10()
/go/src/github.com/cilium/cilium/pkg/k8s/watchers/cilium_node.go:96 +0x59
Goroutine 179 (running) created at:
github.com/cilium/cilium/pkg/k8s/watchers.(*K8sWatcher).ciliumNodeInit()
/go/src/github.com/cilium/cilium/pkg/k8s/watchers/cilium_node.go:96 +0x8d
github.com/cilium/cilium/pkg/k8s/watchers.(*K8sWatcher).EnableK8sWatcher·dwrap·21()
/go/src/github.com/cilium/cilium/pkg/k8s/watchers/watcher.go:438 +0x58
Signed-off-by: Paul Chaignon <paul@cilium.io>
pchaigno
added
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approved these changes
Feb 10, 2022
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We need to backport this to v1.11 since #17871, the pull request fixes here, will be backported as well. |
maintainer-s-little-helper
bot
moved this from Needs backport from master
to Backport pending to v1.10
in 1.11.2
jibi
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maintainer-s-little-helper
bot
moved this from Backport pending to v1.10
to Backport done to v1.11
in 1.11.2
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The way our agent startup is structured can lead to a data race on the
EnableBPFMasqueradeflag. In the main thread, we initialize k8s watchers via goroutines which may end up using flagEnableBPFMasquerade. We then update the value of that flag. So we can have a race between the main thread and a k8s watcher goroutine. The full stack traces for the data race are shown below.Moving the k8s watcher initialization after the flags are fully updated removes this data race.
Click to show the stack traces.
Fixes: #18727.