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[kube-proxy/ipvs] Protect Netlink calls with a mutex #72361

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Dec 27, 2018
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[kube-proxy/ipvs] Protect Netlink calls with a mutex #72361

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23 changes: 23 additions & 0 deletions pkg/util/ipvs/ipvs_linux.go
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,7 @@ import (
"fmt"
"net"
"strings"
"sync"
"syscall"

libipvs "github.com/docker/libnetwork/ipvs"
Expand All @@ -34,6 +35,7 @@ import (
type runner struct {
exec utilexec.Interface
ipvsHandle *libipvs.Handle
mu sync.Mutex // Protect Netlink calls
}

// Protocol is the IPVS service protocol type
Expand All @@ -58,6 +60,8 @@ func (runner *runner) AddVirtualServer(vs *VirtualServer) error {
if err != nil {
return err
}
runner.mu.Lock()
defer runner.mu.Unlock()
return runner.ipvsHandle.NewService(svc)
}

Expand All @@ -67,6 +71,8 @@ func (runner *runner) UpdateVirtualServer(vs *VirtualServer) error {
if err != nil {
return err
}
runner.mu.Lock()
defer runner.mu.Unlock()
return runner.ipvsHandle.UpdateService(svc)
}

Expand All @@ -76,6 +82,8 @@ func (runner *runner) DeleteVirtualServer(vs *VirtualServer) error {
if err != nil {
return err
}
runner.mu.Lock()
defer runner.mu.Unlock()
return runner.ipvsHandle.DelService(svc)
}

Expand All @@ -85,7 +93,10 @@ func (runner *runner) GetVirtualServer(vs *VirtualServer) (*VirtualServer, error
if err != nil {
return nil, err
}
runner.mu.Lock()
ipvsSvc, err := runner.ipvsHandle.GetService(svc)
runner.mu.Unlock()
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Why not use 'defer' ?

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We could get the lock at the beginning of each function and use defer everywhere to make everything consistent. I chose to release the lock as quickly as possible. We do not need to keep the lock to call toVirtualServer in GetVirtualServer for instance.

I'm completely open to changing this if it makes the code easier to read and the optimization is not worth it.

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What happens if GetService() encounters error ?
I am yet to get familiar with Go lang. Not sure if the unlocking would be skipped in some situation.

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The error is returned as a value, and only inspected after unlocking, so the mutex will be released in any case.

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True.


if err != nil {
return nil, err
}
Expand All @@ -98,7 +109,9 @@ func (runner *runner) GetVirtualServer(vs *VirtualServer) (*VirtualServer, error

// GetVirtualServers is part of ipvs.Interface.
func (runner *runner) GetVirtualServers() ([]*VirtualServer, error) {
runner.mu.Lock()
ipvsSvcs, err := runner.ipvsHandle.GetServices()
runner.mu.Unlock()
if err != nil {
return nil, err
}
Expand All @@ -115,6 +128,8 @@ func (runner *runner) GetVirtualServers() ([]*VirtualServer, error) {

// Flush is part of ipvs.Interface. Currently we delete IPVS services one by one
func (runner *runner) Flush() error {
runner.mu.Lock()
defer runner.mu.Unlock()
return runner.ipvsHandle.Flush()
}

Expand All @@ -128,6 +143,8 @@ func (runner *runner) AddRealServer(vs *VirtualServer, rs *RealServer) error {
if err != nil {
return err
}
runner.mu.Lock()
defer runner.mu.Unlock()
return runner.ipvsHandle.NewDestination(svc, dst)
}

Expand All @@ -141,6 +158,8 @@ func (runner *runner) DeleteRealServer(vs *VirtualServer, rs *RealServer) error
if err != nil {
return err
}
runner.mu.Lock()
defer runner.mu.Unlock()
return runner.ipvsHandle.DelDestination(svc, dst)
}

Expand All @@ -153,6 +172,8 @@ func (runner *runner) UpdateRealServer(vs *VirtualServer, rs *RealServer) error
if err != nil {
return err
}
runner.mu.Lock()
defer runner.mu.Unlock()
return runner.ipvsHandle.UpdateDestination(svc, dst)
}

Expand All @@ -162,7 +183,9 @@ func (runner *runner) GetRealServers(vs *VirtualServer) ([]*RealServer, error) {
if err != nil {
return nil, err
}
runner.mu.Lock()
dsts, err := runner.ipvsHandle.GetDestinations(svc)
runner.mu.Unlock()
if err != nil {
return nil, err
}
Expand Down