137 lines
4.0 KiB
Go
137 lines
4.0 KiB
Go
// Copyright 2016 CNI authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package testhelpers provides common support behavior for tests
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package testhelpers
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import (
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"fmt"
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"os"
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"runtime"
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"sync"
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"golang.org/x/sys/unix"
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. "github.com/onsi/ginkgo"
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. "github.com/onsi/gomega"
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)
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func getCurrentThreadNetNSPath() string {
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pid := unix.Getpid()
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tid := unix.Gettid()
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return fmt.Sprintf("/proc/%d/task/%d/ns/net", pid, tid)
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}
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func GetInodeCurNetNS() (uint64, error) {
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return GetInode(getCurrentThreadNetNSPath())
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}
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func GetInode(path string) (uint64, error) {
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file, err := os.Open(path)
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if err != nil {
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return 0, err
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}
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defer file.Close()
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return GetInodeF(file)
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}
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func GetInodeF(file *os.File) (uint64, error) {
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stat := &unix.Stat_t{}
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err := unix.Fstat(int(file.Fd()), stat)
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return stat.Ino, err
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}
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/*
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A note about goroutines, Linux namespaces and runtime.LockOSThread
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In Linux, network namespaces have thread affinity.
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In the Go language runtime, goroutines do not have affinity for OS threads.
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The Go runtime scheduler moves goroutines around amongst OS threads. It
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is supposed to be transparent to the Go programmer.
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In order to address cases where the programmer needs thread affinity, Go
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provides runtime.LockOSThread and runtime.UnlockOSThread()
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However, the Go runtime does not reference count the Lock and Unlock calls.
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Repeated calls to Lock will succeed, but the first call to Unlock will unlock
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everything. Therefore, it is dangerous to hide a Lock/Unlock in a library
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function, such as in this package.
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The code below, in MakeNetworkNS, avoids this problem by spinning up a new
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Go routine specifically so that LockOSThread can be called on it. Thus
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goroutine-thread affinity is maintained long enough to perform all the required
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namespace operations.
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Because the LockOSThread call is performed inside this short-lived goroutine,
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there is no effect either way on the caller's goroutine-thread affinity.
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* */
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func MakeNetworkNS(containerID string) string {
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namespace := "/var/run/netns/" + containerID
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err := os.MkdirAll("/var/run/netns", 0600)
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Expect(err).NotTo(HaveOccurred())
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// create an empty file at the mount point
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mountPointFd, err := os.Create(namespace)
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Expect(err).NotTo(HaveOccurred())
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mountPointFd.Close()
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var wg sync.WaitGroup
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wg.Add(1)
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// do namespace work in a dedicated goroutine, so that we can safely
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// Lock/Unlock OSThread without upsetting the lock/unlock state of
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// the caller of this function. See block comment above.
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go (func() {
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defer wg.Done()
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runtime.LockOSThread()
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defer runtime.UnlockOSThread()
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defer GinkgoRecover()
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// capture current thread's original netns
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currentThreadNetNSPath := getCurrentThreadNetNSPath()
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originalNetNS, err := unix.Open(currentThreadNetNSPath, unix.O_RDONLY, 0)
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Expect(err).NotTo(HaveOccurred())
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defer unix.Close(originalNetNS)
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// create a new netns on the current thread
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err = unix.Unshare(unix.CLONE_NEWNET)
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Expect(err).NotTo(HaveOccurred())
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// bind mount the new netns from the current thread onto the mount point
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err = unix.Mount(currentThreadNetNSPath, namespace, "none", unix.MS_BIND, "")
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Expect(err).NotTo(HaveOccurred())
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// reset current thread's netns to the original
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_, _, e1 := unix.Syscall(unix.SYS_SETNS, uintptr(originalNetNS), uintptr(unix.CLONE_NEWNET), 0)
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Expect(e1).To(BeZero())
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})()
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wg.Wait()
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return namespace
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}
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func RemoveNetworkNS(networkNS string) error {
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err := unix.Unmount(networkNS, unix.MNT_DETACH)
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err = os.RemoveAll(networkNS)
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return err
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}
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