Add a way to get a pid of a process

Signed-off-by: Flavio Crisciani <flavio.crisciani@docker.com>

internal/procfs/procfs_linux.go

@@ -0,0 +1,105 @@
+package procfs
+
+/*
+Copyright 2015 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+import (
+	"bytes"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"regexp"
+	"strconv"
+	"strings"
+	"unicode"
+
+	"github.com/sirupsen/logrus"
+)
+
+// PidOf finds process(es) with a specified name (regexp match)
+// and return their pid(s)
+func PidOf(name string) ([]int, error) {
+	if len(name) == 0 {
+		return []int{}, fmt.Errorf("name should not be empty")
+	}
+	re, err := regexp.Compile("(^|/)" + name + "$")
+	if err != nil {
+		return []int{}, err
+	}
+	return getPids(re), nil
+}
+
+func getPids(re *regexp.Regexp) []int {
+	pids := []int{}
+
+	dirFD, err := os.Open("/proc")
+	if err != nil {
+		return nil
+	}
+	defer dirFD.Close()
+
+	for {
+		// Read a small number at a time in case there are many entries, we don't want to
+		// allocate a lot here.
+		ls, err := dirFD.Readdir(10)
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil
+		}
+
+		for _, entry := range ls {
+			if !entry.IsDir() {
+				continue
+			}
+
+			// If the directory is not a number (i.e. not a PID), skip it
+			pid, err := strconv.Atoi(entry.Name())
+			if err != nil {
+				continue
+			}
+
+			cmdline, err := ioutil.ReadFile(filepath.Join("/proc", entry.Name(), "cmdline"))
+			if err != nil {
+				logrus.Infof("Error reading file %s: %+v", filepath.Join("/proc", entry.Name(), "cmdline"), err)
+				continue
+			}
+
+			// The bytes we read have '\0' as a separator for the command line
+			parts := bytes.SplitN(cmdline, []byte{0}, 2)
+			if len(parts) == 0 {
+				continue
+			}
+			// Split the command line itself we are interested in just the first part
+			exe := strings.FieldsFunc(string(parts[0]), func(c rune) bool {
+				return unicode.IsSpace(c) || c == ':'
+			})
+			if len(exe) == 0 {
+				continue
+			}
+			// Check if the name of the executable is what we are looking for
+			if re.MatchString(exe[0]) {
+				// Grab the PID from the directory path
+				pids = append(pids, pid)
+			}
+		}
+	}
+
+	return pids
+}

internal/procfs/procfs_linux_test.go

@@ -0,0 +1,36 @@
+package procfs
+
+import (
+	"os"
+	"path/filepath"
+	"regexp"
+	"runtime"
+	"testing"
+
+	"gotest.tools/assert"
+)
+
+func TestPidOf(t *testing.T) {
+	pids, err := PidOf(filepath.Base(os.Args[0]))
+	assert.NilError(t, err)
+	assert.Check(t, len(pids) == 1)
+	assert.DeepEqual(t, pids[0], os.Getpid())
+}
+
+func BenchmarkGetPids(b *testing.B) {
+	if runtime.GOOS == "darwin" || runtime.GOOS == "windows" {
+		b.Skipf("not supported on GOOS=%s", runtime.GOOS)
+	}
+
+	re, err := regexp.Compile("(^|/)" + filepath.Base(os.Args[0]) + "$")
+	assert.Check(b, err == nil)
+
+	for i := 0; i < b.N; i++ {
+		pids := getPids(re)
+
+		b.StopTimer()
+		assert.Check(b, len(pids) > 0)
+		assert.Check(b, pids[0] == os.Getpid())
+		b.StartTimer()
+	}
+}

vendor/github.com/docker/libnetwork/osl/namespace_linux.go

@@ -394,13 +394,10 @@ func (n *networkNamespace) InvokeFunc(f func()) error {
 // InitOSContext initializes OS context while configuring network resources
 func InitOSContext() func() {
 	runtime.LockOSThread()
-	if err := ns.SetNamespace(); err != nil {
-		logrus.Error(err)
-	}
 	return runtime.UnlockOSThread
 }
 
-func nsInvoke(path string, prefunc func(nsFD int) error, postfunc func(callerFD int) error) error {
+func nsInvoke(path string, prefunc, postfunc func(int) error) error {
 	defer InitOSContext()()
 
 	newNs, err := netns.GetFromPath(path)
@@ -415,10 +412,14 @@ func nsInvoke(path string, prefunc func(nsFD int) error, postfunc func(callerFD
 		return fmt.Errorf("failed in prefunc: %v", err)
 	}
 
+	// save the current namespace (host namespace)
+	curNs, _ := netns.Get()
 	if err = netns.Set(newNs); err != nil {
 		return err
 	}
-	defer ns.SetNamespace()
+	defer curNs.Close()
+	// will restore the previous namespace before unlocking the thread
+	defer netns.Set(curNs)
 
 	// Invoked after the namespace switch.
 	return postfunc(ns.ParseHandlerInt())
@@ -651,7 +652,10 @@ func (n *networkNamespace) ApplyOSTweaks(types []SandboxType) {
 	for _, t := range types {
 		switch t {
 		case SandboxTypeLoadBalancer:
-			kernel.ApplyOSTweaks(loadBalancerConfig)
+			nsInvoke(n.nsPath(),
+				func(nsFD int) error { return nil },
+				func(callerFD int) error { kernel.ApplyOSTweaks(loadBalancerConfig); return nil },
+			)
 		}
 	}
 }