avoid port collision

patch.diff

commit adf8c8ad610f925ee424002326a68e0cca97df66 (HEAD -> test_integration_1.22)
Author: Antonio Ojea <[email protected]>
Date:   Fri Oct 8 01:04:38 2021 +0200

    don't get available port from the ephemeral range

diff --git a/test/integration/framework/etcd.go b/test/integration/framework/etcd.go
index aa1d36a86ab..7d2020be4e8 100644
--- a/test/integration/framework/etcd.go
+++ b/test/integration/framework/etcd.go
@@ -20,10 +20,12 @@ import (
        "context"
        "fmt"
        "io/ioutil"
+       "math/rand"
        "net"
        "os"
        "os/exec"
        "runtime"
+       "strconv"
        "strings"
        "time"
 
@@ -49,15 +51,28 @@ func getEtcdPath() (string, error) {
 }
 
 // getAvailablePort returns a TCP port that is available for binding.
+// avoiding the ephemeral range, to avoid collisions on tests that generate
+// multiple connections. By defaylt Linux uses ports in the range 32768 - 60999
+// sysctl net.ipv4.ip_local_port_range
+// net.ipv4.ip_local_port_range = 32768    60999
 func getAvailablePort() (int, error) {
-       l, err := net.Listen("tcp", ":0")
-       if err != nil {
-               return 0, fmt.Errorf("could not bind to a port: %v", err)
+       rand.Seed(time.Now().UnixNano())
+       // get ports from the range 2048 - 8096
+       min := 2048
+       max := 8096
+       for i := min; i < max; i++ {
+               port := rand.Intn(max-min+1) + min
+               p := strconv.Itoa(port)
+               l, err := net.Listen("tcp", ":"+p)
+               if err == nil {
+                       // It is possible but unlikely that someone else will bind this port before we
+                       // get a chance to use it.
+                       defer l.Close()
+                       return l.Addr().(*net.TCPAddr).Port, nil
+               }
        }
-       // It is possible but unlikely that someone else will bind this port before we
-       // get a chance to use it.
-       defer l.Close()
-       return l.Addr().(*net.TCPAddr).Port, nil
+
+       return 0, fmt.Errorf("not available port in the range %d-%d", min, max)
 }