Do not use netns as ID or for entropy

ContainerID is now required so use that
or generate random bytes.

Fixes #5

diff --git a/ip/link.go b/ip/link.go
index 59865cf..c99f4f3 100644 (file)
--- a/ip/link.go
+++ b/ip/link.go
@@ -15,7 +15,7 @@
 package ip
 
 import (
-       "crypto/sha512"
+       "crypto/rand"
        "fmt"
        "net"
        "os"
@@ -23,7 +23,7 @@ import (
        "github.com/appc/cni/Godeps/_workspace/src/github.com/vishvananda/netlink"
 )
 
-func makeVeth(name, peer string, mtu int) (netlink.Link, error) {
+func makeVethPair(name, peer string, mtu int) (netlink.Link, error) {
        veth := &netlink.Veth{
                LinkAttrs: netlink.LinkAttrs{
                        Name:  name,
@@ -39,37 +39,65 @@ func makeVeth(name, peer string, mtu int) (netlink.Link, error) {
        return veth, nil
 }
 
+func makeVeth(name string, mtu int) (peerName string, veth netlink.Link, err error) {
+       for i := 0; i < 10; i++ {
+               peerName, err = RandomVethName()
+               if err != nil {
+                       return
+               }
+
+               veth, err = makeVethPair(name, peerName, mtu)
+               switch {
+               case err == nil:
+                       return
+
+               case os.IsExist(err):
+                       continue
+
+               default:
+                       err = fmt.Errorf("failed to make veth pair: %v", err)
+                       return
+               }
+       }
+
+       // should really never be hit
+       err = fmt.Errorf("failed to find a unique veth name")
+       return
+}
+
 // RandomVethName returns string "veth" with random prefix (hashed from entropy)
-func RandomVethName(entropy string) string {
-       h := sha512.New()
-       h.Write([]byte(entropy))
-       return fmt.Sprintf("veth%x", h.Sum(nil)[:5])
+func RandomVethName() (string, error) {
+       entropy := make([]byte, 4)
+       _, err := rand.Reader.Read(entropy)
+       if err != nil {
+               return "", fmt.Errorf("failed to generate random veth name: %v", err)
+       }
+
+       // NetworkManager (recent versions) will ignore veth devices that start with "veth"
+       return fmt.Sprintf("veth%x", entropy), nil
 }
 
 // SetupVeth sets up a virtual ethernet link.
 // Should be in container netns.
-// TODO(eyakubovich): get rid of entropy and ask kernel to pick name via pattern
-func SetupVeth(entropy, contVethName string, mtu int, hostNS *os.File) (hostVeth, contVeth netlink.Link, err error) {
-       // NetworkManager (recent versions) will ignore veth devices that start with "veth"
-       hostVethName := RandomVethName(entropy)
-       hostVeth, err = makeVeth(hostVethName, contVethName, mtu)
+func SetupVeth(contVethName string, mtu int, hostNS *os.File) (hostVeth, contVeth netlink.Link, err error) {
+       var hostVethName string
+       hostVethName, contVeth, err = makeVeth(contVethName, mtu)
        if err != nil {
-               err = fmt.Errorf("failed to make veth pair: %v", err)
                return
        }
 
-       if err = netlink.LinkSetUp(hostVeth); err != nil {
-               err = fmt.Errorf("failed to set %q up: %v", hostVethName, err)
+       if err = netlink.LinkSetUp(contVeth); err != nil {
+               err = fmt.Errorf("failed to set %q up: %v", contVethName, err)
                return
        }
 
-       contVeth, err = netlink.LinkByName(contVethName)
+       hostVeth, err = netlink.LinkByName(hostVethName)
        if err != nil {
-               err = fmt.Errorf("failed to lookup %q: %v", contVethName, err)
+               err = fmt.Errorf("failed to lookup %q: %v", hostVethName, err)
                return
        }
 
-       if err = netlink.LinkSetUp(contVeth); err != nil {
+       if err = netlink.LinkSetUp(hostVeth); err != nil {
                err = fmt.Errorf("failed to set %q up: %v", contVethName, err)
                return
        }