pkg/meta/bandwidth: increase IfbDeviceName size

* Increase entroy from 2 bytes to 7 bytes to prevent collisions
* Extract common library function for hash with prefix
* Refactor portmap plugin to use library function

fixes #347

Co-authored-by: Cameron Moreau <cmoreau@pivotal.io>
Co-authored-by: Mikael Manukyan <mmanukyan@pivotal.io>

plugins/meta/portmap/portmap.go

@@ -20,6 +20,7 @@ import (
 	"sort"
 	"strconv"
 
+	"github.com/containernetworking/plugins/pkg/utils"
 	"github.com/containernetworking/plugins/pkg/utils/sysctl"
 	"github.com/coreos/go-iptables/iptables"
 )
@@ -172,7 +173,7 @@ func genToplevelDnatChain() chain {
 func genDnatChain(netName, containerID string) chain {
 	return chain{
 		table:       "nat",
-		name:        formatChainName("DN-", netName, containerID),
+		name:        utils.MustFormatChainNameWithPrefix(netName, containerID, "DN-"),
 		entryChains: []string{TopLevelDNATChainName},
 	}
 }
@@ -323,11 +324,9 @@ func enableLocalnetRouting(ifName string) error {
 // genOldSnatChain is no longer used, but used to be created. We'll try and
 // tear it down in case the plugin version changed between ADD and DEL
 func genOldSnatChain(netName, containerID string) chain {
-	name := formatChainName("SN-", netName, containerID)
-
 	return chain{
 		table:       "nat",
-		name:        name,
+		name:        utils.MustFormatChainNameWithPrefix(netName, containerID, "SN-"),
 		entryChains: []string{OldTopLevelSNATChainName},
 	}
 }

plugins/meta/portmap/utils.go

@@ -15,7 +15,6 @@
 package main
 
 import (
-	"crypto/sha512"
 	"fmt"
 	"net"
 	"strconv"
@@ -24,8 +23,6 @@ import (
 	"github.com/vishvananda/netlink"
 )
 
-const maxChainNameLength = 28
-
 // fmtIpPort correctly formats ip:port literals for iptables and ip6tables -
 // need to wrap v6 literals in a []
 func fmtIpPort(ip net.IP, port int) string {
@@ -62,12 +59,6 @@ func getRoutableHostIF(containerIP net.IP) string {
 	return ""
 }
 
-func formatChainName(prefix, name, id string) string {
-	chainBytes := sha512.Sum512([]byte(name + id))
-	chain := fmt.Sprintf("CNI-%s%x", prefix, chainBytes)
-	return chain[:maxChainNameLength]
-}
-
 // groupByProto groups port numbers by protocol
 func groupByProto(entries []PortMapEntry) map[string][]int {
 	if len(entries) == 0 {