[release-v1.33] Sanitize K8s node names to meet load balancer target displayname requirements (#1182)

* Sanitize K8s node names to meet load balancer target displayname requirements

* Add PR Review suggestions

---------

Co-authored-by: Maximilian Geberl <maximilian.geberl@digits.schwarz>

Author: stackit-ske

pkg/ccm/loadbalancer_spec.go

@@ -1,8 +1,10 @@
 package ccm
 
 import (
+	"crypto/sha256"
 	"fmt"
 	"net/netip"
+	"regexp"
 	"slices"
 	"strconv"
 	"strings"
@@ -200,6 +202,11 @@ var appoximateFlavorsMap = map[string]string{
 	"22b37153-8817-4c85-9805-92426b2f903c": p10, // t2i.1
 }
 
+var (
+	// invalidTargetDisplayNameCharsRegexp matches any character that is NOT alphanumeric or a hyphen
+	invalidTargetDisplayNameCharsRegexp = regexp.MustCompile(`[^a-zA-Z0-9-]`)
+)
+
 // proxyProtocolEnableForPort determines whether portNumber should use the TCP proxy protocol (instead of TCP).
 func proxyProtocolEnableForPort(tcpProxyProtocolEnabled bool, tcpProxyProtocolPortFilter []uint16, portNumber int32) bool {
 	if !tcpProxyProtocolEnabled {
@@ -480,7 +487,7 @@ func lbSpecFromService(
 			address := node.Status.Addresses[j]
 			if address.Type == corev1.NodeInternalIP {
 				targets = append(targets, loadbalancer.Target{
-					DisplayName: &node.Name,
+					DisplayName: new(sanitizeNodeName(node.Name)),
 					Ip:          &address.Address,
 				})
 				break
@@ -754,3 +761,24 @@ func compareLBwithSpec(lb *loadbalancer.LoadBalancer, spec *loadbalancer.CreateL
 
 	return fulfills, immutableChanged
 }
+
+// sanitizeNodeName returns a node name which fits in the DisplayName of a target.
+// Replaces not allowed chars with
+func sanitizeNodeName(nodeName string) string {
+	var sanitizedNodeName string
+	sanitizedNodeName = invalidTargetDisplayNameCharsRegexp.ReplaceAllString(nodeName, "-")
+
+	// return node name if not to long and if not contain any invalid chars
+	if len(sanitizedNodeName) <= 63 &&
+		nodeName == sanitizedNodeName {
+		return nodeName
+	}
+
+	if len(sanitizedNodeName) > 54 {
+		sanitizedNodeName = sanitizedNodeName[0:54]
+	}
+
+	sanitizedNodeName += fmt.Sprintf("-%x", sha256.Sum256([]byte(nodeName)))[:8]
+
+	return sanitizedNodeName
+}

pkg/ccm/loadbalancer_spec_test.go

@@ -1989,3 +1989,37 @@ var _ = DescribeTable("compareLBwithSpec",
 		},
 	}),
 )
+
+var _ = DescribeTable("sanitizeNodeName",
+	func(name, safe string) {
+		Expect(sanitizeNodeName(name)).To(Equal(safe))
+	},
+	Entry("Already safe",
+		"localhost",
+		"localhost",
+	),
+	Entry("Already safe",
+		"node-01",
+		"node-01",
+	),
+	Entry("Already safe exact 63 chars",
+		"node-0123456789012345678901234567890123456789001234567890123456",
+		"node-0123456789012345678901234567890123456789001234567890123456",
+	),
+	Entry("replace dots",
+		"node-01.example.com",
+		"node-01-example-com-7c98300",
+	),
+	Entry("shorten",
+		"a-very-long-node-01234567890123456789012345678901234567890.example.com",
+		"a-very-long-node-0123456789012345678901234567890123456-519d04d",
+	),
+	Entry("shorten and replace dots",
+		"a.very.long.node-01234567890123456789012345678901234567890.example.com",
+		"a-very-long-node-0123456789012345678901234567890123456-f80f0fa",
+	),
+	Entry("replace dots exact 54 chars",
+		"a.very.long.node-0123456789012345678901234.example.com",
+		"a-very-long-node-0123456789012345678901234-example-com-e241059",
+	),
+)