probes: migrate leftover API from pkg/probe

This also refactors HaveIPv6Support into returning an error instead of a
bool to keep feature probing APIs consistent across the package and adds
a small test for the probe.

Fixes: #25621.

Signed-off-by: Robin Gögge <r.goegge@isovalent.com>

daemon/cmd/kube_proxy_replacement.go

@@ -30,7 +30,6 @@ import (
 	"github.com/cilium/cilium/pkg/mountinfo"
 	"github.com/cilium/cilium/pkg/node"
 	"github.com/cilium/cilium/pkg/option"
-	"github.com/cilium/cilium/pkg/probe"
 	"github.com/cilium/cilium/pkg/safeio"
 	"github.com/cilium/cilium/pkg/sysctl"
 	wgTypes "github.com/cilium/cilium/pkg/wireguard/types"
@@ -275,7 +274,7 @@ func probeKubeProxyReplacementOptions() error {
 	if option.Config.EnableSocketLB {
 		// Try to auto-load IPv6 module if it hasn't been done yet as there can
 		// be v4-in-v6 connections even if the agent has v6 support disabled.
-		probe.HaveIPv6Support()
+		probes.HaveIPv6Support()
 
 		if option.Config.EnableMKE {
 			if probes.HaveProgramHelper(ebpf.CGroupSockAddr, asm.FnGetCgroupClassid) != nil ||

pkg/datapath/linux/probes/probes.go

@@ -504,6 +504,18 @@ func HaveOuterSourceIPSupport() (err error) {
 	return nil
 }
 
+// HaveIPv6Support tests whether kernel can open an IPv6 socket. This will
+// also implicitly auto-load IPv6 kernel module if available and not yet
+// loaded.
+func HaveIPv6Support() error {
+	fd, err := unix.Socket(unix.AF_INET6, unix.SOCK_STREAM, 0)
+	if errors.Is(err, unix.EAFNOSUPPORT) || errors.Is(err, unix.EPROTONOSUPPORT) {
+		return ErrNotSupported
+	}
+	unix.Close(fd)
+	return nil
+}
+
 // CreateHeaderFiles creates C header files with macros indicating which BPF
 // features are available in the kernel.
 func CreateHeaderFiles(headerDir string, probes *FeatureProbes) error {

pkg/datapath/linux/probes/probes_test.go

@@ -312,3 +312,9 @@ func TestOuterSourceIPProbe(t *testing.T) {
 		t.Fatal(err)
 	}
 }
+
+func TestIPv6Support(t *testing.T) {
+	if err := HaveIPv6Support(); err != nil {
+		t.Fatal(err)
+	}
+}