chore: add eBPF unit tests

internal/upf/ebpf/control_test.go

@@ -0,0 +1,97 @@
+// Copyright 2026 Ella Networks
+// SPDX-License-Identifier: Apache-2.0
+
+//go:build linux
+
+package ebpf
+
+import (
+	"bytes"
+	"encoding/binary"
+	"testing"
+)
+
+// GTP-U control-message handling and ICMPv6 Router Solicitation interception.
+// PMTU / frag-needed generation needs a small-MTU device and is deferred to the
+// netns harness.
+
+// TestGTPControlMessages checks GTP-U control-message dispatch: an echo request
+// is answered (XDP_TX, addresses/ports swapped, type set to echo response);
+// other control messages are passed to the kernel.
+func TestGTPControlMessages(t *testing.T) {
+	requireProgTestRun(t)
+
+	obj := loadN3N6Program(t)
+
+	const (
+		gtpEchoRequest     = 1
+		gtpEchoResponse    = 2
+		gtpErrorIndication = 26
+		gtpEndMarker       = 254
+	)
+
+	t.Run("echo request gets response", func(t *testing.T) {
+		in := gtpControlFrame(gtpEchoRequest)
+
+		action, out := runXDPOut(t, obj.UpfN3N6EntrypointFunc, in)
+
+		if action != XDP_TX {
+			t.Fatalf("got XDP action %d, want XDP_TX (%d)", action, XDP_TX)
+		}
+
+		if len(out) != len(in) {
+			t.Fatalf("frame length changed: got %d, want %d", len(out), len(in))
+		}
+
+		if out[ethHdrLen+20+8+1] != gtpEchoResponse {
+			t.Errorf("GTP message type = %d, want %d (echo response)", out[ethHdrLen+20+8+1], gtpEchoResponse)
+		}
+
+		if !bytes.Equal(out[26:30], testUPFN3IP[:]) || !bytes.Equal(out[30:34], testGNBIP[:]) {
+			t.Errorf("outer IPs not swapped: src=%v dst=%v", out[26:30], out[30:34])
+		}
+
+		if src, dst := binary.BigEndian.Uint16(out[34:36]), binary.BigEndian.Uint16(out[36:38]); src != GTPUDPPort || dst != 3000 {
+			t.Errorf("UDP ports not swapped: src=%d dst=%d, want %d/%d", src, dst, GTPUDPPort, 3000)
+		}
+
+		if !bytes.Equal(out[0:6], []byte{0x02, 0, 0, 0, 0, 0x01}) || !bytes.Equal(out[6:12], []byte{0x02, 0, 0, 0, 0, 0x02}) {
+			t.Errorf("MAC addresses not swapped: dst=%x src=%x", out[0:6], out[6:12])
+		}
+	})
+
+	passThrough := []struct {
+		name    string
+		msgType uint8
+	}{
+		{"echo response passes", gtpEchoResponse},
+		{"error indication passes", gtpErrorIndication},
+		{"end marker passes", gtpEndMarker},
+	}
+
+	for _, tc := range passThrough {
+		t.Run(tc.name, func(t *testing.T) {
+			if action := runXDP(t, obj.UpfN3N6EntrypointFunc, gtpControlFrame(tc.msgType)); action != XDP_PASS {
+				t.Fatalf("got XDP action %d, want XDP_PASS (%d)", action, XDP_PASS)
+			}
+		})
+	}
+}
+
+// TestRouterSolicitationIntercept checks that an inner ICMPv6 Router
+// Solicitation, after decapsulation, is intercepted and dropped (the RA is
+// generated in userspace).
+func TestRouterSolicitationIntercept(t *testing.T) {
+	requireProgTestRun(t)
+
+	const teid = 0x52530001
+
+	obj := loadN3N6Program(t)
+	putForwardingUplinkPDR(t, obj, teid, 0)
+
+	action := runXDP(t, obj.UpfN3N6EntrypointFunc, uplinkGPDU(teid, innerIPv6ICMPv6RS(testUEv6)))
+
+	if action != XDP_DROP {
+		t.Fatalf("Router Solicitation not intercepted: got XDP action %d, want XDP_DROP (%d)", action, XDP_DROP)
+	}
+}