Properly generate the EUI64 interface identifier from an Ethernet address

Fixed a bug where the interface identifier was not properly generated from an
Ethernet address.

Tests: Unittests to make sure the functions generating the EUI64 interface
identifier are correct.
PiperOrigin-RevId: 285494562

3 files changed, 59 insertions, 10 deletions

diff --git a/pkg/tcpip/header/BUILD b/pkg/tcpip/header/BUILD
index 8392cb9e5..f1d837196 100644
--- a/pkg/tcpip/header/BUILD
+++ b/pkg/tcpip/header/BUILD
@@ -38,12 +38,15 @@ go_test(
     size = "small",
     srcs = [
         "checksum_test.go",
+        "ipv6_test.go",
         "ipversion_test.go",
         "tcp_test.go",
     ],
     deps = [
         ":header",
+        "//pkg/tcpip",
         "//pkg/tcpip/buffer",
+        "@com_github_google_go-cmp//cmp:go_default_library",
     ],
 )
 
diff --git a/pkg/tcpip/header/ipv6.go b/pkg/tcpip/header/ipv6.go
index 5275b34d4..fc671e439 100644
--- a/pkg/tcpip/header/ipv6.go
+++ b/pkg/tcpip/header/ipv6.go
@@ -278,33 +278,34 @@ func SolicitedNodeAddr(addr tcpip.Address) tcpip.Address {
 	return solicitedNodeMulticastPrefix + addr[len(addr)-3:]
 }
 
-// EthernetAdddressToEUI64IntoBuf populates buf with a EUI-64 from a 48-bit
-// Ethernet/MAC address.
+// EthernetAdddressToModifiedEUI64IntoBuf populates buf with a modified EUI-64
+// from a 48-bit Ethernet/MAC address, as per RFC 4291 section 2.5.1.
 //
 // buf MUST be at least 8 bytes.
-func EthernetAdddressToEUI64IntoBuf(linkAddr tcpip.LinkAddress, buf []byte) {
+func EthernetAdddressToModifiedEUI64IntoBuf(linkAddr tcpip.LinkAddress, buf []byte) {
 	buf[0] = linkAddr[0] ^ 2
 	buf[1] = linkAddr[1]
 	buf[2] = linkAddr[2]
-	buf[3] = 0xFE
+	buf[3] = 0xFF
 	buf[4] = 0xFE
 	buf[5] = linkAddr[3]
 	buf[6] = linkAddr[4]
 	buf[7] = linkAddr[5]
 }
 
-// EthernetAddressToEUI64 computes an EUI-64 from a 48-bit Ethernet/MAC address.
-func EthernetAddressToEUI64(linkAddr tcpip.LinkAddress) [IIDSize]byte {
+// EthernetAddressToModifiedEUI64 computes a modified EUI-64 from a 48-bit
+// Ethernet/MAC address, as per RFC 4291 section 2.5.1.
+func EthernetAddressToModifiedEUI64(linkAddr tcpip.LinkAddress) [IIDSize]byte {
 	var buf [IIDSize]byte
-	EthernetAdddressToEUI64IntoBuf(linkAddr, buf[:])
+	EthernetAdddressToModifiedEUI64IntoBuf(linkAddr, buf[:])
 	return buf
 }
 
 // LinkLocalAddr computes the default IPv6 link-local address from a link-layer
 // (MAC) address.
 func LinkLocalAddr(linkAddr tcpip.LinkAddress) tcpip.Address {
-	// Convert a 48-bit MAC to an EUI-64 and then prepend the link-local
-	// header, FE80::.
+	// Convert a 48-bit MAC to a modified EUI-64 and then prepend the
+	// link-local header, FE80::.
 	//
 	// The conversion is very nearly:
 	//	aa:bb:cc:dd:ee:ff => FE80::Aabb:ccFF:FEdd:eeff
@@ -313,7 +314,7 @@ func LinkLocalAddr(linkAddr tcpip.LinkAddress) tcpip.Address {
 		0: 0xFE,
 		1: 0x80,
 	}
-	EthernetAdddressToEUI64IntoBuf(linkAddr, lladdrb[IIDOffsetInIPv6Address:])
+	EthernetAdddressToModifiedEUI64IntoBuf(linkAddr, lladdrb[IIDOffsetInIPv6Address:])
 	return tcpip.Address(lladdrb[:])
 }
 
diff --git a/pkg/tcpip/header/ipv6_test.go b/pkg/tcpip/header/ipv6_test.go
new file mode 100644
index 000000000..42c5c6fc1
--- /dev/null
+++ b/pkg/tcpip/header/ipv6_test.go
@@ -0,0 +1,45 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package header_test
+
+import (
+	"testing"
+
+	"github.com/google/go-cmp/cmp"
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+)
+
+const linkAddr = tcpip.LinkAddress("\x02\x02\x03\x04\x05\x06")
+
+func TestEthernetAdddressToModifiedEUI64(t *testing.T) {
+	expectedIID := [header.IIDSize]byte{0, 2, 3, 255, 254, 4, 5, 6}
+
+	if diff := cmp.Diff(expectedIID, header.EthernetAddressToModifiedEUI64(linkAddr)); diff != "" {
+		t.Errorf("EthernetAddressToModifiedEUI64(%s) mismatch (-want +got):\n%s", linkAddr, diff)
+	}
+
+	var buf [header.IIDSize]byte
+	header.EthernetAdddressToModifiedEUI64IntoBuf(linkAddr, buf[:])
+	if diff := cmp.Diff(expectedIID, buf); diff != "" {
+		t.Errorf("EthernetAddressToModifiedEUI64IntoBuf(%s, _) mismatch (-want +got):\n%s", linkAddr, diff)
+	}
+}
+
+func TestLinkLocalAddr(t *testing.T) {
+	if got, want := header.LinkLocalAddr(linkAddr), tcpip.Address("\xfe\x80\x00\x00\x00\x00\x00\x00\x00\x02\x03\xff\xfe\x04\x05\x06"); got != want {
+		t.Errorf("got LinkLocalAddr(%s) = %s, want = %s", linkAddr, got, want)
+	}
+}