Export ipv6 address helpers

This is useful for Fuchsia.

PiperOrigin-RevId: 214619681
Change-Id: If5a60dd82365c2eae51a12bbc819e5aae8c76ee9

3 files changed, 37 insertions, 36 deletions

diff --git a/pkg/tcpip/header/ipv6.go b/pkg/tcpip/header/ipv6.go
index 066e48a9a..66c778fe1 100644
--- a/pkg/tcpip/header/ipv6.go
+++ b/pkg/tcpip/header/ipv6.go
@@ -202,3 +202,35 @@ func IsV6MulticastAddress(addr tcpip.Address) bool {
 	}
 	return addr[0] == 0xff
 }
+
+// SolicitedNodeAddr computes the solicited-node multicast address. This is
+// used for NDP. Described in RFC 4291. The argument must be a full-length IPv6
+// address.
+func SolicitedNodeAddr(addr tcpip.Address) tcpip.Address {
+	const solicitedNodeMulticastPrefix = "\xff\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xff"
+	return solicitedNodeMulticastPrefix + addr[len(addr)-3:]
+}
+
+// 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::.
+	//
+	// The conversion is very nearly:
+	//	aa:bb:cc:dd:ee:ff => FE80::Aabb:ccFF:FEdd:eeff
+	// Note the capital A. The conversion aa->Aa involves a bit flip.
+	lladdrb := [16]byte{
+		0:  0xFE,
+		1:  0x80,
+		8:  linkAddr[0] ^ 2,
+		9:  linkAddr[1],
+		10: linkAddr[2],
+		11: 0xFF,
+		12: 0xFE,
+		13: linkAddr[3],
+		14: linkAddr[4],
+		15: linkAddr[5],
+	}
+	return tcpip.Address(lladdrb[:])
+}
diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go
index 468201d77..9b5fa3f6e 100644
--- a/pkg/tcpip/network/ipv6/icmp.go
+++ b/pkg/tcpip/network/ipv6/icmp.go
@@ -153,13 +153,6 @@ const (
 	icmpV6LengthOffset = 25
 )
 
-// solicitedNodeAddr computes the solicited-node multicast address.
-// This is used for NDP. Described in RFC 4291.
-func solicitedNodeAddr(addr tcpip.Address) tcpip.Address {
-	const solicitedNodeMulticastPrefix = "\xff\x02\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01\xff"
-	return solicitedNodeMulticastPrefix + addr[len(addr)-3:]
-}
-
 var broadcastMAC = tcpip.LinkAddress([]byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff})
 
 var _ stack.LinkAddressResolver = (*protocol)(nil)
@@ -171,7 +164,7 @@ func (*protocol) LinkAddressProtocol() tcpip.NetworkProtocolNumber {
 
 // LinkAddressRequest implements stack.LinkAddressResolver.
 func (*protocol) LinkAddressRequest(addr, localAddr tcpip.Address, linkEP stack.LinkEndpoint) *tcpip.Error {
-	snaddr := solicitedNodeAddr(addr)
+	snaddr := header.SolicitedNodeAddr(addr)
 	r := &stack.Route{
 		LocalAddress:      localAddr,
 		RemoteAddress:     snaddr,
diff --git a/pkg/tcpip/network/ipv6/icmp_test.go b/pkg/tcpip/network/ipv6/icmp_test.go
index 0a0563964..e548784ac 100644
--- a/pkg/tcpip/network/ipv6/icmp_test.go
+++ b/pkg/tcpip/network/ipv6/icmp_test.go
@@ -36,33 +36,9 @@ const (
 	linkAddr1 = tcpip.LinkAddress("\x0a\x0b\x0c\x0d\x0e\x0f")
 )
 
-// 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::.
-	//
-	// The conversion is very nearly:
-	//	aa:bb:cc:dd:ee:ff => FE80::Aabb:ccFF:FEdd:eeff
-	// Note the capital A. The conversion aa->Aa involves a bit flip.
-	lladdrb := [16]byte{
-		0:  0xFE,
-		1:  0x80,
-		8:  linkAddr[0] ^ 2,
-		9:  linkAddr[1],
-		10: linkAddr[2],
-		11: 0xFF,
-		12: 0xFE,
-		13: linkAddr[3],
-		14: linkAddr[4],
-		15: linkAddr[5],
-	}
-	return tcpip.Address(lladdrb[:])
-}
-
 var (
-	lladdr0 = linkLocalAddr(linkAddr0)
-	lladdr1 = linkLocalAddr(linkAddr1)
+	lladdr0 = header.LinkLocalAddr(linkAddr0)
+	lladdr1 = header.LinkLocalAddr(linkAddr1)
 )
 
 type testContext struct {
@@ -106,7 +82,7 @@ func newTestContext(t *testing.T) *testContext {
 	if err := c.s0.AddAddress(1, ProtocolNumber, lladdr0); err != nil {
 		t.Fatalf("AddAddress lladdr0: %v", err)
 	}
-	if err := c.s0.AddAddress(1, ProtocolNumber, solicitedNodeAddr(lladdr0)); err != nil {
+	if err := c.s0.AddAddress(1, ProtocolNumber, header.SolicitedNodeAddr(lladdr0)); err != nil {
 		t.Fatalf("AddAddress sn lladdr0: %v", err)
 	}
 
@@ -120,7 +96,7 @@ func newTestContext(t *testing.T) *testContext {
 	if err := c.s1.AddAddress(1, ProtocolNumber, lladdr1); err != nil {
 		t.Fatalf("AddAddress lladdr1: %v", err)
 	}
-	if err := c.s1.AddAddress(1, ProtocolNumber, solicitedNodeAddr(lladdr1)); err != nil {
+	if err := c.s1.AddAddress(1, ProtocolNumber, header.SolicitedNodeAddr(lladdr1)); err != nil {
 		t.Fatalf("AddAddress sn lladdr1: %v", err)
 	}