Prefer matching labels and longest matching prefix

...when performing source address selection for IPv6.

These are defined in RFC 6724 section 5 rule 6 (prefer matching label)
and rule 8 (use longest matching prefix).

This change also considers ULA of global scope instead of its own scope,
as per RFC 6724 section 3.1:

   Also, note that ULAs are considered as global, not
   site-local, scope but are handled via the prefix policy table as
   discussed in Section 10.6.

Test: stack_test.TestIPv6SourceAddressSelectionScope

Startblock:
  has LGTM from peterjohnston
  and then
  add reviewer brunodalbo
PiperOrigin-RevId: 348580996

1 files changed, 1 insertions, 43 deletions

diff --git a/pkg/tcpip/header/ipv6_test.go b/pkg/tcpip/header/ipv6_test.go
index 426a873b1..e3fbd64f3 100644
--- a/pkg/tcpip/header/ipv6_test.go
+++ b/pkg/tcpip/header/ipv6_test.go
@@ -215,48 +215,6 @@ func TestLinkLocalAddrWithOpaqueIID(t *testing.T) {
 	}
 }
 
-func TestIsV6UniqueLocalAddress(t *testing.T) {
-	tests := []struct {
-		name     string
-		addr     tcpip.Address
-		expected bool
-	}{
-		{
-			name:     "Valid Unique 1",
-			addr:     uniqueLocalAddr1,
-			expected: true,
-		},
-		{
-			name:     "Valid Unique 2",
-			addr:     uniqueLocalAddr1,
-			expected: true,
-		},
-		{
-			name:     "Link Local",
-			addr:     linkLocalAddr,
-			expected: false,
-		},
-		{
-			name:     "Global",
-			addr:     globalAddr,
-			expected: false,
-		},
-		{
-			name:     "IPv4",
-			addr:     "\x01\x02\x03\x04",
-			expected: false,
-		},
-	}
-
-	for _, test := range tests {
-		t.Run(test.name, func(t *testing.T) {
-			if got := header.IsV6UniqueLocalAddress(test.addr); got != test.expected {
-				t.Errorf("got header.IsV6UniqueLocalAddress(%s) = %t, want = %t", test.addr, got, test.expected)
-			}
-		})
-	}
-}
-
 func TestIsV6LinkLocalMulticastAddress(t *testing.T) {
 	tests := []struct {
 		name     string
@@ -346,7 +304,7 @@ func TestScopeForIPv6Address(t *testing.T) {
 		{
 			name:  "Unique Local",
 			addr:  uniqueLocalAddr1,
-			scope: header.UniqueLocalScope,
+			scope: header.GlobalScope,
 			err:   nil,
 		},
 		{