net: SplitHostPort: adjust error message for missing port in IPv6 addresses

An hostport of "[::1]" now results in the same error message
"missing port in address" as the hostport value "127.0.0.1",
so SplitHostPort won't complain about "too many colons
in address" anymore for an IPv6 address missing a port.

Added tests checking the error values.

Fixes #4526.

R=dave, rsc, mikioh.mikioh
CC=golang-dev
https://golang.org/cl/7038045

src/pkg/net/ip_test.go

@@ -269,6 +269,28 @@ var splitjointests = []struct {
 	{"127.0.0.1", "1234", "127.0.0.1:1234"},
 	{"::1", "80", "[::1]:80"},
 	{"google.com", "https%foo", "google.com:https%foo"}, // Go 1.0 behavior
+	{"", "0", ":0"},
+	{"127.0.0.1", "", "127.0.0.1:"},           // Go 1.0 behaviour
+	{"www.google.com", "", "www.google.com:"}, // Go 1.0 behaviour
+}
+
+var splitfailuretests = []struct {
+	HostPort string
+	Err      string
+}{
+	{"www.google.com", "missing port in address"},
+	{"127.0.0.1", "missing port in address"},
+	{"[::1]", "missing port in address"},
+	{"::1", "too many colons in address"},
+
+	// Test cases that didn't fail in Go 1.0
+	{"[foo:bar]", "missing port in address"},
+	{"[foo:bar]baz", "missing port in address"},
+	{"[foo]:[bar]:baz", "too many colons in address"},
+	{"[foo]bar:baz", "missing port in address"},
+	{"[foo]:[bar]baz", "unexpected '[' in address"},
+	{"foo[bar]:baz", "unexpected '[' in address"},
+	{"foo]bar:baz", "unexpected ']' in address"},
 }
 
 func TestSplitHostPort(t *testing.T) {
@@ -277,6 +299,16 @@ func TestSplitHostPort(t *testing.T) {
 			t.Errorf("SplitHostPort(%q) = %q, %q, %v; want %q, %q, nil", tt.Join, host, port, err, tt.Host, tt.Port)
 		}
 	}
+	for _, tt := range splitfailuretests {
+		if _, _, err := SplitHostPort(tt.HostPort); err == nil {
+			t.Errorf("SplitHostPort(%q) should have failed", tt.HostPort)
+		} else {
+			e := err.(*AddrError)
+			if e.Err != tt.Err {
+				t.Errorf("SplitHostPort(%q) = _, _, %q; want %q", tt.HostPort, e.Err, tt.Err)
+			}
+		}
+	}
 }
 
 func TestJoinHostPort(t *testing.T) {

src/pkg/net/ipsock.go

@@ -77,23 +77,62 @@ func SplitHostPort(hostport string) (host, port string, err error) {
 }
 
 func splitHostPort(hostport string) (host, port, zone string, err error) {
+	j, k := 0, 0
+
 	// The port starts after the last colon.
 	i := last(hostport, ':')
 	if i < 0 {
-		err = &AddrError{"missing port in address", hostport}
-		return
+		goto missingPort
 	}
-	host, port = hostport[:i], hostport[i+1:]
-	// Can put brackets around host ...
-	if len(host) > 0 && host[0] == '[' && host[len(host)-1] == ']' {
-		host = host[1 : len(host)-1]
-	} else {
-		// ... but if there are no brackets, no colons.
-		if byteIndex(host, ':') >= 0 {
-			err = &AddrError{"too many colons in address", hostport}
+
+	if hostport[0] == '[' {
+		// Expect the first ']' just before the last ':'.
+		end := byteIndex(hostport, ']')
+		if end < 0 {
+			err = &AddrError{"missing ']' in address", hostport}
 			return
 		}
+		switch end + 1 {
+		case len(hostport):
+			// There can't be a ':' behind the ']' now.
+			goto missingPort
+		case i:
+			// The expected result.
+		default:
+			// Either ']' isn't followed by a colon, or it is
+			// followed by a colon that is not the last one.
+			if hostport[end+1] == ':' {
+				goto tooManyColons
+			}
+			goto missingPort
+		}
+		host = hostport[1:end]
+		j, k = 1, end+1 // there can't be a '[' resp. ']' before these positions
+	} else {
+		host = hostport[:i]
+
+		if byteIndex(host, ':') >= 0 {
+			goto tooManyColons
+		}
 	}
+	if byteIndex(hostport[j:], '[') >= 0 {
+		err = &AddrError{"unexpected '[' in address", hostport}
+		return
+	}
+	if byteIndex(hostport[k:], ']') >= 0 {
+		err = &AddrError{"unexpected ']' in address", hostport}
+		return
+	}
+
+	port = hostport[i+1:]
+	return
+
+missingPort:
+	err = &AddrError{"missing port in address", hostport}
+	return
+
+tooManyColons:
+	err = &AddrError{"too many colons in address", hostport}
 	return
 }