net/http: normalize empty port in URL.Host's ":port"

- Ensures that the empty port and preceeding ":"
in a URL.Host are stripped.
Normalize the empty port in a URL.Host's ":port" as
mandated by RFC 3986 Section 6.2.3 which states that:
`Likewise an explicit ":port", for which the port is empty or
the default for the scheme, is equivalent to one where the port
and its ":" delimiter are elided and thus should be
removed by scheme-based normalization.`

- Moves function `hasPort` from client.go (where it was defined but
not used directly), to http.go the common area.

Fixes #14836

Change-Id: I2067410377be9c71106b1717abddc2f8b1da1c03
Reviewed-on: https://go-review.googlesource.com/22140
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/src/net/http/http.go b/src/net/http/http.go
index 7484348f52..a121628632 100644
--- a/src/net/http/http.go
+++ b/src/net/http/http.go
@@ -4,6 +4,10 @@
 
 package http
 
+import (
+	"strings"
+)
+
 // maxInt64 is the effective "infinite" value for the Server and
 // Transport's byte-limiting readers.
 const maxInt64 = 1<<63 - 1
@@ -18,3 +22,16 @@ type contextKey struct {
 }
 
 func (k *contextKey) String() string { return "net/http context value " + k.name }
+
+// Given a string of the form "host", "host:port", or "[ipv6::address]:port",
+// return true if the string includes a port.
+func hasPort(s string) bool { return strings.LastIndex(s, ":") > strings.LastIndex(s, "]") }
+
+// removeEmptyPort strips the empty port in ":port" to ""
+// as mandated by RFC 3986 Section 6.2.3.
+func removeEmptyPort(host string) string {
+	if hasPort(host) {
+		return strings.TrimSuffix(host, ":")
+	}
+	return host
+}