Add streaming command execution & port forwarding

Add streaming command execution & port forwarding via HTTP connection
upgrades (currently using SPDY).

pkg/util/net.go

@@ -19,6 +19,7 @@ package util
 import (
 	"fmt"
 	"net"
+	"net/url"
 	"strings"
 )
 
@@ -61,3 +62,24 @@ func (ipnet *IPNet) Set(value string) error {
 func (*IPNet) Type() string {
 	return "ipNet"
 }
+
+// FROM: http://golang.org/src/net/http/client.go
+// 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, "]") }
+
+// FROM: http://golang.org/src/net/http/transport.go
+var portMap = map[string]string{
+	"http":  "80",
+	"https": "443",
+}
+
+// FROM: http://golang.org/src/net/http/transport.go
+// canonicalAddr returns url.Host but always with a ":port" suffix
+func CanonicalAddr(url *url.URL) string {
+	addr := url.Host
+	if !hasPort(addr) {
+		return addr + ":" + portMap[url.Scheme]
+	}
+	return addr
+}