net/http: make Transport send WebSocket upgrade requests over HTTP/1

WebSockets requires HTTP/1 in practice (no spec or implementations
work over HTTP/2), so if we get an HTTP request that looks like it's
trying to initiate WebSockets, use HTTP/1, like browsers do.

This is part of a series of commits to make WebSockets work over
httputil.ReverseProxy. See #26937.

Updates #26937

Change-Id: I6ad3df9b0a21fddf62fa7d9cacef48e7d5d9585b
Reviewed-on: https://go-review.googlesource.com/c/137437
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/net/http/request.go b/src/net/http/request.go
index ac3302934f..967de7917f 100644
--- a/src/net/http/request.go
+++ b/src/net/http/request.go
@@ -1371,3 +1371,10 @@ func requestMethodUsuallyLacksBody(method string) bool {
 	}
 	return false
 }
+
+// requiresHTTP1 reports whether this request requires being sent on
+// an HTTP/1 connection.
+func (r *Request) requiresHTTP1() bool {
+	return hasToken(r.Header.Get("Connection"), "upgrade") &&
+		strings.EqualFold(r.Header.Get("Upgrade"), "websocket")
+}