http2: case insensitive handling for 100-continue

rfc 9110, section 10.1.1 states that the Expect field value is case-insensitive. Fixes golang/go#57824 Change-Id: Ie0e2662c58a2933087e0d35935c04ec61026a41d Reviewed-on: https://go-review.googlesource.com/c/net/+/463096 Auto-Submit: Damien Neil <dneil@google.com> Run-TryBot: Damien Neil <dneil@google.com> Reviewed-by: Damien Neil <dneil@google.com> Reviewed-by: Matthew Dempsky <mdempsky@google.com> TryBot-Result: Gopher Robot <gobot@golang.org>

Author: fraenkel

http2/server.go

@@ -2192,7 +2192,7 @@ func (sc *serverConn) newWriterAndRequestNoBody(st *stream, rp requestParam) (*r
 tlsState = sc.tlsState
 }
 
-needsContinue := rp.header.Get("Expect") == "100-continue"
+needsContinue := httpguts.HeaderValuesContainsToken(rp.header["Expect"], "100-continue")
 if needsContinue {
 rp.header.Del("Expect")
 }

http2/server_test.go

@@ -2332,7 +2332,7 @@ func TestServer_Response_Automatic100Continue(t *testing.T) {
 }, func(st *serverTester) {
 st.writeHeaders(HeadersFrameParam{
 StreamID: 1, // clients send odd numbers
-BlockFragment: st.encodeHeader(":method", "POST", "expect", "100-continue"),
+BlockFragment: st.encodeHeader(":method", "POST", "expect", "100-Continue"),
 EndStream: false,
 EndHeaders: true,
 })