http2, internal/httpcommon: factor out common request header logic for h2/h3

HTTP/2 and HTTP/3 use the same set of pseudo-headers to represent
requests and responses. Move the http2 package's logic for validating
an http.Request and converting it to a set of pseudo-headers into
internal/httpcommon so it can be shared with HTTP/3.

For golang/go#70914

Change-Id: I80561752e821ccd0da2a811034c44f3f71064434
Reviewed-on: https://go-review.googlesource.com/c/net/+/643780
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Brad Fitzpatrick <[email protected]>
Commit-Queue: Damien Neil <[email protected]>
Reviewed-by: Jonathan Amsterdam <[email protected]>
Auto-Submit: Damien Neil <[email protected]>

Author: neild

http2/http2.go

@@ -415,23 +415,6 @@ func (s *sorter) SortStrings(ss []string) {
 	s.v = save
 }
 
-// validPseudoPath reports whether v is a valid :path pseudo-header
-// value. It must be either:
-//
-//   - a non-empty string starting with '/'
-//   - the string '*', for OPTIONS requests.
-//
-// For now this is only used a quick check for deciding when to clean
-// up Opaque URLs before sending requests from the Transport.
-// See golang.org/issue/16847
-//
-// We used to enforce that the path also didn't start with "//", but
-// Google's GFE accepts such paths and Chrome sends them, so ignore
-// that part of the spec. See golang.org/issue/19103.
-func validPseudoPath(v string) bool {
-	return (len(v) > 0 && v[0] == '/') || v == "*"
-}
-
 // incomparable is a zero-width, non-comparable type. Adding it to a struct
 // makes that struct also non-comparable, and generally doesn't add
 // any size (as long as it's first).

http2/server.go

@@ -50,6 +50,7 @@ import (
 
 	"golang.org/x/net/http/httpguts"
 	"golang.org/x/net/http2/hpack"
+	"golang.org/x/net/internal/httpcommon"
 )
 
 const (
@@ -812,8 +813,7 @@ const maxCachedCanonicalHeadersKeysSize = 2048
 
 func (sc *serverConn) canonicalHeader(v string) string {
 	sc.serveG.check()
-	buildCommonHeaderMapsOnce()
-	cv, ok := commonCanonHeader[v]
+	cv, ok := httpcommon.CachedCanonicalHeader(v)
 	if ok {
 		return cv
 	}