caddyhttp: Implement handler abort; new 'abort' directive (close #3871) (#3983)

* caddyhttp: Implement handler abort; new 'abort' directive (close #3871)

* Move abort directive ordering; clean up redirects

Seems logical for the end-all of handlers to go at the... end.

The Connection header no longer needs to be set there, since Close is
true, and the static_response handler now does that.

caddyconfig/httpcaddyfile/builtins.go

@@ -40,6 +40,7 @@ func init() {
 	RegisterHandlerDirective("root", parseRoot)
 	RegisterHandlerDirective("redir", parseRedir)
 	RegisterHandlerDirective("respond", parseRespond)
+	RegisterHandlerDirective("abort", parseAbort)
 	RegisterHandlerDirective("route", parseRoute)
 	RegisterHandlerDirective("handle", parseHandle)
 	RegisterDirective("handle_errors", parseHandleErrors)
@@ -502,6 +503,15 @@ func parseRespond(h Helper) (caddyhttp.MiddlewareHandler, error) {
 	return sr, nil
 }
 
+// parseAbort parses the abort directive.
+func parseAbort(h Helper) (caddyhttp.MiddlewareHandler, error) {
+	h.Next() // consume directive
+	for h.Next() || h.NextBlock(0) {
+		return nil, h.ArgErr()
+	}
+	return &caddyhttp.StaticResponse{Abort: true}, nil
+}
+
 // parseRoute parses the route directive.
 func parseRoute(h Helper) (caddyhttp.MiddlewareHandler, error) {
 	sr := new(caddyhttp.Subroute)

caddyconfig/httpcaddyfile/directives.go

@@ -69,6 +69,7 @@ var directiveOrder = []string{
 	"php_fastcgi",
 	"file_server",
 	"acme_server",
+	"abort",
 }
 
 // directiveIsOrdered returns true if dir is

modules/caddyhttp/autohttps.go

@@ -410,7 +410,6 @@ func (app *App) makeRedirRoute(redirToPort uint, matcherSet MatcherSet) Route {
 				StatusCode: WeakString(strconv.Itoa(http.StatusPermanentRedirect)),
 				Headers: http.Header{
 					"Location": []string{redirTo},
-					"Connection": []string{"close"},
 				},
 				Close: true,
 			},

modules/caddyhttp/staticresp.go

@@ -42,6 +42,11 @@ type StaticResponse struct {
 	// If true, the server will close the client's connection
 	// after writing the response.
 	Close bool `json:"close,omitempty"`
+
+	// Immediately and forcefully closes the connection without
+	// writing a response. Interrupts any other HTTP streams on
+	// the same connection.
+	Abort bool `json:"abort,omitempty"`
 }
 
 // CaddyModule returns the Caddy module information.
@@ -101,10 +106,18 @@ func (s *StaticResponse) UnmarshalCaddyfile(d *caddyfile.Dispenser) error {
 }
 
 func (s StaticResponse) ServeHTTP(w http.ResponseWriter, r *http.Request, _ Handler) error {
-	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
+	// close the connection immediately
+	if s.Abort {
+		panic(http.ErrAbortHandler)
+	}
 
 	// close the connection after responding
-	r.Close = s.Close
+	if s.Close {
+		r.Close = true
+		w.Header().Set("Connection", "close")
+	}
+
+	repl := r.Context().Value(caddy.ReplacerCtxKey).(*caddy.Replacer)
 
 	// set all headers
 	for field, vals := range s.Headers {