ESP8266WebServer chunked transfer is broken

[hvxl]

Basic Infos

• This issue complies with the issue POLICY doc.
• I have read the documentation at readthedocs and the issue is not addressed there.
• I have tested that the issue is present in current master branch (aka latest git).
• I have searched the issue tracker for a similar issue.
• If there is a stack dump, I have decoded it.
• I have filled out all fields below.

Platform

• Hardware: [ESP-12]
• Core Version: [074a801]
• Development Env: [Arduino IDE]
• Operating System: [openSUSE]

Settings in IDE

• Module: [NodeMCU 1.0 (ESP-12E Module)]
• Flash Mode: [qio]
• Flash Size: [4MB]
• lwip Variant: [v2 Lower Memory]
• Reset Method: [nodemcu]
• Flash Frequency: [40Mhz]
• CPU Frequency: [80Mhz]
• Upload Using: [SERIAL]
• Upload Speed: [921600] (serial upload only)

Problem Description

Since 2.6.2 chunked HTTP is broken because the web server sends chunk lengths in the wrong location. For one thing, it's sending a chunk length before the headers. For example, the sketch below results in the following data being transmitted (as reported by wireshark):

71
HTTP/1.1 200 OK
Content-Type: text/plain
Accept-Ranges: none
Transfer-Encoding: chunked
Connection: close


0

Webserver bug!

Git bisect indicates that 36f9034 is the first bad commit.

MCVE Sketch

#include <ESP8266WebServer.h>

ESP8266WebServer server(80);

void handleRoot() {
  server.setContentLength(CONTENT_LENGTH_UNKNOWN);
  server.send(200, "text/plain", "");
  server.sendContent("Webserver bug!");
}

void setup() {
  Serial.begin(115200);
  WiFi.begin();
  while (WiFi.status() != WL_CONNECTED) delay(500);
  Serial.println(WiFi.localIP());
  server.on("/", HTTP_GET, handleRoot);
  server.begin();
}

void loop() {
  server.handleClient();
}

Debug Messages