Description
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: [2019/03/21 git 8961bba]
- Development Env: Arduino IDE
- Operating System: Any
Settings in IDE
- Module: Generic ESP8266 Module
- lwip Variant: v1.4
- Flash Mode: dout
- Flash Size: 4MB
- CPU Frequency: 80Mhz
- Upload Using: SERIAL
- Upload Speed: 115200 (serial upload only)
Problem Description
Using ESPAsyncTCP, ESPAsyncWebServer, AsyncWebSocket, lwip v1.4
It is impossible to receive data-chunk larger than MSS size via websockets if MTU of the client device is different from 1500. I can see data is sent to the router, but fragmenting does not work properly, so router refuses to send the data further. Surprisingly, HTML is sent properly.
I was able to find one related issue:
#2437
This was already fixed in lwip2. Related issue + fix:
http://savannah.nongnu.org/bugs/?46384
http://git.savannah.gnu.org/cgit/lwip.git/commit/src?id=8e8571da6a6771f9d2d82bbd0b5a6c27474ce0fc
Can we apply this patch to the local tree here and rebuild liblwip_gcc.a so pre built option works too?
MCVE Sketch
Gist of the sketch, to avoid blowing up the issue with long strings:
https://gist.github.com/mcspr/00e95d3ea8d680aeaa04cbe8a707ba8d
Debug Messages
On Windows machine with MTU of 1492 (meaning, MSS is auto calculated to be 1452)
> netsh interface ipv4 set subinterface "WLAN" mtu=1492
In browser, using lwip v1.4:
SDK:2.2.2-dev(c0eb301)/Core:unix-2.6.0-dev=-194000/lwIP:1.4.0rc2/BearSSL:6778687
client connected
Same log with lwip2 low memory:
SDK:2.2.2-dev(c0eb301)/Core:unix-2.6.0-dev=-194000/lwIP:STABLE-2_1_2_RELEASE/glue:1.1-2-ga501b57/BearSSL:6778687
client connected
aaaaaaaaaaaaaa...
aaaaaaaaaaaaaa...