This repo offers a link layer for esp82xx-nonos-sdk-2. The original goal is to try and use a recent lwIP version for stability reasons. Currently lwIP-v2 is implemented, other IP stacks could be tried.

lwIP version currently used: STABLE_2.1.2

• used by default in esp8266 arduino core (initial pull request)
• TCP is more stable (example1 and example2)
• UDP/TCP codes using lwIP-1.4 need some updates - two examples: arduino and sming
• IPv6 working in Arduino
• SACK-out enabled in Arduino
• NAT support (patch for lwIP-2.1.2, based on previous works, check in patches/)
• esp-open-sdk fork with lwip2 (oldref)

• with Arduino:
  • Install the git version of the esp8266 arduino core
  • Head to tools/sdk/lwip2/
  • Run make install

Remember the MSS footprint: 4*MSS bytes in RAM per tcp connection. The lowest recommanded value is 536.

Espressif binary libraries rely on their lwip implementation. The idea, as described in this comment is to wrap espressif calls, and rewrite them for a new tcp implementation.

Example with lwip1.4's ethernet_input() called by espressif binary blobs finally reaching lwip2's:

-- LWIP2-----------------------------------
#define ethernet_input ethernet_input_LWIP2
- lwip2's ethernet_input_LWIP2_is called
                            (/ \)
                             | |
-- glue (new side)-----------^-v-----------
                             | |
glue_ethernet_input          | |
- maps structures glue->new  |
- calls ethernet_input_LWIP2(^ v)
- maps structures new->glue    |
                             | |
-- glue (old side)-----------^-v-----------
                             | |
ethernet_input():            | |
- maps structures old->glue  | 
- calls glue_ethernet_input (^ v)
- maps structures glue->old    |
                             | |
- espressif blobs -----------^-v-----------
XXXXXXXXXXXXXXXXXXXXXXXXXXXX | | XXXXXXXXXX
wifi calls    ethernet_input(/ \) XXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
-------------------------------------------

Original cleaning and port of espressif's patch set from lwIP-v1.4 to lwIP-v2 with references to lwIP-git-sha1

Discussion on how further work could done

First version of this implementation

Second version for arduino only