[lwip-users] internet over PPP and NAT issue

[Asaf Manasse]

LWIP team hallo,

I am trying to establish Access Point product based on Marvell MW302 WiFi MCU, using the SDK provided by Marvell.

Marvell SDK implement IP Stack using LWIP version 1.4.X ( last commit : 88a57dc98d9793d74f8e1c52729b50188d5a0b4f ) , integrated with wifi.

I have established to implement PPPOS over USB to 3G modem.

These 2 network interfaces (PPP and wlan) are bridged using LWIP NAT implementation of Company called RT-Thread

(taken from https://github.com/RT-Thread/rt-thread/tree/master/components/net/lwip_nat , I have a permission from RT-Thread to use there code ).

at this point we have a internet connection to the wifi clients but with connectivity issues:

1. connection is not stable (from test I can may be guess it's unstable upload).

2. WireShark log reveals multiple Duplicated ACK and TCP RST.

3. tcp debug print: 

[3236.092616] : -+-+-+-+-+-+-+-+-+-+-+-+-+-+ tcp_input: flags 

[3236.096609] : tcp_input: no PCB match found, resetting.

[3236.111094] : tcp_rst: seqno 0 ackno 3423651674.

4. pbuf debug print:

pbuf_header: failed as xxx < yyy (not enough space for new header size)

configurations:

* disabled IP_FORWARD.

* set PPP MRU to be 1020 (USB connection bottlenech)

is there any additional information you need for better understanding of the issue?

Asaf Manasse