Re: [lwip-users] internet over PPP and NAT issue

[Sylvain Rochet]

Hi Asaf,

On Wed, Jun 21, 2017 at 10:17:52AM +0000, Asaf Manasse wrote:
> 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)

Well, you are using an unsupported version of lwIP as well as 
unsupported third party NAT support, and from what I understand a wifi 
driver provided in a ugly binary blob. PPP in lwIP 1.4.1 is actually 
more than a decade out of date and as such is even more unsupported than 
anything else.

Anyway, please have a look on Git commits 4283ecf774, c0aef7dd6b, and 
ab9feb2e35, maybe that's the issue. At least this is what came to my 
mind.

Sylvain

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