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Re: [lwip-users] link down and netconn problem

From: Martin Velek
Subject: Re: [lwip-users] link down and netconn problem
Date: Tue, 6 Oct 2009 18:19:50 +0200


thank you for tip. I have to define my own error with positive value.
Currently, I am using a macro netconn_err that sets error to ERR_OK
before every transmitt, netconn_err(conn) = ERR_OK. I do not think,
that a) and b) is a good solution, but it works.


2009/10/6 Kieran Mansley <address@hidden>:
> On Tue, 2009-10-06 at 14:17 +0200, Martin Velek wrote:
>> Hello,
>> my EMAC driver is capable to detect link down(unplugging eth. cable).
>> This situation is returned in low_level_output by ERR_IF and
>> netif->flags &= ~NETIF_FLAG_LINK_UP. This is a normal behavior,
>> netconn_sendto returns ERR_IF.
>> However after plugging cable and sending next packet, this operation
>> fails also with ERR_IF. I have tried to trace programm and this is a
>> sequence of called functions:
>> netconn_sendto
>> netconn_send
>> do_send - return.
>> The first line of do_send function contains "if
>> (!ERR_IS_FATAL(msg->conn->err)) " that causes return without checking
>> the line status.
>> Does it mean, that before any netconn_sendto I should set conn->err to 
>> ERR_OK?
> ERR_IF is deemed to be a fatal error: one from which the connection
> cannot recover.  Clearly in your case this is wrong: unplugging and
> replugging the cable is not a permanent state so not a fatal error.
> What we probably need to do is split ERR_IF into two: one to describe
> fatal errors such as not being able to add the netif, and another
> describing transient errors such as the link going down.  Your
> low_level_output could then return whichever of these is appropriate.
> On a related note, does anyone know why ERR_INPROGRESS is fatal?  I
> don't think it should be.
> Kieran
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