Re: [lwip-users] smtp app & tcp_connect vs lwip_connect

[Newman, Adam]

Hi Simon, thanks for your reply.

You wrote:

There's no need to do that, just use smtp_send_mail_int() , like this:
tcpip_callback(smtp_send_mail_int, your_mail_req)
where your_mail_req is a pointer to a struct smtp_send_request.

I followed this advice, and also removed the malloc for simplicity... and now the test has run stable for 20 minutes and counting (and my server is flooding with emails) :)

I probably should have added a big ATTENTION/EXAMPLE not for this somewhere...

I was already using smtp_send_mail_int, and looking again I see there are mentions of tcpip_callback everywhere in the comments. I think what threw me was the code example at the top of smtp.c, because it doesn't mention the use of tcpip_callback when smtp_sent_mail_int is mentioned as the NON_SYS==0 approach.

Thanks again for writing this application and for your help!
Adam.

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From: lwip-users-bounces+address@hidden [lwip-users-bounces+address@hidden on behalf of address@hidden address@hidden
Sent: 07 February 2015 20:07
To: Mailing list for lwIP users
Subject: Re: [lwip-users] smtp app & tcp_connect vs lwip_connect

Newman, Adam wrote:

The comments for the smtp app state that the smtp_send_request should be created somewhere safe for interrupt context. Is this at all related to the above unsafe-ness

Yes. That is, if I understood you correctly. You should use smtp_send_mail_int (see below) when not calling from tcip_thread.

or a seperate issue? I'm not certain when an object that never gets deleted would ever be unsafe for interrupt context but that probably just reflects my level of knowledge on the topic.

Yes, it is.

I did try creating each smtp_send_request object using a heap_malloc but it still crashes in tcp_input.

You did not do that from within tcpip_thread, did you?

Is this an issue folks are familiar with i.e. is there a silver bullet?

Yes: obey lwIP's threading requirements!!!

Or, is it better (and safer) to avoid tcp_connect directly from the application

If you mean 'application thread' by 'application', then: yes!

and write my own smtp implementation using lwip_connect?

There's no need to do that, just use smtp_send_mail_int() , like this:
tcpip_callback(smtp_send_mail_int, your_mail_req)
where your_mail_req is a pointer to a struct smtp_send_request. I probably should have added a big ATTENTION/EXAMPLE not for this somewhere...

Simon

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