Re: [lwip-users] Possible SNTP bug

[ake . forslund]

Hi,

The (possible) bug is present in 1.4.0
as well, I sent a mail about it just yesterday. My guess is that the best
way to go about this is to free the pbuf during retry. To do that safely
I think we need to remove the pcb using udp_remove(pcb) aswell since the
server might still send a response and if we don't remove the pcb it will
try to store data in a pbuf that no longer exist. 

To do this we should prefrebly send
the pcb with the timeout to smtp_retry() somehow.

Note that this is just guesses and assumptions,
I don't know the system good enought to be sure of anything I say... I'll
do some tests this week and see if I can get something working. If you
manage to patch the problem in the meantime I'd be glad if you'd share
your fix with me.

Best Regards
/Åke
-----------------------------
Åke Forslund
0433-273296
NIBE AB
Box 14
S-285 21  Markaryd
Tel +46-(0)433-273296

From:	"Bernhard 'Gustl' Bauer" <address@hidden>
To:	Mailing list for lwIP users <address@hidden>
Date:	2011-08-29 13:38
Subject:	[lwip-users] Possible SNTP bug
Sent by:	address@hidden

---

Hi,

I'm using lwip 1.3, NO_SYS. I know it is not up to date, but the contrib
1.4 for sntp has not changed much since 1.3 and I checked the differences.

My problem is: the HEAP has an overflow when the time server could not
be reached. The pbuf_alloc() in sntp_send_request() has no matching 
pbuf_free() in this case. The only pbuf_free() I found is in 
sntp_recv(), so pbuf can only be freed when there is an answer. 
sntp_send() is called repeatedly by sntp_retry().

Even when the time server can be reached there is a slight increase in
used HEAP space. But this could be dropped packets which would have the
same effect due to the above error.

I can think of 2 solutions: Use always the same pbuf, or free it during
sntp_retry. Some pointers how to do this the right way would be great.

TIA

Gustl


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