I've updated the remaining comments to mention the same priority on git
master
Another thing you could do is have your application track number of
active connections, make sure enough TCP pcbs are configured and then
close the listener pcb once the maximum is reach.
Joel
On 10/24/2017 10:38 AM, Mattia Settin wrote:
Yes
The main problem was related that the tcp_kill_prio() kills the active
pcb with a priority equals to the pcb passaed in input.
For my specific web server application, this lead to send a (sporadic)
RST ACK to the client, when the tcp_alloc fails to allocate new
connection.
br
On Tue, Oct 24, 2017 at 4:34 PM, Axel Lin <axel....@ingics.com
<mailto:axel....@ingics.com>> wrote:
2017-10-24 16:37 GMT+08:00 Axel Lin <axel....@ingics.com
<mailto:axel....@ingics.com>>:
> 2017-10-24 1:13 GMT+08:00 Mattia Settin <mattia.set...@gmail.com
<mailto:mattia.set...@gmail.com>>:
>> Dear all
>> After a week of debugging I finally find the issue. The problem
is related to priority in pcb.
>> Taking a deep look I saw that the priority in the stack 1.4.1
is change, in particular:
>> Tcp_alloc return e pcb with a prior equal to the prior passed
in input.
>> Tcp_listen_with_backlog return e pcb with a prior equal to the
pcb.prior passed in input.
>> This two changes lead to a sporadic RST ACK call from the
kill_prio routine.
>> Finally I fix this issue removing the equal condition in the
kill_prio function.
>
> The comment on the code seems confusion for "the same priority
case":
> (I check the latest git tree)
>
> Th comment on the caller:
> /* Try killing active connections with lower priority than
> the new one. */
> LWIP_DEBUGF(TCP_DEBUG, ("tcp_alloc: killing connection
with
> prio lower than %d\n", prio));
> tcp_kill_prio(prio);
>
> But the comment on tcp_kill_prio() function:
> /**
> * Kills the oldest active connection that has the same or lower
priority than
> * 'prio'.
The comment for tcp_kill_prio() is updated by:
commit 6a4c30fe5d65 fixed bug #31723 (tcp_kill_prio() kills pcbs with
the same prio) by updating its documentation only
And take a look at bug #31723: tcp_kill_prio() kills pcbs with the
same prio
According to its documentation, tcp_kill_prio() kills "the oldest
active connection that has lower priority than prio". However, the
current code also kills connections with a priority equal to 'prio'.
We should either change the documentation or the implementation.
The downside of the current implementation is that every call to
tcp_new() can lead to aborting an old (active) connection.
This has been in there since revision 1.1 of tcp.c, so changing it
might involve changing applications relying on this (like I have one
:).
I'm wondering if it should change the implementation rather than the
documentation.
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--
Mattia Settin
System engineer
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