[lwip-users] lwip reply delayed after long communication idle time

[Jochen Strohbeck]

Hello,

I see the following strange behavior on my ARM controller (here IP=x.100).
After not communicating a for some time (guess half an hour or more) a
request from the host (here IP=x.9) the controller reply is delayed for ca.
3 seconds and seems to cause a TCP re-transmission. After this the reply
time of the controller is as usual. This delay and/or re-transmission may
cause problems for some applications.

Seems like the lwip forgets the IP of the sender after a certain idle time,
right?
Is this a normal behaviour of lets say TCP?
How can I get rid of this or control this?

And yes, I'm still using lwip 1.4 for now.

Thanks,
Jochen


4159    17434.296389    192.168.0.9     192.168.0.100   ICMP    74      Echo 
(ping) request 
id=0x0001, seq=4480/32785, ttl=128 (reply in 4160)
4160    17434.296667    192.168.0.100   192.168.0.9     ICMP    74      Echo 
(ping) reply   
id=0x0001, seq=4480/32785, ttl=255 (request in 4159)
(communication idle) 
4161    26195.148858    192.168.0.9     192.168.0.100   TCP     66      52513 → 
80 [SYN] Seq=0
Win=64240 Len=0 MSS=1460 WS=256 SACK_PERM=1
4162    26198.039871    de:bd:00:00:00:29       Broadcast       ARP     60      
Who has 192.168.0.9?
Tell 192.168.0.100
4163    26198.039884    Dell_7a:2c:51   de:bd:00:00:00:29       ARP     42      
192.168.0.9 is at
98:e7:43:7a:2c:51
4164    26198.148361    192.168.0.9     192.168.0.100   TCP     66      [TCP 
Retransmission]
52513 → 80 [SYN] Seq=0 Win=64240 Len=0 MSS=1460 WS=256 SACK_PERM=1
:



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