lwIP - A Lightweight TCP/IP stack - Bugs: bug #65630, issue to download file bigger than...
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bug #65630: issue to download file bigger than 6KB using using https protocol
Submitter: | Stefano Oliveri <stf12> | ||
Submitted: | Tue 23 Apr 2024 09:12:30 AM UTC | ||
Category: | None | Severity: | 3 - Normal |
Item Group: | Faulty Behaviour | Status: | None |
Privacy: | Public | Assigned to: | None |
Open/Closed: | Open | Planned Release: | None |
lwIP version: | 2.2.0 |
Tue 30 Apr 2024 03:22:25 PM UTC, comment #1: |
Stefano Oliveri <stf12> |
Tue 23 Apr 2024 09:12:30 AM UTC, original submission:
Hello,
|
Stefano Oliveri <stf12> |
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Follows 1 latest change.
Date | Changed by | Updated Field | Previous Value | => | Replaced by |
---|---|---|---|---|---|
2024-04-23 | stf12 | Attached File | - | Added bug_fota_https.zip, #55958 |
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Corresponding source code
Hello,
I was able, finally, to move forward and make my application works.
The issue I noted (I am sure it depends on my integration of lwIP and Mbed TLS in the application), analyzing the communication sniffed with Wireshark, was a TCP Zero Window. I am trying to understand this mechanism, so any comment is welcome.
This TCP window size depends on the TCP_WND. At the beginning it 7300 in my case, and it worked fine without TLS. When I added the support the TCP window start to shrink when I download "not small" file until the Zero Window problem occurs.
By increasing TCP_WND up to 21900 my application (seems to) works fine with both http and https.
There are a couple of question in my mind I would like to understand:
1. is this analysis correct? Is that the root cause? Or the TCP/IP should be able to work also with small TCP Window?
2. How to size correctly the TCP_WND option?
Best regards,
Stefano