[lwip-devel] [bug #63554] httpc_get_file_dns causes hard fault in tcp_input on RPi Pico W

[Zhang Maiyun]

URL:
  <https://savannah.nongnu.org/bugs/?63554>

                 Summary: httpc_get_file_dns causes hard fault in tcp_input on
RPi Pico W
                 Project: lwIP - A Lightweight TCP/IP stack
               Submitter: myzhang1029
               Submitted: Wed 21 Dec 2022 01:33:14 AM UTC
                Category: TCP
                Severity: 3 - Normal
              Item Group: None
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: git head


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Follow-up Comments:


-------------------------------------------------------
Date: Wed 21 Dec 2022 01:33:14 AM UTC By: Zhang Maiyun <myzhang1029>
When I use httpc_get_file_dns to GET the host dyn.dns.he.net on a Raspberry Pi
Pico,
the device enters a hard fault and hangs. It seems that the error corrupts the
stack
because gdb is unable to produce a proper unwinding (through the JTAG/SWD
interface).
I was able to reliable reproduce the hang on a second RPi Pico W with a GET
request to
any paths, as long as they use the host dyn.dns.he.net. Other hosts, like
bing.com or
example.com, succeed without any problem.

By using print-debugging, I was able to narrow down the hang to line 568 in
src/core/tcp_in.c:

if (inseg.p != NULL) {


Attached are the source files of a minimal example (also available at
https://github.com/myzhang1029/codes/tree/main/rpi-pico/2022_lwip_httpc_bug_reprex).






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File Attachments:


-------------------------------------------------------
Date: Wed 21 Dec 2022 01:33:14 AM UTC  Name: reprex.c  Size: 1KiB   By:
myzhang1029

<http://savannah.nongnu.org/bugs/download.php?file_id=54131>
-------------------------------------------------------
Date: Wed 21 Dec 2022 01:33:14 AM UTC  Name: lwipopts.h  Size: 5KiB   By:
myzhang1029

<http://savannah.nongnu.org/bugs/download.php?file_id=54132>

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