[lwip-devel] [bug #56708] ip6_debug_print is called in ip6_input at the wrong place

[Gunar Schorcht]

URL:
  <https://savannah.nongnu.org/bugs/?56708>

                 Summary: ip6_debug_print is called in ip6_input at the wrong
place
                 Project: lwIP - A Lightweight TCP/IP stack
            Submitted by: gschorcht
            Submitted on: Fri 02 Aug 2019 12:19:38 PM UTC
                Category: IPv6
                Severity: 3 - Normal
              Item Group: Faulty Behaviour
                  Status: None
                 Privacy: Public
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
         Planned Release: None
            lwIP version: git head

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Details:

The call of function `ip6_debug_print` to print the header of a received IPv6
packet is at the wrong place in function `ip6_input`.

In current source, function `ip6_debug_print` is called in [line 1044 in
ip6.c](http://git.savannah.nongnu.org/cgit/lwip.git/tree/src/core/ipv6/ip6.c#n1044).
However, this is after the header has been already removed with

<code>
`pbuf_remove_header(p, IP6_HLEN)`;

</code>

in [line 704 in
ipv6](http://git.savannah.nongnu.org/cgit/lwip.git/tree/src/core/ipv6/ip6.c#n1044).
Therefore, the call results into an output that makes no sense, for example:

<code>
IPv6 header:
+-------------------------------+
|  3 |    3  |       638977     | (ver, class, flow)
+-------------------------------+
|     39724     |  127  |   45  | (plen, nexth, hopl)
+-------------------------------+
|     0 |  196e |  6012 |  7080 | (src)
|  f128 |     0 |   204 |   5a0 |
+-------------------------------+
|   7d0 |   101 |  6ad3 |  9b1a | (dest)
|   7d1 |  5425 |  7c22 |     0 |
+-------------------------------+
ip6_input: p->len 24 p->tot_len 24
</code>

In this example, the payload (TCP Header) is interpreted as IPv6 Header. Also
the given length of `*p` is less than the minimum size of 40 byte of an IPv6
header.

>From my point of view, the debug output should be placed at [line 697 in
ip6.c](http://git.savannah.nongnu.org/cgit/lwip.git/tree/src/core/ipv6/ip6.c#n697).




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