Re: [lwip-devel] PING_USE_SOCKETS==0 causes abort()

[address@hidden]

Already fixed, thanks for reporting. Most of these apps are meant as an 
example of how to use the API only, which explains why some of them have 
undiscovered bugs (and also why ping_recv was so careless about input 
checks).

BTW, since it uses a RAW pcb (which means an IP pcb with a custom 
next-protocol), it does know the incoming packet is an IP packet (the 
raw recv-callbacks are called from ip4.c). However, it is not adapted 
for use with IPv6, yet.

Simon


Gisle Vanem wrote:
> I've build latest lwIP (from Git) and built the src\contrib\app\test-app
> program using MSVC. After some time using the port-scanner nmap against
> it, the app calls abort() via LWIP_ERROR() in pbuf_header():
>
>    if (header_size_increment<  0){
>      increment_magnitude = -header_size_increment;
>      /* Check that we aren't going to move off the end of the pbuf */
>      LWIP_ERROR("increment_magnitude<= p->len", (increment_magnitude<= p->len), 
> return 1;);
>
>
> Assertion "increment_magnitude<= p->len" failed at line 524 in pbuf.c
> Got SIGABRT. Backtrace:
>    stackwalker.cpp (1046): StackWalker::ShowCallstack
>    exc-abort.cpp (99): new_abort_handler
>    winsig.c (586): raise
>    abort.c (74): abort
>    pbuf.c (525): pbuf_header
>    ping.c (239): ping_recv
>    raw.c (123): raw_input
>    ip4.c (532): ip_input
>    etharp.c (1351): ethernet_input
>    tcpip.c (114): tcpip_thread
>
> The nice traceback is produces by inserting a line in
> src\contrib\ports\win32\test.c:
>    LoadLibrary("exc-abort.dll");
>
> added before lwip_init(). It's available here:
> http://home.broadpark.no/~gvanem/misc/exc-abort.zip
>
> All this is with '#define PING_USE_SOCKETS 0". Hence the raw API
> is used. Using PING_USE_SOCKET=1, everything is okay. Isn't
> ping supporsed to use the raw API?
>
> Seems the handling of ICMP_ECHO in ping_recv() is too careless.
> Not knowing the details of the raw API, how does ping_recv() know
> it's even receiving a IP-packet? Seems it's just assuming the packet
> is>  PBUF_IP_HLEN.
>
> --gv
>
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