[lwip-devel] [patch #10358] dhcp_start : save dhcp memory type flag.

[Shawn Silverman]

Follow-up Comment #3, patch #10358 (project lwip):

[comment #2 comment #2:]
> 
> [comment #1 comment #1:]
> > [comment #0 original submission:]
> > > dhcp_start reset all dhcp flags, so a statically allocated struct dhcp
which was inited by dhcp_set_struct will try to release its memory in
dhcp_cleanup, and that is incorrect.
> > 
> > dhcp_cleanup() isn't supposed to be called if using dhcp_set_struct(). See
the dhcp_cleanup() docs in dhcp.c:
> > 
> >  * ATTENTION: Only use this when not using dhcp_set_struct() to allocate
the
> >  *            struct dhcp since the memory is passed back to the heap.
> > 
> 
> I think maybe the doc of dhcp_cleanup() is outdated, because after version
2.2.0 the dhcp_cleanup() was designed to accept struct dhcp which allocated by
 dhcp_set_struct(), the dhcp_cleanup() can prevent passing external data to
heap by check flag DHCP_FLAG_EXTERNAL_MEM.
> The problem is this flag will be cleared in dhcp_start(), cause
dhcp_cleanup() pass external memory to heap incorrectly, and my patch is used
to fix this problem.
> 

I see what you're saying. I'll suggest changing the comment and fixing the
flag, however.

Change:

    /* save dhcp memory type flag, so we can restore it after clear data
structure */
    dhcp_flags = dhcp->flags & DHCP_FLAG_EXTERNAL_MEM;


To this:

    /* save memory type flag so we can restore it after clearing the structure
*/
    dhcp_flags |= DHCP_FLAG_EXTERNAL_MEM;




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