Re: [lwip-users] Bug in ip_addr.c concerning Broadcast.

[Leon Woestenberg]

Rodney,

your observation is correct, ip_addr_isbroadcast() did not
check whether the given address argument actually was on the
same network as the given interface was on.

I have fixes this in CVS.

It could be argued that this should be checked elsewhere (BSD
does that check elsewhere).

So, what I wonder, did you find cases in lwIP where the function
could be called with an IP address outside the netif network address?

Regards,

Leon.

On Fri, 19 Nov 2004 16:54:34 -0600, "Rodney Brown" <address@hidden>
said:
> I believe I've found a bug in ipp_addr.c and wanted some confirmation
> before
> fixing it.
> 
> Snippet from ip_addr_isbroadcast(struct ip_addr *addr, struct netif
> *netif)
> .
> .
>   /* host identifier bits are all ones? => network broadcast address */
>   else if ((addr->addr & ~netif->netmask.addr) ==
>            (ip_addr_broadcast.addr & ~netif->netmask.addr))
>     return 1;
> 
> 
> addr is the destination. netif is the device's information. If the
> destination IP is 123.123.123.63, and the local subnet is
> 255.255.255.192,
> the routine will return true, no matter what subnet the address is on.
> 
> Should the code read:  ??
> 
>   else if (((addr->addr & ~netif->netmask.addr) ==
>             (ip_addr_broadcast.addr & ~netif->netmask.addr)) &&
>            ((addr->addr & netif->netmask.addr) == 
>               (netif->ip_addr.addr & netif->netmask.addr)))
> 
>     return 1;
> 
> This checks to be sure the device and destination are on the same subnet,
> and that the last address on that subnet is the destination.
> 
> Thanks,
> Rodney
> 
> 
> 
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