[Dnsmasq-discuss] [PATCH] dnsmasq 2.47 introduced a work-around for errant Windows behaviour, in that it did not assign IP addresses ending in .255 or .0 within the class c range even when using supernetting. 15 years on, the Windows versions that were broken in this way have reached end of support, and so we can now swing these addresses into use.

[Geert Stappers]

On Tue, Sep 24, 2024 at 08:52:37AM +0200, Jan Ceuleers wrote:
> Signed-off-by: Jan Ceuleers <jan.ceuleers at gmail.com>
> Reviewed-by: Wang Xiaobo <xiangbo.wang at nokia-sbell.com>
> ---
>  src/dhcp.c | 9 +--------
>  1 file changed, 1 insertion(+), 8 deletions(-)
> 
> diff --git a/src/dhcp.c b/src/dhcp.c
> index b65facd..586117d 100644
> --- a/src/dhcp.c
> +++ b/src/dhcp.c
> @@ -821,16 +821,9 @@ int address_allocate(struct dhcp_context *context,
>  	      if (addr.s_addr == d->router.s_addr)
>  		break;
>  
> -	    /* Addresses which end in .255 and .0 are broken in Windows even when using 
> -	       supernetting. ie dhcp-range=192.168.0.1,192.168.1.254,255,255,254.0
> -	       then 192.168.0.255 is a valid IP address, but not for Windows as it's
> -	       in the class C range. See  KB281579. We therefore don't allocate these 
> -	       addresses to avoid hard-to-diagnose problems. Thanks Bill. */	    
>  	    if (!d &&
>  		!lease_find_by_addr(addr) && 
> -		!config_find_by_address(daemon->dhcp_conf, addr) &&
> -		(!IN_CLASSC(ntohl(addr.s_addr)) || 
> -		 ((ntohl(addr.s_addr) & 0xff) != 0xff && ((ntohl(addr.s_addr) & 0xff) != 0x0))))
> +		!config_find_by_address(daemon->dhcp_conf, addr))
>  	      {
>  		/* in consec-ip mode, skip addresses equal to
>  		   the number of addresses rejected by clients. This
> -- 
> 2.34.1
> 


For marking the patch as "got feedback":


On Mon, Sep 30, 2024 at 02:22:38PM +0200, Jan Ceuleers wrote:
> 
> Dear Simon and other list participants,
> 
> Thank you for the feedback. The discussion has convinced me that the
> balance between risk and potential benefit is not favourable.
> 
> I also take the point that making this special treatment configurable,
> while enabling the small benefits to be realised for those willing to
> take the associated risks, would require the admin to be very
> well-informed in order to make the appropriate decision.
> 
> Thank you again.
> 
> Cheers, Jan
> 


Groeten
Geert Stappers
-- 
Silence is hard to parse