Handling MED value

[Eiichiro Watanabe]

> But it seems that your problem is not exactly with signedness, but with
> overflow (instead of saturation). Overflow works also the same for
> signed and unsigned ones.
>
> I thought about this some time ago and probably the best solution would
> be to switch BIRD completely to unsigned behavior (as most route properties
> with 32bit ranage are defined as unsigned) in some major release.
>
It's good idea.
  
>> I tried a workaround below, but it fails to load bird.conf with a syntax error message.
>>
>> bird>  configure
>> Reading configuration from /etc/bird.conf
>> /etc/bird.conf, line 123: Number out of range
>
> What version of BIRD do you use? In the current version, it loads just fine (when i fixed missing
> '}'). But the code does not do what you expect, even if the numeric operations (comparison)
> would be unsigned 32bit - in that case the condition 'bgp_med + 100<  4294967295' would be
> always satisfied.
>
I am using 1.3.4 on Debian/GNU Linux(64bit).
  
> You can write the function like this:
>
> function TEST()
> int n;
> {
>    if (source = RTS_BGP) then {
>      n = bgp_med + 100;
>      if (n>= 0&&  n<  100) then
>        bgp_med = n;
>      else
>        bgp_med = 4294967295;
> }
>
uum..., It's strange.
That fails on my environment.
"bgp_med = 4294967295;" statement in line 93 also looks to fail.

bird> configure
Reading configuration from /etc/bird.conf
/etc/bird.conf, line 93: Number out of range

However, I've realized this as a workaround.

function TEST()
int n;
{
   if (source = RTS_BGP ) then {
     if defined(bgp_med) then {
       n = bgp_med + 100;
       if (n >= 0 && n < 100) then
         bgp_med = 0 - 1;
       else
         bgp_med = n;
     } else {
       bgp_med = 100;
     }
   }
   return true;
}

Any comments?

Thanks,
Eiichiro

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Eiichiro Watanabe
Internet Multifeed Co.