[PATCH] Remove dead code in netstat from route.c

[Alexander V. Chernikov]

On 12.07.2011 11:10, Garrett Cooper wrote:
> On Mon, Jul 11, 2011 at 11:16 PM, Alexander V. Chernikov
> <melifaro at ipfw.ru>  wrote:
>> Garrett Cooper wrote:
>>> Hi,
>>>      While trying to determine how to print out routes via kvm for
>>> net-snmp, I noticed that there's a chunk of code from the 4.4 BSD Lite
>>> days that isn't executed in netstat as NewTree is always 0. The
>>> following patch removes that dead code and gets the FreeBSD source for
>>> netstat more in line with NetBSD and OpenBSD's copy.
>>> Thanks!
>>
>> Hello!
>>
>> This code is still working (I've tested it several months ago). Using
>> RT_DUMP sysctl gives us less information than KVM, but this is much more
>>   better way of requesting infromation:
>> KVM heavily assumes RADIX rtee is used and simply implement walking the
>> tree in userland (p_tree()) which is quite hackish. Since some dynamic
>> routing software can change massive amounts of data at once (BGP session
>> with full-view going up/down) or physical interface with several hundred
>> vlans goes up/down - requesting routing data via KVM can lead to fully
>> unexpected behaviour. Calling this on regular basis on net-snmp is not
>> the best thing one can do.
>>
>> Additionally, there can be address families where RADIX is unnecessary
>> complicated since only direct key match is required (MPLS, for example).
>> Moving from RADIX implementation for such family will require a lot of
>> 'if (af == AF_MPLS)' code in many base userland utilities since
>> assumption that RADIX is used do exists in many places, unfortunately.
>>
>> Requesting routes via KVM is completely undocumented and kernel
>> internals dependent way. From the other side, NET_RT_DUMP sysctl is
>> documented in sysctl(3) and is used by all major routing software
>> (quagga, bird,openbgp). It also brings us more RADIX-dependent which
>> should be avoided.
>
>      That's a compelling argument, but why is NewTree hardwired to 0
> then (apart from the fact that kvm works with non-live kernel images)?
I don't know - It was too long ago :)
Walking RADIX directly gives an advantage of accessing its internal 
fields like "refcount" and "use" values which we are get used to see in
'netstat -rn' output, for example.

> Thanks,
> -Garrett
>