confused with if_baudrate

[Hartmut.Brandt at dlr.de]

Hi,

the 64-bit statistics counters are also likely to be wrong, if the polling interval is too short (it is determined by the interface in the system with the highest baudrate). This can be fixed by setting begemotIfPoll to an appropriate value in bsnmp, though.

harti
________________________________________
From: owner-freebsd-net at freebsd.org [owner-freebsd-net at freebsd.org] on behalf of Maksim Yevmenkin [maksim.yevmenkin at gmail.com]
Sent: Friday, November 18, 2011 9:53 PM
To: Juli Mallett
Cc: freebsd-net
Subject: Re: confused with if_baudrate

On Thu, Nov 17, 2011 at 1:39 PM, Juli Mallett <jmallett at freebsd.org> wrote:
> On Thu, Nov 17, 2011 at 13:12, Maksim Yevmenkin
> <maksim.yevmenkin at gmail.com> wrote:
>> hello,
>>
>> i'm a little bit confused about if_baudrate. from system headers
>>
>> #define if_baudrate     if_data.ifi_baudrate
>>
>> and
>>
>> u_long  ifi_baudrate;           /* linespeed */
>>
>> so, i'm taking this as if_baudrate really should be an interface line
>> speed in megabits per second. am i correct? if so, then it appears
>> that at least some drivers lie about true line speed. for example from
>> ixgbe(4)
>>
>>        ifp->if_baudrate = 1000000000;
>>
>> it looks like its order of magnitude lower (i.e. 1 gigabit per second
>> instead of 10 gigabits per second). am i missing something here or its
>> just a typo?
>
> ixgbe's developer is excessively concerned about overflow on 32-bit
> hosts (and unwilling to correct it under a preprocessor conditional),
> unlike several of the other 10GbE driver developers, although I think
> one 10GbE driver opts to omit if_baudrate entirely.

well, this is unfortunate as if_baudrate reported as part of ifmib,
so, when interface is monitored over snmp value of ifSpeed and
HCOutSpeed can not be trusted :(

thanks,
max
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