Date: Thu, 17 Nov 2011 14:01:04 -0800 From: YongHyeon PYUN <pyunyh@gmail.com> To: Juli Mallett <jmallett@freebsd.org> Cc: freebsd-net <freebsd-net@freebsd.org>, Maksim Yevmenkin <maksim.yevmenkin@gmail.com> Subject: Re: confused with if_baudrate Message-ID: <20111117220104.GD11828@michelle.cdnetworks.com> In-Reply-To: <CACVs6=_HOGNhc84hL7yN1NxmS%2BEO5ykEQhOAQuBvjiyxe9JPrg@mail.gmail.com> References: <CAFPOs6oVZ-%2B8%2B37SoDQmSawAOYnZBAQbLstPaJ5i3wScd8WVeQ@mail.gmail.com> <CACVs6=_HOGNhc84hL7yN1NxmS%2BEO5ykEQhOAQuBvjiyxe9JPrg@mail.gmail.com>
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On Thu, Nov 17, 2011 at 01:39:24PM -0800, Juli Mallett wrote: > On Thu, Nov 17, 2011 at 13:12, Maksim Yevmenkin > <maksim.yevmenkin@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. > Probably the driver could have used something like this. ifp->if_baudrate = IF_Gbps(10UL); I think the driver should update if_baudrate depending on resolved speed(lost link, resolved speed etc). And if we really care about overflowing if_baudrate on 32bit machines, the IF_Gbps macro could be conditionally defined. > Thanks, > Juli.
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