Date: Wed, 20 Aug 2014 11:41:47 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-hackers@freebsd.org Cc: Brooks Davis <brooks@freebsd.org>, "Pokala, Ravi" <rpokala@panasas.com> Subject: Re: Common storage of original MAC address Message-ID: <201408201141.47933.jhb@freebsd.org> In-Reply-To: <20140818081223.GA6099@spindle.one-eyed-alien.net> References: <D0168955.11C3AD%rpokala@panasas.com> <20140818081223.GA6099@spindle.one-eyed-alien.net>
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On Monday, August 18, 2014 4:12:23 am Brooks Davis wrote: > On Sun, Aug 17, 2014 at 11:31:19PM +0000, Pokala, Ravi wrote: > > Hi folks, > > > > At attach-time, the NIC drivers call ether_ifattach(), which stores the > > MAC address in the sockaddr_dl. If the MAC is subsequently changed (like > > by adding the interface to a lagg), if_setlladdr() changes the value in > > the sockaddr_dl. At least, that's the way I'm reading things - is that > > correct? > > > > If so, then we do not keep a copy of the original MAC address. For a > > couple of reasons (diagnostics, asset tracking and reporting), it would be > > very nice if the original MAC were kept somewhere, even after the working > > MAC was changed by if_setlladdr(). > > > > Up till now, Panasas has been saving the original MAC in the softc of > > specific network drivers that we use, and making it accessible via a > > sysctl. That's something we have to do on a per-driver basis, and > > something we have to keep track of on our own. We'd like to put that > > information in a structure all the NIC drivers already use, and get that > > code upstream. Storing it would require a simple change to > > ether_ifattach() to stash it in the new location in addition to in the > > sockaddr_dl, and adding some standard way (a new ioctl or sysctl?) to > > access it. Notably, it would not require changing all the individual > > drivers. > > > > Are there any objections to this idea? Any suggestions as to where we > > might stash the original MAC? > > I think I'd store the original address in struct arpcom at attach time > and publish it in the dev.<driver>.<unit> sysctl namespace. ifnets and device_t's aren't necessarily 1:1 (some multiport NIC drivers might only create a device_t for the adapter). -- John Baldwin
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