On Thu, 2013-03-28 at 16:30 -0700, Ben Greear wrote: > On 03/28/2013 04:01 PM, Dan Williams wrote: > > On Thu, 2013-03-28 at 23:44 +0100, Johannes Berg wrote: > >> On Thu, 2013-03-28 at 17:42 -0500, Dan Williams wrote: > >> > >>>> Well, you can do DHCP a second or so, I'd think? And EAPOL much quicker, > >>>> of course. I don't really see any reasonable minimum time? We might want > >>>> to enforce a max though, maybe. > >>> > >>> Not quite. A lot is dependent on the server itself, and I've had users > >>> on university and corporate networks report it sometimes takes 30 to 60 > >>> seconds for the whole DHCP transaction to complete (DISCOVER, REQUEST, > >>> OFFER, ACK). Sometimes there's a NAK in there if the server doesn't > >>> like your lease, which means you need another round-trip. So in many > >>> cases, it's a couple round-trips and each of these packets may or may > >>> not get lost in noisy environments. > >> > >> Oh, yes, of course. However, we're talking about optimising the good > >> cases, not the bad ones. Think of it this way: if it goes fast, we > >> shouldn't make it slow by putting things like powersave or similar in > >> the way. If it's slow, then it'll still work, just slower. But when > >> "slower" only means a few hundred milliseconds, it doesn't matter if > >> everything takes forever (30-60 secs) > > > > True, but at least 4 or 5 seconds is the minimum time I'd recommend here > > for DHCP. > > Couldn't dhcp just turn off the critical protection as soon as it is done? > > Then, you only need to worry about the max time allowed. Yes, that's really what I meant. 4 - 5 seconds is the "best worst-case scenario", clearly when a lease is acquired the critical protection would be turned off by the connection manager. But if something doesn't turn it off, and the 802.11 stack needs a timeout value, I would suggest 4 or 5 seconds for that. Dan > Also, you would probably need to enforce in the kernel that only > x out of y time in any given period can be locked, otherwise lots > of different dhclient processes (perhaps erroneously spawned..or > running on lots of different VIFs) could basically disable scanning > or channel changes... > > Thanks, > Ben > -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
