On 03/29/2013 12:30 AM, 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? That is the idea. It just seemed sane to have some minimum specified, but I guess its value depends on the protocol that needs protection as this API is not limited to DHCP. I will remove the minimum. Also I think DHCP should not use the API to protect the whole transaction, but only when there is a message exchange being initiated. > Then, you only need to worry about the max time allowed. True, but I think that also depends on the protocol and possibly also on the solution in the driver to increase a more reliable connection. Some solution may have a negative effect on other functions (eg. bluetooth) which require another maximum timeout opposed to suppressing a scanning. With DHCP in mind I would say somewhere between 5-10 sec. is (more than) enough. > 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... True. Will try to come up with some sane solution for this. Gr. AvS -- 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
