Rapid DHCP: Or, how do Macs get on the network so fast?

Post by caf » Wed, Jul 13, 2011, 5:44 AM UTC

hristov wrote: post #146

dotBen wrote: post #4

There already exists a minimal DHCP client implementation in the Linux kernel, but it lacks certain features such as configuring the DNS nameservers. I wonder if it is possible to use the kernel-level DHCP client to instantly request the IP address while asynchronously initiating the more functional user-mode dhclient? Once dhclient is up, and the kernel DHCP client has obtained an IP address it could just pass that…

The whole kernel discussion seems to be a red herring. The reason the android device was so slow is because the DHCP server timed out twice on a DHCP request. Those two timeouts caused 10s of the 11s delay. I think there probably was something wrong with the DHCP server configuration.

Post by [deleted] » Wed, Jul 13, 2011, 5:53 AM UTC

aaronblohowiak wrote: post #53

cbs wrote: post #32

Earlier quoted context omitted.

The lower level networking protocols do rely on some levels of peer trust, but carefully controlling that trust has come a long way in the last decade. If I'm correct in assuming by "actual security" you mean "physical security" you're making some pretty broad and faulty statements (even about layer 1). There are many networking devices and techniques for hardening hostile networks at layer 2. Layer 3 is IP; to say l…

Sorry, I double-posted accidentally and it looks like I deleted the wrong one. I meant that layers 1-4 should not be relied upon to provide your application security. You are right that there are cool advances that can be worthwhile to slow down attackers, but I think that in most circumstances, you will want to make your guarantees higher up the stack* *I am not a security expert

Post by caf » Wed, Jul 13, 2011, 6:04 AM UTC

pohl wrote: post #59

juliano_q wrote: post #41

The mac implementation is good for 99% of the times, since it is really fast, but the 1% of the times that it steals an ip adress it is really a pain in the ass. I don't mind to wait a few seconds to get a connection in the stardard way.

...but the 1% of the times that it steals an ip adress... Could someone explain how we're imagining this might happen? If my Dell Precision laptop is using the contended IP Address, then why didn't its interface's mac address get returned by the ARP who-has request for that IP?

Post by smutticus » Wed, Jul 13, 2011, 6:52 AM UTC

saurik wrote: post #15

> This network recognition technique allows the Mac to very rapidly discover if it is connected to a known network. If the network is recognized (and presumably if the Mac knows that the DHCP lease is still active), it immediately and presumptuously configures its IP interface with the address it knows is good for this network. Ok, seriously? That isn't a bug in an implementation somewhere, but in fact a feature that…

Post by [deleted] » Wed, Jul 13, 2011, 7:04 AM UTC

shinratdr wrote: post #119

sid0 wrote: post #94

Earlier quoted context omitted.

And yet it is exactly as dickish and disrespectful of others. Just like Apple as a whole, it seems.

Meh. Treating developers and the back end gingerly results in no benefit for consumers, in fact by and large it results in in a pretty clear loss. Characterize it however you wish, as a user I'm going to go with the platform that focuses on pleasing me rather than making the lives of other users or developers easier.