Tuning or disabling wake-on-network without disabling WOL
I see I'm not the only one who objects to this new feature. I'm getting constant unwanted wakeups.
SSH port scans are just one cause of spurious wakeups. I've been capturing the network traffic into my Mac, and sometimes it wakes for no apparent reason at all.
Prior to Snow Leopard, I could remotely turn on my Mac by logging into a low power Linux system with SSH and running a command-line program (ether-wake) that generated the magic packet. (The magic packet is not an IP packet, so it won't pass through routers; it has to be originated on the same Ethernet segment). The only option Snow Leopard has is to turn off Wake On Network, and that disables Wake On LAN entirely. There's no way to restore the functionality I had prior to Snow Leopard!
I can see how command-line programs might not satisfy some Mac users, so the sleep proxy subsystem really needs a set of Preferences to let the user specify which events (i.e., which network services) will or will not wake the machine. The user should also have the option of disabling all wakeups in response to normal network requests while retaining the ability to wake up the system with an explicit, authenticated remote request through the sleep proxy device (e.g., the Airport base station).
Packet tracing shows that as the Mac prepares to enter sleep mode, it sends a series of DNS Update messages to the sleep proxy listing the services that it supports. When the Mac is asleep, the proxy answers ARPs for the sleeping host, and it answers service discovery requests for the sleeping Mac. In this way, the proxy intercepts IP packets intended for the Mac, issues the Magic Packet to the Mac to wake it up, and then forwards the service requests, allowing the Mac to reclaim its IP address with ARP. So one way to tell whether a Mac is sleeping with the proxy service activated is to ARP for its IP address with a command like "arpping"; during sleep, the proxy will answer those ARPs with its own Ethernet MAC address.
