WWDC2001 Session 303

Transcript

Kind: captions Language: en never configuration and mobility architecture on Mac os10 in particular going to be talking about the particular pieces that we have and how they interact and not going to be talking about api's today unfortunately because what we have today is all private and it's a work in progress so what we're looking what we're looking from you guys today in particular is some feedback on the kinds of configuration questions you'd like to answer we have some api's and I'll talk about that a little bit later so what are some of the goals that we have and we'd like to support dynamic network configuration changes on Mac OS 9 everybody was used to the idea that you know you don't have to reboot your computer to make a change so Mac OS 10 has that now as well the other thing that we wanted on top of what we have in nine is the ability to configure multiple network interfaces at the same time and actually make use of them in a sensible way the other goal that we have is to avoid user intervention when it's possible so a couple of examples you've got a laptop that you're using for work and at home and you're working on some project at home and you're using the network you put the systems asleep you bring it to work you plug it in and it just works because using DHCP and it figures out a new address and it just works or if that's not possible you switch locations and you pick up your new config just like on nine another config that uses a multihoming is the LAN and Airport configured simultaneously so your system prefers land over airport wild land is connected but when land excuse me this connects the system switches over to using airport automatically so to be able to support this kind of thing we have a set of requirements the first thing that we need some sort of low-level Network events so when the link status changes we need to be able to find out about it and do something we need some sort of persistent storage to be able to store the never configs we also knew we needed some sort of dynamic store just to be able to store temporary information or dynamic information as its generated such as information from a DHCP client a server or a PPP server the other thing we need is some mechanism to be able to apply some configuration to the system together requirement we have is some sort of flexible schema in both the persistent and dynamic store to be able to allow for future expansion so what we've come up with is a system configuration architecture and we've decided to call it system configuration architecture not the network configuration architecture because we wanted to generalize the concepts we knew where we're going to solve some general problems and wanted to make the services general our solution leverages core foundation pretty heavily using run loop source technology and all the property list types and objects the other point about the network configuration architecture is that it's open source all the source code we have today that shipping and Mac os10 is available in Darwin you can check out the projects and see what it does unfortunately as I mentioned before it's all private API so you can't technically really rely on it but it's there for you to look at and understand so the system configuration architecture contains three main pieces the dynamic store system configuration preferences and the configuration agents the dynamic store stores the current system configuration information it's a snapshot of the state of the system the other thing the dynamic store provides is notification services the system configuration preferences provides system persistent storage for configuration information this is where the sets and different locations are stored the configuration agents apply the configuration that the user is chosen to the system and interact with a dynamic store so here's a little diagram that illustrates the relationship between the agents the dynamic store and the preferences where each of the individual agents are interact the dynamic store and some configuration source hmm so what is the dynamic store then a dynamic store contains the current system configuration information it's a snapshot of basically how the system is configured it's not persistent across reboots so every time the system starts up the contents are regenerated it's a dictionary so it's a set of key value pairs where the key is a CS string this format is a hierarchical namespace much like a URL we've encoded it using a domain prefix in a path so in the example there there's a state : prefix and the path is network Global DNS the value is any CF property list type normally a CF dictionary so that you can contain multiple properties within a specific key so the way the dynamic store notifications work is a client decides that it's interested in a particular key and registers to receive notifications and the notifications are level triggered rather than edge triggered what we mean here is when a key changes you aren't provided a key and its value you're provided that the key has changed and then it's up to you to go and verify what the value is we're trying to avoid creating big long streams of event buffers that you know when the system gets really busy may over run mm-hmm the dynamic store is hosted by the system configuration server which is actually daemon in the system called config D and I call it the heart of the mobility architecture because everything that happens with respect to networking goes through the dynamic store so the second major piece of our architecture is the system configuration preferences it's a persistent storage as I mentioned before for the system setup information like CF preferences but it actually has notifications when things change the other thing that it has is that it's accessible easily from system Damon's and the source code for it is in Darwin whereas CF preference currently is not in Darwin we use CF property list types for just about everything and when the file is written out to disk it's serialized as XML and the default preferences for the system that are used to store all the network configurations is in VAR DB system configuration preferences XML so what do the system preferences contain currently we've defined four main preferences the current set Network Services sets and system the current set contains a link to the currently active set it's free Matala contains the network services contains a complete list of all the network services that have been defined across all sets and assets the set preference is just that it's a list of sets and system contains the items that are not location sensitive such as the computer name so what's a set in the set is the complete configuration for a single location it contains the list of network services that are defined for that location and also contains the order of the network services for that location so here's where you would prefer LAN / built-in airport a network service what we mean by that as a collection of network entities which are just a set of properties for a specific area of interest which I'll mention in the next slide but it's the the network service is the the configuration for a single network connection or interface and it's identified by a unique network service ID a network entity is a list of properties for a single protocol or area of interest an example there would be ipv4 or PPP there's a set of properties that are associated with the protocol or the area of interest so here's a diagram of what we have in terms of the preferences and their relationships to each other you can see the current set contains a path to a a property inside sets that points to which set is currently active so when you go into the location popup on the under the Apple menu the thing that it's meant manipulating is the current set and so you notice there we're pointing at set K set K is a dictionary that contains a sub dictionary called Network and the subjection area network contains two sub dictionaries itself one called service and the other global inside service we have links to the individual services that are active for that set so you notice I D X points to IDX in network services and inside I D X and network services we have a set of network entities in this case the configuration method for ipv4 is set the DHCP and the interface entity has a device name of en 0 so we've identified the vise and the configuration method inside system there's a computer name that's pretty much all we store there now but it's there for anything that doesn't change depending on location so the third main category of the architecture is the configuration agent configuration agent manages some aspect of the configuration it's associated with one or more configuration sources basically things that can be configured or provide configuration information and it has a well defined role so from the original diagram the relationship is that the agent interacts with the dynamic store and it manages some configuration source or multiple configuration sources so here's the list of a number of the agents we have in Mac OS 10 today first one is the kernel event monitor and the second is the Preferences monitor the IP configuration server IP monitor and PvP controller I'm going to go into more detail on each of these in the upcoming slides so we'll start with the colonel event monitor colonel event monitor is an agent whose sole purpose in life is to maintain the link status and the interface state of all the interfaces in the system so what happens is it opens up a colonel event socket and receives colonel events that interfaces are added the link status has changed addressing has changed and when it receives those events it populates the dynamic store with the values in this case the link status on zn0 has changed and the colonel event monitor is updated a key in the dynamic store that says that the link status is done active so as I mentioned before it maintains the network interface state and it manages the colonel event socket it maintains a list of network interface names in a key that's encoded as state : network interface that's actually a dictionary that contains an interfaces array that contains the name of each interface that's defined in the system so if you want to know an interface has changed has been added to the system you would receive notifications on that key the other thing that it maintains currently is the link status of each interface and we've encoded that as state : network interface interface name link which is a dictionary that contains inactive property which is a boolean by updating the dynamic store in such a way the colonel event monitor provides notifications for other agents in particular the IP configuration agent as we'll see in an upcoming slide the second configuration agent and I'd like to talk about is the Preferences monitor preferences monitors sole purpose in life is to take the current set dictionary and load it into the dynamic store so it's configuration sources the system configuration preferences it maps the current set dictionary into the de flat into the dynamic store and the mapping process amounts to a flattening process and the next couple of slides try to illustrate that so here's the dictionary before we flatten it so if you look at it we've got a dictionary that contains property that's a string called user visible name and it's set the work land it also contains a sub dictionary called DNS the DNS contain server addresses at a domain name after flattening that'll become two dictionaries the first dictionary is encoded as the dictionary at that root node and the second dictionary is encoded as just the dictionary at that second node with all the other elements removed so if you look at it again we go from that to that and the key and the key that's generated for the the mapped the dictionary encodes its path so the mapping excuse me the mapping amounts to a dictionary tree traversal where we start at the root and at Dick edek each dictionary no we compute a key and a value the key is the path of the dictionary within the preference and the value is the node with all the sub dictionaries removed mmm also part of the mapping process we resolve all the references and links so there's pasta there's a possibility that there are links inside the preference will resolve those and fully populate them the other thing that it does is it eliminates dictionaries that are inactive that have been marked by the user interface or some other entity and it also eliminates empty dictionary so if you have a dictionary that doesn't contain any keys effectively the the entire keys just just just destroyed mmm and before putting it into the dynamic store it adds a set up colon prefix to the to the key that's its name space within the dynamic store so why do we do the mapping the reason why we do the mapping is to provide finer grain that is per dictionary notifications the other notifications that we would get without it would just be simply that the preferences had changed so instead of doing that we we I can actually generate fine-grain notifications by keeping track of the current mapping and the new mapping and computing a difference between the new and the old and triggering notifications on the keys that have changed so the benefits of doing this are that a single agent understands the preferences layout and other agents only have to know the dynamic store layout so it provides a layer of abstraction so I'm going to talk about the next agent which is the IP configuration agent type II configuration agent configures Ethernet devices for IP using a manual DHCP and boopie the way it works is it's triggered off of notifications out of setup so anytime someone switches locations it reads the configuration at a setup that the Preferences monitor loaded and applies the configuration to the interface that's associated with the particular config anytime the user goes into the control panel and changes a key the IP configuration agent wakes up and applies to the new config to the system I mean once it's configured an interface it writes the dynamic store keys to indicate that it's done its configuration and the configuration is active in particular it writes the IP address and subnet mask and for bootp and dhcp it supplies router and dns info the other feature of the IP configuration agent is that it detects the link status so the kernel event monitor is providing notifications that the link status is going up and down the IP configuration agent notices when the link goes down and stays down for some period currently set at four seconds and Dee configures the interface when that period is expired and when the link becomes active again it knows that it's going to retry the configuration method so you can take a computer and plug it into one network and then plug it into another it'll retry the configuration method and if you're using DHCP you can grab a new address automatically the fourth age and I'm going to talk about is the PvP controller agent pvp controller does a similar task to the IP configuration agent except that it manages pvp interfaces for IP so it does dial-up modem connections and PPP over ethernet it's just like the IP configuration agent it reads its configuration from the setup keys and it's notified when the user makes changes as well and once the interface has been brought up and configured it writes dynamic store state keys when the configuration is applied so it's going to supply IP address destination address and a router and when the PPP server supplies it it's going to supply DNS as well the other thing it does is it creates PPP interfaces as it needs it and interacts with dialers which brings us to the fifth agent epi monitor agent it's actually the thing that decides which interface or service is going to be primary and what we mean by a primary service interface we mean the one that's associated with the default route and the default DNS for the system since the system currently can only make use of a single DNS in the system you have to pick some interface and so what we do is we allow the user to select which one they want by ordering them so it consumes the information provided by the IP configuration in PvP controller agents and waits for changes to appear when a service comes online decides that okay that's the interface or service I'm going to use and it'll exit a primary and takes the configuration that's supplied both in the backend the the permanent preferences and the dynamic information and applies it to the system as I mentioned before there's a service order array that decides which service is going to be primary when you're in a multi home situation so now I'm going to call my colleague Allen Nathanson up here to do a demo for you and show you some of the things I've been talking about so döner went over and sort of gave a good overview of what we've got and my job is to sort of show you a little bit of the stuff under the covers and show you that it's real so the first thing that I like to do is crank up system preferences and I've already picked the network pane here and we have pre-configured a couple of different locations automatic is the one that you would get first time you go over and crank up your system I've got a service called none and if you could look at the the Advanced tab you can see that all of the three ports have been turned off this is the one that I use when I'm flying from the east coast to the west coast and don't want to go over and disturb the the airplanes networking and then I've got a couple other configurations here the WWDC air and LAN and this configuration has got all three network services enabled with the airport interface having a little bit of priority over the the built-in Ethernet which has priority over the internal modem and the idea here is that if the airport interface is available we'll use that and if not we'll try going going over and using the built-in Ethernet and if that's not there off to the internal modem and a very similar configuration is the WWDC LAN and air and if you go over and look at the difference this one's got the the built-in Ethernet being on so these are the configurations that I've got a couple other things to look at in the built in Ethernet configuration it's set up from manual IP addressing IP address subnet mask a router some DNS information this is what you'd have to do if you didn't have a DHCP server available to to provide all the information for you in the airport case we're set up for using DHCP and nothing else has been provided so we're sort of like relying on the DHCP server to provide the configuration information so this is what we've got from the the top side of the the view this is what you as a user what government set up for your configuration preferences and all of this gets stored in that configuration store in the preferences store which is the next thing that I'm going to go over and show you it's all stored in an XML file and happen to have a handy dandy reference the the route dictionary of the Preferences file has got four preferences that we've currently defined the current set the network services is a dictionary of services that we've got the sets is a dictionary of the sets which have currently been defined and then the system so the current set says that well let's go let's go over and look at sets for a second for different services were configured set zero is the automatic set you can tell that based on its user defined name set one is the WWDC LAN LAN has priority over airport service set two is the airport services got priority over the land and set three is my none so if we go over and chase down current sets pointing to sets one we can open this up and within the network configuration of the circuit of this set we've got a couple of pieces of information the global information which Dieterle alluded to within the ipv4 configuration here's the service order array and it goes over and says that the prior relative priority of the services for this set is service ID 1 followed by service ID 2 followed by service ID 0 and these are all strings so that's the global state and then within the services again we have the three services service 0 1 & 2 and one of the things that dieter mentioned was that we have the ability to put in some links so service ID 0 is really gonna be grabbed from network services 3 imagine going over and chasing this that's why we have programs service ID 1 is network services for and service ID 2 is network services 5 and we can go over and go into network services and here's 3 4 & 5 3 if you go look at its user defined name this is the configuration for the internal modem 4 is the configuration for the built-in Ethernet and 5 jumps around along is the configuration for the airport within the the airport configuration we go look at the ipv4 and how it's going to be configured and set up for DHCP if you remember the airport configuration we didn't have any information for DNS so there's an empty dns dictionary one thing that you'll see if you go over and look at the preferences as they're stored right now there's a couple of dictionaries which sort of like why is this here and the big reason behind that is we're trying to go over and remember things for the UI there's a an active flag that we'll go over and show up which the preferences monitor looks at and says ignore this for now it's not relevant to the configuration so the airport configuration is set up for DHCP and the built-in Ethernet configuration is set up for manual addressing and the addresses that will get applied there's the IP address there's the subnet mask and there's the default route and then up here in the dns dictionary you have the domains that are being searched and a list of addresses for the DNS servers so this is what sort of at the very bottom of the food chain is stored preferences so the next thing to do is to go over and look at what's in the dynamic store and when putting all of this stuff together I wrote a little command line tool to go take a peek into the dynex dynamic store and exercise the api's and it's just something that comes in real handy so this is the system configuration utility gives you a little prompt and you go over and open up a session with config D with the system configuration server and there's a whole bunch of commands that you can do and I'm gonna go over and show you a small handful of them there's a list command which you can go over and say show me a list of keys in the dynamic store that match this prefix so here's keys that relate to the current state of the system and here's a list of keys that relate to the stored preferences and what you end up doing is we do a get of a given key and then we go over and show the results of what that information gets fetched out of the dynamic store and you can see that we've got the subnet masks we've got the addresses the config method is manual the default route is here so this is really just a me it's the flattened version of what's stored in the configuration preferences if you want to go over and look at things like what the current link status is get the state it goes over and says oh the active flag and a boolean value and this version of this command doesn't split out things as well as I'd like there's a couple of other things you can do as far as notifications and what I'm going to do here is I want to go over and say let's go over and watch for a notification of something changing so I see do a notification ad and I want to go over and watch for changes to the built-in Ethernet so at this point the command is sitting here it'll go over and it's told the system configuration daemon to let it know when something happens to the link status on en0 and if I reach behind here and yank out the cable an event just happened and it turns out everything else is going on behind the scenes and it's going over and reconfiguring things you plug it back in again and link status comes back up it's flexible and that you can go over and specify which keys you want to go over and watch for and you can use it for one configuration or another so if I want to go over and say let's watch for another key and now we're watching for this key also let me go over and bring up another window and open a connection to the server and we'll go over and create a new dictionary this is a key-value hello is the key and the the value is everyone so the contents of the dictionary so the key is hello the value is everyone and then when we go over and say let's go add this key to the dynamic store do you go over and watch the top window when I go over to add the key it sees the change so you go over in tile this together with the link status coming up and down and what's been configured and everything sort of just puts - puts itself together so the last thing to go over and show you there's a little app that I put together to watch what's happening on the system and what you have here on on the left side is a list of the services as they've been configured so this is the information that comes from the network setup from the system preferences network pane it's the information that's stored in the preferences that XML file that was loaded into the dynamics door and the right side is the current status of the network interfaces so here we've got the built in Ethernet it's config method was manual there's the addressing information and airport was configured for DHCP the built in Ethernet state goes over has the same addresses that were requested you can see the link status is up the airport interface also is up because we've got an airport within range these are the addresses that were picked up from the DHCP server and and the router that came with it also up on the top here we go over and see which location we're currently set to and the service order so service order ID one is going to be the primary interface if it's available and service I do you want us to built in Ethernet and you go over and see that since the Ethernet is up it is the primary interface if I go and actually change the location I'm going to switch this to B instead of being the land having priority with the airport following I'll switch it to at the airport interface having priority with the land and you notice that the primary interface changed to en 1 the nice thing about watching this is it if you go over and said Lana's got priority over the airport and you go over and unplug the cable if you watch the primary interface which is currently the Ethernet when I disconnect it it sees the link status go down it waits 4 seconds and the primary interface switches and if you plug it back in again it goes over and revalue what really waits what needs to be primary interface comes up you've got new addresses it goes over and switch a state and right before you get on the plane you go over to turn off all your network services everything gets turned off so that's what I've got thanks Alan so what do we have in terms of API today well what we have is we have a system configuration framework it contains mostly low-level api is to access the dynamic store and the preferences we have some higher-level api's we have reach ability api is that parallel the OT will dial api is that i'm sure some of you are familiar with as i mentioned when i started out all of these aps are currently private and we are working very hard to make some api's public what can you what can so one of the things that we realize is that since we have mostly low-level api s there's not much in the way of isolation between you and the you know preferences format or the dynamic store format so you're kind of running pretty bare to the metal in terms of knowing exactly how we've implemented things so we'd like to implement some more higher level api is to provide some isolation here so that you avoid having schema specific information embedded in your code the other thing is to avoid duplicating code so we're definitely viewing this as something that's going to evolve evolve and grow as needs become apparent to us and we can provide some common api's that now are useful to many developers so the networking some related sessions that it actually one of them has already happened that was this morning the network overview we're talking about network configuration etwork protocols and api's the other one if you want to get more information on core foundation there's a core foundation overview over at the civic auditorium across the street friday morning at 9:00 so who can you contact if you have questions about this thomas wires the man you'll be back up on stage in a couple more slides for if you want to take a look at the api's that we have today you're welcome to go to Darwin and check out the source code there are four projects that we have that are implementing pretty much everything that I've talked about today config D contains the system configuration framework which contains api's for the dynamic store and the preferences and it also contains source code for config D which is the configuration server the other thing project to check out is config D plugins this contains the most of the agents it contains the IP monitor in the Preferences monitor that I talked about today third project is bootp bootp contains the IP configuration agent and PPP contains the PPP controller you