[Mpvdapi] 回复： MIF API Design Team

[Dapeng Liu <[e-mail]>]

Hi Hui and Erik,  

Attachment is the draft I mentioned during the discussion. It was written before the Dallas meeting and it may not reflect the latest consensus we have.  

I am trying to update it.  



--  
Dapeng Liu


在 2015年7月5日 星期日，下午3:27，Hui Deng 写道：

> Hi Erik
>   
> I guess that everbody is busy with deadline,
> could you kindly help to write down a draft about this proposal and then present it during coming MIF sesson,  
> then we get more people to review on how Android implement this.
>   
> Thanks a lot for your kind work
> Best regards,
>   
> DENG Hui
>  
>   
> > From: [e-mail] (mailto:[e-mail])
> > Date: Mon, 15 Jun 2015 19:55:15 +0900
> > Subject: Re: MIF API Design Team
> > To: [e-mail] (mailto:[e-mail])
> > CC: [e-mail] (mailto:[e-mail]); [e-mail] (mailto:[e-mail]); [e-mail] (mailto:[e-mail])
> >  
> > Sorry about that: it's back to back 3GPP and now Android release issues.
> >  
> > I spent the weekend reworking some notes on the things I described in
> > Dallas. That's not coming together quickly enough so let me lay
> > everything out here instead. In so doing I will try to describe more
> > about the approach Android took to see if people even think it makes
> > sense.
> >  
> > Let's assume for the sake of argument that C API definitions are
> > nicely isolated, maybe in some #include <netpvd.h> header file.
> >  
> > [1] Provisioning domains are represented by a "handle" kind of class,
> > android.net.Network:
> >  
> > https://developer.android.com/reference/android/net/Network.html
> >  
> > These are essentially handles to identify instances of attaches to
> > provisioning domains. The underlying identifier values are not
> > recycled (except after a really long time). Multiple temporally
> > disparate attaches to the same network each get a new instance
> > value--we have not yet found it of value to try to de-duplicate
> > attaches. Applications that want to know if you're attached to
> > "Starbucks" so they can startup and auto-sign-in use the relevant
> > handle value to query parameters (like SSID).
> >  
> > I would propose that a C API would have something like
> >  
> > typedef uint64_t pvd_handle_t
> > #define PVD_HANDLE_UNSPEC ((pvd_handle_t)0)
> >  
> > [2] Once an application has received a Network handle [let's save how
> > that happens for later] it can request that certain operations be
> > performed specifically within the associated PVD. Currently these
> > operations include:
> >  
> > [bind a file descriptor to a PVD to force packets to be sent using
> > the PVD's routing table]
> > android.net.Network#bindSocket()
> > https://developer.android.com/reference/android/net/Network.html#bindSocket(java.net.Socket)
> >  
> > [perform DNS lookups using a PVD's DNS servers]
> > android.net.Network#getAllByName()
> > https://developer.android.com/reference/android/net/Network.html#getAllByName(java.lang.String)
> >  
> > [set the PVD for all file descriptors and DNS lookups for a
> > process, unless otherwise overridden]
> > android.net.ConnectivityManager#setProcessDefaultNetwork()
> > https://developer.android.com/reference/android/net/ConnectivityManager.html#setProcessDefaultNetwork(android.net.Network)
> >  
> > I would propose that a C API have at least the following:
> >  
> > [a] get/setsockopt(int fd, SOL_SOCKET, SO_PVD_HANDLE, &pvd_handle_t);
> > [b] getaddrinfo/getnameinfo some taking a pvd_handle_t
> > [c] discussion of recvmsg/sendmsg/accept semantics
> >  
> > Note that the last is particularly tricky. Operating systems need to
> > know how to "mark" incoming packets that would cause a new connection
> > such that they have the correct pvd_handle_t associated. This has
> > lots of impact on suitable address selection as well.
> >  
> > The C API should also have at least the following:
> >  
> > [d] system, process, and per-thread pvd_handle get/set calls
> >  
> > // These values are used by PVD-aware function calls when a PVD index
> > // is not explicitly specified.
> > pvd_handle_t pvd_system_default();
> >  
> > // Same as above, but operates at a per-process level. If no
> > // process-specific default has been set this MUST return the value
> > // of a call to pvd_system_default().
> > pvd_handle_t pvd_process_default();
> >  
> > // Same as above, but operates at a per-thread level. If no
> > // thread-specific default has been set this MUST return the value
> > // of a call to pvd_current_process_default().
> > pvd_handle_t pvd_thread_default();
> >  
> > int pvd_set_system_default(pvd_handle_t); // 0 or -1 && errno = EFOO
> > int pvd_set_process_default(pvd_handle_t); // 0 or -1 && errno = EFOO
> > int pvd_set_thread_default(pvd_handle_t); // 0 or -1 && errno = EFOO
> >  
> > [e] good discussion of a variety of EFOO errno return values.
> >  
> > When a PVD has gone away (e.g. we disconnected from WIFI), subsequent
> > operations on the associated pvd_handle should fail with errno =
> > ENONET.
> >  
> > [f] good discussion of how the process and thread default values
> > behave across fork/exec
> >  
> > FWIW, Android uses all of the above when NetworkMonitor is validating
> > a network--it does DNS lookups within the PVD, makes pvd-bound sockets
> > used for HTTP Direct or Proxy connections to check connectivity to a
> > URL:
> >  
> > https://android.googlesource.com/platform/frameworks/base/+/master/services/core/java/com/android/server/connectivity/NetworkMonitor.java
> >  
> > [3] the device has to build up configuration data continuously over
> > time, as DHCP results come back, and RAs come in bringing new prefixes
> > or new DNS servers.
> >  
> > Not that it's relevant, but Android accumulates these in an
> > android.net.LinkProperties object:
> >  
> > https://developer.android.com/reference/android/net/LinkProperties.html
> >  
> > as we currently only support a 1:1 mapping of PVDs to physical interfaces.
> >  
> > The means by which the operating system allocates pvd_handles, gathers
> > this data and associates it with a pvd_handle (including marking
> > incoming packets that would causes a new connection) might best be
> > left for a separate document, since sections 1 and 2 and background
> > theory will require a fair amount of text.
> >  
> > [4] Android lets processes register callbacks to be called when
> > certain network properties change, or when a new network shows up, or
> > one goes away. This is how applications receive the handles (Network
> > objects).
> >  
> > The UNIX way of doing these sorts of things...well, frequently leaves
> > much to be desired...but we should support multiple event-driven
> > models, I think.
> >  
> > [5] we'll want an API for an application to pass in a handle and get
> > an ever expanding list of parameters (expanding as we think to add
> > them and write documents about them).
> >  
> > The Android ConnectivityManager mitigates all this stuff and passes
> > around NetworkInfo objects which encapsulate extra information like
> > SSIDs, whether the Network is Ethernet, Mobile, Wi-Fi, or whether it's
> > metered, and so on.
> >  
> > The closest UNIX-style analogy here would be some interface that is
> > getsockopt()-like, I think. Something like:
> >  
> > int pvd_get_attribute(pvd_handle_t, PVD_ATTR_(HWTYPE|METERED|...),
> > void *returned_blob);
> >  
> > And then it will be possible for code to be written like
> >  
> > #ifdef PVD_ATTR_HTTP_PROXY_URL
> >  
> > char proxyString[PVD_ATTR_HTTP_PROXY_URL_MAXLEN];
> > memset(proxyString, 0, sizeof(proxyString));
> > if (!pvg_get_attribute(pvd_handle, PVD_ATTR_HTTP_PROXY_URL, proxyString)) {
> > perror("Sadness!");
> > return -1;
> > }
> >  
> > #endif
> >  
> >  
> > ---
> >  
> > That's a massive brain dump, and I apologize for it and also that it's so late.
> >  
> > Let me know what y'all think.
> > -Erik
> >  
> > On Mon, Jun 8, 2015 at 11:18 PM, Hui Deng <[e-mail] (mailto:[e-mail])> wrote:
> > > Hi Erik
> > >
> > > We are waiting for your lead to start this work asap. Feel free to us know
> > > when you are ready.
> > >
> > > Hi Ian, thanks a lot for letting us know that you are going to work with a
> > > university on the implementations.
> > > Erik was quite busy for 3GPP SA2 work recently, we are waiting for his
> > > return to lead the work.
> > >
> > > Best regards,
> > >
> > > DENG Hui
> > >
> > >
> > >> From: [e-mail] (mailto:[e-mail])
> > >> Subject: MIF API Design Team
> > >> Date: Mon, 8 Jun 2015 14:07:02 +0200
> > >> CC: [e-mail] (mailto:[e-mail])
> > >> To: [e-mail] (mailto:[e-mail])
> > >>
> > >> Hi Hui,
> > >>
> > >> My apologies for not being in contact sooner. Things don’t always move as
> > >> quickly as hoped around here!
> > >>
> > >> The current status is that we have provisionally obtained the necessary
> > >> resources to start working on a proof of concept implementation of the MIF
> > >> architecture. We will be doing this in partnership with a University.
> > >>
> > >> Tomorrow (9th July) we will start the scoping work with the implementor.
> > >> What I want to come out of this work is a proof of concept implementation of
> > >> the MIF architecture on a ‘generic’ Linux based platform. As Eric is working
> > >> on an Android implementation for the mobile use case, I think that this
> > >> should complement his work quite well and serve to provide some good
> > >> implementation experience which can be fed back into the update of the MIF
> > >> API document.
> > >>
> > >> I’ve sent a subscription request to the MIF API design team mailing list.
> > >> Once we’ve got some firmer details agreed with the implementors, I’ll make
> > >> an announcement on the m/l of what we’re doing and we can discuss what the
> > >> best way of aligning the two implementation efforts.
> > >>
> > >> Best regards,
> > >> Ian
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