[webkit-dev] Networking proxy on iOS

[Daniel Olegovich Lazarenko]

Thank you for such a fast reply. That is amazing! :)
Back to questions...

> Are you primarily focused on a custom networking layer (e.g. your own
HTTP implementation?),
> or with custom protocol handling for non-http protocols?

I'm primarily concerned about HTTP and friends (HTTPS, SPDY, HTTP2), but if
there are any other widely used protocols that's also interesting. FTP
support is not interesting for me. Do you have any other specific things in
mind?

If there's a custom proprietary protocol that people handle in the app with
their own code, for example, acme://acme.com:1234, then proxying this thing
is not very interesting to me, because it's very easy to proxy my own
protocol handled by my own code. There's a case when "acme" is provided by
some 3rd party, and the app author doesn't have the processing code. In
such case it might be interesting to proxy it as well, but then again, I'm
asking for a concrete example of such protocol (in WebKit context).

> I’m not sure it’s useful for WebKit to spend energy testing and
maintaining a mechanism
> that *only* allows for HTTP-handling replacement and doesn’t also allow
for
> the oft-requested feature of custom protocol handling.

I understand your concerns. Let's say that we forget the httpProxy solution
for now, and discuss the 2nd UIProcess-networking approach a bit more.

> You seem to dismiss the Networking process’ crash recovery aspect.
> "because in practice we know that most of the crashes happen in the
WebProcess parts”.
> I’m curious what data you’re using to make that claim?

Well, I'm not dismissing it, it's definitely a trade off that an app author
will make by choosing to enable this option.
The data comes from our web browser apps. We certainly see networking
faults, but in total it was usually a minor part of all the WebKit crashes.
To not sound subjective, I've looked through our current app version, which
already has enough data to judge, and in the top WebKit crashes there are
none in the network code. Most are crashes in JavaScriptCore, DOM and
graphics subsystems. This is the experience we have over many versions and
years of service. I might be able to show you the data in private if you
want, although I'm sure that you have your own crash analysis system with
much more data.

> The Networking process provides significant benefit unrelated to crash
recovery
> that should not be abandoned for convenience sake. e.g. Sandboxing.
> Especially when moving the networking to the UI process
> would also end up moving 3rd party code execution into the UI process,
> this seems like an unacceptable regression.

Let's discuss the sandboxing a little bit. First of all, and correct me if
I'm wrong: I thought that there's no 3rd party code execution in the
networking process, and all the JS execution happens inside the WebProcess.
The code that we want to run is our own code that we control that we
implement in a safe and secure manner. In this sense it's no less secure.
In the end we are always protected by the iOS/Mac sandbox. Maybe I'm wrong
about JS here, or do you have some other use case in mind?

> Debugging the multi process architecture of WebKit2
> has not gotten any harder in years, active developers have all adapted,
> and new developers tend to pick it up pretty quickly. This is not a
useful point.

I'm sorry that you are rejecting this. Of course you can adapt to that, but
it inevitably has a steeper learning curve, and takes longer time. Many app
developers come from a single-process background and find multi-process
debugging much harder. Often it's a real challenge to understand what's
going on. I'm sure that you in your team have multiple stories that show
how non-trivial it is, and tricks about dealing with it. Nevertheless, I
agree, it's not a decisive point.



On Thu, May 19, 2016 at 6:43 PM, Brady Eidson <beidson at apple.com> wrote:

>
> On May 19, 2016, at 8:41 AM, Daniel Olegovich Lazarenko <danielo at opera.com>
> wrote:
>
> I'd like to ask your for advice about implementation of a custom
> networking layer
>
>
> Are you primarily focused on a custom networking layer (e.g. your own HTTP
> implementation?), or with custom protocol handling for non-http protocols?
>
> ...with WKWebView on iOS.
>
>
> WKWebView is an API that ships on both OS X and iOS. When a design aspect
> of it affects both platforms (such as the networking behavior), we must
> consider both platforms.
>
> Our current solution is based on NSURLProtocol, and the issues we had with
> it in 2014 are unresolved:
> https://bugs.webkit.org/show_bug.cgi?id=137302
> https://bugs.webkit.org/show_bug.cgi?id=138131
>
> It was kind of a shoehorn hack, and so it was rejected by Benjamin Poulain
> and Alexey Proskuryakov among other reviewers.
>
>
> I’m not sure it’s useful for WebKit to spend energy testing and
> maintaining a mechanism that *only* allows for HTTP-handling replacement
> and doesn’t also allow for the oft-requested feature of custom protocol
> handling.
>
> Now I'm again looking for a better solution.
> I'd really like to discuss it with somebody responsible,
>
>
> There is no single person responsible; the project works largely on
> consensus. When dealing with platform specific concerns such as this, it
> works on consensus of the platform owners.
>
> That said, I have been the primary caretaker of the Networking process
> since it’s inception, as well one of the primary caretakers of Mac/iOS
> networking in general for many years, so I’ll share my thoughts below.
>
> There's currently 2 solutions I'm weighting:
>
>    1. Pass and use NetworkProcessCreationParameters.httpProxy to
>    NSURLSessionConfiguration (in NetworkSession and maybe other places). The
>    httpProxy solution is easy to implement and would look clean design-wise.
>    It would let us spawn an HTTP proxy on localhost and filter the traffic
>    there. There might be some complications, because it's not fully
>    transparent to the client side. For example HTTPS will have issues. All in
>    all this could be a fine short-term solution.
>
> While ToT WebKit contains an NSURLSession-based networking implementation
> for Mac/iOS, it also still contains an NSURLConnection implementation,
> which is unaffected by NSURLSession considerations.
>
> That a solution doesn’t work on all supported platforms is not a deal
> breaker, but it certainly makes it less interesting than one that does.
>
> HTTPS losing reliability is likely an unacceptable red flag.
>
> I’m not sure it’s useful for WebKit to spend energy testing and
> maintaining a mechanism that *only* allows for HTTP-handling replacement
> and doesn’t also allow for the oft-requested feature of custom protocol
> handling.
>
>
>    1. Add a new mode to the NetworkProcess, which would do all networking
>    in UIProcess (instead of spawning a new process). A mode would be optional
>    and controlled with some configuration setting (or NSUserDefaults).
>
> The UIProcess solution is harder to implement, and it will affect more
> code. It is somewhat controversial. One of the reasons of splitting out a
> NetworkProcess was to have it respawn after crashes. Nevertheless we can
> take this risk, because in practice we know that most of the crashes happen
> in the WebProcess parts.
>
>
> You seem to dismiss the Networking process’ crash recovery aspect.
> "because in practice we know that most of the crashes happen in the
> WebProcess parts”.  I’m curious what data you’re using to make that claim?
>
>  I don't see any other significant downsides of having the UIProcess
> handling networking.
>
>
> The Networking process provides significant benefit unrelated to crash
> recovery that should not be abandoned for convenience sake. e.g. Sandboxing.
>
> Especially when moving the networking to the UI process would also end up
> moving 3rd party code execution into the UI process, this seems like an
> unacceptable regression.
>
> In addition it can simplify the NetworkProcess debugging.
>
>
> Debugging the multi process architecture of WebKit2 has not gotten any
> harder in years, active developers have all adapted, and new developers
> tend to pick it up pretty quickly. This is not a useful point.
>
> Thanks,
> ~Brady
>
>
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