[webkit-dev] Networking proxy on iOS

[Brady Eidson]

> 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=137302>
> https://bugs.webkit.org/show_bug.cgi?id=138131 <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:
> 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.
> 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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