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71d27abb97
The current ProtocolServer was really only used for requests, and with the recent introduction of the WebSocket service, long-lasting connections with another server are not part of it. To better reflect this, this commit renames it to RequestServer. This commit also changes the existing 'protocol' portal to 'request', the existing 'protocol' user and group to 'request', and most mentions of the 'download' aspect of the request to 'request' when relevant, to make everything consistent across the system. Note that LibProtocol still exists as-is, but the more generic Client class and the more specific Download class have both been renamed to a more accurate RequestClient and Request to match the new names. This commit only change names, not behaviors.
49 lines
3.3 KiB
Markdown
49 lines
3.3 KiB
Markdown
# SerenityOS Browser process architecture
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*NOTE: This document is partly aspirational, in that the state of the code does not yet fully reflect what's described here. Implementation is underway.*
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The SerenityOS web browser (**"Browser"**) uses a multi-process architecture to improve stability and security in the face of arbitrary (and possibly hostile) web content.
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## Process overview
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Every instance of the **Browser** application can have one or more tabs open. Each tab has a unique **WebContent** service process spawned on its behalf.
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Two important aspects of web browsing are further separated from the **WebContent** process: *network requests* and *image decoding*, segregated to the **RequestServer** and **ImageDecoder** processes respectively.
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All processes and are aggressively sandboxed using the `pledge()` and `unveil()` mechanisms. Furthermore, all processes except **Browser** run as an unprivileged user, separate from the primary logged-in desktop user.
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### Process: WebContent
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This process hosts the main HTML/CSS engine (**LibWeb**.) It also runs JavaScript (**LibJS**.) It gets input events from **Browser** and paints the web content into shared bitmaps. It can only communicate with the outside world via **RequestServer**.
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### Process: RequestServer
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This process can use networking protocols (like HTTP, HTTPS, and Gemini) to request files from the outside world. Each **WebContent** process gets its own **RequestServer** to do uploading or downloading on its behalf.
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For DNS lookups, **RequestServer** asks for help from the system's global **LookupServer** service, which handles all outgoing DNS requests.
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### Process: ImageDecoder
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This process can decode images (PNG, JPEG, BMP, ICO, PBM, etc.) into bitmaps. Each image is decoded in a fresh **ImageDecoder** process. These are strongly sandboxed and can't do much except receive encoded bitmap data and return a bitmap to **WebContent** if decoding successful.
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### How processes are spawned
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To get a fresh **WebContent** process, anyone with the suitable file system permissions can spawn one by connecting to the socket at `/tmp/portal/webcontent`. This socket is managed by **SystemServer** and will spawn a new instance of **WebContent** for every connection.
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The same basic concept applies to **RequestServer** and **ImageDecoder** as well, except that those services are spawned by **WebContent** as needed, not by **Browser**.
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## Class overview
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In the GUI application process, a `OutOfProcessWebView` widget is placed somewhere in a window, and it takes care of spawning all of the helper processes, etc.
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Internally, the `OutOfProcessWebView` has a `WebContentClient` object that implements the client side of the **WebContent** IPC protocol.
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The `WebContentClient` speaks to a `WebContent::ClientConnection` in the **WebContent** process. Internally, the `WebContent::ClientConnection` has a `WebContent::PageHost` which hosts the **LibWeb** engine's main `Web::Page` object.
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Inside **LibWeb**, a `Web::Page` has a main `Web::Frame`, which may have subframes corresponding to `<frame>` or `<iframe>` HTML elements. Each `Web::Frame` has a `Web::Document`, which is the root node of the DOM tree.
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Describing the **LibWeb** object model in detail is outside the scope of this document.
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