The total size of an IPC inputStream message must be less than 1mb. When we
compose the message for the multiplex stream, each sub stream collaborates with
its own size, deciding if it's better to be a pipe stream (IPCRemoteStream) or
a full serialized one.
Differential Revision: https://phabricator.services.mozilla.com/D18543
--HG--
extra : moz-landing-system : lando
Before this set of patches, the decision of exposing the stream as a pipe was
centralized in IPCStreamUtils, based on the total expectation size of the IPC
message. This triggers issues when multiplex inputStreams contain something
that cannot be sent as a pipe (IPCBlobInputStream, for instance), or something
that it's better to do not set as a pipe (nsFileInputStream), together with
memory streams (nsStringInputStream), which could make the IPC message greater
then what accepted (1mb).
These patches move the "pipe vs non-pipe" choice into the single inputStream
implementation.
In the current code there are 3 main issues:
1. nsFileStream is not really thread-safe. There is nothing to protect the
internal members and we see crashes.
2. nsPipeInputStream doesn't implement ::Seek() method and that caused issues
in devtools when a nsHttpChannel sends POST data using a pipe. In order to fix
this, bug 1494176 added a check in nsHttpChannel: if the stream doesn't
implement ::Seek(), let's clone it. This was an hack around nsPipeInputStream,
and it's bad.
3. When nsHttpChannel sends POST data using a file stream, nsFileStream does
I/O on main-thread because of the issue 2. Plus, ::Seek() is called on the
main-thread causing issue 1.
Note that nsPipeInputStream implements only ::Tell(), of the nsISeekableStream
methods. It doesn't implement ::Seek() and it doesn't implement ::SetEOF().
With this patch I want to fix point 2 and point 3 (and consequentially issue 1
- but we need a separate fix for it - follow up). The patch does:
1. it splits nsISeekableStream in 2 interfaces: nsITellableStream and
nsISeekableStream.
2. nsPipeInputStream implements only nsITellableStream. Doing this, we don't
need the ::Seek() check for point 2 in nsHttpChannel: a simple QI check is
enough.
3. Because we don't call ::Seek() in nsHttpChannel, nsFileStream doesn't do I/O
on the main-thread, and we don't crash doing so.
Andrea Marchesini
Sylvestre Ledru
Ben Kelly