* fix(all): introduce and use iox.ReadAllContext
This improvement over the ioutil.ReadAll utility returns early
if the context expires. This enables us to unblock stuck code in
case there's censorship confounding the TCP stack.
See https://github.com/ooni/probe/issues/1417.
Compared to the functionality postulated in the above mentioned
issue, I choose to be more generic and separate limiting the
maximum body size (not implemented here) from using the context
to return early when reading a body (or any other reader).
After implementing iox.ReadAllContext, I made sure we always
use it everywhere in the tree instead of ioutil.ReadAll.
This includes many parts of the codebase where in theory we don't
need iox.ReadAllContext. Though, changing all the places makes
checking whether we're not using ioutil.ReadAll where we should
not be using it easy: `git grep` should return no lines.
* Update internal/iox/iox_test.go
* fix(ndt7): treat context errors as non-errors
The rationale is explained by the comment documenting reduceErr.
* Update internal/engine/experiment/ndt7/download.go
This diff breaks the circular dependency between session and
tunnel, by introducing the concept of early session.
An early session is a session that is able to fetch the psiphon
configuration file _only_ if it's embedded in the binary.
This breaks `miniooni --tunnel=psiphon` for users who have
access to the OONI backend. They are not the users we are
writing this feature for, though, so I think this is reasonable.
At the same time, this opens up the possibility of creating
a psiphon tunnel when constructing a session, which is the
approach I was following in https://github.com/ooni/probe-cli/pull/286.
This work is part of https://github.com/ooni/probe/issues/985.
Once this diff is in, I can land https://github.com/ooni/probe-cli/pull/286.
We use an optional build tag to hide this configuration. When you
choose this configuration, you need to provide the encrypted config
as well as the corresponding decryption key.
This is not the final design. This is an interim design to start
working and experimenting with this functionality. The general
idea here is to support psiphon in the binaries we build without
committing the psiphon config to the repository itself.
Part of https://github.com/ooni/probe/issues/985
