Motivation:
When an error is hit during a read loop, a channel is able to tolerate
that error without closing. This is done for a number of reasons, but
the most important one is accepting sockets for already-closed
connections, which can trigger all kinds of errors on the read path.
Unfortunately, there was an edge-case in the code for handling this
case. If one or more reads in the loop had succeeded before the error
was caught, the inner code would be expecting a call to readIfNeeded,
but the outer code wouldn't make it. This would lead to autoRead
channels being wedged open.
Modifications:
This patch extends the Syscall Abstraction Layer to add support for
server sockets. It adds two tests: one for the basic accept flow, and
then one for the case discussed above.
This patch also refactors the code in BaseSocketChannel.readable0 to
more clearly show the path through the error case. There were a number
of early returns and partial conditionals that led to us checking the
same condition in a number of places. This refactor makes it clearer
that it is possible to exit this code in the happy path, with a
tolerated error, which should be considered the same as reading
_something_.
Result:
Harder to wedge a channel open.
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