Revert "As Martin pointed out, there is a race condition in the old code where a pipe could start shutting down after disconnection, but the new one could connect first. This connection would not get a pipe created for it, so the messages could never flow. The simplest way round this would be a flag, but it is possibly for a very bouncy but fast connection to go up and down twice I imagine, so instead I have added a counter. This starts at zero, and will null out the pipe if terminate is called while it is zero. On a disconnect situation the counter is incremented, and the pipe is the not nulled if the value is non zero. In the terminated function it is decremented for each pipe that is shut down, and the assertion that the terminated pipe == the current pipe is skipped while it is non-zero. This should deal with the race condition and not allow any extra terminated() calls without hitting the assertion."

This reverts commit a5f7300d.

Revert "Filter read and write activated calls from the pipe to the session, and delay shutdown in terminated until the final pipe is shutdown."

This reverts commit a90c1db7.

This reverts commit d8f3487e.

This reverts commit 029d3dfa.

This reverts commit dde69fb9.

This reverts commit 33459029, reversing
changes made to 889b0e6f.

This reverts commit 7b105865, reversing
changes made to 33459029.

This reverts commit 4aa5ba3d.
Unintentional merge

This commit removes the countdown flag and adds a set to store the pipes
that are currently being disconnected.

Fix race conditions in {tcp,ipc}_connecter

Once the object has been terminated, it is unsafe for this object
to refer to its parent.

The bug was responsible for occasional
test_shutdown_stress failures.

Add a new section to the connect delay test that disconnects and
reconnects a socket to ensure that some messages are appropriately
blocked.

Filter read and write activated calls from the pipe to the session, and delay shutdown in terminated until the final pipe is shutdown.

As Martin pointed out, there is a race condition in the old code where a pipe could start shutting down after disconnection, but the new one could connect first. This connection would not get a pipe created for it, so the messages could never flow. The simplest way round this would be a flag, but it is possibly for a very bouncy but fast connection to go up and down twice I imagine, so instead I have added a counter. This starts at zero, and will null out the pipe if terminate is called while it is zero. On a disconnect situation the counter is incremented, and the pipe is the not nulled if the value is non zero. In the terminated function it is decremented for each pipe that is shut down, and the assertion that the terminated pipe == the current pipe is skipped while it is non-zero. This should deal with the race condition and not allow any extra terminated() calls without hitting the assertion.

Use struct keyword consistently with sockaddr and sockaddr_in

Small code simplification

Fix the message decoder to ignore reserved flags.

Failing to clear the reserved flags, the decoder may produce
messages with 'identity' and 'shared' flags set.
This unintended modification of message flags can lead to memory
errors or asserion failures.

Fixes issue #309

Use the hiccup mechanism to notify the socket end of the pair of the change in state, and have it shutdown that end, and shutdown the local end normally. This seems to resolve the shutdown and race condition issues.

Consolidate TCP-specific common code into their own files.

The TCP keepalive tuning code has been moved into the newly added
files; this also allows future TCP-specific code to be added into
these files, without bloating the IP level code and establishes a
known file structure for other IP-based transports.

Remember: this is a no-op change, hence no API or functionality
was changed as part of this commit.

Change connection failure test to use an invalid hostname

- invalid hostname set to 0mq.is.the.best (naturally!)
- issue happens as other valid-like non-existent hostnames were
  redirected by buggy Cable/ISP DNS servers

Reverted to a simpler shutdown. This seems to disconnect and reconnect the pipe properly, but there is a problem in overall shutdown when the pipe has blocked and reconnected - the session seems to get terminated() called on it only in shutdown for the original pipe, by which point it has been replaced. I am not sure at the moment why this only happens then, but this does mean this patch is broken at the moment

Remove unused variable which causes build to fail with -Werror

Check if SO_NOSIGPIPE is defined

Bumped version for next release (3.3.0)