extmod/network_ppp: Allow stream=None to suspend PPP.

This allows the stream to be set to `None`, which essentially stops all PPP
communication without disconnecting the session.

This allows replacing the stream on-the-fly to suspend it, for example to
send AT commands to a modem without completely disconnecting and
re-establishing the PPP connection:

    uart = ppp.config('stream')
    ppp.config(stream=None)
    uart.write(b'+++')
    # do some AT commands
    uart.write(b'ATO\r\n')
    ppp.config(stream=uart)

Any attempted communication by PPP while the stream is not connected will
register as simple packet loss to the LwIP stack because we return 0 for
any write calls, and protocols like TCP will then automatically handle
retrying.

Signed-off-by: Daniël van de Giessen <daniel@dvdgiessen.nl>

0 files changed, 0 insertions, 0 deletions