The
tty
node type is both a netgraph node type and a TTY hook.
The node has a single hook called
hook.
Incoming bytes received on the tty device are sent out on this hook,
and frames received on
hook
are transmitted out on the tty device.
No modification to the data is performed in either direction.
While the hook is installed on a tty, the normal read and write
operations are unavailable, returning
EIO.
Incoming data is delivered directly to ng_tty via the tty bypass hook as a
buffer pointer and length, this is converted to a mbuf and passed to the peer.
The node supports an optional
"hot character".
If the driver can not deliver data directly to the tty bypass hook then each
character is input one at a time.
If set to non-zero and bypass mode is unavailable, incoming
data from the tty device is queued until this character is seen.
This avoids sending lots of mbufs containing a small number of bytes,
but introduces potentially infinite latency.
The default hot character is 0x7e, consistent with
hook
being connected to a
ng_async(4)
type node.
The hot character has no effect on the transmission of data.
