Netgraph/mpd over USB modem problems

[Danny Braniss]

look for a tcflush(..., TCIFLUSH)
this did not work properly last time i checked, and screwed up the
communicarions with a smart card usb reader.

	danny

> Hi all,
> 
> I've been battling this unsuccessfully for a while now, and hope
> someone can shed some light on how to fix this.
> 
> I'm trying to achieve a PPP dialup connection via a USB modem using
> netgraph mpd. However there appears to be a problem between netgraph's
> ng_tty node and /dev/ucom0, which I can't figure out/fix.
> 
> The initial mpd chat script works fine, and AT commands successfully
> establish a call between the local (USB) and remote modem. When DCD
> comes up, the netgraph nodes kick in, and the netgraph chain (ng_ppp
> -> ng_tty -> etc) is automatically (and correctly) formed.
> 
> LCP packets are then sucessfully transmitted to the remote PPP host
> via the USB port and modem. However, the subsequent responses arriving
> at the local USB port, are not forwarded up the stack i.e., are not
> received by the netgraph node(s).
> 
> It's possible (although not completely confirmed) that this is somehow
> related to the changing line-disciplines from TTYDISC (during the chat
> phase) to NETGRAPHDISC (during LCP/PPP phase) when the netgraph nodes
> are formed.
> 
> I've verified that with the USB & serial modems (same modem actually):
> 
> a. user-space PPP works on both /dev/cuaa0 and /dev/ucom0
> b. mpd works on /dev/cuaa0 but NOT /dev/ucom0
> 
> indicating that the individual components seem to work, but the
> netgraph/USB combination has problems. The only difference between the
> relevant serial and USB config files is: /dev/cuaa0 is changed to
> /dev/ucom0 when switching from serial to USB.
> 
> I've tested this on GENERIC FreeBSD versions 4.9R, 5.2.1R and
> yesterday, on a new installation of 5.3-RC2 -- all without success.
> All releases display seemingly identical behaviour, i.e., establishing
> the call successfully, but not receiving incoming LCP frames.  :-(
> 
> Anyone have any experience running netgraph nodes with USB modems?
> Even more generally, anyone know if netgraph is even _meant_ to work
> with USB...?
> 
> Desperately,
> vick
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