Christian writes: > OK, maybe i do not understand everything correctly, let me in short > explain what i have: > > I have a device which gives me a function to transmit data in a hdlc > frame, so i can just call some function like: > > tx_frame(char *p, int l); OK. Is that in the kernel or outside of the kernel? If it's in the kernel, then it sounds like that should be used to construct a device driver that works as a synchronous serial interface. Pppd can then open the driver and work normally -- no pty needed. (This -- writing a device driver -- isn't a really PPP issue.) If it's in user space, then I believe you'll need to re-encode the data using AHDLC so that you can pass it over a pty. > then i tried to use pppd with stdin/stdout, but this obviously did not > work, because there is no boundaries in stdin/stdout so it will fail > when data packets increase in size or in speed, also i needed to enable > the sync option which made it work for a few small slowly coming packets. > > I assume sync=no hdlc, "Sync" means that the device driver is assumed to perform basic HDLC-like framing. This means that when pppd writes a single frame, it'll be transmitted raw (no prepended octets, such as HDLC address or control, as pppd itself supplies these), with bit-stuffing and FCS generation being the responsibility of the driver. That is not true of ptys. Note that the problem is *NOT* just with pppd itself. Pppd does not actually handle the data packets. Even if you can "trick" pppd into using some non-sync device as though it were sync, you still need to deal with the fact that data packets (IP, for instance) are handled in the kernel. > and when not using the sync option pppd will do > hdlc on stdin/stdout, maybe you can enlighten that to me a bit? When "sync" isn't used, pppd assumes that the driver is asynchronous, and it uses AHDLC (RFC 1662) coding on the line. > I have read that i can set a pty end into N_HDLC mode, so that each read > returns exactly 1 packet, do you think i can handle my task in that way ? Maybe. I've never seen that done, and I don't know of any system where that works. If it works on Linux, then I guess you may have found a solution. -- James Carlson 42.703N 71.076W <carlsonj@xxxxxxxxxxxxxxx> - To unsubscribe from this list: send the line "unsubscribe linux-ppp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
