Codes and references for PPP implementation

marcoapc · October 19, 2024, 10:44pm

This source code and algorithms are under MIT license, some of it can be used in Haiku:

eclipse-threadx/rtos-docs/blob/main/rtos-docs/netx-duo/netx-duo-ppp/chapter1.md

---
title: Chapter 1 - Introduction to the NetX Duo Point-to-Point Protocol (PPP)
description: This chapter introduces the NetX Duo Point-to-Point Protocol (PPP) module.
---

# Chapter 1 - Introduction to the NetX Duo Point-to-Point Protocol (PPP)

Typically, NetX Duo applications connect to the actual physical network through Ethernet. This provides network access that is both fast and efficient. However, there are situations where the application does not have Ethernet access. In such cases, the application may still connect to the network through a serial interface connected directly to another network member. The most common software protocol used to manage such a connection is the Point-to-Point Protocol (PPP).

Although serial communication is relatively straightforward, the PPP is somewhat complex. The PPP is actually comprised of multiple protocols, such as the Link Control Protocol (LCP), Internet Protocol Control Protocol (IPCP), Password Authentication Protocol (PAP), and the Challenge-Handshake Authentication Protocol (CHAP). The LCP is the main protocol for PPP. This is where the basic components of the link are dynamically negotiated in a peer-to-peer fashion. Once the basic characteristics of the link have been successfully negotiated, the PAP and/or CHAP are used to ensure a connected peer is valid. If both peers are valid, the IPCP is then utilized to negotiate the IP addresses used by the peers. Once IPCP completes, PPP is then able to send and receive IP packets.

NetX Duo views the PPP primarily as a device driver. The *nx_ppp_driver* function is supplied to the NetX Duo IP create function, *nx_ip_create*. Otherwise, NetX Duo does not have any direct knowledge of PPP.

## PPP Serial Communication

The NetX Duo PPP package requires the application to provide a serial communication driver. The driver must support 8-bit characters and may also employ software flow control. It is the application's responsibility to initialize the driver, which should be done prior to creating the PPP instance.

In order to send PPP packets, a serial driver output byte routine must be provided to PPP (specified in the *nx_ppp_create* function). This serial driver byte output routine will be called repetitively in order to transmit the entire PPP packet. It is the serial driver's responsibility to buffer the output. On the receive side, the application's serial driver must call the PPP *nx_ppp_byte_receive* function whenever a new byte arrives. This is typically done from within the context of an Interrupt Service Routine (ISR). The *nx_ppp_byte_receive* function places the incoming byte into a circular buffer and alerts the PPP receive thread of its presence.

## PPP Over Ethernet Communication

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The source code is under a permissive license, but I believe it is more for references and implementation ideas:

pvalue · October 21, 2024, 4:25am

Back in the future ?

marcoapc · October 21, 2024, 2:17pm

PPP is important for using 3G, 4G, 5G modems, also some trivialities with line connections.

https://dev.haiku-os.org/query?component=Network+%26+Internet%2FPPP&status=!closed