急求：PPPOE协议问题？？？

ITHJF

PPPOE协议是内核级协议，还是用户级协议？
怎么调用PPPOE协议提供的接口？

hahasasa

man pppoe




DESCRIPTION
       pppoe  is a user-space client for PPPoE (Point-to-Point Protocol over Ethernet) for Linux and other UNIX systems.  pppoe works in concert with the pppd PPP daemon to provide a PPP connection over Ethernet, as is used by many ADSL service providers.

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PPPOE BACKGROUND
       PPPoE (Point-to-Point Protocol over Ethernet) is described in RFC 2516 and is a protocol which allows the session abstraction to be maintained over bridged Ethernet  networks.

       PPPoE works by encapsulating PPP frames in Ethernet frames.  The protocol has two distinct stages:  The discovery and the session stage.

       In the discovery stage, the host broadcasts a special PADI (PPPoE Active Discovery Initiation) frame to discover any access concentrators.  The access concentrators (typically, only one access concentrator) reply with PADO (PPPoE Active Discovery Offer) packets, announcing their presence and the services they offer.  The host  picks  one of the access concentrators and transmits a PADR (PPPoE Active Discovery Request) packet, asking for a session.  The access concentrator replies with a PADS (PPPoE Active Discovery Session-Confirmation) packet.  The protocol then moves to the session stage.

       In the session stage, the host and access concentrator exchange PPP frames embedded in Ethernet frames.  The normal Ethernet MTU is 1500 bytes,  but  the  PPPoE  overhead plus  two  bytes  of  overhead  for the encapsulated PPP frame mean that the MTU of the PPP interface is at most 1492 bytes.  This causes all kinds of problems if you are using a Linux machine as a firewall and interfaces behind the firewall have an MTU greater than 1492.  In fact, to be safe, I recommend setting the MTU of machines behind the firewall to 1412, to allow for worst-case TCP and IP options in their respective headers.

       Normally,  PPP  uses the Link Control Protocol (LCP) to shut down a PPP link.  However, the PPPoE specification allows the link to be shut down with a special PADT (PPPoE Active Discovery Terminate) packet.  This client recognizes this packet and will correctly terminate if a terminate request is received for the PPP session.

[ 本帖最后由 hahasasa 于 2007-9-17 12:00 编辑 ]

platinum

PPPoE 是二层协议，内核级用户级都使用

hahasasa

which line is it at? in .config

ITHJF

我要的是PPPOE协议的底层接口，而不是协议的运行原理，我要编程的！请问高手指点一二！

platinum

那应该看一下 pppoe-server 的源代码，它实际上就是调用了内核态的 pppoe 协议接口实现的 pppoe 服务