82 lines
2.6 KiB
ReStructuredText
82 lines
2.6 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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X.25 Device Driver Interface
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============================
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Version 1.1
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Jonathan Naylor 26.12.96
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This is a description of the messages to be passed between the X.25 Packet
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Layer and the X.25 device driver. They are designed to allow for the easy
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setting of the LAPB mode from within the Packet Layer.
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The X.25 device driver will be coded normally as per the Linux device driver
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standards. Most X.25 device drivers will be moderately similar to the
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already existing Ethernet device drivers. However unlike those drivers, the
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X.25 device driver has a state associated with it, and this information
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needs to be passed to and from the Packet Layer for proper operation.
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All messages are held in sk_buff's just like real data to be transmitted
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over the LAPB link. The first byte of the skbuff indicates the meaning of
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the rest of the skbuff, if any more information does exist.
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Packet Layer to Device Driver
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-----------------------------
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First Byte = 0x00 (X25_IFACE_DATA)
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This indicates that the rest of the skbuff contains data to be transmitted
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over the LAPB link. The LAPB link should already exist before any data is
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passed down.
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First Byte = 0x01 (X25_IFACE_CONNECT)
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Establish the LAPB link. If the link is already established then the connect
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confirmation message should be returned as soon as possible.
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First Byte = 0x02 (X25_IFACE_DISCONNECT)
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Terminate the LAPB link. If it is already disconnected then the disconnect
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confirmation message should be returned as soon as possible.
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First Byte = 0x03 (X25_IFACE_PARAMS)
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LAPB parameters. To be defined.
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Device Driver to Packet Layer
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-----------------------------
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First Byte = 0x00 (X25_IFACE_DATA)
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This indicates that the rest of the skbuff contains data that has been
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received over the LAPB link.
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First Byte = 0x01 (X25_IFACE_CONNECT)
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LAPB link has been established. The same message is used for both a LAPB
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link connect_confirmation and a connect_indication.
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First Byte = 0x02 (X25_IFACE_DISCONNECT)
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LAPB link has been terminated. This same message is used for both a LAPB
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link disconnect_confirmation and a disconnect_indication.
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First Byte = 0x03 (X25_IFACE_PARAMS)
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LAPB parameters. To be defined.
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Requirements for the device driver
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----------------------------------
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Packets should not be reordered or dropped when delivering between the
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Packet Layer and the device driver.
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To avoid packets from being reordered or dropped when delivering from
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the device driver to the Packet Layer, the device driver should not
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call "netif_rx" to deliver the received packets. Instead, it should
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call "netif_receive_skb_core" from softirq context to deliver them.
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