Madwifi无线发送数据过程

最新推荐文章于 2024-04-27 23:03:32 发布

cybertan

最新推荐文章于 2024-04-27 23:03:32 发布

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分类专栏： wireless学习文章标签： function interface report output buffer

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本文详细解析了无线网络中数据包从内核到物理层的发送过程，包括IEEE 802.11标准下数据包的封装、加密、传输队列选择等关键步骤，并介绍了信标帧的触发与发送机制。

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数据发送过程：

The kernel calls ieee80211_hardstart() (dev->hard_start_xmit of the virtual interface) to transmit a packet, which in turn calls ath_hardstart() (dev_hard_start_xmit of the physical interface). The function ath_hardstart() encapsulates the ethernet packet into 802.11 packet. The function ath_tx_start() encrypts the packets if necessary, maps the skb to DMA buffer and selects a transmit queues acording the priority of the packets (QoS control). The function ath_tx_txqaddbuf() inserts the buffer into the selected transmit queue and calls the HAL function to start a transmission.

Management packets are generated within the 802.11 layer. They are transmitted from the function ieee80211_mgmt_output().

Beacon messages are trigered by HAL. When it's time to send a beacon, the HAL issues an interrupt, then the function ath_beacon_send() is invoked to send the beacon message. The beacon messages are directly passed to the HAL to transmit.

After the HAL successfully transmited a packet, an interrupt is generated (ath_intr() ) to report the transmission of the packet as shown in the following figure. The function ath_tx_tasklet() updates infomation for this transmission. If there is a virtual interface working in monitor mode, the packet is passed to the monitor interface in function ath_tx_capture() .