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1How the new TCP output machine [nyi] works.
2
3
4Data is kept on a single queue. The skb->users flag tells us if the frame is
5one that has been queued already. To add a frame we throw it on the end. Ack
6walks down the list from the start.
7
8We keep a set of control flags
9
10
11 sk->tcp_pend_event
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13 TCP_PEND_ACK Ack needed
14 TCP_ACK_NOW Needed now
15 TCP_WINDOW Window update check
16 TCP_WINZERO Zero probing
17
18
19 sk->transmit_queue The transmission frame begin
20 sk->transmit_new First new frame pointer
21 sk->transmit_end Where to add frames
22
23 sk->tcp_last_tx_ack Last ack seen
24 sk->tcp_dup_ack Dup ack count for fast retransmit
25
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27Frames are queued for output by tcp_write. We do our best to send the frames
28off immediately if possible, but otherwise queue and compute the body
29checksum in the copy.
30
31When a write is done we try to clear any pending events and piggy back them.
32If the window is full we queue full sized frames. On the first timeout in
33zero window we split this.
34
35On a timer we walk the retransmit list to send any retransmits, update the
36backoff timers etc. A change of route table stamp causes a change of header
37and recompute. We add any new tcp level headers and refinish the checksum
38before sending.
39