| How the new TCP output machine [nyi] works. |
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| Data is kept on a single queue. The skb->users flag tells us if the frame is |
| one that has been queued already. To add a frame we throw it on the end. Ack |
| walks down the list from the start. |
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| We keep a set of control flags |
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| sk->tcp_pend_event |
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| TCP_PEND_ACK Ack needed |
| TCP_ACK_NOW Needed now |
| TCP_WINDOW Window update check |
| TCP_WINZERO Zero probing |
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| sk->transmit_queue The transmission frame begin |
| sk->transmit_new First new frame pointer |
| sk->transmit_end Where to add frames |
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| sk->tcp_last_tx_ack Last ack seen |
| sk->tcp_dup_ack Dup ack count for fast retransmit |
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| Frames are queued for output by tcp_write. We do our best to send the frames |
| off immediately if possible, but otherwise queue and compute the body |
| checksum in the copy. |
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| When a write is done we try to clear any pending events and piggy back them. |
| If the window is full we queue full sized frames. On the first timeout in |
| zero window we split this. |
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| On a timer we walk the retransmit list to send any retransmits, update the |
| backoff timers etc. A change of route table stamp causes a change of header |
| and recompute. We add any new tcp level headers and refinish the checksum |
| before sending. |
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