- NewReno congestion control algorithm is used to solve the problem
of network congestion breakdown. NewReno congestion control includes
slow start, collision avoidance, fast retransmission, and fast
recovery. The implementation refers to RFC6582 and RFC5681.
- In addition, we optimize the congestion algorithm. In the conflict
avoidance stage, the maximum congestion window max_cwnd is used to
limit the excessive growth of cwnd and prevent network jitter
caused by congestion. Maximum congestion window max_cwnd is updated
with the current congestion window cwnd and the update weight is
0.875 when an RTO timeout occurs.
Signed-off-by: liqinhui <liqinhui@xiaomi.com>
We have a case that an http server gives out-of-ordered ACKs, and NuttX client makes `ofoseg`s with length 0, trying to rebuild / put them into `ofosegs` array, which is not intended (no available data and should be skipped). This breaks later logic and finally crashed in `tcp_ofoseg_bufsize` (`ofosegs[i].data` is `NULL`, which should never happen in normal logic).
Note:
- `iob_trimhead` won't return `NULL` when it's applying on normal IOB.
- Keep `dev->d_iob == NULL` to avoid `iob_trimhead` changed.
- `iob_free_chain` will do nothing when applied to `NULL`.
Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>
According to RFC 2525, Section 2.17:
"When an application closes a connection in such a way that it can no longer read any received data, the TCP SHOULD, per section 4.2.2.13 of RFC 1122, send a RST if there is any unread received data, or if any new data is received."
When our TCP socket is closed (even when the thread has exited), the peer can keep sending data and NuttX keeps replying ACK (we've tried for ~12h). This is not a good behavior (also different from Linux), so send RST instead of ACK for data receiving in FIN_WAIT.
Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>
Receiving an ACK indicating TCP Window Update will not set ACKDATA flag (because tx_unacked is 0) in our TCP stack. Then this ACK won't let us send anything after receiving it, even if it updates snd_wnd. So we need to check whether we can send data immediately when our snd_wnd is updated (especially from 0), otherwise we will only send next data after timer expiry.
Signed-off-by: Zhe Weng <wengzhe@xiaomi.com>
l3/l4 stack will decouple the reference of d_buf gradually, Only legacy
devices still retain d_buf support, new net devices will use d_iob
Signed-off-by: chao an <anchao@xiaomi.com>
Otherwise, when a long test triggers multiple timeout retransmissions,
the late timeout retransmissions are always delayed between 24 and 48 seconds
Signed-off-by: zhanghongyu <zhanghongyu@xiaomi.com>
(conn->sndseq was updated in multiple places that was unreasonable and complicated).
This optimization is the same as it was done for tcp_send_unbuffered.
Wrong unackseq calculation locked conn->tx_unacked at non-zero values
even if all ACKs were received.
This issue is the same as it was with tcp_send_unbuffered.
Wrong unackseq calculation locked conn->tx_unacked at non-zero values
even if all ACKs were received. Thus unbuffered psock_tcp_send() never completed.
* Do not accept the window in old segments.
Implement SND.WL1/WL2 things in the RFC.
* Do not accept the window in the segment w/o ACK bit set.
The window is an offset from the ack seq.
(maybe it's simpler to just drop segments w/o ACK though)
* Subtract snd_wnd by the amount of the ack advancement.
* It doesn't make sense to have this conditional on our own
SO_KEEPALIVE support. (CONFIG_NET_TCP_KEEPALIVE)
Actually we don't have a control on the peer tcp stack,
who decides to send us keep-alive probes.
* We should respond them for non ESTABLISHED states. eg. FIN_WAIT_2
See also:
https://github.com/apache/incubator-nuttx/pull/3919#issuecomment-868248576
* Move the code to advance rcvseq for user data from tcp_input
to receive handlers.
Motivation: allow partial ack.
* If we drop a segment, ignore FIN as well. Note than tcp FIN bit is
logically after the user data in the same segment.
* Fixes the case where the window was small but not zero.
* tcp_recvfrom: Remove tcp_ackhandler. Instead, simply schedule TX for
a possible window update and make tcp_appsend decide.
* Replace rcv_wnd (the last advertized window size value) with
rcv_adv. (the window edge sequence number advertized to the peer)
rcv_wnd was complicated to deal with because its base (rcvseq) is
also moving.
* tcp_appsend: Send a window update even if there are no other reasons
to send an ack.
Namely, send an update if it increases the window by
* 2 * mss
* or the half of the max possible window size
Urgent data preceded "normal" data in the TCP payload. If the urgent data is larger than the size of the TCP payload, this indicates that the entire payload is urgent data and that urgent data continues in the next packet.
This case was handled correctly for the case where urgent data was present but was not being handled correctly in the case where the urgent data was NOT present.
