While it's a neat idea, it doesn't work well in reality.
* Many of modern tcp stacks don't obey the "ack every other packet"
rule these days. (Linux, macOS, ...)
* Even if a traditional TCP implementation is assumed, we can't
predict/control which packets are acked reliably. For example,
window updates can easily mess up our strategy.
tcp_timer: eliminated false decrements of conn->timer in case of multiple network adapters.
The false timer decrements sometimes provoked TCP spurious retransmissions due to premature timeouts.
The resulting time complexities are as follows:
* devif_callback_alloc() time complexity is O(1) (i.e. O(n) to fill the whole list).
* devif_callback_free() time complexity is O(1) (i.e. O(n) to empty the whole list).
* devif_conn_event() time complexity is O(n).
In case of enabled packet forwarding mode, packets were forwarded in a reverse order
because of LIFO behavior of the connection event list.
The issue exposed only during high network traffic. Thus the event list started to grow
that resulted in changing the order of packets inside of groups of several packets
like the following: 3, 2, 1, 6, 5, 4, 8, 7 etc.
Remarks concerning the connection event list implementation:
* Now the queue (list) is FIFO as it should be.
* The list is singly linked.
* The list has a head pointer (inside of outer net_driver_s structure),
and a tail pointer is added into outer net_driver_s structure.
* The list item is devif_callback_s structure.
It still has two pointers to two different list chains (*nxtconn and *nxtdev).
* As before the first argument (*dev) of the list functions can be NULL,
while the other argument (*list) is effective (not NULL).
* An extra (*tail) argument is added to devif_callback_alloc()
and devif_conn_callback_free() functions.
* devif_callback_alloc() time complexity is O(1) (i.e. O(n) to fill the whole list).
* devif_callback_free() time complexity is O(n) (i.e. O(n^2) to empty the whole list).
* devif_conn_event() time complexity is O(n).
Because of this, it will take some time to detangle the licensing under net/. Many new features, original features were added to the NuttX network. Clearly, any references to Adam Dunkels in the files that implement these new features that have no counterpart in uIP 1.0 are errors.
This PR removes the references and converts the license headers to Apache 2.0 where possible. The affected files include only (1) the implementation of IPv6 (including neighbor support under ICMPv6) and (2) Raw sockets. Neither of these features are present in uIP 1.0 and the licenses can be freely updated.
Gregory Nutt has submitted the SGA
UVC Ingenieure has submitted the SGA
Max Holtzberg has submitted the ICLA
as a result we can migrate the licenses to Apache.
Signed-off-by: Alin Jerpelea <alin.jerpelea@sony.com>
Summary:
- The critical section was added in Mar 2018 to improve
stability in SMP mode
- However, I noticed that this critical section is no longer
needed
Impact:
- None
Testing:
- Tested with spresense:wifi_smp and spresense:rndis_smp
Signed-off-by: Masayuki Ishikawa <Masayuki.Ishikawa@jp.sony.com>
* 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.
Fix a wrong assertion in:
```
commit 98ec46d726
Author: YAMAMOTO Takashi <yamamoto@midokura.com>
Date: Tue Jul 20 09:10:43 2021 +0900
tcp_send_buffered.c: fix iob allocation deadlock
Ensure to put the wrb back onto the write_q when blocking
on iob allocation. Otherwise, it can deadlock with other
threads doing the same thing.
```
I forget to submit this with https://github.com/apache/incubator-nuttx/pull/4257
With an applictation using mbedtls, I observed retransmitted segments
with corrupted user data, detected by the peer tls during mac processing.
Looking at the packet dump, I suspect that a wrb which has been put back
onto the write_q for retransmission was partially sent but fully acked.
Note: it's normal for a retransmission to be acked before sent.
In that case, the bug fixed in this commit would cause the wrb have
a wrong sequence number, possibly the same as the next wrb. It matches
what I saw in the packet dump. That is, the broken segments contain the
payload identical to one of the previous segment.
