Do not bother to preserve segment boundaries in the tcp
readahead queues.
* Avoid wasting the tail IOB space for each segments.
Instead, pack the newly received data into the tail space
of the last IOB. Also, advertise the tail space as
a part of the window.
* Use IOB chain directly. Eliminate IOB queue overhead.
* Allow to accept only a part of a segment.
* This change improves the memory efficiency.
And probably more importantly, allows less-confusing
recv window advertisement behavior.
Previously, even when we advertise N bytes window,
we often couldn't actually accept N bytes. Depending on
the segment sizes and IOB configurations, it was causing
segment drops.
Also, the previous code was moving the right edge of the
window back and forth too often, even when nothing in
the system was competing on the IOBs. Shrinking the
window that way is a kinda well known recipe to confuse
the peer stack.
* 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
Request the TCP ACK to estimate the receive window after handle
any data already buffered in a read-ahead buffer.
Change-Id: Id998a1125dd2991d73ba4bef081ddcb7adea4f0d
Signed-off-by: chao.an <anchao@xiaomi.com>
MSG_DONTWAIT (since Linux 2.2)
Enables nonblocking operation; if the operation would block, the
call fails with the error EAGAIN or EWOULDBLOCK. This provides
similar behavior to setting the O_NONBLOCK flag (via the fcntl(2)
F_SETFL operation), but differs in that MSG_DONTWAIT is a per-call
option, whereas O_NONBLOCK is a setting on the open file description
(see open(2)), which will affect all threads in the calling process
and as well as other processes that hold file descriptors referring
to the same open file description.
Author: Gregory Nutt <gnutt@nuttx.org>
net/tcp: Fix errors found in build testing.
Recent re-organization moved some functions from net/inet to net/tcp and net/udp. This include references to nxsem_wait(), SEM_PRIO_NONE, and other internal NuttX semaphore functions. These all failed to compile because nuttx/semaphore.h was not included in any of the files.
