✎ soc:2010:cooldavid:journal:week8

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==== Several TCP fixes ====
=== Separating the xfer interface closing routines from tcp_close ===
The original Receive flow of TCP stack pass the data to upper layer
while the TCP state transition and response still in progress.
But when upper layer received some specific data, it might send data
through the current TCP connection, or close the current TCP connection.
This issue makes the TCP state hard to maintain.

After we separating the xfer interface closing routines from tcp_close,
we have the opportunity to handle the TCP state, and shutdown the deliver
interface at different but more suitable place.

While receiving data, we deliver the data to upper layer after we FULLY
updated/handled the TCP state. So that any actions that the upper layer
might do to the TCP stack would be at safer timing.

=== Distinguish passive and active close with proper actions ===
The original design of TCP stack dose not distinguish passive and active
close, support is to make close action more compatible with ''RFC 793''
and having the ability to take the advantage of release all resources
when passive closing.

=== Fix possible misjudged SYN/FIN ACKed status ===
gPXE did not check the ACK number while receiving a response from remote
server with ACK flag set. gPXE assumes the remote server ACKed the SYN/FIN
sent by gPXE if **ANY** received a packet from remote server with ACK flag
set. The error might occur when the packet is out-of-order.

=== Update the rule for ignore xmit while timer was fired ==
If the retransmit timer was fired due to ACK to remote host and
without data, we should send the latest ACK(force_send) update
to remote host instead of ignoring it.

=== Waiting for TCP to fully close ===
While using scripts, if the downloaded image is not bootable,
the gPXE exits faster than it have the opportunity to gracefully
closing the TCP connection. Which might lead the TCP state of
remote server not closed.

[[http://git.etherboot.org/?p=people/cooldavid/gpxe.git;a=commitdiff;h=0bee38ff68e777ca2f563a2d7d5348cfe533232c|This commit]] waits for TCP
to fully close by polling remaining ACKs from remote server and let
the gPXE reply the correct response before shutdown the xfer interface.

It is somehow hacky, hoping we can find better solution.

=== Randomize TCP bind port ===
To reduce possible TCP port collision.

Trace: • project_plan • design • derekpryor • project_plan • ideas • notes • the_kernel • adir • acknowledgements • winvista • mdeck • 2009 • derekpryor-proposal • notes • 2010 • notes • ideas • scratch • info • project_plan