TCP connections by using the MTU of the interface. Also added
a knob, mss_ifmtu, to force all connections to use the MTU of
the interface to calculate the advertised MSS.
meeting of IETF #41 by Amy Hughes <ahughes@isi.edu>, and in an upcoming
internet draft from Hughes, Touch, and Heidemann.
CWM eliminates line-rate bursts after idle periods by counting pending
(unacknowledged) packets and limiting the congestion window to the
initial congestion window plus the pending packet count. This has the
effect of allowing us to use the window as long as we continue to transmit,
but as soon as we stop transmitting, we go back to a slow-start (also known
as `use it or lose it').
This is not enabled by default. You can enable this behavior by patching
the "tcp_cwm" global (set it to non-zero) or by building a kernel with the
TCP_CWM option.
to ACK immediately any packet that arrived with PSH set. This breaks
delayed ACKs in a few specific common cases that delayed ACKs were
supposed to help, and ends up not making much (if any) difference in
the case where where this ACK-on-PSH change was supposed to help.
Per discussion with several members of the TCPIMPL and TCPSAT IETF
working groups.
code, as clarified in the TCPIMPL WG meeting at IETF #41: If the SYN
(active open) or SYN,ACK (passive open) was retransmitted, the initial
congestion window for the first slow start of that connection must be
one segment.
RTO estimation changes. Under some circumstances it would return a value
of 0, while the old Van Jacobson RTO code would return a minimum of 3.
This would result in 12 retransmissions, each 1 second apart.
This takes care of those instances, and ensures that t_rttmin is
used everywhere as a lower bound.
change pfil_add_hook to put output filters at the tail of the queue,
while continuing to place input filters at the head of the queue. update
the two users of these functions, and document these changes.
fixes PR#4593.
in the packet. This fixes a bug that was resulting in extra packets
in retransmissions (the second packet would be 12 bytes long,
reflecting the RFC1323 timestamp option size).
results in reserved ephemeral ports starting at the top (as per
current practice), and shouldn't have a negative effect on normal
ephemeral ports...
* initialise inpt_lastlow in in_pcbinit
* IP_PORTRANGE socket option, which controls how the ephemeral ports
are allocated. it takes the following settings:
IP_PORTRANGE_DEFAULT use anonportmin (49152) -> anonportmax (65535)
IP_PORTRANGE_HIGH as IP_PORTRANGE_DEFAULT (retained for FreeBSD
compat reasons, where these are separate)
IP_PORTRANGE_LOW use 600 -> 1023. only works if uid==0.
* in_pcb flag INP_ANONPORT. set if port was allocated ephmerally
* support sysctl net.inet.ip.anonportmin (lowest ephemeral port)
and net.inet.ip.anonportmax (highest ephemeral port).
these can't be set to >65535, < IPPORT_RESERVED (unless IPNOPRIVPORTS
is defined), and anonportmin has to be < anonportmax.
* use a cleaner way of only cycling through the available set once;
this will be useful for when a random allocation scheme is used
* define IPPORT_ANON{MIN,MAX} instead of IPPORT_USER{LOW,HIGH}
so_linger is used as an argument to tsleep(), so was stuffed with
clockticks for the TCP linger time. However, so_linger is set directly from
l_linger if the linger time is specified, and l_linger is seconds (although
this is not currently documented anywhere). Fix this to set the TCP
linger time in seconds, and multiply so_linger by hz when tsleep() is
called to actually perform the linger.
- When running the slow timers, skip PCBs in LISTEN state.
- When processing the persist timer, drop the connection if the connection
idle time exceeds the maximum backoff for retransmit. Part of
kern/2335 (pete@daemon.net).
- If we fail to allocate mbufs for the outgoing segment, free the header
and abort.
From Stevens:
- Ensure the persist timer is running if the send window reaches zero.
Part of the fix for kern/2335 (pete@daemon.net).
The sysctl'able variable "tcp_init_win", when set to 0, selects an
auto-tuning algorithm for selecting the initial window, based on transmit
segment size, per discussion in the IETF tcpimpl working group.
Default initial window is still 1 segment, but will soon become 2 segments,
per discussion in tcpimpl.
in tcp_output(), and it will only be cleared in tcp_output() if the ACK was
transmitted sucessfully. Also, don't count delayed ACKs here, let tcp_output()
count them.
