suggestion in draft-floyd-incr-init-win-03. Rather than scaling cwnd back
by the ratio of new segment size to old segment size, we perform a slow start
using the Initial Window, computed with the new segment size.
- Don't use home-grown queue manipulation. Use <sys/queue.h> instead. The
data structures are a little larger, but we are otherwise wasting the
memory chunk anyway (we're already a 64-byte malloc bucket).
- Fix a bug in the cache-is-full case: if the oldest element removed from
the first non-empty bucket was the only element in the bucket, the
bucket wouldn't be removed from the bucket cache, causing queue corruption
later.
- Optimize the syn cache timers by using PRT timers rather than home-grown
decrement-and-propagate timers.
This code is now a fair bit smaller, and significantly easier to read
and understand.
conditional (tcp_compat_42). The kernel config option TCP_COMPAT_42
will still enable this by default, or disable this by default if the
option is not included (i.e. current behavior). This will be made a
sysctl soon.
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.
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.
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).
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.
pseudo-device rnd # /dev/random and in-kernel generator
in config files.
o Add declaration to all architectures.
o Clean up copyright message in rnd.c, rnd.h, and rndpool.c to include
that this code is derived in part from Ted Tyso's linux code.
- Don't overload t_maxseg. Previous behavior was to set it to the min
of the peer's advertised MSS, our advertised MSS, and tcp_mssdflt
(for non-local networks). This breaks PMTU discovery running on
either host. Instead, remember the MSS we advertise, and use it
as appropriate (in silly window avoidance).
- Per last bullet, split tcp_mss() into several functions for handling
MSS (ours and peer's), and performing various tasks when a connection
becomes ESTABLISHED.
- Introduce a new function, tcp_segsize(), which computes the max size
for every segment transmitted in tcp_output(). This will eventually
be used to hook in PMTU discovery.
use of mbuf external storage and increasing performance (by eliminating
an m_pullup() for clusters in the IP reassembly code).
Changes from Koji Imada <koji@math.human.nagoya-u.ac.jp>, in PR #3628
and #3480, with ever-so-slight integration changes by me.
(like the alpha). Biggest problem: IP headers were overlayed with
structure which included pointers, and which therefore didn't overlay
properly on 64-bit machines. Solution: instead of threading pointers
through IP header overlays, add a "queue element" structure to do
the threading, and point it at the ip headers.
* Convert several data structures to use queue.h.
* Split in_pcbnotify() into two parts; one for notifying a specific PCB, and
one for notifying all PCBs for a particular foreign address.
* Don't add the extra 1/8 of the mss when ramping up the congestion window.
* Scale the RTT values slightly to adjust for rounding errors.
* Set the lower bound of the RTO to RTT+2.
