* t_partialacks<0 means we are not in fast recovery.
* t_partialacks==0 means we are in fast recovery, but we have not received
any partial acks yet.
* t_partialacks>0 means we are in fast recovery, and we have received
partial acks.
This is used to implement 2 changes in RFC 3782:
* We keep the notion that we are in fast recovery separate from t_dupacks, so
it is not reset due to out-of-order acks. (This affects both the Reno and
NewReno cases.)
* We only reset the retransmit timer on the first partial ack -- preventing us
from possibly taking one RTO per segment once fast recovery is initiated.
As before, it is hard to measure any difference between Reno and NewReno in the
real-world cases that I've tested.
1) If an echoed RFC 1323 time stamp appears to be later than the current time,
ignore it and fall back to old-style RTT calculation. This prevents ending
up with a negative RTT and panicking later.
2) Fix NewReno. This involves a few changes:
a) Implement the send_high variable in RFC 2582. Our implementation is
subtly different; it is one *past* the last sequence number transmitted
rather than being equal to it. This simplifies some logic and makes
the code smaller. Additional logic was required to prevent sequence
number wraparound problems; this is not mentioned in RFC 2582.
b) Make sure we reset t_dupacks on new acks, but *not* on a partial ack.
All of the new ack code is pushed out into tcp_newreno(). (Later this
will probably be a pluggable function.) Thus t_dupacks keeps track of
whether we're in fast recovery all the time, with Reno or NewReno, which
keeps some logic simpler.
c) We do not need to update snd_recover when we're not in fast recovery.
See tech-net for an explanation of this.
d) In the gratuitous fast retransmit prevention case, do not send a packet.
RFC 2582 specifically says that we should "do nothing".
e) Do not inflate the congestion window on a partial ack. (This is done by
testing t_dupacks to see whether we're still in fast recovery.)
This brings the performance of NewReno back up to the same as Reno in a few
random test cases (e.g. transferring peer-to-peer over my wireless network).
I have not concocted a good test case for the behavior specific to NewReno.
support IPv6 if KAME IPSEC (RFC is not explicit about how we make data stream
for checksum with IPv6, but i'm pretty sure using normal pseudo-header is the
right thing).
XXX
current TCP MD5 signature code has giant flaw:
it does not validate signature on input (can't believe it! what is the point?)
(MD5 signatures for TCP, as used with BGP). Credit for original
FreeBSD code goes to Bruce M. Simpson, with FreeBSD sponsorship
credited to sentex.net. Shortening of the setsockopt() name
attributed to Vincent Jardin.
This commit is a minimal, working version of the FreeBSD code, as
MFC'ed to FreeBSD-4. It has received minimal testing with a ttcp
modified to set the TCP-MD5 option; BMS's additions to tcpdump-current
(tcpdump -M) confirm that the MD5 signatures are correct. Committed
as-is for further testing between a NetBSD BGP speaker (e.g., quagga)
and industry-standard BGP speakers (e.g., Cisco, Juniper).
NOTE: This version has two potential flaws. First, I do see any code
that verifies recieved TCP-MD5 signatures. Second, the TCP-MD5
options are internally padded and assumed to be 32-bit aligned. A more
space-efficient scheme is to pack all TCP options densely (and
possibly unaligned) into the TCP header ; then do one final padding to
a 4-byte boundary. Pre-existing comments note that accounting for
TCP-option space when we add SACK is yet to be done. For now, I'm
punting on that; we can solve it properly, in a way that will handle
SACK blocks, as a separate exercise.
In case a pullup to NetBSD-2 is requested, this adds sys/netipsec/xform_tcp.c
,and modifies:
sys/net/pfkeyv2.h,v 1.15
sys/netinet/files.netinet,v 1.5
sys/netinet/ip.h,v 1.25
sys/netinet/tcp.h,v 1.15
sys/netinet/tcp_input.c,v 1.200
sys/netinet/tcp_output.c,v 1.109
sys/netinet/tcp_subr.c,v 1.165
sys/netinet/tcp_usrreq.c,v 1.89
sys/netinet/tcp_var.h,v 1.109
sys/netipsec/files.netipsec,v 1.3
sys/netipsec/ipsec.c,v 1.11
sys/netipsec/ipsec.h,v 1.7
sys/netipsec/key.c,v 1.11
share/man/man4/tcp.4,v 1.16
lib/libipsec/pfkey.c,v 1.20
lib/libipsec/pfkey_dump.c,v 1.17
lib/libipsec/policy_token.l,v 1.8
sbin/setkey/parse.y,v 1.14
sbin/setkey/setkey.8,v 1.27
sbin/setkey/token.l,v 1.15
Note that the preceding two revisions to tcp.4 will be
required to cleanly apply this diff.
individually, create a tcpcb template pre-initialized (and pre-zero'd)
with the static and mostly-static tcpcb parameters. The template is
now copied into the new tcpcb, which zeros and initializes most of the
tcpcb in one pass. The template is kept up-to-date as TCP sysctl
variables are changed.
Combined with the previous sb_max change, TCP socket creation is now
25% faster.
cooperating with the callout code in working around the race
condition caused by the TCP code's use of the callout facility.
Instead of unconditionally releasing memory in tcp_close() and
SYN_CACHE_PUT(), check whether any of the related callout handlers
are about to be invoked (but have not yet done callout_ack()), and
if so, just mark the associated data structure (tcpcb or syn cache
entry) as "dead", and test for this (and release storage) in the
callout handler functions.
sent from. This change avoid a linear search through all mbufs when using
large TCP windows, and therefore permit high-speed connections on long
distances.
Tested on a 1 Gigabit connection between Luleå and San Francisco, a distance
of about 15000km. With TCP windows of just over 20 Mbytes it could keep up
with 950Mbit/s.
After discussions with Matt Thomas and Jason Thorpe.
be inserted into ktrace records. The general change has been to replace
"struct proc *" with "struct lwp *" in various function prototypes, pass
the lwp through and use l_proc to get the process pointer when needed.
Bump the kernel rev up to 1.6V
Do a little mbuf rework while here. Change all uses of MGET*(*, M_WAIT, *)
to m_get*(M_WAIT, *). These are not performance critical and making them
call m_get saves considerable space. Add m_clget analogue of MCLGET and
make corresponding change for M_WAIT uses.
Modify netinet, gem, fxp, tulip, nfs to support MBUFTRACE.
Begin to change netstat to use sysctl.
as necessary:
* Implement a new mbuf utility routine, m_copyup(), is is like
m_pullup(), except that it always prepends and copies, rather
than only doing so if the desired length is larger than m->m_len.
m_copyup() also allows an offset into the destination mbuf, which
allows space for packet headers, in the forwarding case.
* Add *_HDR_ALIGNED_P() macros for IP, IPv6, ICMP, and IGMP. These
macros expand to 1 if __NO_STRICT_ALIGNMENT is defined, so that
architectures which do not have strict alignment constraints don't
pay for the test or visit the new align-if-needed path.
* Use the new macros to check if a header needs to be aligned, or to
assert that it already is, as appropriate.
Note: This code is still somewhat experimental. However, the new
code path won't be visited if individual device drivers continue
to guarantee that packets are delivered to layer 3 already properly
aligned (which are rules that are already in use).
all open TCP connections in tcp_slowtimo() (which is called 2x
per second). It's fairly rare for TCP timers to actually fire,
so saving this list traversal is good, especially if you want
to scale to thousands of open connections.
and call it directly from tcp_slowtimo() (via a table) rather
than going through tcp_userreq().
This will allow us to call TCP timers directly from callouts,
in a future revision.
Instead of incrementing t_idle and t_rtt in tcp_slowtimo(), we now
take a timstamp (via tcp_now) and use subtraction to compute the
delta when we actually need it (using unsigned arithmetic so that
tcp_now wrapping is handled correctly).
Based on similar changes in FreeBSD.
ISS attacks (which we already fend off quite well).
1. First-cut implementation of RFC1948, Steve Bellovin's cryptographic
hash method of generating TCP ISS values. Note, this code is experimental
and disabled by default (experimental enough that I don't export the
variable via sysctl yet, either). There are a couple of issues I'd
like to discuss with Steve, so this code should only be used by people
who really know what they're doing.
2. Per a recent thread on Bugtraq, it's possible to determine a system's
uptime by snooping the RFC1323 TCP timestamp options sent by a host; in
4.4BSD, timestamps are created by incrementing the tcp_now variable
at 2 Hz; there's even a company out there that uses this to determine
web server uptime. According to Newsham's paper "The Problem With
Random Increments", while NetBSD's TCP ISS generation method is much
better than the "random increment" method used by FreeBSD and OpenBSD,
it is still theoretically possible to mount an attack against NetBSD's
method if the attacker knows how many times the tcp_iss_seq variable
has been incremented. By not leaking uptime information, we can make
that much harder to determine. So, we avoid the leak by giving each
TCP connection a timebase of 0.
entering rtentry's for hosts we're not actually communicating
with.
Do this by invoking the ctlinput for the protocol, which is
responsible for validating the ICMP message:
* TCP -- Lookup the connection based on the address/port
pairs in the ICMP message.
* AH/ESP -- Lookup the SA based on the SPI in the ICMP message.
If validation succeeds, ctlinput is responsible for calling
icmp_mtudisc(). icmp_mtudisc() then invokes callbacks registered
by protocols (such as TCP) which want to take some sort of special
action when a path's MTU changes. For TCP, this is where we now
refresh cached routes and re-enter slow-start.
As a side-effect, this fixes the problem where TCP would not be
notified when a path's MTU changed if AH/ESP were being used.
XXX Note, this is only a fix for the IPv4 case. For the IPv6
XXX case, we need to wait for the KAME folks.
Reviewed by sommerfeld@netbsd.org and itojun@netbsd.org.
basis. default: 100pps
set default value for net.inet.tcp.rstratelimit to 0 (disabled),
NOTE: it does not work right for smaller-than-1/hz interval. maybe we should
nuke it, or make it impossible to set smaller-than-1/hz value.
due to massive changes in KAME side.
- IPv6 output goes through nd6_output
- faith can capture IPv4 packets as well - you can run IPv4-to-IPv6 translator
using heavily modified DNS servers
- per-interface statistics (required for IPv6 MIB)
- interface autoconfig is revisited
- udp input handling has a big change for mapped address support.
- introduce in4_cksum() for non-overwriting checksumming
- introduce m_pulldown()
- neighbor discovery cleanups/improvements
- netinet/in.h strictly conforms to RFC2553 (no extra defs visible to userland)
- IFA_STATS is fixed a bit (not tested)
- and more more more.
TODO:
- cleanup os-independency #ifdef
- avoid rcvif dual use (for IPsec) to help ifdetach
(sorry for jumbo commit, I can't separate this any more...)
RTM_IFINFO is now 0xf, 0xe is RTM_OIFINFO which returns the old (if_msghdr14)
struct with 32bit counters (binary compat, conditioned on COMPAT_14).
Same for sysctl: node 3 is renamed NET_RT_OIFLIST, NET_RT_IFLIST is now node 4.
Change rt_msg1() to add an mbuf to the mbuf chain instead of just panic()
when the message is larger than MHLEN.
MSS advertisement must always be:
max(if mtu) - ip hdr siz - tcp hdr siz
We violated this in the previous code so it was fixed.
tcp_mss_to_advertise() now takes af (af on wire) as its argument,
to compute right ip hdr siz.
tcp_segsize() will take care of IPsec header size.
One thing I'm not really sure is how to handle IPsec header size in
*rxsegsizep (inbound segment size estimation).
The current code subtracts possible *outbound* IPsec size from *rxsegsizep,
hoping that the peer is using the same IPsec policy as me.
It may not be applicable, could TCP gulu please comment...
mycroft