o Remove unused and redundant TCP option definitions
o Replace usage of MAX_TCPOPTLEN with the correctly constructed and
derived MAX_TCPOPTLEN

Remove tcp_minmssoverload DoS detection logic. The problem it tried to
protect us from wasn't really there and it only bloats the code. Should
the problem surface in the future we can simply resurr

Remove tcp_minmssoverload DoS detection logic. The problem it tried to
protect us from wasn't really there and it only bloats the code. Should
the problem surface in the future we can simply resurrect it from cvs
history.

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Consolidate insertion of TCP options into a segment from within tcp_output()
and syncache_respond() into its own generic function tcp_addoptions().

tcp_addoptions() is alignment agnostic and does op

Consolidate insertion of TCP options into a segment from within tcp_output()
and syncache_respond() into its own generic function tcp_addoptions().

tcp_addoptions() is alignment agnostic and does optimal packing in all cases.

In struct tcpopt rename to_requested_s_scale to just to_wscale.

Add a comment with quote from RFC1323: "The Window field in a SYN (i.e.,
a <SYN> or <SYN,ACK>) segment itself is never scaled."

Reviewed by: silby, mohans, julian
Sponsored by: TCP/IP Optimization Fundraise 2005

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Expose smoothed RTT and RTT variance measurements to userland via
socket option TCP_INFO.
Note that the units used in the original Linux API are in microseconds,
so use a 64-bit mantissa to convert F

Expose smoothed RTT and RTT variance measurements to userland via
socket option TCP_INFO.
Note that the units used in the original Linux API are in microseconds,
so use a 64-bit mantissa to convert FreeBSD's internal measurements
from struct tcpcb from ticks.

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Add missing TH_PUSH to the TH_FLAGS enumeration.

Submitted by: Andre Albsmeier <Andre.Albsmeier-at-siemens.com>
PR: kern/85203

Fix up the comment for MAX_SACK_BLKS.

Submitted by: Noritoshi Demizu

Rewrite of tcp_sack_option(). Kentaro Kurahone (NetBSD) pointed out
that if we sort the incoming SACK blocks, we can update the scoreboard
in one pass of the scoreboard. The added overhead of sorting

Rewrite of tcp_sack_option(). Kentaro Kurahone (NetBSD) pointed out
that if we sort the incoming SACK blocks, we can update the scoreboard
in one pass of the scoreboard. The added overhead of sorting upto 4
sack blocks is much lower than traversing (potentially) large
scoreboards multiple times. The code was updating the scoreboard with
multiple passes over it (once for each sack option). The rewrite fixes
that, reducing the complexity of the main loop from O(n^2) to O(n).

Submitted by: Mohan Srinivasan, Noritoshi Demizu.
Reviewed by: Raja Mukerji.

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/* -> /*- for license, minor formatting changes

Do export the advertised receive window via the tcpi_rcv_space field of
struct tcp_info.

Implement parts of the TCP_INFO socket option as found in Linux 2.6.
This socket option allows processes query a TCP socket for some low
level transmission details, such as the current send, bandwidt

Implement parts of the TCP_INFO socket option as found in Linux 2.6.
This socket option allows processes query a TCP socket for some low
level transmission details, such as the current send, bandwidth, and
congestion windows. Linux provides a 'struct tcpinfo' structure
containing various variables, rather than separate socket options;
this makes the API somewhat fragile as it makes it dificult to add
new entries of interest as requirements and implementation evolve.
As such, I've included a large pad at the end of the structure.
Right now, relatively few of the Linux API fields are filled in, and
some contain no logical equivilent on FreeBSD. I've include __'d
entries in the structure to make it easier to figure ou what is and
isn't omitted. This API/ABI should be considered unstable for the
time being.

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Remove RFC1644 T/TCP support from the TCP side of the network stack.

A complete rationale and discussion is given in this message
and the resulting discussion:

http://docs.freebsd.org/cgi/mid.cgi?

Remove RFC1644 T/TCP support from the TCP side of the network stack.

A complete rationale and discussion is given in this message
and the resulting discussion:

http://docs.freebsd.org/cgi/mid.cgi?4177C8AD.6060706

Note that this commit removes only the functional part of T/TCP
from the tcp_* related functions in the kernel. Other features
introduced with RFC1644 are left intact (socket layer changes,
sendmsg(2) on connection oriented protocols) and are meant to
be reused by a simpler and less intrusive reimplemention of the
previous T/TCP functionality.

Discussed on: -arch

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White space cleanup for netinet before branch:

- Trailing tab/space cleanup
- Remove spurious spaces between or before tabs

This change avoids touching files that Andre likely has in his working
se

White space cleanup for netinet before branch:

- Trailing tab/space cleanup
- Remove spurious spaces between or before tabs

This change avoids touching files that Andre likely has in his working
set for PFIL hooks changes for IPFW/DUMMYNET.

Approved by: re (scottl)
Submitted by: Xin LI <delphij@frontfree.net>

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Add support for TCP Selective Acknowledgements. The work for this
originated on RELENG_4 and was ported to -CURRENT.

The scoreboarding code was obtained from OpenBSD, and many
of the remaining chan

Add support for TCP Selective Acknowledgements. The work for this
originated on RELENG_4 and was ported to -CURRENT.

The scoreboarding code was obtained from OpenBSD, and many
of the remaining changes were inspired by OpenBSD, but not
taken directly from there.

You can enable/disable sack using net.inet.tcp.do_sack. You can
also limit the number of sack holes that all senders can have in
the scoreboard with net.inet.tcp.sackhole_limit.

Reviewed by: gnn
Obtained from: Yahoo! (Mohan Srinivasan, Jayanth Vijayaraghavan)

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Remove advertising clause from University of California Regent's
license, per letter dated July 22, 1999 and email from Peter Wemm,
Alan Cox and Robert Watson.

Approved by: core, peter, alc, rwatson

Shorten the name of the socket option used to enable TCP-MD5 packet
treatment.

Submitted by: Vincent Jardin

Initial import of RFC 2385 (TCP-MD5) digest support.

This is the first of two commits; bringing in the kernel support first.
This can be enabled by compiling a kernel with options TCP_SIGNATURE
and

Initial import of RFC 2385 (TCP-MD5) digest support.

This is the first of two commits; bringing in the kernel support first.
This can be enabled by compiling a kernel with options TCP_SIGNATURE
and FAST_IPSEC.

For the uninitiated, this is a TCP option which provides for a means of
authenticating TCP sessions which came into being before IPSEC. It is
still relevant today, however, as it is used by many commercial router
vendors, particularly with BGP, and as such has become a requirement for
interconnect at many major Internet points of presence.

Several parts of the TCP and IP headers, including the segment payload,
are digested with MD5, including a shared secret. The PF_KEY interface
is used to manage the secrets using security associations in the SADB.

There is a limitation here in that as there is no way to map a TCP flow
per-port back to an SPI without polluting tcpcb or using the SPD; the
code to do the latter is unstable at this time. Therefore this code only
supports per-host keying granularity.

Whilst FAST_IPSEC is mutually exclusive with KAME IPSEC (and thus IPv6),
TCP_SIGNATURE applies only to IPv4. For the vast majority of prospective
users of this feature, this will not pose any problem.

This implementation is output-only; that is, the option is honoured when
responding to a host initiating a TCP session, but no effort is made
[yet] to authenticate inbound traffic. This is, however, sufficient to
interwork with Cisco equipment.

Tested with a Cisco 2501 running IOS 12.0(27), and Quagga 0.96.4 with
local patches. Patches for tcpdump to validate TCP-MD5 sessions are also
available from me upon request.

Sponsored by: sentex.net

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Disable the minmssoverload connection drop by default until the detection
logic is refined.

Reduce TCP_MINMSS default to 216. The AX.25 protocol (packet radio)
is frequently used with an MTU of 256 because of slow speeds and a
high packet loss rate.

Limiters and sanity checks for TCP MSS (maximum segement size)
resource exhaustion attacks.

For network link optimization TCP can adjust its MSS and thus
packet size according to the observed path M

Limiters and sanity checks for TCP MSS (maximum segement size)
resource exhaustion attacks.

For network link optimization TCP can adjust its MSS and thus
packet size according to the observed path MTU. This is done
dynamically based on feedback from the remote host and network
components along the packet path. This information can be
abused to pretend an extremely low path MTU.

The resource exhaustion works in two ways:

o during tcp connection setup the advertized local MSS is
exchanged between the endpoints. The remote endpoint can
set this arbitrarily low (except for a minimum MTU of 64
octets enforced in the BSD code). When the local host is
sending data it is forced to send many small IP packets
instead of a large one.

For example instead of the normal TCP payload size of 1448
it forces TCP payload size of 12 (MTU 64) and thus we have
a 120 times increase in workload and packets. On fast links
this quickly saturates the local CPU and may also hit pps
processing limites of network components along the path.

This type of attack is particularly effective for servers
where the attacker can download large files (WWW and FTP).

We mitigate it by enforcing a minimum MTU settable by sysctl
net.inet.tcp.minmss defaulting to 256 octets.

o the local host is reveiving data on a TCP connection from
the remote host. The local host has no control over the
packet size the remote host is sending. The remote host
may chose to do what is described in the first attack and
send the data in packets with an TCP payload of at least
one byte. For each packet the tcp_input() function will
be entered, the packet is processed and a sowakeup() is
signalled to the connected process.

For example an attack with 2 Mbit/s gives 4716 packets per
second and the same amount of sowakeup()s to the process
(and context switches).

This type of attack is particularly effective for servers
where the attacker can upload large amounts of data.
Normally this is the case with WWW server where large POSTs
can be made.

We mitigate this by calculating the average MSS payload per
second. If it goes below 'net.inet.tcp.minmss' and the pps
rate is above 'net.inet.tcp.minmssoverload' defaulting to
1000 this particular TCP connection is resetted and dropped.

MITRE CVE: CAN-2004-0002
Reviewed by: sam (mentor)
MFC after: 1 day

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Include <sys/cdefs.h> so the visibility conditionals are available.
(This should have been included with the previous revision.)

Use visibility conditionals. Only TCP_NODELAY ends up being defined
in the standards case.

o Minor style(9)ism to make consistent with -STABLE

o IPFW incorrectly handled filtering in the presence of previously
reserved and now allocated TCP flags in incoming packets. This patch
stops overloading those bits in the IP firewall rules, and

o IPFW incorrectly handled filtering in the presence of previously
reserved and now allocated TCP flags in incoming packets. This patch
stops overloading those bits in the IP firewall rules, and moves
colliding flags to a seperate field, ipflg. The IPFW userland
management tool, ipfw(8), is updated to reflect this change. New TCP
flags related to ECN are now included in tcp.h for reference, although
we don't currently implement TCP+ECN.

o To use this fix without completely rebuilding, it is sufficient to copy
ip_fw.h and tcp.h into your appropriate include directory, then rebuild
the ipfw kernel module, and ipfw tool, and install both. Note that a
mismatch between module and userland tool will result in incorrect
installation of firewall rules that may have unexpected effects. This
is an MFC candidate, following shakedown. This bug does not appear
to affect ipfilter.

Reviewed by: security-officer, billf
Reported by: Aragon Gouveia <aragon@phat.za.net>

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Implement TCP NewReno, as documented in RFC 2582. This allows
better recovery for multiple packet losses in a single window.
The algorithm can be toggled via the sysctl net.inet.tcp.newreno,
which d

Implement TCP NewReno, as documented in RFC 2582. This allows
better recovery for multiple packet losses in a single window.
The algorithm can be toggled via the sysctl net.inet.tcp.newreno,
which defaults to "on".

Submitted by: Jayanth Vijayaraghavan <jayanth@yahoo-inc.com>

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tcp updates to support IPv6.
also a small patch to sys/nfs/nfs_socket.c, as max_hdr size change.

Reviewed by: freebsd-arch, cvs-committers
Obtained from: KAME project