tcp: separate syn cache stuffs into tcp_syncache.[ch] files

No functional change.

remove ip{,6}_id.c

branches: 1.14.24;
Rumpify netipsec

Note that we should modularize netipsec and reduce reverse symbol references
(referencing symbols of netipsec from net, netinet and netinet6) though,
the task needs lots of code changes. Prior to doing so, rumpifying it and
having ATF tests should be useful.

branches: 1.13.2; 1.13.4;
purge rump/net of component-specific opt directories

Move defines of INET and INET6 from opt_inet.h to Makefile.inc

As discussed with pooka@
fixes current issues with ipv6 on rump being broken

branches: 1.11.6;
Separate inet and inet6, allows inet6-only rump kernels.

branches: 1.10.2;
default portalgo to random_start, for less connections from port 65535

cosmetic: put portalgo.c in the conceptually right place

branches: 1.8.4; 1.8.14;
Reduces the resources demanded by TCP sessions in TIME_WAIT-state using
methods called Vestigial Time-Wait (VTW) and Maximum Segment Lifetime
Truncation (MSLT).

MSLT and VTW were contributed by Coyote Point Systems, Inc.

Even after a TCP session enters the TIME_WAIT state, its corresponding
socket and protocol control blocks (PCBs) stick around until the TCP
Maximum Segment Lifetime (MSL) expires. On a host whose workload
necessarily creates and closes down many TCP sockets, the sockets & PCBs
for TCP sessions in TIME_WAIT state amount to many megabytes of dead
weight in RAM.

Maximum Segment Lifetimes Truncation (MSLT) assigns each TCP session to
a class based on the nearness of the peer. Corresponding to each class
is an MSL, and a session uses the MSL of its class. The classes are
loopback (local host equals remote host), local (local host and remote
host are on the same link/subnet), and remote (local host and remote
host communicate via one or more gateways). Classes corresponding to
nearer peers have lower MSLs by default: 2 seconds for loopback, 10
seconds for local, 60 seconds for remote. Loopback and local sessions
expire more quickly when MSLT is used.

Vestigial Time-Wait (VTW) replaces a TIME_WAIT session's PCB/socket
dead weight with a compact representation of the session, called a
"vestigial PCB". VTW data structures are designed to be very fast and
memory-efficient: for fast insertion and lookup of vestigial PCBs,
the PCBs are stored in a hash table that is designed to minimize the
number of cacheline visits per lookup/insertion. The memory both
for vestigial PCBs and for elements of the PCB hashtable come from
fixed-size pools, and linked data structures exploit this to conserve
memory by representing references with a narrow index/offset from the
start of a pool instead of a pointer. When space for new vestigial PCBs
runs out, VTW makes room by discarding old vestigial PCBs, oldest first.
VTW cooperates with MSLT.

It may help to think of VTW as a "FIN cache" by analogy to the SYN
cache.

A 2.8-GHz Pentium 4 running a test workload that creates TIME_WAIT
sessions as fast as it can is approximately 17% idle when VTW is active
versus 0% idle when VTW is inactive. It has 103 megabytes more free RAM
when VTW is active (approximately 64k vestigial PCBs are created) than
when it is inactive.

branches: 1.7.2;
Support carp. It would be nice to support this as its own component,
but there's about 1000 lines of #ifdef which disagree with my wish.

Split-off IPv4 re-assembly mechanism into a separate module. Abstract
into ip_reass_init(), ip_reass_lookup(), etc (note: abstraction is not
yet complete). No functional changes to the actual mechanism.

OK matt@

branches: 1.5.2;
Globally define -Wno-pointer-sign, as it has become a pointless
exercise of "add it to every Makefile individually".

XXX: should autosynchronize with the rest of the kernel buildflags
in sys/conf/Makefile.kern.inc.

branches: 1.4.2;
Support IPv6 in rump. I'd have liked to introduce a netinet6
component, but due to ifdef happiness permeating the sources, it's
a compile decision for now, so netinet pulls in both inet and inet6.

One issue, one single issue: the loopback interface still needs to
be created for IPv6 to work. I have patches to take care of it
automatically if the appropriate component (net) is present, but
they require a bit more testing before commit.

branches: 1.3.2; 1.3.4;
Better define GATEWAY in opt_gateway.h instead of the Makefile so
UPDATE builds don't go all coocoo.

enable GATEWAY

branches: 1.1.2; 1.1.4; 1.1.10;
Deal with the ld.so/linkset brokenness and compile all of libnet
and libnetinet into a big bunch for now. If they were separate
libraries, the DOMAIN_DEFINE() in the latter on the linkline would
not get noticed at "boot" time because of the abovementioned
brokenness. One of these days I'll add code to dlopen() the
libraries and resplit them, but this will allow things to work
until then.