tcp: use const argument in the TCP hostcache KPI

The hostcache can't modify tcpcb, inpcb or connection info.

tcp: mechanically rename hostcache metrics structure fields

Use hc_ prefix instead of rmx_. The latter stands for "route metrix" and
is an artifact from the 90-ies, when TCP caching was embedded in

tcp: mechanically rename hostcache metrics structure fields

Use hc_ prefix instead of rmx_. The latter stands for "route metrix" and
is an artifact from the 90-ies, when TCP caching was embedded into the
routing table. The rename should have happened back in 97d8d152c28bb.

No functional change. Done with sed(1) command:

s/rmx_(mtu|ssthresh|rtt|rttvar|cwnd|sendpipe|recvpipe|granularity|expire|q|hits|updates)/hc_\1/g

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tcp_hostcache: remove unnecessary socketvar.h

sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

tcp(4): Fix a typo in a sysctl description

- s/entires/entries/

MFC after: 3 days

tcp_hostcache: use SMR for lookups, mutex(9) for updates.

In certain cases, e.g. a SYN-flood from a limited set of hosts,
the TCP hostcache becomes the main contention point. To solve
that, this cha

tcp_hostcache: use SMR for lookups, mutex(9) for updates.

In certain cases, e.g. a SYN-flood from a limited set of hosts,
the TCP hostcache becomes the main contention point. To solve
that, this change introduces lockless lookups on the hostcache.

The cache remains a hash, however buckets are now CK_SLIST. For
updates a bucket mutex is obtained, for read an SMR section is
entered.

Reviewed by: markj, rscheff
Differential revision: https://reviews.freebsd.org/D29729

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Fix off-by-one error in KASSERT from 02f26e98c7f4.

tcp_hostcache: make THC_LOCK/UNLOCK macros to work with hash head pointer.
Not a functional change.

tcp_hostcache: style(9)

Reviewed by: rscheff

tcp_hostcache: remove extraneous check.
All paths leading here already checked this setting.

Reviewed by: rscheff

tcp_hostcache: implement tcp_hc_updatemtu() via tcp_hc_update.
Locking changes are planned here, and without this change too
much copy-and-paste would be between these two functions.

Reviewed by: rs

tcp_hostcache: implement tcp_hc_updatemtu() via tcp_hc_update.
Locking changes are planned here, and without this change too
much copy-and-paste would be between these two functions.

Reviewed by: rscheff

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tcp: Use jenkins_hash32() in hostcache

As other parts of the base tcp stack (eg.
tcp fastopen) already use jenkins_hash32,
and the properties appear reasonably good,
switching to use that.

Reviewed

tcp: Use jenkins_hash32() in hostcache

As other parts of the base tcp stack (eg.
tcp fastopen) already use jenkins_hash32,
and the properties appear reasonably good,
switching to use that.

Reviewed By: tuexen, #transport, ae
MFC after: 2 weeks
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29515

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tcp_hostcache.c: remove unneeded includes.

Reviewed by: rscheff

tcp_hostcache: add bool argument for tcp_hc_lookup() to tell are we
looking to only read from the result, or to update it as well.
For now doesn't affect locking, but allows to push stats and expire

tcp_hostcache: add bool argument for tcp_hc_lookup() to tell are we
looking to only read from the result, or to update it as well.
For now doesn't affect locking, but allows to push stats and expire
update into single place.

Reviewed by: rscheff

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tcp_hostcache: hide rmx_hits/rmx_updates under ifdef.

They have little value unless you do some profiling investigations,
but they are performance bottleneck.

Reviewed by: rscheff

Remove tcp_hostcache.h. Everything is private.

Reviewed by: rscheff

fix typo in 38ea2bd0698e

Use sbuf_drain unconditionally

After making sbuf_drain safe for external use,
there is no need to protect the call.

MFC after: 2 weeks
Reviewed By: tuexen, #transport
Sponsored by: NetApp, Inc.
Dif

Use sbuf_drain unconditionally

After making sbuf_drain safe for external use,
there is no need to protect the call.

MFC after: 2 weeks
Reviewed By: tuexen, #transport
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29545

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tcp: Shouldn't drain empty sbuf

MFC after: 2 weeks
Reviewed By: tuexen, #transport
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29524

tcp: Add hash histogram output and validate bucket length accounting

Provide a histogram output to check, if the hashsize or
bucketlimit could be optimized. Also add some basic sanity
checks around

tcp: Add hash histogram output and validate bucket length accounting

Provide a histogram output to check, if the hashsize or
bucketlimit could be optimized. Also add some basic sanity
checks around the accounting of the hash utilization.

MFC after: 2 weeks
Reviewed By: tuexen, #transport
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29506

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tcp: For hostcache performance, use atomics instead of counters

As accessing the tcp hostcache happens frequently on some
classes of servers, it was recommended to use atomic_add/subtract
rather tha

tcp: For hostcache performance, use atomics instead of counters

As accessing the tcp hostcache happens frequently on some
classes of servers, it was recommended to use atomic_add/subtract
rather than (per-CPU distributed) counters, which have to be
summed up at high cost to cache efficiency.

PR: 254333
MFC after: 2 weeks
Sponsored by: NetApp, Inc.
Reviewed By: #transport, tuexen, jtl
Differential Revision: https://reviews.freebsd.org/D29522

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tcp: Make hostcache.cache_count MPSAFE by using a counter_u64_t

Addressing the underlying root cause for cache_count to
show unexpectedly high values, by protecting all arithmetic on
that global v

tcp: Make hostcache.cache_count MPSAFE by using a counter_u64_t

Addressing the underlying root cause for cache_count to
show unexpectedly high values, by protecting all arithmetic on
that global variable by using counter(9).

PR: 254333
Reviewed By: tuexen, #transport
MFC after: 2 weeks
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29510

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tcp: drain tcp_hostcache_list in between per-bucket locks

Explicitly drain the sbuf after completing each hash bucket
to minimize the work performed while holding the hash
bucket lock.

PR: 254333

tcp: drain tcp_hostcache_list in between per-bucket locks

Explicitly drain the sbuf after completing each hash bucket
to minimize the work performed while holding the hash
bucket lock.

PR: 254333
MFC after: 2 weeks
Reviewed By: tuexen, jhb, #transport
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29483

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tcp: reduce memory footprint when listing tcp hostcache

In tcp_hostcache_list, the sbuf used would need a large (~2MB)
blocking allocation of memory (M_WAITOK), when listing a
full hostcache. This m

tcp: reduce memory footprint when listing tcp hostcache

In tcp_hostcache_list, the sbuf used would need a large (~2MB)
blocking allocation of memory (M_WAITOK), when listing a
full hostcache. This may stall the requestor for an indeterminate
time.

A further optimization is to return the expected userspace
buffersize right away, rather than preparing the output of
each current entry of the hostcase, provided by: @tuexen.

This makes use of the ready-made functions of sbuf to work
with sysctl, and repeatedly drain the much smaller buffer.

PR: 254333
MFC after: 2 weeks
Reviewed By: #transport, tuexen
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29471

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Merge ^/head r358269 through r358399.