tcp: refactor register_tcp_functions_as_names()

Refactor register_tcp_functions_as_names() such that either all or
no (in error cases) registrations happen atomically (while holding
the tcp_function

tcp: refactor register_tcp_functions_as_names()

Refactor register_tcp_functions_as_names() such that either all or
no (in error cases) registrations happen atomically (while holding
the tcp_function_lock write lock). Also ensure that the TCP function
block is not already registered.
This avoids situations, where some registrations were performed and
then they were removed without holding a lock in between or checking
ref counts.

Reviewed by: cc
MFC after: 1 week
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D45947

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tcp: simplify stack switching protocol

Before this patch, a stack (tfb) accepts a tcpcb (tp), if the
tp->t_state is TCPS_CLOSED or tfb->tfb_tcp_handoff_ok is not NULL
and tfb->tfb_tcp_handoff_ok(tp)

tcp: simplify stack switching protocol

Before this patch, a stack (tfb) accepts a tcpcb (tp), if the
tp->t_state is TCPS_CLOSED or tfb->tfb_tcp_handoff_ok is not NULL
and tfb->tfb_tcp_handoff_ok(tp) returns 0.
After this patch, the only check is tfb->tfb_tcp_handoff_ok(tp)
returns 0. tfb->tfb_tcp_handoff_ok must always be provided.
For existing TCP stacks (FreeBSD, RACK and BBR) there is no
functional change. However, the logic is simpler.

Reviewed by: lstewart, peter_lei_ieee_.org, rrs
MFC after: 1 week
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D45253

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Remove $FreeBSD$: two-line nroff pattern

Remove /^\.\\"\n\.\\"\s*\$FreeBSD\$$\n/

man(9): Some markup fixes

- whitespace at end of input line
- skipping paragraph macro: Pp after Sh

MFC after: 3 days

Merge ^/head r319548 through r319778.

Add the infrastructure to support loading multiple versions of TCP
stack modules.

It adds support for mangling symbols exported by a module by prepending
a string to them. (This avoids overlapping s

Add the infrastructure to support loading multiple versions of TCP
stack modules.

It adds support for mangling symbols exported by a module by prepending
a string to them. (This avoids overlapping symbols in the kernel linker.)

It allows the use of a macro as the module name in the DECLARE_MACRO()
and MACRO_VERSION() macros.

It allows the code to register stack aliases (e.g. both a generic name
["default"] and version-specific name ["default_10_3p1"]).

With these changes, it is trivial to compile TCP stack modules with
the name defined in the Makefile and to load multiple versions of the
same stack simultaneously. This functionality can be used to enable
side-by-side testing of an old and new version of the same TCP stack.
It also could support upgrading the TCP stack without a reboot.

Reviewed by: gnn, sjg (makefiles only)
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D11086

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Merge ^/head r308870 through r309105.

Fix various mdoc issues reported by mandoc -Tlint.

Merge ^/head r303250 through r304235.

MFhead @ r304232

Here we update the modular tcp to be able to switch to an
alternate TCP stack in other then the closed state (pre-listen/connect).
The idea is that *if* that is supported by the alternate stack, it

Here we update the modular tcp to be able to switch to an
alternate TCP stack in other then the closed state (pre-listen/connect).
The idea is that *if* that is supported by the alternate stack, it
is asked if its ok to switch. If it approves the "handoff" then we
allow the switch to happen. Also the fini() function now gets a flag
to tell if you are switching away *or* the tcb is destroyed. The
init() call into the alternate stack is moved to the end so the
tcb is more fully formed before the init transpires.

Sponsored by: Netflix Inc.
Differential Revision: D6790

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Document support for alternate TCP stacks.

Differential Revision: https://reviews.freebsd.org/D6940
Reviewed by: hiren
Approved by: re (gjb)
Sponsored by: Juniper Networks