MFC r357272:

Merge r357271 from the clang1000-import branch:

Fix the following -Werror warning from clang 10.0.0 in bsnmpd:

usr.sbin/bsnmpd/modules/snmp_bridge/bridge_port.c:1235:43: error: overlapping comparisons always evaluate to true [-Werror,-Wtautological-overlap-compare]
begemotBridgeStpPortEnable_enabled ||
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~

Work around it by casting the enum values to the type of val->v.integer.

MFstable/11 r310901:

MFC r310648:

style(9): clean up trailing whitespace

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Spelling fixes for usr.sbin/

Keep the snmp_bridge(3) module up to date with if_bridge(4) and add an
object to control the value of the new 'PRIVATE' bridge members' flag.
While here, remove stale '__unused' compiler directives.

Reviewed by: bz
Approved by: re (bmah), bz (mentor)

Keep in sync with the if_bridge(4) module (rev. 1.20 if_bridgevar.h,
1.12 bridgestp.h) and rename all PointToPoint related variables
from P2P to PTP (s/P2P/PTP/g s/p2p/ptp/g).

Approved by: bz (mentor)

Do not add 'default:' cases inside a switch() on an enum like the
SNMP option argument. That way the compiler will give a warning in
case of a missing or an extra but unknown 'case:'.
Do the same for SNMP LEAF objects to be prepared once gensnmptree will
auto-generate enums for those too.
Add an abort() after the switch() instead of the 'default:' to catch
any errors. The nice side effect is that the compiler will correctly
track supposed to be 'uninitialized' variables with that.

When trying to set a value sanity check it before calling the OS
dependent API of snmp_bridge to tell whether it is an attempt to
set a bad value or a general error.

Suggested by: harti (first part)
Approved by: bz (mentor)

Instead of explicitly initializing variables to avoid compiler warnings,
add a default case to handle the situation when the variables are not
initialized.
Furthermore, abort() if the snmp agent passes an invalid option to the
bridge module. As the option (SET, GET, GETNEXT, COMMIT, ROLLBACK) is
determined by the snmp agent based on the operation requested by user,
this behaviour is unlikely to be abused as a source for a DoS, but if
ever hit will likely reveal a problem in the snmp agent or bridge
module.

Approved by: bz (mentor)

Add support for RSTP (RFC4318) to the SNMP bridge monitoring module.

Approved by: bz (mentor)

Bring in a SNMP module to support monitoring if_bridge(4) interfaces
via bsnmpd(1). The module implements IETF BRIDGE-MIB as defined in
RFC4188 and a private BEGEMOT-BRIDGE-MIB.

Sponsored by: Google Summer of Code 2006
Reviewed by: bz
Approved by: bz (mentor)