MFC r307882: bsnmpd: fix SNMPv3

This change fixes SNMPv3 for bsnmpd in stable/11.
Note this is already fixed in stable/12 and above.

Original commit log:

Fix a regression introduced in SVN r256678 that breaks USM header parsing

Reviewed by: bz@

(cherry picked from commit 1108712cb5b14130380c93b00f4e9ef2a797a07d)

Git Hash: 271f9f2e8b93f0724d00b5405f8b53f6695408b2
Git Author: syrinx@FreeBSD.org

MFC r310729:

Prevent improper memory accesses after calling snmp_pdu_free and snmp_value_free

snmp_pdu_free: set pdu->nbindings to 0 to limit the damage that
could happen if a pdu was reused after calling the function, and
as both stack and heap allocation types are used in contrib/bsnmp
and usr.sbin/bsnmpd.

snmp_value_free: NULL out value->v.octetstring.octets after calling
free on it to prevent a double-free from occurring.

MFC r310501:

Be more strict about IpAddress type in snmp_value_parse(..)

- Use inet_pton with AF_INET instead of doing longhand with sscanf.
- Use gethostbyname2 with AF_INET to ensure that the hostname isn't
accidentally parsed with another address family, e.g. AF_INET6.

NB: IpAddress per RFC-2578 is IPv4 only. Work is in progress to add
the InetAddress type and friends documented in RFC-4001 and
elsewhere (which supports IPv4, IPv6, and more).

MFC r310500,r310660:

r310500:

Minor style(9) fixes

- Trailing whitespace cleanup
- Sort variables in snmp_dialog(..) by alignment

No functional change

r310660:

style(9): fix whitespace in pdu_encode_secparams(..)

MFC r310648:

style(9): clean up trailing whitespace

MFC r310499:

Sort #includes

No functional change

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Fix SNMP Error response PDUs and properly encode them when using v3 auth/encryption.

Reported by: harti@

Bring in a SNMP module that allows configuration of SNMPv3 Notification targets.

Sponsored by: The FreeBSD Foundation
Reviewed by: philip
Approved by: philip

Silence the compiler warnings in libbsnmp by removing several (now)
unsed parameters.

Sponsored by: The FreeBSD Foundation
Reviewed by: philip@

In bsnmpd(1) add support for SNMPv3 message processing model, including message authentication, packet encryption & view-based access control (RFC 3412, 3414, 3415).

Sponsored by: The FreeBSD Foundation
Reviewed by: philip@ (mostly)
Approved by: philip@

This commit was generated by cvs2svn to compensate for changes in r150920,
which included commits to RCS files with non-trunk default branches.

Virgin import of bsnmpd 1.11

Virgin import of bsnmpd 1.7

Virgin import of bsnmpd 1.5a

Virgin import of bsnmp 1.4