Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

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

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

Don't free memory that is going to be used as error string.

PR: bin/178121
Submitted by: Garrett Cooper <yaneurabeya gmail.com>

if_lagg: allow to invoke SIOCSLAGGPORT multiple times in a row

Currently, 'ifconfig laggX down' does not remove members from this
lagg(4) interface. So, 'service netif stop laggX' followed by
'service netif start laggX' will choke, because "stop" will leave
interfaces attached to the laggX and ifconfig from the "start" will
refuse to add already-existing interfaces.

The real-world case is when I am bundling together my Ethernet and
WiFi interfaces and using multiple profiles for accessing network in
different places: system being booted up with one profile, but later
this profile being exchanged to another one, followed by 'service
netif restart' will not add WiFi interface back to the lagg: the
"stop" action from 'service netif restart' will shut down my main WiFi
interface, so wlan0 that exists in the lagg0 will be destroyed and
purged from lagg0; the "start" action will try to re-add both
interfaces, but since Ethernet one is already in lagg0, ifconfig will
refuse to add the wlan0 from WiFi interface.

Since adding the interface to the lagg(4) when it is already here
should be an idempotent action: we're really not changing anything,
so this fix doesn't change the semantics of interface addition.

Approved by: thompsa
Reviewed by: emaste
MFC after: 1 week

Add the ability to set which packet layers are used for the load balance hash
calculation.

Do no spam the ifconfig output for the aggregated interface with 'laggdev laggX'.

Allow the LACP state to be queried from userland which at the moment is the
actor and partner peer info. Print out the active aggregator and per port data
in verbose mode from ifconfig.

Approved by: re (mux)

Catch up with variable name changes in struct lagg_protos.

Rename the trunk(4) driver to lagg(4) as it is too similar to vlan trunking.

The name trunk is misused as the networking term trunk means carrying multiple
VLANs over a single connection. The IEEE standard for link aggregation (802.3
section 3) does not talk about 'trunk' at all while it is used throughout IEEE
802.1Q in describing vlans.

The lagg(4) driver provides link aggregation, failover and fault tolerance.

Discussed on: current@