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

Use printb() instead of rolling its own routine to display
bits in options=<>.

Pointed out by: ume
MFC after: 3 days

Suppress an options line when no bit is on.

Reviewed by: hrs
MFC after: 3 days

- Use size_t instead of int when appropriate;
- Use C99 sparse initialization.

With these changes ifconfig(8) is WARNS=2 clean.

Fix and add a workaround on an issue of EtherIP packet with reversed
version field sent via gif(4)+if_bridge(4). The EtherIP
implementation found on FreeBSD 6.1, 6.2, 6.3, 7.0, 7.1, and 7.2 had
an interoperability issue because it sent the incorrect EtherIP
packets and discarded the correct ones.

This change introduces the following two flags to gif(4):

accept_rev_ethip_ver: accepts both correct EtherIP packets and ones
with reversed version field, if enabled. If disabled, the gif
accepts the correct packets only. This flag is enabled by
default.

send_rev_ethip_ver: sends EtherIP packets with reversed version field
intentionally, if enabled. If disabled, the gif sends the correct
packets only. This flag is disabled by default.

These flags are stored in struct gif_softc and can be set by
ifconfig(8) on per-interface basis.

Note that this is an incompatible change of EtherIP with the older
FreeBSD releases. If you need to interoperate older FreeBSD boxes and
new versions after this commit, setting "send_rev_ethip_ver" is
needed.

Reviewed by: thompsa and rwatson
Spotted by: Shunsuke SHINOMIYA
PR: kern/125003
MFC after: 2 weeks