Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

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

Make net.inet.ip.sourceroute, net.inet.ip.accept_sourceroute, and
net.inet.ip.process_options vnet-aware. Revert changes in r271545.

Suggested by: bz

In ip_stripoptions():
- Remove unused argument and incorrect comment.
- Fixup ip_len after stripping.

Add function ip_checkrouteralert(), which will be used
by IGMPv3 to check for the IPv4 Router Alert [RFC2113]
option in a pulled-up IP mbuf chain.

Normalize style a bit: reduce pseudo-randomness of comment layout and
white space. Remove 'register'.

Move MAX_IPOPTLEN and struct ipoption back into ip_var.h as
userland programs depend on it.

Pointed out by: le
Sponsored by: TCP/IP Optimization Fundraise 2005

Consolidate all IP Options handling functions into ip_options.[ch] and
include ip_options.h into all files making use of IP Options functions.

From ip_input.c rev 1.306:
ip_dooptions(struct mbuf *m, int pass)
save_rte(m, option, dst)
ip_srcroute(m0)
ip_stripoptions(m, mopt)

From ip_output.c rev 1.249:
ip_insertoptions(m, opt, phlen)
ip_optcopy(ip, jp)
ip_pcbopts(struct inpcb *inp, int optname, struct mbuf *m)

No functional changes in this commit.

Discussed with: rwatson
Sponsored by: TCP/IP Optimization Fundraise 2005