nft event monitor

The following series implements a basic nftables monitor via Netlink messages.

Most of the work in first patches is related to refactorization/generalization of code.

The final patch is the big one.

About the syntax, i'm proposing:
% nft monitor [added|deleted] [tables|chains|sets|elements|rules] [xml|json]

The straight-forward way of test this new feature is to simply run:
% nft monitor

Other examples:
* report new tables in XML format
% nft monitor added tables xml
* report deleted elements in standar nft syntax
% nft monitor deleted elements
* report all added/deleted rules in JSON format
% nft monitor rules json

Handling set/set_elems is one of the harders parts of event reporting. I've succesfully tested many cases (maps, named sets, anon-sets..), but I guess more tuning can be done in the future, with some additional use and testing by the community.

Please comment.

regards.
---

Arturo Borrero Gonzalez (8):
rule: allow to print sets in plain format
netlink: add netlink_delinearize_set() func
rule: generalize chain_print()
netlink: add netlink_delinearize_chain() func
netlink: add netlink_delinearize_table() func
netlink: refactorize set_elem conversion from netlink
netlink: add socket error reporting helper function
src: add events reporting

 doc/nftables.xml   |    1 
 include/mnl.h      |    3 
 include/netlink.h  |   11 +
 include/nftables.h |    1 
 include/rule.h     |   10 +
 src/evaluate.c     |    1 
 src/mnl.c          |   45 ++-
 src/netlink.c      |  746 ++++++++++++++++++++++++++++++++++++++++++++++------
 src/parser.y       |   90 ++++++
 src/rule.c         |  163 +++++++++++
 src/scanner.l      |    5 
 11 files changed, 957 insertions(+), 119 deletions(-)

Arturo Borrero Gonzalez