net: another round of extack handling for routing

This set focuses on passing extack through lwtunnel and MPLS with additional catches for IPv4 route add and minor cleanups in MPLS encountered passing the extack arg around.

v2
- mindful of bloat adding duplicate messages
+ refactored prefix and prefix length checks in ipv4's fib_table_insert and fib_table_del
+ refactored label check in mpls

- split mpls cleanups into 2 patches
+ move nla_get_via up in af_mpls to avoid forward declaration

David Ahern (9):
net: ipv4: refactor key and length checks
net: ipv4: Add extack message for invalid prefix or length
net: lwtunnel: Add extack to encap attr validation
net: add extack arg to lwtunnel build state
net: Fill in extack for mpls lwt encap
net: mpls: Pull common label check into helper
net: mpls: Add extack messages for route add and delete failures
net: mpls: Make nla_get_via in af_mpls.c
net: mpls: remove unnecessary initialization of err

 include/linux/netlink.h   |  10 ++
 include/net/ip_fib.h      |   3 +-
 include/net/lwtunnel.h    |  22 ++--
 net/core/lwt_bpf.c        |   5 +-
 net/core/lwtunnel.c       |  38 +++++--
 net/ipv4/fib_frontend.c   |  13 ++-
 net/ipv4/fib_lookup.h     |   3 +-
 net/ipv4/fib_semantics.c  |  20 ++--
 net/ipv4/fib_trie.c       |  34 +++---
 net/ipv4/ip_tunnel_core.c |  11 +-
 net/ipv6/ila/ila_lwt.c    |   5 +-
 net/ipv6/route.c          |   6 +-
 net/ipv6/seg6_iptunnel.c  |   5 +-
 net/mpls/af_mpls.c        | 266 +++++++++++++++++++++++++++++-----------------
 net/mpls/internal.h       |   4 +-
 net/mpls/mpls_iptunnel.c  |  17 +--
 16 files changed, 301 insertions(+), 161 deletions(-)

2.11.0 (Apple Git-81)