Merge net branch into master

Main changes:

- MQTT improvements
- TCP fixes
- IEEE 802.15.4 RFD preliminary features (active/passive scan,
  association, disassociation), plus a dedicated "ieee15_4" shell
  module.

----------------------------------------------------------------
Andy Ross (3):
      net: tcp: Select correct source address for SYNACK packets
      net: tcp: Swap tcp->context backpointers
      net: tcp: Precompute appdata properly

Flavio Santes (14):
      net/protocols: Remove unnecessary assignement in Makefiles
      net/nbuf: Introduce the net_nbuf_linear_copy routine
      net/mqtt: Make input arguments const
      net/mqtt: Improve indentation
      net/mqtt: Use the right data type
      net/mqtt: Add missing function prototypes
      net/mqtt: Add the mqtt_rx_publish routine
      net/mqtt: Improve buffer error handling in mqtt_tx routines
      net/mqtt: Improve error handling in mqtt_rx_connack routine
      net/mqtt: Add the reception callback
      net/mqtt: Allow an MQTT publisher app to receive msgs
      net/mqtt: Allow an MQTT subscriber app to receive msgs
      net/dns: Introduce the qname_copy routine
      net/dns: Fix documentation issues

Leandro Pereira (4):
      net: tcp: Be more consistent with namespaces for private funcs
      net: tcp: Remove unused `retransmit_timer` field from `net_tcp`
      net: tcp: Store return value of net_buf_frags_len() on a size_t
      net: tcp: Use appdatalen when acknowledging packets

Luiz Augusto von Dentz (2):
      net: if: Add NET_IF_UP flag
      net: l2: Add enable callback

Maureen Helm (1):
      net: samples: Fix stale yaip references

Tomasz Bursztyka (15):
      net: event: Fix misplaced comment
      net: event: Notify on interface being put down or up
      net: ieee802154: Add grounds for passive scan
      net: ieee802154: Integrate beacon frame handling
      samples: net: ieee802154: Once cc2520 is up, let's initiate a scan
      net: ieee802154: Add PAN association request
      net: ieee802154: Integrate MAC Command frames handling
      net: ieee80215: Add Active Scan request
      net: ieee802154: Add PAN disassociation request
      net: ieee802154: Handle disassocation notification from PAN coordinator
      samples: ieee802154: Let's proceed with an active scan
      net: ieee802154: Fix logging primitive in mgmt part
      net: ieee802154: Expose basic network parameters through net mgmt API
      net: ieee802154: Add a shell module named 'ieee15_4'
      samples: net: Add IEEE 802.15.4 shell module on cc2520 sample

 include/net/dns_client.h                           |   7 +-
 include/net/ieee802154.h                           | 116 +++++-
 include/net/mqtt.h                                 |  60 +++-
 include/net/nbuf.h                                 |  16 +
 include/net/net_event.h                            |  21 +-
 include/net/net_if.h                               |  47 ++-
 include/net/net_l2.h                               |   9 +-
 samples/net/dhcpv4_client/src/Makefile             |   1 -
 samples/net/ieee802154/cc2520/prj.conf             |   6 +-
 .../net/ieee802154/cc2520/src/ieee802154_test.c    |  57 ++-
 samples/net/zperf/src/Makefile                     |   2 +-
 subsys/net/ip/ipv4.c                               |  14 +-
 subsys/net/ip/ipv4.h                               |   4 +-
 subsys/net/ip/ipv6.c                               |  16 +-
 subsys/net/ip/ipv6.h                               |   2 +
 subsys/net/ip/l2/bluetooth.c                       |  22 +-
 subsys/net/ip/l2/dummy.c                           |   2 +-
 subsys/net/ip/l2/ethernet.c                        |   2 +-
 subsys/net/ip/l2/ieee802154/Kconfig                |   9 +
 subsys/net/ip/l2/ieee802154/Makefile               |   1 +
 subsys/net/ip/l2/ieee802154/ieee802154.c           |  22 +-
 subsys/net/ip/l2/ieee802154/ieee802154_mgmt.c      | 390 +++++++++++++++++++++
 subsys/net/ip/l2/ieee802154/ieee802154_mgmt.h      |  66 ++++
 subsys/net/ip/l2/ieee802154/ieee802154_shell.c     | 289 +++++++++++++++
 subsys/net/ip/nbuf.c                               |  39 +++
 subsys/net/ip/net_context.c                        |  77 +++-
 subsys/net/ip/net_if.c                             |  89 ++++-
 subsys/net/ip/tcp.c                                |  33 +-
 subsys/net/ip/tcp.h                                |  10 +-
 subsys/net/lib/dns/Makefile                        |   2 -
 subsys/net/lib/dns/dns_client.c                    |  62 +---
 subsys/net/lib/dns/dns_pack.c                      |  66 ++++
 subsys/net/lib/dns/dns_pack.h                      |  22 ++
 subsys/net/lib/mqtt/Makefile                       |   2 -
 subsys/net/lib/mqtt/mqtt.c                         | 351 ++++++++++++++++---
 subsys/net/lib/mqtt/mqtt_pkt.c                     |  16 +-
 subsys/net/lib/mqtt/mqtt_pkt.h                     |   4 +-
 tests/net/tcp/src/main.c                           |  26 +-
 38 files changed, 1746 insertions(+), 234 deletions(-)
 create mode 100644 subsys/net/ip/l2/ieee802154/ieee802154_mgmt.h
 create mode 100644 subsys/net/ip/l2/ieee802154/ieee802154_shell.c

Change-Id: I72434b20cec53c004d7e7c03a24eab03a1d52c25
Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>