[batadv,v10 0/2] batman-adv: increase DAT DHT timeout

["Linus Lüssing" <linus.luessing@c0d3.blue>]

This patchset increases the DAT DHT timeout to reduce the amount
of broadcasted ARP Replies.

To increase the timeout only for DAT DHT entries added via DHT-PUT but
not for any other entry in the DAT cache the DAT cache and DAT DHT
concepts are split into two separate hash tables (PATCH 1/2).

PATCH 2/2 then increases the timeout for DAT DHT entries from 5 to
30 minutes.

The motivation for this patchset is based on the observations made here:
https://www.open-mesh.org/projects/batman-adv/wiki/DAT_DHCP_Snooping

In tests at Freifunk Lübeck with ~180 mesh nodes and Gluon
this reduced the ARP broadcast overhead, measured over 7 days, as
follows:

- Total:           6677.66 bits/s -> 677.26 bits/s => -89.86%
                   11.92 pkts/s   -> 1.21 pkts/s   => -89.85%

- from gateways: 5618.02 bits/s   -> 212.28        => -96.22%
                   10.03 pkts/s   -> 0.38 pkts/s   => -96.21%

Also see graphics and a few more test details here:
- https://www.open-mesh.org/projects/batman-adv/wiki/DAT_DHCP_Snooping#Result-2

Regards,
Linus

---

Changelog v10:
- PATCH 1/3: removed, already applied
- PATCH 0/2: cover letter: removed test time period and "v5" reference
- PATCH 1/2:
  - fixed kerneldoc in batadv_dat_hash_free(),
    replaced "bat_priv" with "hash"
  - added missing kerneldoc in batadv_dat_snoop_incoming_arp_reply()
    for is_dht_put
  - rebase to current main branch:
    - adopted new bat_priv kernel doc description,
      "soft interface" -> "mesh interface"
    - adopted variable rename from soft_iface to mesh_iface

Changelog v9:
- PATCH 1/3:
  - fixed typo in a comment: ENOENT -> ENONET

Changelog v8:
- PATCH 1/3:
  - fixing / cleaning up includes
  - fixing function kernel doc titles
  - fixing bugs introduced in v7 in the error handling of
    batadv_orig_dump() and batadv_neigh_dump(), using a goto
    pattern with more explicit labels

Changelog v7:
- adding PATCH 1/3 to add the batadv_netlink_get_softif() wrapper to
  reduce the amount of duplicate code, both in the current code base
  but also for the next PATCH 2/3

Changelog v6:
- removed renaming+deprecation of BATADV_P_DAT_CACHE_REPLY in PATCH 1/2
- small commit message rewording in PATCH 1/2

Changelog v5:
- rebased to current main branch
  -> removed now obsolete debugfs code

Changelog v4:
- rebased to: acfc9a214d01695
  ("batman-adv: genetlink: make policy common to family")

Changelog v3:

formerly:
 "batman-adv: Increase purge timeout on DAT DHT candidates"
 https://patchwork.open-mesh.org/patch/17728/
- fixed the potential jiffies overflow and jiffies initialization
  issues by replacing the last_dht_update timeout variable with
  a split of DAT cache and DAT DHT into two separate hash tables
  -> instead of maintaining two timeouts in one DAT entry two DAT
     entries are created and maintained in their respective DAT
     cache and DAT DHT hash tables

Changelog v2:

formerly:
 "batman-adv: Increase DHCP snooped DAT entry purge timeout in DHT"
 (https://patchwork.open-mesh.org/patch/17364/)
- removed the extended timeouts flag in the DHT-PUT messages introduced
  in v1 again
- removed DHCP dependency

Linus Lüssing (2):
  batman-adv: split DAT cache into DAT cache and DAT DHT
  batman-adv: increase DAT DHT timeout

 include/uapi/linux/batman_adv.h        |   5 +
 net/batman-adv/distributed-arp-table.c | 337 +++++++++++++++++++------
 net/batman-adv/distributed-arp-table.h |  13 +-
 net/batman-adv/main.h                  |   3 +-
 net/batman-adv/netlink.c               |   5 +
 net/batman-adv/routing.c               |   7 +-
 net/batman-adv/types.h                 |   7 +-
 7 files changed, 288 insertions(+), 89 deletions(-)

-- 
2.55.0