package/network/services/hostapd/patches/019-mesh-use-deterministic-channel-on-channel-switch.patch

   1 From fc8ea40f6130ac18d9c66797de2cf1d5af55d496 Mon Sep 17 00:00:00 2001
   2 From: Markus Theil <markus.theil@tu-ilmenau.de>
   3 Date: Tue, 30 Jun 2020 14:19:07 +0200
   4 Subject: [PATCH 19/19] mesh: use deterministic channel on channel switch
   5
   6 This patch uses a deterministic channel on DFS channel switch
   7 in mesh networks. Otherwise, when switching to a usable but not
   8 available channel, no CSA can be sent and a random channel is choosen
   9 without notification of other nodes. It is then quite likely, that
  10 the mesh network gets disconnected.
  11
  12 Fix this by using a deterministic number, based on the sha256 hash
  13 of the mesh ID, in order to use at least a different number in each
  14 mesh network.
  15
  16 Signed-off-by: Markus Theil <markus.theil@tu-ilmenau.de>
  17 ---
  18  src/ap/dfs.c                 | 20 +++++++++++++++++++-
  19  src/drivers/driver_nl80211.c |  4 ++++
  20  2 files changed, 23 insertions(+), 1 deletion(-)
  21
  22 --- a/src/ap/dfs.c
  23 +++ b/src/ap/dfs.c
  24 @@ -17,6 +17,7 @@
  25  #include "ap_drv_ops.h"
  26  #include "drivers/driver.h"
  27  #include "dfs.h"
  28 +#include "crypto/crypto.h"
  29
  30
  31  static int dfs_get_used_n_chans(struct hostapd_iface *iface, int *seg1)
  32 @@ -480,9 +481,14 @@ dfs_get_valid_channel(struct hostapd_ifa
  33         int num_available_chandefs;
  34         int chan_idx, chan_idx2;
  35         int sec_chan_idx_80p80 = -1;
  36 +       bool is_mesh = false;
  37         int i;
  38         u32 _rand;
  39
  40 +#ifdef CONFIG_MESH
  41 +       is_mesh = iface->mconf;
  42 +#endif
  43 +
  44         wpa_printf(MSG_DEBUG, "DFS: Selecting random channel");
  45         *secondary_channel = 0;
  46         *oper_centr_freq_seg0_idx = 0;
  47 @@ -502,8 +508,20 @@ dfs_get_valid_channel(struct hostapd_ifa
  48         if (num_available_chandefs == 0)
  49                 return NULL;
  50
  51 -       if (os_get_random((u8 *) &_rand, sizeof(_rand)) < 0)
  52 +       /* try to use deterministic channel in mesh, so that both sides
  53 +        * have a chance to switch to the same channel */
  54 +       if (is_mesh) {
  55 +#ifdef CONFIG_MESH
  56 +               u64 hash[4];
  57 +               const u8 *meshid[1] = { &iface->mconf->meshid[0] };
  58 +               const size_t meshid_len = iface->mconf->meshid_len;
  59 +
  60 +               sha256_vector(1, meshid, &meshid_len, (u8 *)&hash[0]);
  61 +               _rand = hash[0] + hash[1] + hash[2] + hash[3];
  62 +#endif
  63 +       } else if (os_get_random((u8 *) &_rand, sizeof(_rand)) < 0)
  64                 return NULL;
  65 +
  66         chan_idx = _rand % num_available_chandefs;
  67         dfs_find_channel(iface, &chan, chan_idx, skip_radar);
  68         if (!chan) {
  69 --- a/src/drivers/driver_nl80211.c
  70 +++ b/src/drivers/driver_nl80211.c
  71 @@ -9473,6 +9473,10 @@ static int nl80211_switch_channel(void *
  72         if (ret)
  73                 goto error;
  74
  75 +       if (drv->nlmode == NL80211_IFTYPE_MESH_POINT) {
  76 +               nla_put_flag(msg, NL80211_ATTR_HANDLE_DFS);
  77 +       }
  78 +
  79         /* beacon_csa params */
  80         beacon_csa = nla_nest_start(msg, NL80211_ATTR_CSA_IES);
  81         if (!beacon_csa)