82 lines
2.6 KiB
Diff
82 lines
2.6 KiB
Diff
From fc8ea40f6130ac18d9c66797de2cf1d5af55d496 Mon Sep 17 00:00:00 2001
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From: Markus Theil <markus.theil@tu-ilmenau.de>
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Date: Tue, 30 Jun 2020 14:19:07 +0200
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Subject: [PATCH 19/19] mesh: use deterministic channel on channel switch
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This patch uses a deterministic channel on DFS channel switch
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in mesh networks. Otherwise, when switching to a usable but not
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available channel, no CSA can be sent and a random channel is choosen
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without notification of other nodes. It is then quite likely, that
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the mesh network gets disconnected.
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Fix this by using a deterministic number, based on the sha256 hash
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of the mesh ID, in order to use at least a different number in each
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mesh network.
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Signed-off-by: Markus Theil <markus.theil@tu-ilmenau.de>
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---
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src/ap/dfs.c | 20 +++++++++++++++++++-
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src/drivers/driver_nl80211.c | 4 ++++
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2 files changed, 23 insertions(+), 1 deletion(-)
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--- a/src/ap/dfs.c
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+++ b/src/ap/dfs.c
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@@ -17,6 +17,7 @@
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#include "ap_drv_ops.h"
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#include "drivers/driver.h"
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#include "dfs.h"
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+#include "crypto/crypto.h"
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static int dfs_get_used_n_chans(struct hostapd_iface *iface, int *seg1)
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@@ -480,9 +481,14 @@ dfs_get_valid_channel(struct hostapd_ifa
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int num_available_chandefs;
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int chan_idx, chan_idx2;
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int sec_chan_idx_80p80 = -1;
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+ bool is_mesh = false;
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int i;
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u32 _rand;
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+#ifdef CONFIG_MESH
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+ is_mesh = iface->mconf;
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+#endif
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+
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wpa_printf(MSG_DEBUG, "DFS: Selecting random channel");
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*secondary_channel = 0;
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*oper_centr_freq_seg0_idx = 0;
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@@ -502,8 +508,20 @@ dfs_get_valid_channel(struct hostapd_ifa
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if (num_available_chandefs == 0)
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return NULL;
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- if (os_get_random((u8 *) &_rand, sizeof(_rand)) < 0)
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+ /* try to use deterministic channel in mesh, so that both sides
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+ * have a chance to switch to the same channel */
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+ if (is_mesh) {
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+#ifdef CONFIG_MESH
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+ u64 hash[4];
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+ const u8 *meshid[1] = { &iface->mconf->meshid[0] };
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+ const size_t meshid_len = iface->mconf->meshid_len;
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+
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+ sha256_vector(1, meshid, &meshid_len, (u8 *)&hash[0]);
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+ _rand = hash[0] + hash[1] + hash[2] + hash[3];
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+#endif
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+ } else if (os_get_random((u8 *) &_rand, sizeof(_rand)) < 0)
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return NULL;
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+
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chan_idx = _rand % num_available_chandefs;
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dfs_find_channel(iface, &chan, chan_idx, skip_radar);
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if (!chan) {
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--- a/src/drivers/driver_nl80211.c
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+++ b/src/drivers/driver_nl80211.c
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@@ -9872,6 +9872,10 @@ static int nl80211_switch_channel(void *
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if (ret)
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goto error;
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+ if (drv->nlmode == NL80211_IFTYPE_MESH_POINT) {
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+ nla_put_flag(msg, NL80211_ATTR_HANDLE_DFS);
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+ }
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+
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/* beacon_csa params */
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beacon_csa = nla_nest_start(msg, NL80211_ATTR_CSA_IES);
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if (!beacon_csa)
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