我尝试在 Debian（Bullseye 和 Bookworm）上使用 hostapd 设置 WiFi AP，并设置自动信道选择 (ACS) channel=0。/etc/hostapd/hostapd.conf在具有不同硬件的多个系统上，这不起作用，即我们没有找到任何可以正常工作的系统。
有两种情况：
- 启动
hostapd.service后，但几秒钟后悄悄地“成功”停止，没有出现错误消息：Aug 17 22:54:23 NanoPiR6C systemd[1]: hostapd.service - Access point and authentication server for Wi-Fi and Ethernet was skipped because of an unmet condition check (ConditionFileNotEmpty=/etc/hostapd/hostapd.conf). Aug 17 22:54:36 NanoPiR6C systemd[1]: Starting hostapd.service - Access point and authentication server for Wi-Fi and Ethernet... Aug 17 22:54:36 NanoPiR6C hostapd[2230]: wlan0: interface state UNINITIALIZED->COUNTRY_UPDATE Aug 17 22:54:36 NanoPiR6C hostapd[2230]: ACS: Automatic channel selection started, this may take a bit Aug 17 22:54:36 NanoPiR6C hostapd[2230]: wlan0: interface state COUNTRY_UPDATE->ACS Aug 17 22:54:36 NanoPiR6C hostapd[2230]: wlan0: ACS-STARTED Aug 17 22:54:36 NanoPiR6C systemd[1]: Started hostapd.service - Access point and authentication server for Wi-Fi and Ethernet. Aug 17 22:54:42 NanoPiR6C systemd[1]: hostapd.service: Deactivated successfully. - 和
hostapd.service进程崩溃，也导致内核错误：
问题是，在这种情况下，进程会变成无法杀死的僵尸进程：SIGTERM 和 SIGKILL 不起作用，systemctl 挂起直到超时，重启也会挂起，直到 systemd 尝试杀死 hostapd 进程超时。此外，该服务有一个自动重启计划，因此 hostapd 进程会在一段时间后堆积起来。Aug 17 23:12:32 ROCKPiS systemd[1]: Starting Access point and authentication server for Wi-Fi and Ethernet... Aug 17 23:12:32 ROCKPiS hostapd[586]: Configuration file: /etc/hostapd/hostapd.conf Aug 17 23:12:32 ROCKPiS hostapd[586]: wlan0: interface state UNINITIALIZED->COUNTRY_UPDATE Aug 17 23:12:32 ROCKPiS hostapd[586]: ACS: Automatic channel selection started, this may take a bit Aug 17 23:12:32 ROCKPiS kernel: Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 Aug 17 23:12:32 ROCKPiS kernel: Mem abort info: Aug 17 23:12:32 ROCKPiS kernel: ESR = 0x0000000096000004 Aug 17 23:12:32 ROCKPiS kernel: EC = 0x25: DABT (current EL), IL = 32 bits Aug 17 23:12:32 ROCKPiS kernel: SET = 0, FnV = 0 Aug 17 23:12:32 ROCKPiS kernel: EA = 0, S1PTW = 0 Aug 17 23:12:32 ROCKPiS kernel: FSC = 0x04: level 0 translation fault Aug 17 23:12:32 ROCKPiS kernel: Data abort info: Aug 17 23:12:32 ROCKPiS kernel: ISV = 0, ISS = 0x00000004 Aug 17 23:12:32 ROCKPiS kernel: CM = 0, WnR = 0 Aug 17 23:12:32 ROCKPiS kernel: user pgtable: 4k pages, 48-bit VAs, pgdp=0000000004be1000 Aug 17 23:12:32 ROCKPiS kernel: [0000000000000000] pgd=0000000000000000, p4d=0000000000000000 Aug 17 23:12:32 ROCKPiS kernel: Internal error: Oops: 96000004 [#1] PREEMPT SMP Aug 17 23:12:32 ROCKPiS kernel: Modules linked in: nft_chain_nat xt_MASQUERADE nf_nat nft_counter xt_state xt_conntrack nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 nft_compat nf_tables nfnetlink 8723ds cfg80211 snd_soc_pcm5102a rfkill snd_soc_rk3308 snd_soc_simple_card snd_soc_simple_card_utils snd_soc_core snd_pcm_dmaengine snd_pcm nvmem_rockchip_otp snd_timer snd soundcore cpufreq_dt ip_tables x_tables autofs4 realtek dwmac_rk stmmac_platform stmmac pcs_xpcs Aug 17 23:12:33 ROCKPiS kernel: CPU: 0 PID: 586 Comm: hostapd Not tainted 5.15.93-rockchip64 #23.02.2 Aug 17 23:12:33 ROCKPiS kernel: Hardware name: Radxa ROCK Pi S (DT) Aug 17 23:12:33 ROCKPiS kernel: pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--) Aug 17 23:12:33 ROCKPiS kernel: pc : __pi_memcmp+0xd8/0x110 Aug 17 23:12:33 ROCKPiS kernel: lr : _rtw_memcmp+0x14/0x28 [8723ds] Aug 17 23:12:33 ROCKPiS kernel: sp : ffff80000a88b480 Aug 17 23:12:33 ROCKPiS kernel: x29: ffff80000a88b480 x28: 0000000000000000 x27: 00000000000003e8 Aug 17 23:12:33 ROCKPiS kernel: x26: 0000000000000000 x25: ffff000005146448 x24: 0000000000000000 Aug 17 23:12:33 ROCKPiS kernel: x23: ffff000005394100 x22: 0000000000000000 x21: 0000000000000000 Aug 17 23:12:33 ROCKPiS kernel: x20: ffff80000a747000 x19: ffff000005394100 x18: 0000000000000000 Aug 17 23:12:33 ROCKPiS kernel: x17: 0000000000000000 x16: 0000000000000000 x15: 0000aaaac19a9640 Aug 17 23:12:33 ROCKPiS kernel: x14: 0000097b00040008 x13: ffff800001178178 x12: ffff000008471000 Aug 17 23:12:33 ROCKPiS kernel: x11: 0000000000000999 x10: 0000000000000008 x9 : 0000000000000040 Aug 17 23:12:33 ROCKPiS kernel: x8 : ffff00000545a460 x7 : ffff80000a88b3c0 x6 : 0000000000000001 Aug 17 23:12:33 ROCKPiS kernel: x5 : 0000000000000001 x4 : 0000000000000030 x3 : 0000000000000001 Aug 17 23:12:33 ROCKPiS kernel: x2 : 0000000000000003 x1 : ffff8000012c7400 x0 : 0000000000000000 Aug 17 23:12:33 ROCKPiS kernel: Call trace: Aug 17 23:12:33 ROCKPiS kernel: __pi_memcmp+0xd8/0x110 Aug 17 23:12:33 ROCKPiS kernel: cfg80211_rtw_scan+0x234/0x5e0 [8723ds] Aug 17 23:12:33 ROCKPiS kernel: cfg80211_scan+0x1d0/0x360 [cfg80211] Aug 17 23:12:33 ROCKPiS kernel: nl80211_trigger_scan+0x598/0x690 [cfg80211] Aug 17 23:12:33 ROCKPiS kernel: genl_family_rcv_msg_doit.isra.15+0x10c/0x150 Aug 17 23:12:33 ROCKPiS kernel: genl_rcv_msg+0xf0/0x1d8 Aug 17 23:12:33 ROCKPiS kernel: netlink_rcv_skb+0x5c/0x120 Aug 17 23:12:33 ROCKPiS kernel: genl_rcv+0x38/0x50 Aug 17 23:12:33 ROCKPiS kernel: netlink_unicast+0x1cc/0x2a0 Aug 17 23:12:33 ROCKPiS kernel: netlink_sendmsg+0x1dc/0x448 Aug 17 23:12:33 ROCKPiS kernel: sock_sendmsg+0x4c/0x58 Aug 17 23:12:33 ROCKPiS kernel: ____sys_sendmsg+0x274/0x2b8 Aug 17 23:12:33 ROCKPiS kernel: ___sys_sendmsg+0x84/0xc8 Aug 17 23:12:33 ROCKPiS kernel: __sys_sendmsg+0x6c/0xc0 Aug 17 23:12:33 ROCKPiS kernel: __arm64_sys_sendmsg+0x24/0x30 Aug 17 23:12:33 ROCKPiS kernel: invoke_syscall+0x44/0x108 Aug 17 23:12:33 ROCKPiS kernel: el0_svc_common.constprop.3+0x94/0xf8 Aug 17 23:12:33 ROCKPiS kernel: do_el0_svc+0x24/0x98 Aug 17 23:12:33 ROCKPiS kernel: el0_svc+0x20/0x50 Aug 17 23:12:33 ROCKPiS kernel: el0t_64_sync_handler+0x90/0xb8 Aug 17 23:12:33 ROCKPiS kernel: el0t_64_sync+0x180/0x184 Aug 17 23:12:33 ROCKPiS kernel: Code: d65f03c0 d503201f b1001042 540000c3 (b8404403) Aug 17 23:12:33 ROCKPiS kernel: ---[ end trace 98281908e07a73eb ]--- Aug 17 23:12:33 ROCKPiS systemd[1]: hostapd.service: Control process exited, code=killed, status=11/SEGV Aug 17 23:12:33 ROCKPiS systemd[1]: hostapd.service: Failed with result 'signal'. Aug 17 23:12:33 ROCKPiS systemd[1]: Failed to start Access point and authentication server for Wi-Fi and Ethernet.
下面是一个测试的例子hostapd.conf：
interface=wlan0
driver=nl80211
ssid=myssid
country_code=DE
hw_mode=g
channel=0
ieee80211n=1
wmm_enabled=1
macaddr_acl=0
auth_algs=1
ignore_broadcast_ssid=0
wpa=2
wpa_passphrase=mypassword
wpa_key_mgmt=WPA-PSK
wpa_pairwise=TKIP
rsn_pairwise=CCMP
ctrl_interface=/run/hostapd
启用/禁用 WiFi 4 ( ieee80211n=1) 和 5 ( ieee80211ac=1) 以及在 2.4 GHz ( hw_mode=g) 和 5 GHz 模式 ( hw_mode=a) 之间切换没有任何区别。我还尝试删除一些设置并添加示例附带的所有内容/usr/share/doc/hostapd/examples/hostapd.conf。无论我如何快速切换到channel=0或channel=acs_survey，在所有测试系统上hostapd都不起作用。
我是不是漏掉了什么，ACS 是否需要其他明确设置才能正常工作？否则，如果它在大多数（我们所有）系统上都不起作用，为什么这是默认设置（通常是合理的）？