hostapd启用channel=0（ACS自动信道选择）失败的问题求助

大家好，我现在在Debian Bullseye和Bookworm系统上尝试用hostapd搭建WiFi AP，想要启用自动信道选择（ACS），于是在/etc/hostapd/hostapd.conf里设置了channel=0。但试了好几台不同硬件的机器，居然没有一台能成功运行，目前遇到两种故障情况：

情况一：服务启动后几秒无报错自动停止 #

hostapd.service能正常启动，但过几秒就会“成功”停止，没有任何错误提示，日志如下：

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.

情况二：服务崩溃并触发内核错误 #

这种情况更严重，hostapd进程直接崩溃，还会抛出内核错误日志，而且进程会变成不可杀死的僵尸进程：SIGTERM、SIGKILL都没用，执行systemctl操作会一直卡到超时，甚至重启系统时也会卡在systemd尝试杀死hostapd的环节。另外因为服务设置了自动重启，时间久了会堆积一堆僵尸进程。

相关日志如下：

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.

我使用的测试配置文件 #

以下是我测试用的hostapd.conf内容：

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

我已经尝试过的操作 #

• 启用/禁用WiFi 4（ieee80211n=1）和WiFi 5（ieee80211ac=1）
• 在2.4GHz（hw_mode=g）和5GHz（hw_mode=a）模式之间切换
• 增减配置项，甚至完全照搬/usr/share/doc/hostapd/examples/hostapd.conf里的示例配置

但不管怎么调整，只要把channel设为0或者acs_survey，所有测试机器都会出现上述故障。

想请教大家：是不是我漏了某个必须的配置项才能让ACS正常工作？或者为什么这个看起来很实用的默认功能，在我们的大部分（甚至所有）机器上都无法运行呢？

备注：内容来源于stack exchange，提问作者MichaIng