I have an Intel NUC (NUC6i3SYB) with an integrated Intel 8260 wifi interface (rev 3a) that runs Ubuntu 17.04 Server AMD64. The wifi interface is set up as an access point with hostapd. The problem is that the wifi connection breaks every now and then, not because of poor signal quality (the system is 3 meters away from my notebook and phone), but because of something strange happening when traffic is being sent/received. I'm not talking about heavy load, even when you go to a webpage like Amazon or similar, the connection gets killed and my notebook or phone gets disconnected. When I look at the dmesg output on the NUC, I get this error message:
[ 90.846007] WARNING: CPU: 0 PID: 1345 at /build/linux-Fk60NP/linux-4.10.0/drivers/net/wireless/intel/iwlwifi/mvm/tx.c:507 iwl_mvm_tx_skb_non_sta+0x368/0x410 [iwlmvm]
[ 90.846009] Modules linked in: ftdi_sio usbserial ccm ipt_MASQUERADE nf_nat_masquerade_ipv4 xt_conntrack iptable_nat nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_filter nls_iso8859_1 arc4 iwlmvm mac80211 8250_dw snd_hda_codec_hdmi snd_hda_codec_realtek snd_soc_skl snd_soc_skl_ipc snd_soc_sst_ipc snd_soc_sst_dsp snd_hda_ext_core snd_soc_sst_match snd_soc_core snd_hda_codec_generic snd_compress intel_rapl ac97_bus x86_pkg_temp_thermal intel_powerclamp coretemp snd_pcm_dmaengine kvm_intel snd_hda_intel snd_hda_codec kvm snd_hda_core iwlwifi snd_hwdep snd_pcm irqbypass intel_cstate intel_rapl_perf cfg80211 snd_timer cdc_ether snd usbnet ir_lirc_codec ir_rc6_decoder soundcore lirc_dev joydev input_leds hci_uart btusb r8152 btrtl btbcm btqca btintel mii shpchp bluetooth mei_me
[ 90.846136] idma64 acpi_als mei virt_dma rc_rc6_mce intel_lpss_pci intel_pch_thermal kfifo_buf ite_cir mac_hid industrialio rc_core intel_lpss_acpi intel_lpss acpi_pad ib_iser rdma_cm iw_cm ib_cm ib_core configfs iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi ip_tables x_tables autofs4 btrfs algif_skcipher af_alg uas usb_storage dm_crypt raid10 raid456 async_raid6_recov async_memcpy async_pq async_xor async_tx xor raid6_pq libcrc32c raid1 raid0 multipath linear hid_generic usbhid crct10dif_pclmul crc32_pclmul ghash_clmulni_intel pcbc i915 aesni_intel aes_x86_64 crypto_simd glue_helper cryptd i2c_algo_bit drm_kms_helper e1000e syscopyarea sysfillrect sdhci_pci ptp sysimgblt fb_sys_fops ahci pps_core drm libahci sdhci video pinctrl_sunrisepoint i2c_hid pinctrl_intel hid fjes
[ 90.846288] CPU: 0 PID: 1345 Comm: hostapd Not tainted 4.10.0-19-generic #21-Ubuntu
[ 90.846292] Hardware name: /NUC6i3SYB, BIOS SYSKLi35.86A.0044.2016.0512.1734 05/12/2016
[ 90.846294] Call Trace:
[ 90.846309] dump_stack+0x63/0x81
[ 90.846317] __warn+0xcb/0xf0
[ 90.846324] warn_slowpath_null+0x1d/0x20
[ 90.846360] iwl_mvm_tx_skb_non_sta+0x368/0x410 [iwlmvm]
[ 90.846387] iwl_mvm_mac_tx+0x11e/0x1d0 [iwlmvm]
[ 90.846473] ieee80211_tx_frags+0x14d/0x220 [mac80211]
[ 90.846542] __ieee80211_tx+0x81/0x180 [mac80211]
[ 90.846612] ieee80211_tx+0x10f/0x150 [mac80211]
[ 90.846690] ieee80211_xmit+0x9c/0xf0 [mac80211]
[ 90.846742] __ieee80211_tx_skb_tid_band+0x5c/0x70 [mac80211]
[ 90.846790] ieee80211_mgmt_tx+0x432/0x4b0 [mac80211]
[ 90.846849] cfg80211_mlme_mgmt_tx+0xd8/0x2b0 [cfg80211]
[ 90.846896] nl80211_tx_mgmt+0x223/0x380 [cfg80211]
[ 90.846908] genl_family_rcv_msg+0x1dd/0x3c0
[ 90.846918] ? skb_queue_tail+0x43/0x50
[ 90.846924] ? __netlink_sendskb+0x3e/0x60
[ 90.846932] genl_rcv_msg+0x59/0xa0
[ 90.846938] ? genl_register_family+0x620/0x620
[ 90.846944] netlink_rcv_skb+0xa4/0xc0
[ 90.846949] genl_rcv+0x28/0x40
[ 90.846955] netlink_unicast+0x18c/0x220
[ 90.846961] netlink_sendmsg+0x2f7/0x3b0
[ 90.846970] ? aa_sock_msg_perm+0x61/0x150
[ 90.846976] sock_sendmsg+0x38/0x50
[ 90.846982] ___sys_sendmsg+0x2c2/0x2d0
[ 90.846993] ? mem_cgroup_commit_charge+0x7e/0x510
[ 90.847003] ? lru_cache_add_active_or_unevictable+0x36/0xb0
[ 90.847010] __sys_sendmsg+0x54/0x90
[ 90.847017] SyS_sendmsg+0x12/0x20
[ 90.847025] entry_SYSCALL_64_fastpath+0x1e/0xad
[ 90.847029] RIP: 0033:0x7f38b91ae237
[ 90.847033] RSP: 002b:00007ffd1aebfd58 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
[ 90.847039] RAX: ffffffffffffffda RBX: 00007f38b9466b58 RCX: 00007f38b91ae237
[ 90.847042] RDX: 0000000000000000 RSI: 00007ffd1aebfd90 RDI: 0000000000000005
[ 90.847045] RBP: 00007f38b9466b00 R08: 0000000000000000 R09: 0000000000000000
[ 90.847048] R10: 0000558c24284bc0 R11: 0000000000000246 R12: 00007f38b9466b58
[ 90.847051] R13: 0000000000004010 R14: 00007f38b9466b58 R15: 000000000000270f
[ 90.847055] ---[ end trace 0b40a0c2dc41b9dd ]---
I already tried to improve the situation by putting all Intel firmware files that could be missing into /lib/firmware, but that did not help and now I'm running out of ideas. While researching the problem, I've seen many complaints about this issue, but I did not find a solution yet. Any ideas?
The problem occurs irregularly, sometimes I can use the wifi for 10 minutes, then out of a sudden the connection collapses and produces the error given above. I then need to disable, wait a few seconds, and then re-enable wifi on my notebook or Android phone in order to regain a connection.
Update: as requested, here's some more output:
$ dmesg | grep iwl
[ 80.760481] iwlwifi 0000:01:00.0: enabling device (0000 -> 0002)
[ 80.798983] iwlwifi 0000:01:00.0: Direct firmware load for iwlwifi-8000C-26.ucode failed with error -2
[ 80.799277] iwlwifi 0000:01:00.0: Direct firmware load for iwlwifi-8000C-25.ucode failed with error -2
[ 80.799569] iwlwifi 0000:01:00.0: Direct firmware load for iwlwifi-8000C-24.ucode failed with error -2
[ 80.799863] iwlwifi 0000:01:00.0: Direct firmware load for iwlwifi-8000C-23.ucode failed with error -2
[ 81.056948] iwlwifi 0000:01:00.0: loaded firmware version 22.391740.0 op_mode iwlmvm
[ 81.164325] iwlwifi 0000:01:00.0: Detected Intel(R) Dual Band Wireless AC 8260, REV=0x208
[ 81.166714] iwlwifi 0000:01:00.0: L1 Enabled - LTR Enabled
[ 81.167661] iwlwifi 0000:01:00.0: L1 Enabled - LTR Enabled
[ 81.309925] ieee80211 phy0: Selected rate control algorithm 'iwl-mvm-rs'
[ 81.313046] iwlwifi 0000:01:00.0 wlp1s0: renamed from wlan0
[ 81.509457] iwlwifi 0000:01:00.0: L1 Enabled - LTR Enabled
[ 81.509820] iwlwifi 0000:01:00.0: L1 Enabled - LTR Enabled
[ 81.647630] iwlwifi 0000:01:00.0: L1 Enabled - LTR Enabled
[ 81.648398] iwlwifi 0000:01:00.0: L1 Enabled - LTR Enabled
[ 82.065513] iwlwifi 0000:01:00.0: L1 Enabled - LTR Enabled
[ 82.066461] iwlwifi 0000:01:00.0: L1 Enabled - LTR Enabled
[ 82.203449] iwlwifi 0000:01:00.0: L1 Enabled - LTR Enabled
[ 82.203759] iwlwifi 0000:01:00.0: L1 Enabled - LTR Enabled
[ 90.846007] WARNING: CPU: 0 PID: 1345 at /build/linux-Fk60NP/linux-4.10.0/drivers/net/wireless/intel/iwlwifi/mvm/tx.
:507 iwl_mvm_tx_skb_non_sta+0x368/0x410 [iwlmvm]
[ 90.846009] Modules linked in: ftdi_sio usbserial ccm ipt_MASQUERADE nf_nat_masquerade_ipv4 xt_conntrack iptable_nat
nf_conntrack_ipv4 nf_defrag_ipv4 nf_nat_ipv4 nf_nat nf_conntrack iptable_filter nls_iso8859_1 arc4 iwlmvm mac80211 8250
dw snd_hda_codec_hdmi snd_hda_codec_realtek snd_soc_skl snd_soc_skl_ipc snd_soc_sst_ipc snd_soc_sst_dsp snd_hda_ext_cor
snd_soc_sst_match snd_soc_core snd_hda_codec_generic snd_compress intel_rapl ac97_bus x86_pkg_temp_thermal intel_power
lamp coretemp snd_pcm_dmaengine kvm_intel snd_hda_intel snd_hda_codec kvm snd_hda_core iwlwifi snd_hwdep snd_pcm irqbyp
ss intel_cstate intel_rapl_perf cfg80211 snd_timer cdc_ether snd usbnet ir_lirc_codec ir_rc6_decoder soundcore lirc_dev
joydev input_leds hci_uart btusb r8152 btrtl btbcm btqca btintel mii shpchp bluetooth mei_me
[ 90.846360] iwl_mvm_tx_skb_non_sta+0x368/0x410 [iwlmvm]
[ 90.846387] iwl_mvm_mac_tx+0x11e/0x1d0 [iwlmvm]
