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Thread: Ubuntu 14.04; bcm4352 wlan unstable: intermittently disconnects

  1. #1
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    Ubuntu 14.04; bcm4352 wlan unstable: intermittently disconnects

    I recently installed Ubuntu 14.04 on a new Lenovo Yoga 3 Pro with a Broadcom BCM4352 wlan adapter. I used to be a Unix sysadmin, but in the intervening 20yrs windows has prob fried my brain. So Ubuntu package mgmt is new to me, but otherwise I'm not really a newbie.

    I've been trying to fix unstable WiFi connectivity all week, researching the numerous threads. However, I believe I have correctly followed the guidelines for installing Broadcom drivers (altho I discovered them after the fact). So, in desperation, I'm resorting to a forum post.

    Here's two thumbnail plots of pings at 5s and 60s intervals respectively, with an otherwise quiet radio environment. Click on them to see periods of "Destination Unreachable" (not just timed out) lasting tens of minutes for just over half the time.

    bcm4352-ping-5s-unreachable-linux.jpg
    bcm4352-ping-60s-unreachable-linux.jpg

    Other machines can successfully use the same wifi with no problems during the periods when the Broadcom driver fails to transmit. And to prove it's not the hardware or the access point, here's pings at 60s intervals from the same machine booted into Win8.1 (also note that when Linux is 'working', there are more unusually delayed pings than with Windows).

    bcm4352-ping-60s-win.jpg

    Workround: disconnect/reconnect from the access point whenever connectivity stalls, but that's not tenable long-term.

    I have ruled out channel switching or security problems, because I'm 300m from the next nearest house, so I've turned off WiFi authentication and there's no reason why there would be any switching between access points or between channels.

    Here's the output from wireless-info:
    Code:
    ########## wireless info START ##########
    
    Report from: 18 Jun 2015 12:49 BST +0100
    
    Booted last: 18 Jun 2015 11:10 BST +0100
    
    Script from: 21 May 2015 09:10 UTC +0000
    
    ##### release ###########################
    
    Distributor ID:    Ubuntu
    Description:    Ubuntu 14.04.2 LTS
    Release:    14.04
    Codename:    trusty
    
    ##### kernel ############################
    
    Linux 3.16.0-41-generic #55~14.04.1-Ubuntu SMP Sun Jun 14 18:43:36 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux
    
    Parameters: ro, quiet, splash, vt.handoff=7
    
    ##### desktop ###########################
    
    Ubuntu
    
    ##### lspci #############################
    
    01:00.0 Network controller [0280]: Broadcom Corporation BCM4352 802.11ac Wireless Network Adapter [14e4:43b1] (rev 03)
        Subsystem: Lenovo Device [17aa:0623]
        Kernel driver in use: wl
    
    ##### lsusb #############################
    
    Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
    Bus 001 Device 005: ID 048d:8386 Integrated Technology Express, Inc. 
    Bus 001 Device 004: ID 1bcf:2c43 Sunplus Innovation Technology Inc. 
    Bus 001 Device 003: ID 0489:e07a Foxconn / Hon Hai 
    Bus 001 Device 002: ID 093a:2510 Pixart Imaging, Inc. Optical Mouse
    Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
    
    ##### PCMCIA card info ##################
    
    ##### rfkill ############################
    
    0: ideapad_wlan: Wireless LAN
        Soft blocked: no
        Hard blocked: no
    1: ideapad_bluetooth: Bluetooth
        Soft blocked: yes
        Hard blocked: no
    2: phy0: Wireless LAN
        Soft blocked: no
        Hard blocked: no
    3: brcmwl-0: Wireless LAN
        Soft blocked: no
        Hard blocked: no
    4: hci0: Bluetooth
        Soft blocked: yes
        Hard blocked: no
    
    ##### lsmod #############################
    
    wl                   6367833  0 
    cfg80211              494362  1 wl
    ideapad_laptop         18278  0 
    sparse_keymap          13948  1 ideapad_laptop
    wmi                    19193  0 
    
    ##### interfaces ########################
    
    auto lo
    iface lo inet loopback
    
    ##### ifconfig ##########################
    
    wlan0     Link encap:Ethernet  HWaddr <MAC 'wlan0' [IF]>  
              inet addr:192.168.1.5  Bcast:192.168.1.255  Mask:255.255.255.0
              inet6 addr: fe80::9248:9aff:fefb:25cf/64 Scope:Link
              UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
              RX packets:7464 errors:0 dropped:0 overruns:0 frame:1833
              TX packets:8980 errors:0 dropped:0 overruns:0 carrier:0
              collisions:0 txqueuelen:1000 
              RX bytes:3759461 (3.7 MB)  TX bytes:1173314 (1.1 MB)
              Interrupt:18 
    
    ##### iwconfig ##########################
    
    lo        no wireless extensions.
    
    wlan0     IEEE 802.11abg  ESSID:"Home-Farm"  
              Mode:Managed  Frequency:2.412 GHz  Access Point: <MAC 'Home-Farm' [AC1]>   
              Retry short limit:7   RTS thr:off   Fragment thr:off
              Power Management:off
              
    
    ##### route #############################
    
    Kernel IP routing table
    Destination     Gateway         Genmask         Flags Metric Ref    Use Iface
    0.0.0.0         192.168.1.254   0.0.0.0         UG    0      0        0 wlan0
    192.168.1.0     0.0.0.0         255.255.255.0   U     9      0        0 wlan0
    
    ##### resolv.conf #######################
    
    nameserver 127.0.1.1
    search lan
    
    ##### network managers ##################
    
    Installed:
    
        NetworkManager
    
    Running:
    
    root       789     1  0 11:10 ?        00:00:00 NetworkManager
    
    ##### NetworkManager info ###############
    
    NetworkManager Tool
    
    State: connected (global)
    
    - Device: wlan0  [Home-Farm] ---------------------------------------------------
      Type:              802.11 WiFi
      Driver:            wl
      State:             connected
      Default:           yes
      HW Address:        <MAC 'wlan0' [IF]>
    
      Capabilities:
        Speed:           144 Mb/s
    
      Wireless Properties
        WEP Encryption:  yes
        WPA Encryption:  yes
        WPA2 Encryption: yes
    
      Wireless Access Points (* = current AP)
        *Home-Farm:      Infra, <MAC 'Home-Farm' [AC1]>, Freq 2412 MHz, Rate 54 Mb/s, Strength 39
    
      IPv4 Settings:
        Address:         192.168.1.5
        Prefix:          24 (255.255.255.0)
        Gateway:         192.168.1.254
    
        DNS:             192.168.1.254
    
    ##### NetworkManager.state ##############
    
    [main]
    NetworkingEnabled=true
    WirelessEnabled=true
    WWANEnabled=true
    WimaxEnabled=true
    
    ##### NetworkManager.conf ###############
    
    [main]
    plugins=ifupdown,keyfile,ofono
    dns=dnsmasq
    
    no-auto-default=<MAC address>,
    
    [ifupdown]
    managed=false
    
    ##### NetworkManager profiles ###########
    
    [[/etc/NetworkManager/system-connections/USR9108]] (600 root)
    [connection] id=USR9108 | type=802-11-wireless
    [802-11-wireless] ssid=USR9108 | mac-address=<MAC 'wlan0' [IF]>
    [ipv6] method=auto
    [ipv4] method=auto
    
    [[/etc/NetworkManager/system-connections/Home-Farm]] (600 root)
    [connection] id=Home-Farm | type=802-11-wireless
    [802-11-wireless] ssid=Home-Farm | mac-address=<MAC 'wlan0' [IF]>
    [ipv6] method=auto
    [ipv4] method=auto
    
    ##### iw reg get ########################
    
    Region: Europe/London (based on set time zone)
    
    country GB:
        (2402 - 2482 @ 40), (N/A, 20)
        (5170 - 5250 @ 40), (N/A, 20)
        (5250 - 5330 @ 40), (N/A, 20), DFS
        (5490 - 5710 @ 40), (N/A, 27), DFS
        (57240 - 65880 @ 2160), (N/A, 40), NO-OUTDOOR
    
    ##### iwlist channels ###################
    
    lo        no frequency information.
    
    wlan0     32 channels in total; available frequencies :
              Channel 01 : 2.412 GHz
              Channel 02 : 2.417 GHz
              Channel 03 : 2.422 GHz
              Channel 04 : 2.427 GHz
              Channel 05 : 2.432 GHz
              Channel 06 : 2.437 GHz
              Channel 07 : 2.442 GHz
              Channel 08 : 2.447 GHz
              Channel 09 : 2.452 GHz
              Channel 10 : 2.457 GHz
              Channel 11 : 2.462 GHz
              Channel 12 : 2.467 GHz
              Channel 13 : 2.472 GHz
              Channel 36 : 5.18 GHz
              Channel 38 : 5.19 GHz
              Channel 40 : 5.2 GHz
              Channel 42 : 5.21 GHz
              Channel 44 : 5.22 GHz
              Channel 46 : 5.23 GHz
              Channel 48 : 5.24 GHz
              Channel 52 : 5.26 GHz
              Channel 54 : 5.27 GHz
              Channel 56 : 5.28 GHz
              Channel 58 : 5.29 GHz
              Channel 60 : 5.3 GHz
              Channel 62 : 5.31 GHz
              Channel 64 : 5.32 GHz
              Channel 100 : 5.5 GHz
              Channel 102 : 5.51 GHz
              Channel 104 : 5.52 GHz
              Channel 106 : 5.53 GHz
              Channel 108 : 5.54 GHz
              Current Frequency:2.412 GHz (Channel 1)
    
    ##### iwlist scan #######################
    
    lo        Interface doesn't support scanning.
    
    Channel occupancy:
    
          1   APs on   Frequency:2.412 GHz (Channel 1)
    
    wlan0     Scan completed :
              Cell 01 - Address: <MAC 'Home-Farm' [AC1]>
                        Channel:1
                        Frequency:2.412 GHz (Channel 1)
                        Quality=29/70  Signal level=-81 dBm  
                        Encryption key:off
                        ESSID:"Home-Farm"
                        Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s
                                  24 Mb/s; 36 Mb/s; 54 Mb/s
                        Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s
                        Mode:Master
                        Extra:tsf=0000000000000000
                        Extra: Last beacon: 68ms ago
    
    ##### module infos ######################
    
    [wl]
    filename:       /lib/modules/3.16.0-41-generic/updates/dkms/wl.ko
    license:        MIXED/Proprietary
    srcversion:     DF2576C38AD45205B3556DD
    depends:        cfg80211
    vermagic:       3.16.0-41-generic SMP mod_unload modversions 
    parm:           passivemode:int
    parm:           wl_txq_thresh:int
    parm:           oneonly:int
    parm:           piomode:int
    parm:           instance_base:int
    parm:           nompc:int
    parm:           intf_name:string
    
    [cfg80211]
    filename:       /lib/modules/3.16.0-41-generic/kernel/net/wireless/cfg80211.ko
    description:    wireless configuration support
    license:        GPL
    author:         Johannes Berg
    srcversion:     33ED2C1448F5AEDBE7AF59E
    depends:        
    intree:         Y
    vermagic:       3.16.0-41-generic SMP mod_unload modversions 
    signer:         Magrathea: Glacier signing key
    sig_key:        42:AE:B7:DF:54:E6:D9:1C:A0:F4:01:21:E2:2F:EA:E6:B2:30:88:16
    sig_hashalgo:   sha512
    parm:           ieee80211_regdom:IEEE 802.11 regulatory domain code (charp)
    parm:           cfg80211_disable_40mhz_24ghz:Disable 40MHz support in the 2.4GHz band (bool)
    
    ##### module parameters #################
    
    [cfg80211]
    cfg80211_disable_40mhz_24ghz: N
    ieee80211_regdom: 00
    
    ##### /etc/modules ######################
    
    lp
    rtc
    
    ##### modprobe options ##################
    
    [/etc/modprobe.d/blacklist-ath_pci.conf]
    blacklist ath_pci
    
    [/etc/modprobe.d/blacklist-bcm43.conf]
    blacklist b43
    blacklist b43legacy
    blacklist ssb
    blacklist bcm43xx
    blacklist brcm80211
    blacklist brcmfmac
    blacklist brcmsmac
    blacklist bcma
    
    [/etc/modprobe.d/blacklist.conf]
    blacklist evbug
    blacklist usbmouse
    blacklist usbkbd
    blacklist eepro100
    blacklist de4x5
    blacklist eth1394
    blacklist snd_intel8x0m
    blacklist snd_aw2
    blacklist i2c_i801
    blacklist prism54
    blacklist bcm43xx
    blacklist garmin_gps
    blacklist asus_acpi
    blacklist snd_pcsp
    blacklist pcspkr
    blacklist amd76x_edac
    
    [/etc/modprobe.d/blacklist-rare-network.conf]
    alias net-pf-3 off
    alias net-pf-6 off
    alias net-pf-9 off
    alias net-pf-11 off
    alias net-pf-12 off
    alias net-pf-19 off
    alias net-pf-21 off
    alias net-pf-36 off
    
    [/etc/modprobe.d/iwlwifi.conf]
    remove iwlwifi \
    (/sbin/lsmod | grep -o -e ^iwlmvm -e ^iwldvm -e ^iwlwifi | xargs /sbin/rmmod) \
    && /sbin/modprobe -r mac80211
    
    [/etc/modprobe.d/mlx4.conf]
    softdep mlx4_core post: mlx4_en
    
    [/etc/modprobe.d/modesetting.conf]
    options cirrus modeset=1
    options mgag200 modeset=1
    
    ##### rc.local ##########################
    
    exit 0
    
    ##### pm-utils ##########################
    
    ##### udev rules ########################
    
    [/etc/udev/rules.d/70-persistent-net.rules]
    # PCI device 0x14e4:0x43b1 (wl)
    SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="<MAC 'wlan0' [IF]>", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="wlan*", NAME="wlan0"
    # USB device 0x:0x (ax88179_178a)
    SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="<MAC address>", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="eth0"
    
    ##### dmesg #############################
    
    [    2.393027] bluetooth hci0: Direct firmware load failed with error -2
    [    2.396088] Bluetooth: hci0: BCM: patch brcm/BCM20702A0-0489-e07a.hcd not found
    [ 5921.193960] ERROR @wl_dev_intvar_get : error (-1)
    
    ########## wireless info END ############
    I've also included the output of dmesg below, because the wireless-info script doesn't reveal the transmit power error:
    Code:
    $ dmesg -T | grep wl
    [Thu Jun 18 11:10:53 2015] wl: module license 'MIXED/Proprietary' taints kernel.
    [Thu Jun 18 11:10:53 2015] wl: module verification failed: signature and/or  required key missing - tainting kernel
    [Thu Jun 18 11:10:54 2015] wlan0: Broadcom BCM43b1 802.11 Hybrid Wireless Controller 6.30.223.248 (r487574)
    [Thu Jun 18 12:49:33 2015] ERROR @wl_dev_intvar_get : error (-1)
    [Thu Jun 18 12:49:33 2015] ERROR @wl_cfg80211_get_tx_power : error (-1)
    Last edited by Bob_Briscoe; June 18th, 2015 at 01:50 PM. Reason: Forgot to decribe radio environment

  2. #2
    Join Date
    Jun 2015
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    13

    Re: Ubuntu 14.04; bcm4352 wlan unstable: intermittently disconnects

    Follow up (and bump): I tried removing the ideapad_laptop module with
    Code:
    sudo modprobe -r ideapad_laptop
    but no improvement. At first, I thought it had fixed it, but as you see from the graph of pings below, just less than an hour afterwards it started to disconnect intermittently again.

    bcm4352-ping-5s-unreachable-linux-ideapad_laptop-r.jpg

    I can find no other indicators that the WiFi is failing to transmit or receive, except... it just doesn't. E.g.
    route and netstat -r both look no different whether the wifi is working or not.
    iwconfig wlan0 and ifconfig wlan0 outputs are no different.

    I'm baffled.

  3. #3
    Join Date
    Mar 2007
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    Promiseland
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    Xubuntu

    Re: Ubuntu 14.04; bcm4352 wlan unstable: intermittently disconnects

    Hello Baffled,

    It appears to me you have driver problems. Recommend you refer to Chilli555's Broadcom HowTo post.
    http://ubuntuforums.org/showthread.php?t=2214110

    Remove all red flagged items before launch.
    Cheers,


    The Linux Command Line at http://linuxcommand.org/

  4. #4
    Join Date
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    Xubuntu

    Re: Ubuntu 14.04; bcm4352 wlan unstable: intermittently disconnects

    Baffled,

    After giving your problem some thought overnight, I don't believe you have driver problems. I think you have poor reception. From the results of both, 'ifconfig' and 'iwconfig', it can be seen your machine is getting it's ip assignment from your router which leads me to believe there is degradation of the wifi signal.

    What is the distance between your wireless router/AP and your Yoga3Pro? Are there any intervening walls, appliances, air conditioning ductwork, microwave ovens, or such?

    I looked up the specs on Lenovo Yoga 3 Pro - impressive. Maybe we can figure this out between the two of us.
    Cheers,


    The Linux Command Line at http://linuxcommand.org/

  5. #5
    Join Date
    Jun 2015
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    13

    Re: Ubuntu 14.04; bcm4352 wlan unstable: intermittently disconnects

    I had already followed Chilli555's Broadcom post (I linked to it in my first posting). Like you, I don't think this is a driver problem. But I'm pretty sure it's not a signal strength issue either - everything so far (and everything below) has happened with the laptop(s) about 5m from the access point.

    Anyway, I'm now much-less-baffled. And I guess I could say I have 'fixed' my problem.

    However, I'm still trying to establish whether I might have got us closer to the cause of many other intermittent connectivity problems that I've seen in a number of posts that ended leaving the OP in mid-air. I suspect that the Linux on my Yoga 3 Pro is (sometimes?) not sending out its ARP requests and responses at a slow enough rate when the peer device only supports a slower variant of 802.11. I would appreciate help determining whether Ubuntu is part of the problem, and if so what needs fixing.

    I've been tracking down the problem with: another older access point; an old WinXP laptop; and wireshark on my Ubuntu 14.04 Yoga 3 Pro and on the WinXP laptop. As keeping track of all the different devices will get complex, I will start with the cast list in order of appearance:

    Ra Lenovo Yoga 3 Pro Ubuntu 14.04 LTS 802.11a/b/g/n/ac new laptop
    Sage SagemCom 2704n 802.11b/g/n new access point / home router recently supplied by my new broadband provider
    Robotics US Robotics 9108 MaxG 802.11a/b/g old access point / home router
    Mut Toshiba Portege R100 WinXP 802.11a/b old laptop
    extras non-speaking parts

    My posts so far have been about Ra connecting to Sage. Recall that I had tested 4 other devices with Sage as the access point, and they all worked fine - without disconnections. That obviously made me suspect the newly installed Ubuntu machine (Ra).

    #1/ Black-holed pings

    First, does anyone know what could cause pings to black-hole without a timeout error? As in the output sample below, seqnos 16-24 just disappear.

    Code:
    Tue 16 Jun 2015 22:01:27 BST  64 bytes from 192.168.1.254: icmp_seq=1 ttl=64 time=2.57 ms 
    Tue 16 Jun 2015 22:01:32 BST  64 bytes from 192.168.1.254: icmp_seq=2 ttl=64 time=2.37 ms 
    Tue 16 Jun 2015 22:01:37 BST  64 bytes from 192.168.1.254: icmp_seq=3 ttl=64 time=2.42 ms 
    Tue 16 Jun 2015 22:01:42 BST  64 bytes from 192.168.1.254: icmp_seq=4 ttl=64 time=1.83 ms 
    Tue 16 Jun 2015 22:01:47 BST  64 bytes from 192.168.1.254: icmp_seq=5 ttl=64 time=3.22 ms 
    Tue 16 Jun 2015 22:01:52 BST  64 bytes from 192.168.1.254: icmp_seq=6 ttl=64 time=2.51 ms 
    Tue 16 Jun 2015 22:01:57 BST  64 bytes from 192.168.1.254: icmp_seq=7 ttl=64 time=5.35 ms 
    Tue 16 Jun 2015 22:02:02 BST  64 bytes from 192.168.1.254: icmp_seq=8 ttl=64 time=2.59 ms 
    Tue 16 Jun 2015 22:02:07 BST  64 bytes from 192.168.1.254: icmp_seq=9 ttl=64 time=3.26 ms 
    Tue 16 Jun 2015 22:02:12 BST  64 bytes from 192.168.1.254: icmp_seq=10 ttl=64 time=2.00 ms 
    Tue 16 Jun 2015 22:02:17 BST  64 bytes from 192.168.1.254: icmp_seq=11 ttl=64 time=2.27 ms 
    Tue 16 Jun 2015 22:02:22 BST  64 bytes from 192.168.1.254: icmp_seq=12 ttl=64 time=1.61 ms 
    Tue 16 Jun 2015 22:02:27 BST  64 bytes from 192.168.1.254: icmp_seq=13 ttl=64 time=1.83 ms 
    Tue 16 Jun 2015 22:02:32 BST  64 bytes from 192.168.1.254: icmp_seq=14 ttl=64 time=1.65 ms 
    Tue 16 Jun 2015 22:02:37 BST  64 bytes from 192.168.1.254: icmp_seq=15 ttl=64 time=2.47 ms 
    Tue 16 Jun 2015 22:03:30 BST  From 192.168.1.254 icmp_seq=25 Destination Host Unreachable 
    Tue 16 Jun 2015 22:03:35 BST  From 192.168.1.254 icmp_seq=26 Destination Host Unreachable 
    Tue 16 Jun 2015 22:03:40 BST  From 192.168.1.254 icmp_seq=27 Destination Host Unreachable 
    Tue 16 Jun 2015 22:03:45 BST  From 192.168.1.254 icmp_seq=28 Destination Host Unreachable 
    Tue 16 Jun 2015 22:03:50 BST  From 192.168.1.254 icmp_seq=29 Destination Host Unreachable 
    Tue 16 Jun 2015 22:03:55 BST  From 192.168.1.254 icmp_seq=30 Destination Host Unreachable 
    Tue 16 Jun 2015 22:04:00 BST  From 192.168.1.254 icmp_seq=31 Destination Host Unreachable 
    Tue 16 Jun 2015 22:04:05 BST  From 192.168.1.254 icmp_seq=32 Destination Host Unreachable 
    Tue 16 Jun 2015 22:04:10 BST  From 192.168.1.254 icmp_seq=33 Destination Host Unreachable 
    Tue 16 Jun 2015 22:04:15 BST  From 192.168.1.254 icmp_seq=34 Destination Host Unreachable 
    Tue 16 Jun 2015 22:04:20 BST  From 192.168.1.254 icmp_seq=35 Destination Host Unreachable
    Note that the output says these DHU messages come from the access point (192.168.1.254). Whereas, later, I noticed I it started reporting DHU from my local IP (192.168.1.5). By the time I had got wireshark on it, I found the DHU errors were not triggered by an actual ICMP response packet with the dest. unreachable code. But I haven't yet managed to reproduce DHU errors reported as coming from the access point, like those above from last Tuesday. So I have not been able to check these with wireshark.

    Expt #2/ Still between Ra and Sage.

    I used wireshark to watch packets leaving and arriving at Ra, particularly around the start and end of each period of disconnection. To take an example (17:48:11 19-Jun-2015) I could see Ra sending 8 Echo Requests (pings) at 5s intervals but no Echo Responses. Ra happened to be trying to open a TCP connection to the router (Sage) at the same time (I had been looking at the router's Web interface). Ra retransmitted the initial TCP segment (SYN) 8 times before giving up, because no SYN/ACKs were coming back the other way. After eight black-holed pings, Ra sent 1 ARP request per second for 3s direct to Sage's MAC, asking "Who has 192.168.1.254?". Given this was Sage's IP address, it was sending to the MAC it was asking for, so I assume it was checking whether something had changed. Then Ra It stopped sending ping requests and started sending 1 ARP request per second to the broadcast MAC, which implies Ra believed its ARP entry for the access point was stale. For about 3 minutes no ARP response (or anything) was sent to Ra. Then, as soon as an ARP response finally appeared from Sage, Ra restarted sending echo requests and also opened four TCP connections, which all get responded to properly and it all sorted itself out (until the next time).

    I am keeping an open mind as to whether the lack of responses from Sage was Sage's fault, or whether Ra switched into sending everything to Sage (including ARP requests) at 802.11ac symbol rate, which Sage wouldn't undersdtand. During the whole outage, Sage was correctly interacting with all the other machines on the subnet - proved by all their packets in the capture (that Ra could see, because it was in promiscuous mode on the wlan and it supports a wider range of rates than all the other machines).

    Unfortunately, I don't have access to Sage, other than through the rudimentary Web GUI. So I can't see whether it sees frames arriving when Ra sends them (it has a received-bytes counter, but it's rounded to the nearest MB).

    Expt #3/ Replaced new access router (Sage) with my old one (Robotics)

    I replaced Sage with Robotics, which I hooked up to my broadband provider. I ran the same ping test at 5s intervals for 3hrs from Ra to Robotics. There were no periods of "destination unreachable" errors:
    bcm4352-ping-5s-linux-ideapad_laptop-r-usr.jpg



    However, I noticed one episode where echo requests from Ra were being black-holed without timeouts and without dest. unreachable errors, which I think shows that Ubuntu is not completely blameless. Over a period of 40s starting 21:31:28 on 19-Jun-2015 (bang in the middle of the plot above), TCP on Ra retransmitted one segment (to a remote machine on the Internet) 8 times. And over the same period 8 ICMP echo requests from the Ubuntu laptop (ICMP sequence nos. 1384-1391) received no response, but there were no ping timeouts. Unlike with Sage, this episode ended when ping request seq 1392 received a response from the Robotics access point. 6us after wireshark saw this response, it saw the Ubuntu laptop send out an ARP request to the access point's MAC asking "Who has 192.168.0.1?" and the access point replied with its own MAC address. Here's a screenshot from wireshark, filtered to display onlly ARP and ICMP:
    bcm4352-ping-5s-linux-ideapad_laptop-r-usr-wireshark.jpg

    My guess is that this string of packets from the Ubuntu machine to Robotics is exactly the same symptom as the packets that caused its connection with the Sagemcom access point to black-hole, but some difference in the Robotics response at the link layer gets the Ubuntu machine back on track. I believe that it could be episodes like these that are causing other people to experience weird outages, dependent on whether their access router can tolerate it.

    However, my evidence is thin. It is just as likely that the fault lies with the Sagemcom router. If anyone can suggest a way to measure whether frames from the Ubuntu machine are received/receivable by the Sagemcom access point, or at least to measure what rate each frame is being sent at, pls shout.

    Expt #4/ Mystery RTT variability

    I reinstalled the ideapad_laptop module with:
    Code:
    $ sudo modprobe ideapad_laptop
    Then I ran ping tests overnight to test the older Robotics access point for longer. The re-inclusion of ideapad_laptop initially seemed to give consistently low (1-2ms) ping times, but later in the night it returned to the variability I had seen without ideadpad_laptop, particularly after about 06:30am when the RTT often hit 100ms - just to go across the room and back.
    bcm4352-ping-60s-linux-usr.jpg

    I tried to find traffic reasons to explain the sudden return to variable RTTs. But there was no evidence of increased traffic from the wireshark capture. Mystery.

    I did not find any further occurrence of black-holed echo requests...

    Expt #5/ The smoking gun

    Nonetheless, next I captured smoking gun evidence against Ra (Ubuntu). I ran wireshark on Ra and found an identical pathological sequence of ARP requests from Ra over 20secs that seemed to go unheard by any other device. As before, Ra started by sending one ARP request per second to the Robotics MAC address, asking "Who has 192.168.0.1?" This was the IP address of Robotics - the machine the ARPs were addressed to, but Ra saw no response. Then Ra sent 17 broadcast ARP requests, once per second. Nothing responded to any of these until the last (which Robotics responded to, and everything sorted itself out).

    bcm4352-ping-60s-linux-usr-wireshark.jpg

    I was running wireshark on my old laptop (Mut) at the same time to check if Ra was correctly broadcasting ARP request at the lowest rate (Mut only supports 802.11b). In general, as expected, Mut only saw unicast ARPs if they were destined for itself, or sent by itself - because all the other devices on the wlan were capable of sending at higher rates. However all machines are meant to broadcast ARP requests at the lowest possible rate, so everyone can hear them. Indeed I checked all the broadcast ARPs that wireshark on Ra saw, and Mut did see them all too, except...

    Mut should have been able to see all 17 of Ra's broadcast ARPs, but it only saw the last one (14:05:09 20-Jun-2015), which seems to be the only one that Robotics saw as well. This strongly suggests that Ra (Ubuntu) broadcasted the first 16 ARP requests at a transmission rate too fast for any of my other device to understand (Ra is my only machine that supports 802.11ac). It may be that Robotics couldn't hear the previous 3 ARP requests directed at it for the same reason.

    ___
    I have kept (haphazard) records of pings, packet captures, arp tables, etc. So if anyone wants to dig deeper, just ask.
    Last edited by Bob_Briscoe; June 20th, 2015 at 09:50 PM. Reason: Reinstanted some attachments that had got lost, because I took >1hr to post

  6. #6
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    Re: Ubuntu 14.04; bcm4352 wlan unstable: intermittently disconnects

    Baffled,

    Don't like to admit this, but this is getting beyond my level of knowledge. Several years ago, I experienced some difficulty with a Broadcom wireless device that I was able to work through with help of an entry by another member of Ubuntu forums. There seem to be a lot of folks that have problems with Broadcom devices, and a few other brands also. It is discouraging to have a new system that has problems connecting consistently.

    I wish I could have been of better assistance. Keep at it. Maybe one of the network gurus will take notice of your problem after the weekend is over. Good luck.
    Cheers,


    The Linux Command Line at http://linuxcommand.org/

  7. #7
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    Re: Ubuntu 14.04; bcm4352 wlan unstable: intermittently disconnects

    OK. Given I've tracked down an intermittent bug (which are the nastiest kind), I certainly hope a 'network guru' notices this thread. I'll summarise, given it's been a long thread:

    The bug is repeatable with Ubuntu 14.04 LTS running on a Lenovo Yoga 3 Pro with a Broadcom bcm4352 802.11ac wireless network adapter.

    Occasionally, usually at intervals of tens of minutes, the wireless adapter transmits packets that neither of my two different lower-rate access points seem to be able to detect. When connected to my 802.11g access point (a US Robotics 9108) this makes network-dependent processes frequently hang for 20secs. When connected to my 802.11n access point (a Sagemcom 2704n) network-dependent processes hang for tens of minutes, and typically for about an hour. Disconnecting and reconnecting from the access point cures the hang... until the next time.

    In both cases, the start of a problem is always detectable by when the laptop unicasts three ARP requests to the access point's MAC address, one per second, asking the access point to confirm the MAC address associated with its IP address. Neither access point seems to be able to detect these packets, so there is no response. The laptop then transmits the same ARP request, still one per second, but to the broadcast MAC address. In the case of the 802.11n access point, it seems to hear none of this, so the laptop continues to hang for tens of minutes, while broadcasting ARP requests every second that nothing else seems to be able to hear. In the case of the 802.11g access point, it seems not to detect the first 16 broadcasts, but it responds to the 17th and the hang ends (after a period of 20 secs).

    While monitoring the wlan with wireshark on an even slower 802.11b adapter on an old laptop, it couldn't see the three unicasts or the first 16 broadcasts. However, like the 802.11g access point, it saw the 17th. Other packets that the Ubuntu laptop sends out during these hang periods (pings, TCP packets etc) all seem not to be responded to by anything, as if they are also undetectable to the access point.

    Questions:
    a) Can someone confirm my config is OK, by checking my wireless-info.txt in my first post - I'm new to Ubuntu?
    b) Does my diagnosis make sense?
    c) Can someone advise how I can downgrade my 802.11ac adapter to 802.11n or g until this is sorted out, so at least I have a stable machine (and it will help confirm the diagnosis). Below doesn't work:
    Code:
    $ iwlist wlan0 modulation
    wlan0     unknown modulation information.
    $ sudo iwconfig wlan0 modu 11g
    Error for wireless request "Set Modulation" (8B2F) :
        SET failed on device wlan0 ; Operation not supported.
    I had to guess '11g' because the iwconfig man page says use iwlist to find valid parameters for your card (but it doesn't - see above), so I noticed '11g' in one of the examples.

    d) Can anyone repeat this bug? It seems possible this would be a kernel problem, perhaps not just specific to Ubuntu. Possibly even a hardware problem.
    Last edited by Bob_Briscoe; June 21st, 2015 at 02:23 PM. Reason: Clarified what I had already unsuccessfully tried.

  8. #8
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    Re: Ubuntu 14.04; bcm4352 wlan unstable: intermittently disconnects

    Is anyone there? I'd really appreciate some help with any of the questions (a-d) in my last post.

    Latest: I found an "expert user" Web GUI on my Sagemcom access router (Sage) <http://{IPaddr}/expert_user.html>, altho still no telnet/ssh access. I manually added the MAC address of my Ubuntu latop (Ra) into the router's ARP cache, and I configured the MAC of Sage into Ra permanently too. When pinging Sage from Ra continually, it still intermittently gave dest host unreachable about half the time for tens of minutes at a time. So ARPs not getting through was a symptom not the cause. It seems all transmissions from Ra to Sage get black-holed during the dead periods, even tho wireshark on Ra thinks it is sending packets.

    Next experiment: I now have access to a LAN statistics page on the router. So when the link next black holes, I will send large numbers of pings and see if they increase the receive statistics on the router. Then I can tell if they are incomprehensible to the router, or whether the router receives them but does nothing about them.
    Last edited by Bob_Briscoe; June 22nd, 2015 at 07:10 PM. Reason: Clarified what I need help with

  9. #9
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    Re: Ubuntu 14.04; bcm4352 wlan unstable: intermittently disconnects

    I would still appreciate an expert confirming whether my Ubutu config is correct (and any of my other 3 questions b-d). I would like to send back my router while I'm still within 2wks of starting with this broadband provider/ However, until someone knowledgeable confirms my Ubuntu config is not at fault, I can't - I'm not confident enough of my Ubuntu knowledge.

    Latest experiment: When pings from my Ubuntu machine to my access router at 0.1sec intervals are showing "dest host unreachable" (or no response at all), the router's packet count for incoming and outgoing is rising consistent with it both receiving the echo requests and returning echo replies. However, wireshark on my Ubuntu machine is only seeing outgoing echo requests, and no incoming echo responses during these periods.

    During the whole black-holing period, Wireshark on my Ubuntu machine sees packets to and from other machines and broadcasts intended for it (eg. ARP), but no incoming unicast packets for itself at all, even tho wireshark sees many packets going out that ought to be responded to (pings) or acknowledged (TCP). So TCP is sending lots of retransmissions but never seeing ACKs or incoming data. The only incoming packets it sees (broadcasted ARP requests from the access router) lead it to send an ARP response immediately, and the router's ARP cache looks healthy throughout (I have removed the permanent MAC addresses I added for testing earlier).

    After tens of minutes wireshark starts to see incoming packets again, and it all gets back to normal,... until the next time...
    Last edited by Bob_Briscoe; June 23rd, 2015 at 12:34 AM. Reason: typo

  10. #10
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    Re: Ubuntu 14.04; bcm4352 wlan unstable: intermittently disconnects

    I tried removing the ideapad_laptop module with...
    This is only sometimes useful to correct or diagnose a hard-blocked wireless; that is, when the switch or key combination has no effect and the wireless is inoperative even with a proper driver. It will have no effect here.

    wlan0 Scan completed :
    Cell 01 - Address: <MAC 'Home-Farm' [AC1]>
    Channel:1
    Frequency:2.412 GHz (Channel 1)
    Quality=29/70 Signal level=-81 dBm
    Encryption key:off
    ESSID:"Home-Farm"
    <snip>
    I feel like most of the trouble is right there: Quality 29/70. In my own situation, when I carry my laptop to the extremes of my property, and the signal strength drops, I have trouble connecting and then, once connected, staying connected. I urge you to find some way to relocate the router, re-orient its antennae, etc. in order to boost its visibility to the Broadcom.

    I am also troubled by the lack of encryption here. In effect, your tax returns and banking details are sitting on the front porch in plain view. I urge you to switch to WPA2-AES with a strong password immediately.

    I replaced Sage with Robotics, which I hooked up to my broadband provider. I ran the same ping test at 5s intervals for 3hrs from Ra to Robotics. There were no periods of "destination unreachable" errors:
    Now I think we're getting somewhere! I wonder if there is a setting in the new router that may be adjusted to help here. About a year ago, I got a new router and had a few issues with my several Intel wireless devices, all running Ubuntu. I experimented and honed a few techniques. Here is what I typically recommend:

    First, check the settings in the router. WPA2-AES is preferred; not any WPA and WPA2 mixed mode and certainly not TKIP. Second, if your router is capable of N speeds, you may have better connectivity with a channel width of 20 MHz in the 2.4 GHz band instead of automatic 20/40 MHz, although it is likely to affect N speeds. I also have better luck with a fixed channel, either 1, 6 or 11, rather than automatic channel selection. Also, be certain the router is not set to use N speeds only; auto B, G and N is preferred. After making these changes, reboot the router.

    Next, I recommend that your regulatory domain be set explicitly. Check yours:
    Code:
    sudo iw reg get
    If you get 00, that is a one-size-maybe-fits-all setting. Find yours here: http://en.wikipedia.org/wiki/ISO_3166-1_alpha-2 Then set it temporarily:
    Code:
    sudo iw reg set IS
    Of course, substitute your country code if not Iceland. Set it permanently:
    Code:
    gksudo gedit /etc/default/crda
    Use nano or kate or leafpad if you don't have the text editor gedit.

    Change the last line to read:
    Code:
    REGDOMAIN=IS
    Proofread carefully, save and close the text editor.

    Next, I'd set IPv6 to Ignore in Network Manager: http://docs.fedoraproject.org/en-US/...pv6-ignore.png This example is for ethernet, but you want wireless.

    I am wondering if the "black holes" are when your 802.11ac device is trying to negotiate up to AC speeds which the router may not provide and, I am quite sure, the driver has, as of yet, poorly or not yet at all supported.

    There are a few parameters available in the driver wl:

    Code:
    parm:           passivemode:int
    parm:           wl_txq_thresh:int
    parm:           oneonly:int
    parm:           piomode:int
    parm:           instance_base:int
    parm:           nompc:int
    parm:           intf_name:string
    And a few in the helper module cfg80211:

    Code:
    parm:           ieee80211_regdom:IEEE 802.11 regulatory domain code (charp)
    parm:           cfg80211_disable_40mhz_24ghz:Disable 40MHz support in the 2.4GHz band (bool)
    There is no documentation about what the driver modules do, at least that Google and I can find, so I am reluctant to suggest adding any parameters. Google finds these quoted in the driver .c code, but I'm not quite sure to do with it.

    Should you be adventurous, the usual process is to create a conf file with the parameter in it, like this:

    Code:
    sudo -i
    echo "options wl some_paramter=1"  >  /etc/modprobe.d/wl.conf
    exit
    If it proves ineffective, remove it:

    Code:
    sudo rm /etc/modprobe.d/wl.conf
    Note that each parameter tells you what the setting should be; for example 'int' wants 0 or 1 or 256 or some such. 'bool' wants Y or N. 'charp' wants, in this case, a country code like US. Yours is already set so you may ignore this.

    Latest: I found an "expert user" Web GUI on my Sagemcom access router (Sage) <http://{IPaddr}/expert_user.html>
    Can we see a screenshot, please? Of course, obscure any personal details like your new WPA2 key. Perhaps there is a setting we can help with.
    "Oh, Ubuntu, you are my favorite Linux-based operating system" --Dr. Sheldon Cooper, Ph.D., Sc.D.

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