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Re: wifi with no encryption: No DHCPOFFERS received

On 2018-12-12 10:30:44 -0500, Dan Ritter wrote:
> Yeah, I think you had a link problem, not a DHCP problem.

I've tried today, and the issue is not always reproducible.
But since there are several access points with the same ESSID,
a reason might be that wicd doesn't always try to connect to
the same one, and one of them at least may yield the error.
This could explain why the connection succeeded with Android.

After stopping the wicd daemon (service wicd stop):

root@zira:/home/vinc17# iw dev wlp61s0 link
Not connected.
root@zira:/home/vinc17# iw dev wlp61s0 scan
command failed: Network is down (-100)
root@zira:/home/vinc17# ifconfig wlp61s0 up
root@zira:/home/vinc17# iw dev wlp61s0 link
Not connected.
root@zira:/home/vinc17# iw dev wlp61s0 scan
[a lot of output]

Something interesting is that not all corresponding to "invites"
are equivalent, e.g.

BSS 00:26:cb:11:1a:82(on wlp61s0)
        last seen: 63544.369s [boottime]
        TSF: 33102324019 usec (0d, 09:11:42)
        freq: 2462
        beacon interval: 100 TUs
        capability: ESS ShortPreamble ShortSlotTime (0x0421)
        signal: -73.00 dBm
        last seen: 3060 ms ago
        Information elements from Probe Response frame:
        SSID: invites
        Supported rates: 11.0* 12.0 18.0 24.0 36.0 48.0 
        DS Parameter set: channel 11
        ERP: <no flags>
        WMM:     * Parameter version 1
                 * u-APSD
                 * BE: CW 15-1023, AIFSN 3
                 * BK: CW 15-1023, AIFSN 7
                 * VI: CW 7-15, AIFSN 2, TXOP 6016 usec
                 * VO: CW 3-7, AIFSN 2, TXOP 3264 usec

BSS 44:ad:d9:bb:d2:42(on wlp61s0)
        last seen: 63544.360s [boottime]
        TSF: 33118289997 usec (0d, 09:11:58)
        freq: 2462
        beacon interval: 102 TUs
        capability: ESS ShortPreamble ShortSlotTime (0x0421)
        signal: -81.00 dBm
        last seen: 3068 ms ago
        SSID: invites
        Supported rates: 11.0* 12.0 18.0 24.0 36.0 48.0 
        DS Parameter set: channel 11
        ERP: <no flags>
        HT capabilities:
                Capabilities: 0x186e
                        HT20/HT40
                        SM Power Save disabled
                        RX HT20 SGI
                        RX HT40 SGI
                        No RX STBC
                        Max AMSDU length: 7935 bytes
                        DSSS/CCK HT40
                Maximum RX AMPDU length 65535 bytes (exponent: 0x003)
                Minimum RX AMPDU time spacing: 8 usec (0x06)
                HT RX MCS rate indexes supported: 0-15
                HT TX MCS rate indexes are undefined
        HT operation:
                 * primary channel: 11
                 * secondary channel offset: no secondary
                 * STA channel width: 20 MHz
                 * RIFS: 0
                 * HT protection: non-HT mixed
                 * non-GF present: 1
                 * OBSS non-GF present: 0
                 * dual beacon: 0
                 * dual CTS protection: 0
                 * STBC beacon: 0
                 * L-SIG TXOP Prot: 0
                 * PCO active: 0
                 * PCO phase: 0
        WMM:     * Parameter version 1
                 * u-APSD
                 * BE: CW 15-1023, AIFSN 3
                 * BK: CW 15-1023, AIFSN 7
                 * VI: CW 7-15, AIFSN 2, TXOP 3008 usec
                 * VO: CW 3-7, AIFSN 2, TXOP 1504 usec

root@zira:/home/vinc17# iw dev wlp61s0 connect invites
root@zira:/home/vinc17# iw dev wlp61s0 link
Connected to 00:26:cb:b8:bf:f2 (on wlp61s0)
        SSID: invites
        freq: 2412
        RX: 22122 bytes (117 packets)
        TX: 4371 bytes (20 packets)
        signal: -76 dBm
        tx bitrate: 24.0 MBit/s

        bss flags:      short-preamble short-slot-time
        dtim period:    2
        beacon int:     100
root@zira:/home/vinc17# dhclient wlp61s0
ping: Warning: source address might be selected on device other than wlp61s0.

and I get an IP address. This always works, and I can see I get
the link immediately or almost immediately.

However, if I do like what wicd does according to its logs, i.e.

[...]
2018/12/11 18:44:15 :: ifconfig wlp61s0 up
2018/12/11 18:44:17 :: enctype is None
2018/12/11 18:44:17 :: ['iwconfig', 'wlp61s0', 'essid', '--', 'invites']
2018/12/11 18:44:17 :: iwconfig wlp61s0 channel 11
2018/12/11 18:44:17 :: iwconfig wlp61s0 ap 00:26:CB:11:1A:82
2018/12/11 18:44:17 :: Running DHCP with NO hostname
2018/12/11 18:44:17 :: /sbin/dhclient -v -cf /var/lib/wicd/dhclient.conf  wlp61s0
[...]

this does not work:

root@zira:/home/vinc17# iwconfig wlp61s0 essid -- invites
root@zira:/home/vinc17# iw dev wlp61s0 link
Not connected.
root@zira:/home/vinc17# iwconfig wlp61s0 channel 11
root@zira:/home/vinc17# iwconfig wlp61s0 ap 00:26:CB:11:1A:82
root@zira:/home/vinc17# iw dev wlp61s0 link
Not connected.

(and still no link after several minutes). Note that the BSS is
different, but that's wicd's fault to choose a wrong one, while
iw is always successful.

I've reported the following bug:

  https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=916348

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
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