Laptop only connects to university wireless once (per day)

ChaosCon · 04-02-2012, 02:28 PM

I've been using Debian testing, XFCE, and Wicd on a new Lenovo x220 (Intel 6205 wireless card), and everything works flawlessly except when I try to connect to our wireless network at school. Everything works great the first time I try to connect to the network in the morning, however, if I leave the building or otherwise switch access points, Wicd continues to stall at "obtaining IP address," leaving me unconnected. Heading home and connecting to the wireless there "resets" the issue, as does jumping into Windows. I initially thought it might be an issue with the DHCP authentication our university uses, but I know very little about that (so it's a shot in the dark), and having determined the initial connection always works, I'm not so sure anymore. What can I do to troubleshoot my connection woes?

nikmit · 04-03-2012, 05:07 AM

tcpdump -i wlan0

Find the name of your wireless interface in the output of ifconfig -a and replace wlan0 if needed.
If you get too much output, you can narrow it down to arp and dhcp with 'tcpdump arp or udp port 67 or 68'

ChaosCon · 04-03-2012, 03:22 PM

Wicd kills the connection, and thus tcpdump, but if I restart it quickly, it only gives me information if the connection works. Otherwise I just get "tcpdump: pcap_loop: The interface went down". If it does work, though, I get the following:

Code:

tcpdump: WARNING: wlan0: no IPv4 address assigned
tcpdump: listening on wlan0, link-type EN10MB (Ethernet), capture size 65535 bytes
16:20:35.117919 IP6 (hlim 1, next-header Options (0) payload length: 36) :: > ff02::16: HBH (rtalert: 0x0000) (padn)[icmp6 sum ok] ICMP6, multicast listener report v2, 1 group record(s) [gaddr ff02::1:ffbf:fdc to_ex, 0 source(s)]
16:20:35.118431 IP (tos 0x10, ttl 128, id 0, offset 0, flags [none], proto UDP (17), length 328)

jefro · 04-03-2012, 10:07 PM

If it works correctly on a common lan then I'd begin to think it is an issue at school. Maybe a lease issue but I don't know why exactly it isn't offering you a new ip. Maybe just too few IP's or you are moving between some ap that can't follow.

nikmit · 04-04-2012, 02:09 AM

Is there anything in /var/log/syslog? It is probably a long shot, but I still have an issue with my ISP, where the first time I connect a linux machine as a router it can't get a DHCP address and I find logs of martian packets in syslog.
For all I can tell, Virgin is using a privately addressed server as part of their DHCP solution...

ChaosCon · 04-04-2012, 07:12 AM

I see a lot of messages that look like

Code:

Apr 03 14:59:21 tesla dhclient: Listening on LPF/wlan0/10:0b:a9:bf:0f:dc
Apr 03 14:59:21 tesla dhclient: Sending on   LPF/wlan0/10:0b:a9:bf:0f:dc
Apr 03 14:59:21 tesla dhclient: Sending on   Socket/fallback
Apr 03 14:59:21 tesla dhclient: DHCPRELEASE on wlan0 to 35.8.2.22 port 67
Apr 03 14:59:21 tesla dhclient: send_packet: Network is unreachable
Apr 03 14:59:21 tesla dhclient: send_packet: please consult README file regarding broadcast address.
Apr 03 14:59:21 tesla kernel: [ 1447.136923] iwlwifi 0000:03:00.0: L1 Disabled; Enabling L0S
Apr 03 14:59:21 tesla kernel: [ 1447.137069] iwlwifi 0000:03:00.0: Radio type=0x1-0x2-0x0
Apr 03 14:59:21 tesla kernel: [ 1447.035482] ADDRCONF(NETDEV_UP): wlan0: link is not ready
Apr 03 14:59:21 tesla dhclient: Internet Systems Consortium DHCP Client 4.2.2
Apr 03 14:59:21 tesla dhclient: Copyright 2004-2011 Internet Systems Consortium.
Apr 03 14:59:21 tesla dhclient: All rights reserved.
Apr 03 14:59:21 tesla dhclient: For info, please visit https://www.isc.org/software/dhcp/

and

Code:

Apr 03 14:59:22 tesla kernel: [ 1448.755357] wlan0: direct probe to 00:0c:e6:d9:57:56 (try 1/3)
Apr 03 14:59:23 tesla kernel: [ 1448.952123] wlan0: direct probe to 00:0c:e6:d9:57:56 (try 2/3)
Apr 03 14:59:23 tesla kernel: [ 1449.151536] wlan0: direct probe to 00:0c:e6:d9:57:56 (try 3/3)
Apr 03 14:59:23 tesla kernel: [ 1449.260562] e1000e 0000:00:19.0: PME# enabled
Apr 03 14:59:23 tesla kernel: [ 1449.351067] wlan0: direct probe to 00:0c:e6:d9:57:56 timed out

in /var/log/syslog around the exact times I tried (and failed) to connect. I'm not really sure what in there would indicate the problem, but that looked the most problematic (and relevant) of all log information.

nikmit · 04-04-2012, 07:31 AM

Quote:

Originally Posted by ChaosCon

I see a lot of messages that look like

Code:

Apr 03 14:59:21 tesla dhclient: send_packet: Network is unreachable
...
Apr 03 14:59:21 tesla kernel: [ 1447.035482] ADDRCONF(NETDEV_UP): wlan0: link is not ready
...

Based on this I think it an issue with establishing the link between your wifi card and the access point - rather than an issue with DHCP. Once you have connected in a spot once, then you go elsewhere and can't connect, then if you go back to the first spot can you connect again?

jlinkels · 04-04-2012, 07:37 AM

Try to delete files like /var/lib/dhcp/dhclient-9fefcd4b-4bdd-4b1e-8b46-826569588e1f-wlan0.lease. It is harmless, only you'll get a different IP address.

I have this same problem on some public access points.

jlinkels

ChaosCon · 04-04-2012, 08:47 AM

Quote:

Originally Posted by nikmit

Based on this I think it an issue with establishing the link between your wifi card and the access point - rather than an issue with DHCP. Once you have connected in a spot once, then you go elsewhere and can't connect, then if you go back to the first spot can you connect again?

Yes. I haven't tried switching buildings (which typically happens in a given day), but if I connect upstairs, head downstairs to a room that's certainly out of range of the original access point, then try to connect upstairs, I get back online no problems.

Quote:

Originally Posted by jlinkels

Try to delete files like /var/lib/dhcp/dhclient-9fefcd4b-4bdd-4b1e-8b46-826569588e1f-wlan0.lease. It is harmless, only you'll get a different IP address.

I have this same problem on some public access points.

jlinkels

I don't have a /var/lib/dhcp/dhclient-*-wlan0.lease, only a /dhclient.leases containing:

Code:

lease {
  interface "wlan0";
  fixed-address 35.13.181.247;
  option subnet-mask 255.255.248.0;
  option time-offset 18000;
  option routers 35.13.176.1;
  option dhcp-lease-time 3600;
  option dhcp-message-type 5;
  option domain-name-servers 35.8.2.5,35.8.2.41;
  option dhcp-server-identifier 35.8.2.22;
  option host-name "dynamic-glosser1-msu.edu-5";
  option netbios-name-servers 35.8.2.25;
  renew 3 2012/04/04 14:07:59;
  rebind 3 2012/04/04 14:33:50;
  expire 3 2012/04/04 14:41:20;
}

However, deleting it doesn't seem to help. =\

nikmit · 04-04-2012, 09:07 AM

It might be worth ruling out ARP issues.

To display and remove entries from the arp table, you can do like below:

Code:

root@gate:~# arp -n
Address                  HWtype  HWaddress           Flags Mask            Iface
192.168.8.94             ether   00:30:05:2c:f7:63   C                     eth2
192.168.8.101            ether   00:30:05:8a:64:30   C                     eth2

root@gate:~# arp -d 192.168.8.101

root@gate:~# arp -n
Address                  HWtype  HWaddress           Flags Mask            Iface
192.168.8.94             ether   00:30:05:2c:f7:63   C                     eth2
192.168.8.101                    (incomplete)                              eth2

Try deleting the arp entry for the wireless gateway before you attempt to connect at a new location.

ChaosCon · 04-05-2012, 11:44 AM

Code:

arp -n

doesn't list anything when I'm unconnected, but I get

Code:

Address                  HWtype  HWaddress           Flags Mask            Iface
35.13.176.1              ether   00:00:50:46:58:f2   C                     wlan0

when I'm actually on the wireless. Did you mean clear it prior to disconnecting, or before connecting to a new location?

nikmit · 04-06-2012, 06:30 AM

Before connecting to a new location.

ChaosCon · 04-07-2012, 03:47 PM

arp gives me nothing to remove if I'm stuck and unable to connect. Anything else it could be?

I really appreciate the help, too!

jefro · 04-09-2012, 03:38 PM

Try to force renew maybe. http://www.cyberciti.biz/faq/howto-l...nt-ip-address/

I still think it is with the university's side. They have some authentication or honey pot or something else going on.

Guess you could ifdown and up the wireless if you think it is on your side.