16384 – wifi cannot be used if too many networks are visible

Bug 16384 - wifi cannot be used if too many networks are visible

Summary: wifi cannot be used if too many networks are visible

Status:	RESOLVED DOCUMENTED

Alias:	None

Product:	Networking
Classification:	Unclassified
Component:	Wireless (show other bugs)
Hardware:	All Linux

Importance:	P1 normal
Assignee:	networking_wireless@kernel-bugs.osdl.org

URL:	http://bugs.meego.com/show_bug.cgi?id...
Keywords:

Depends on:
Blocks:

Reported:	2010-07-14 02:44 UTC by yanshuang.zheng
Modified:	2010-07-14 13:18 UTC (History)
CC List:	3 users (show)

See Also:
Kernel Version:	2.6.33
Subsystem:
Regression:	No
Bisected commit-id:

Attachments
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Description yanshuang.zheng 2010-07-14 02:44:37 UTC

------------------------------------------------
dwmw2intel 2010-07-12 02:36:05 PDT

'iwlist scan' doesn't work very often; most of the time it just does this:

ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 EAGAIN (Resource temporarily
unavailable)
select(0, [], NULL, NULL, {0, 100000})  = 0 (Timeout)
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 EAGAIN (Resource temporarily
unavailable)
select(0, [], NULL, NULL, {0, 100000})  = 0 (Timeout)
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
mmap2(NULL, 266240, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) =
0xb787d000
brk(0x90cf000)                          = 0x90cf000
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
mremap(0xb787d000, 266240, 528384, MREMAP_MAYMOVE) = 0xb77fc000
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
mremap(0xb77fc000, 528384, 1052672, MREMAP_MAYMOVE) = 0xb76fb000
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
mremap(0xb76fb000, 1052672, 2101248, MREMAP_MAYMOVE) = 0xb74fa000
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
mremap(0xb74fa000, 2101248, 4198400, MREMAP_MAYMOVE) = 0xb70f9000
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
mremap(0xb70f9000, 4198400, 8392704, MREMAP_MAYMOVE) = 0xb68f8000
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
mremap(0xb68f8000, 8392704, 16781312, MREMAP_MAYMOVE) = 0xb58f7000
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
mremap(0xb58f7000, 16781312, 33558528, MREMAP_MAYMOVE) = 0xb38f6000
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
mremap(0xb38f6000, 33558528, 67112960, MREMAP_MAYMOVE) = 0xaf8f5000
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
mremap(0xaf8f5000, 67112960, 134221824, MREMAP_MAYMOVE) = 0xa78f4000
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
mremap(0xa78f4000, 134221824, 268439552, MREMAP_MAYMOVE) = 0x978f3000
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
mremap(0x978f3000, 268439552, 536875008, MREMAP_MAYMOVE) = 0x778f2000
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
mremap(0x778f2000, 536875008, 1073745920, MREMAP_MAYMOVE) = 0x378f1000
ioctl(3, SIOCGIWSCAN, 0xbffe6cf8)       = -1 E2BIG (Argument list too long)
mremap(0x378f1000, 1073745920, 2147487744, MREMAP_MAYMOVE) = -1 ENOMEM (Cannot
allocate memory)
mmap2(NULL, 2147487744, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
= -1 ENOMEM (Cannot allocate memory)
mmap2(NULL, 2147618816, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
= -1 ENOMEM (Cannot allocate memory)
mmap2(NULL, 2097152, PROT_NONE, MAP_PRIVATE|MAP_ANONYMOUS|MAP_NORESERVE, -1, 0)
= 0xb76be000
munmap(0xb76be000, 270336)              = 0
munmap(0xb7800000, 778240)              = 0
mprotect(0xb7700000, 135168, PROT_READ|PROT_WRITE) = 0
mmap2(NULL, 2147487744, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
= -1 ENOMEM (Cannot allocate memory)
munmap(0x378f1000, 1073745920)          = 0
write(2, "print_scanning_info: Allocation "..., 39print_scanning_info:
Allocation failed
) = 39
close(3)                                = 0
exit_group(0)                           = ?  

--------------------------------------------------------------
dwmw2intel 2010-07-12 02:36:44 PDT

[    4.173017] iwlagn: Intel(R) Wireless WiFi Link AGN driver for Linux,
2.6.33.5-23.1-netbook-k
[    4.173025] iwlagn: Copyright(c) 2003-2009 Intel Corporation
[    4.173186] iwlagn 0000:09:00.0: enabling device (0104 -> 0106)
[    4.173227] iwlagn 0000:09:00.0: PCI INT A -> GSI 18 (level, low) -> IRQ 18
[    4.173313] iwlagn 0000:09:00.0: setting latency timer to 64
[    4.173422] iwlagn 0000:09:00.0: Detected Intel Wireless WiFi Link 5300AGN
REV=0x24
[    4.196231] iwlagn 0000:09:00.0: Tunable channels: 13 802.11bg, 24 802.11a
channels
[    4.196552] iwlagn 0000:09:00.0: irq 30 for MSI/MSI-X
[ 3754.354641] iwlagn 0000:09:00.0: restoring config space at offset 0xf (was
0x100, writing 0x10b)
[ 3754.354709] iwlagn 0000:09:00.0: restoring config space at offset 0x4 (was
0x4, writing 0xf0100004)
[ 3754.354747] iwlagn 0000:09:00.0: restoring config space at offset 0x3 (was
0x0, writing 0x8)
[ 3754.354787] iwlagn 0000:09:00.0: restoring config space at offset 0x1 (was
0x100000, writing 0x100106)
[ 3755.503129] iwlagn 0000:09:00.0: RF_KILL bit toggled to enable radio.
[ 6244.538332] iwlagn 0000:09:00.0: firmware: requesting iwlwifi-5000-2.ucode
[ 6244.590573] iwlagn 0000:09:00.0: loaded firmware version 8.24.2.12 

-----------------------------------------------------------------------
dwmw2intel 2010-07-12 03:50:09 PDT

I believe the issue is caused by the number of available networks exceeding the
kernel's buffer size.

Comment 1 John W. Linville 2010-07-14 12:59:03 UTC

dwmw2's analysis is almost certainly correct.  Unfortunately, it is a limitation of the wireless extensions API.

The alternative is to use the nl80211 API, embodied in the iw command:

iw dev wlan0 scan trigger
iw dev wlan0 scan dump

Comment 2 David Woodhouse 2010-07-14 13:18:40 UTC

Yeah, I'd already fixed ConnMan and wpa_supplicant in my MeeGo build to use nl80211 (and fall back to wext for the benefit of crappy drivers).

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