cifs: improve handling of network configuration switch (e.g. from eth to wifi)

When switching from a wired network configuration to wifi, my cifs share hangs
for 300 seconds, before CIFS VFS is reconnecting.
This happens every time when (un)docking the notebook.

While this action changes the client's IP address and the routing table, the
server itself is still reachable (via ping/ssh etc).

It appears as if the cifs module is using a static route to the server when
mounting, and therefore cannot reach the server anymore.

Would it be possible to handle this case (network switch / undocking a
notebook) better?

After having found a post on the mailing list [1], I have set the
echo_retries=1 option for cifs.ko and now the timeout is down to "only" 1
minute, which is much better already.

Would it be possible to tune the SMB_ECHO_INTERVAL from user land, e.g. by
using a kernel module parameter?
Then setting this to 30 or 10 seconds might be a good enough workaround for me.

I have also tried re-mounting (mount -o remount) the share, but that did not
trigger a re-connection either. This might also be a good workaround: via
ifup/ifdown scripts any cifs shares could be remounted and trigger a
re-connection to the server, if it is not reachable anymore.

1: http://<email address hidden>/msg06173.html

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: linux-image-3.2.0-26-generic 3.2.0-26.41
ProcVersionSignature: Ubuntu 3.2.0-26.41-generic 3.2.19
Uname: Linux 3.2.0-26-generic x86_64
AlsaVersion: Advanced Linux Sound Architecture Driver Version 1.0.24.
ApportVersion: 2.0.1-0ubuntu10
Architecture: amd64
ArecordDevices:
 **** List of CAPTURE Hardware Devices ****
 card 0: PCH [HDA Intel PCH], device 0: CONEXANT Analog [CONEXANT Analog]
   Subdevices: 1/1
   Subdevice #0: subdevice #0
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: daniel 4488 F.... pulseaudio
 /dev/snd/pcmC0D0p: daniel 4488 F...m pulseaudio
CRDA: Error: [Errno 2] No such file or directory
Card0.Amixer.info:
 Card hw:0 'PCH'/'HDA Intel PCH at 0xf2520000 irq 47'
   Mixer name : 'Intel CougarPoint HDMI'
   Components : 'HDA:14f1506e,17aa21db,00100000 HDA:80862805,80860101,00100000'
   Controls : 26
   Simple ctrls : 8
Card29.Amixer.info:
 Card hw:29 'ThinkPadEC'/'ThinkPad Console Audio Control at EC reg 0x30, fw unknown'
   Mixer name : 'ThinkPad EC (unknown)'
   Components : ''
   Controls : 1
   Simple ctrls : 1
Card29.Amixer.values:
 Simple mixer control 'Console',0
   Capabilities: pswitch pswitch-joined penum
   Playback channels: Mono
   Mono: Playback [on]
Date: Mon Jun 25 19:58:14 2012
HibernationDevice: RESUME=UUID=c06da6a2-76e0-4b5d-a4b0-f346c56d7537
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
MachineType: LENOVO 42992PG
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/vmlinuz-3.2.0-26-generic root=/dev/mapper/vg0-rootlv ro rootflags=subvol=@ quiet splash vt.handoff=7
RelatedPackageVersions:
 linux-restricted-modules-3.2.0-26-generic N/A
 linux-backports-modules-3.2.0-26-generic N/A
 linux-firmware 1.79
SourcePackage: linux
StagingDrivers: mei
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 04/25/2012
dmi.bios.vendor: LENOVO
dmi.bios.version: 8DET61WW (1.31 )
dmi.board.asset.tag: Not Available
dmi.board.name: 42992PG
dmi.board.vendor: LENOVO
dmi.board.version: Not Available
dmi.chassis.asset.tag: No Asset Information
dmi.chassis.type: 10
dmi.chassis.vendor: LENOVO
dmi.chassis.version: Not Available
dmi.modalias: dmi:bvnLENOVO:bvr8DET61WW(1.31):bd04/25/2012:svnLENOVO:pn42992PG:pvrThinkPadX220Tablet:rvnLENOVO:rn42992PG:rvrNotAvailable:cvnLENOVO:ct10:cvrNotAvailable:
dmi.product.name: 42992PG
dmi.product.version: ThinkPad X220 Tablet
dmi.sys.vendor: LENOVO