[Net-snmp-patches] [ net-snmp-Patches-1185358 ] Net-SNMP 5.2 Linux/LVM Patch

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Patches item #1185358, was opened at 2005-04-18 20:30
Message generated for change (Comment added) made by magfr
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 1
Private: No
Submitted By: Nobody/Anonymous (nobody)
Assigned to: Nobody/Anonymous (nobody)
Summary: Net-SNMP 5.2 Linux/LVM Patch

Initial Comment:
The following one-liner add's support for LVM on Linux.

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>Comment By: Magnus Fromreide (magfr)
Date: 2007-12-13 23:55

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It does not exist yet, you have to write it.

The point of using shutdown_<module_name> is that the configure
machinery will detect it and call it automatically during shutdown,
just like it detects init_<module_name> and calls it automatically
during startup.

Try it - add

void shutdown_hr_disk()
{
  /* Do something detectable */
}

to hr_disk.c and rerun configure. Notice that shutdown_hr_disk get
called during agent shutdown.


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Comment By: Arkadiusz Miskiewicz (arekm)
Date: 2007-12-13 08:18

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[arekm@carme-pld net-snmp-5.4.1]$ grep -ri shutdown_hr_disk .
[arekm@carme-pld net-snmp-5.4.1]$

Don't see such one. Where do you see it?

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Comment By: Magnus Fromreide (magfr)
Date: 2007-12-12 23:33

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The inverse function of init_hr_disk would e shutdown_hr_disk, I think you
should use that to clean up your mallocs.

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Comment By: Wes Hardaker (hardaker)
Date: 2007-12-12 16:26

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File Added: net-snmp-lvm.patch

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Comment By: Arkadiusz Miskiewicz (arekm)
Date: 2007-12-12 16:03

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The patch is here
http://cvs.pld-linux.org/cgi-bin/cvsweb.cgi/~checkout~/SOURCES/net-snmp-lvm.patch?rev=1.2;content-type=text%2Fplain
due to sf tracker weakness.

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Comment By: Arkadiusz Miskiewicz (arekm)
Date: 2007-12-12 15:49

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"...only devices in /dev/ are "fine" for use.". I mean "/dev/mapper/" of
course. Uh, closed ticket. No way to attach a patch.

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Comment By: Wes Hardaker (hardaker)
Date: 2007-12-12 15:49

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Re-opening at request of arekm on irc to submit a patch.

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Comment By: Arkadiusz Miskiewicz (arekm)
Date: 2007-12-12 15:49

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"...only devices in /dev/ are "fine" for use.". I mean "/dev/mapper/" of
course. Uh, closed ticket. No way to attach a patch.

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Comment By: Arkadiusz Miskiewicz (arekm)
Date: 2007-12-12 15:44

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Here is my approach to the problem. According to LVM devs only devices in
/dev/ are "fine" for use. /dev/dm-X are internal kernel names exposed
sometimes by udev rules that create such devices. LVM2 tools create only
devices in /dev/mapper/.

So we have /dev/mapper/[0-9a-zA-Z+_\.-]+-[0-9a-zA-Z+_\.-]+ as devices.

My approach is do opendir(/dev/mapper/), look for such devices and add
these with full name.

I use disk_device_first == disk_device_last as indication that user want's
full name without %d or %c expansions (this case was never supported
earlier due to lodev < last_dev condition in for() loop so should be
safe).

HRD_type_index for lvm2 looks to be "4" in my testing.

HRD_info.model is only 40 bytes so it's very short - that why I'm
stripping "/dev/mapper/" there.

Malloced LVM LV names are never freed - well, don't see other way unless
there is some function called at "deinitialisation" of the thing (opposite
to init_hr_disk) - don't see such one.

Example output of snmpwalk:
HOST-RESOURCES-MIB::hrDeviceIndex.1600 = INTEGER: 1600
HOST-RESOURCES-MIB::hrDeviceType.1600 = OID:
HOST-RESOURCES-TYPES::hrDeviceDiskStorage
HOST-RESOURCES-MIB::hrDeviceDescr.1600 = STRING: LVM volume
(vg_sys-lv_home)
HOST-RESOURCES-MIB::hrDeviceID.1600 = OID: SNMPv2-SMI::zeroDotZero
HOST-RESOURCES-MIB::hrDiskStorageAccess.1600 = INTEGER: readWrite(1)
HOST-RESOURCES-MIB::hrDiskStorageMedia.1600 = INTEGER: unknown(2)
HOST-RESOURCES-MIB::hrDiskStorageRemoveble.1600 = INTEGER: false(2)
HOST-RESOURCES-MIB::hrDiskStorageCapacity.1600 = INTEGER: 419430400
KBytes
HOST-RESOURCES-MIB::hrPartitionIndex.1600.1 = INTEGER: 1
HOST-RESOURCES-MIB::hrPartitionLabel.1600.1 = STRING:
"/dev/mapper/vg_sys-lv_home"
HOST-RESOURCES-MIB::hrPartitionID.1600.1 = STRING: "0xfd00"
HOST-RESOURCES-MIB::hrPartitionSize.1600.1 = INTEGER: 419299328 KBytes


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Comment By: Nobody/Anonymous (nobody)
Date: 2007-12-12 12:54

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from freenode@#lvm: < asalor> /dev/dm-* are internal kernel names, use
/dev/mapper/* only (vgscan creates nodes only in /dev/mapper + symlinks)


so net-snmp needs to be extended to support more complicated patterns like
/dev/mapper/xx-yyy

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Comment By: SourceForge Robot (sf-robot)
Date: 2005-11-30 04:20

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This Tracker item was closed automatically by the system. It was
previously set to a Pending status, and the original submitter
did not respond within 180 days (the time period specified by
the administrator of this Tracker).

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Comment By: Radek (radekrat)
Date: 2005-11-15 14:45

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snmpd daemon reports

trace: Add_HR_Disk_entry(): host/hr_disk.c, 619:
host/hr_disk: WARNING! Add_HR_Disk_entry '/dev/dm-%d'
incomplete, 0 created

so I've changed the line to
Add_HR_Disk_entry("/dev/dm-%d", -1, -1, 0, 0, "/dev/dm-%d",
1, 15);

now I get

trace: Add_HR_Disk_entry(): host/hr_disk.c, 624:
host/hr_disk: Add_HR_Disk_entry '/dev/dm-%d' completed, 1
created

which seems to be fine, but no partitions are reported. Why?

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Comment By: Robert Story (rstory)
Date: 2005-06-03 01:51

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drop priority, move to pending due to lack of properly
functioning patch.

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Comment By: Radek (radekrat)
Date: 2005-05-11 13:23

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Doesn't work for me though. The dm partitions are still not
listed :( 

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Comment By: Dave Shield (dts12)
Date: 2005-05-10 14:57

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The first pattern matches disc partitions, the second pattern
(the sixth parameter) matches whole discs.

The other parameters should be viewed as range pairs.
The second pair (parameters 4 & 5) are the list of discs
and are inserted into both patterns.
The third pair (parameters 7 & 8) are the partitions within
a disc, and are inserted into the first pattern only.

You can ignore the first pair (parameters 2 & 3).
Any pair that's not used, should contain -1 or 0 (twice).

In this case, try

  Add_HR_Disk_entry("/dev/dm-%d", -1, -1, 0, 15,
                                   "/dev/dm-%d", 0, 0);
or
  Add_HR_Disk_entry("/dev/dm-%d", -1, -1, 0, 15,
                                   "/dev/dm-%d", -1, -1);

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Comment By: Radek (radekrat)
Date: 2005-05-10 12:47

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Further investigation - it would be at least nice to see all
devmapper partitions, so I've tried to create my own patch

@@ -172,6 +172,7 @@
     Add_HR_Disk_entry("/dev/sd%c%d", -1, -1, 'a', 'p',
"/dev/sd%c", 1, 15);
     Add_HR_Disk_entry("/dev/md%d", -1, -1, 0, 3,
"/dev/md%d", 0, 0);
     Add_HR_Disk_entry("/dev/fd%d", -1, -1, 0, 1,
"/dev/fd%d", 0, 0);
+    Add_HR_Disk_entry("/dev/dm-%d", -1, -1, 0, 15,
"/dev/dm-%d", 0, 15);
 #elif defined(hpux)
 #if defined(hpux10) || defined(hpux11)
     Add_HR_Disk_entry("/dev/rdsk/c%dt%xd%d", 0, 1, 0, 15,

but it doesn't work :( Can you tell me the exact meaning of
all values in the function and why is this not working. The
format is based on the output of `blkid` which on my systems
lists partions as

/dev/hda1:
/dev/sda1:
/dev/sda5:
/dev/sda6:
/dev/sda7:
/dev/sda8:
/dev/sda9:
/dev/dm-0:
/dev/dm-1:
/dev/dm-2:

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Comment By: Radek (radekrat)
Date: 2005-05-10 10:15

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Maybe it would be much nicer to read /proc/partitions - this
should add LVM support for Linux, but also will cover LVM2
partitions, EVMS etc. 

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Comment By: Nobody/Anonymous (nobody)
Date: 2005-05-02 20:45

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I didn't think it was a -proper- patch =) My C leaves alot
to be desired, but it appears to work reliably here, so I
thought I would pass it along.

The format of /dev/mapper is <volumegroup>-<logicalvolname> 

Eg.  

   /dev/mapper/myvg-home
   /dev/mapper/othervg-var

A _whole_ disk is represented as a physical volume in LVM.
And a volume group can be made up of any number of pv's. You
carve logical volumes from the vg's. 

I didn't specify a any numerical ranges (ie, 0 - 0) because
lvm doesn't use the same /dev format as say /dev/hda[0-9]

Any pointers on improving the patch are appreciated =)





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Comment By: Dave Shield (dts12)
Date: 2005-04-29 17:30

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Thanks for the patch, but it doesn't feel quite right.
The two patterns are meant to specify individual
characters or integer values (not strings),
and the value pairs specify the appropriate ranges
for these.  Specifying a range of '0' .. '0' seems unlikely.
Plus the second pattern string isn't even valid C syntax.

What are the ranges of valid /dev/mapper/%s-%s
style devices?  And how does LVM indicate a
"whole disk"?

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