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LD_ISCSI.SO LD_PRELOAD hack

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ld_iscsi.so is a small LD_PRELOAD hack that can be used to make normal
unix utilities such as 'stat' and 'cat' become iSCSI 'aware' and fake
handling an iSCSI URL as a normal read-only file.

See README for examples.
This commit is contained in:
Ronnie Sahlberg
2011-02-05 21:21:52 +11:00
parent eba0a2de81
commit 35821830d6
3 changed files with 297 additions and 1 deletions
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README
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@@ -72,3 +72,31 @@ Header digest is to be used or not.
This can be overridden by an application by calling iscsi_set_header_digest()
if the application wants to force a specific setting.
LD_PRELOAD FUN
==============
There is a small LD_PRELOAD hack in the src directory that intercepts a handful
of system calls and converts ISCSI URLs to look and behave as if they are
normal read-only files.
This allows using standard unix tools to become iscsi aware with no modifications.
For example:
The stat command: this shows the size of the iSCSI LUN as if it was a normal file:
$ LD_PRELOAD=./bin/ld_iscsi.so stat iscsi://127.0.0.1:3262/iqn.ronnie.test/2
File: `iscsi://127.0.0.1:3262/iqn.ronnie.test/2'
Size: 3431540736 Blocks: 0 IO Block: 0 regular file
Device: 0h/0d Inode: 0 Links: 0
Access: (0444/-r--r--r--) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 1970-01-01 10:00:00.000000000 +1000
Modify: 1970-01-01 10:00:00.000000000 +1000
Change: 1970-01-01 10:00:00.000000000 +1000
The cat command, which allows you to read/dump a iSCSI LUN to a file :
$ LD_PRELOAD=./bin/ld_iscsi.so cat iscsi://127.0.0.1:3262/iqn.ronnie.test/2 >copy_of_iscsi_lun
The LD_PRELOAD hack is incomplete and needs more functions to be intercepted before becomming fully functional. Patches welcome!
For now, it is sufficiently complete for trivial commands like stat and cat.
You probably need to implement at least lseek, pread, pwrite before it becomes really useful.