[libvirt] [PATCH 1/2] util: Introduce virISCSINodeNew

[John Ferlan]

On 07/26/2016 12:24 PM, Ján Tomko wrote:
> On Mon, Jul 18, 2016 at 07:37:20AM -0400, John Ferlan wrote:
>> https://bugzilla.redhat.com/show_bug.cgi?id=1356436
>>
>> According to RFC 3721 (https://www.ietf.org/rfc/rfc3721.txt), there are
>> two ways to "discover" targets in/for the iSCSI environment. Discovery
>> is the process which allows the initiator to find the targets to which
>> it has access and at least one address at which each target may be
>> accessed.
>>
>> The method currently implemented in libvirt using the virISCSIScanTargets
>> API is known as "SendTargets" discovery. This method is more useful when
>> the target IP Address and TCP port information are available, e.g. in
>> libvirt terms the "portal". It returns a list of targets for the portal.
>>> From that list, the target can be found. This operation can also fill an
>> iSCSI node table into which iSCSI logins may occur. Commit id '56057900'
>> altered that filling by adding the "--op nonpersistent" since it was
>> not necessarily desired to perform that for non libvirt related targets.
>>
>> The second method is "Static Configuration". This method not only needs
>> the IP Address and TCP port (e.g. portal), but also the iSCSI target
>> name.
>> In libvirt terms this would be the device path field from the iSCSI pool
>> <source> XML. This patch implements the second methodology using that
>> required device path as the targetname.
>>
>> Signed-off-by: John Ferlan <jferlan at redhat.com>
>> ---
>> src/libvirt_private.syms |  1 +
>> src/util/viriscsi.c      | 45
>> +++++++++++++++++++++++++++++++++++++++++++++
>> src/util/viriscsi.h      |  6 ++++++
>> 3 files changed, 52 insertions(+)
>>
>> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
>> index 3580a72..edef70b 100644
>> --- a/src/libvirt_private.syms
>> +++ b/src/libvirt_private.syms
>> @@ -1714,6 +1714,7 @@ iptablesRemoveUdpOutput;
>> virISCSIConnectionLogin;
>> virISCSIConnectionLogout;
>> virISCSIGetSession;
>> +virISCSINodeNew;
>> virISCSINodeUpdate;
>> virISCSIRescanLUNs;
>> virISCSIScanTargets;
>> diff --git a/src/util/viriscsi.c b/src/util/viriscsi.c
>> index e705517..8115d09 100644
>> --- a/src/util/viriscsi.c
>> +++ b/src/util/viriscsi.c
>> @@ -444,6 +444,51 @@ virISCSIScanTargets(const char *portal,
>>     return ret;
>> }
>>
>> +/*
>> + * virISCSINodeNew:
>> + * @portal: address for iSCSI target
>> + * @target: IQN and specific LUN target
>> + *
>> + * Usage of nonpersistent discovery in virISCSIScanTargets is useful
>> primarily
>> + * only when the target IQN is not known; however, since we have the
>> target IQN
>> + * usage of the "--op new" can be done. This avoids problems if "--op
>> delete"
>> + * had been used wiping out the static nodes determined by the
>> scanning of
>> + * all targets.
>> + *
>> + * NB: If already created, subsequent "--op new" commands do not return
>> + * an error.
> 
> If it does not return an error, do we need to ignore non-zero status?

I thought the point of the comment is that subsequent --op new commands
won't cause an error "if" the node record was generated. IOW: It's ok to
have multiple NodeNew commands and those won't cause an error.  If there
was some other failure, then I'd expect to get and report some error.
But for this particular command the code isn't ignoring any error, so
the code isn't ignoring errors...

John
> 
> AFAIK the rest of the code ignoring exit codes was written before iscsiadm
> returned them properly:
> https://github.com/open-iscsi/open-iscsi/commit/2c839a2
> 
> Even this libvirt commit from Jan 2010 speaks of 'older versions of
> iscsiadm':
> http://libvirt.org/git/?p=libvirt.git;a=commitdiff;h=6aabcb5b
> 
> Jan