Message-ID: <4891B3E7.1090109@panasas.com>
Date: Thu, 31 Jul 2008 15:45:27 +0300
From: Boaz Harrosh <bharrosh@panasas.com>
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To: open-iscsi@googlegroups.com
CC: Jeff Garzik <jgarzik@pobox.com>, netdev@vger.kernel.org,
       davem@davemloft.net, michaelc@cs.wisc.edu,
       Steve Wise <swise@opengridcomputing.com>, rdreier@cisco.com,
       daisyc@us.ibm.com, wenxiong@us.ibm.com, bhua@us.ibm.com,
       Divy Le Ray <divy@chelsio.com>, Dimitrios Michailidis <dm@chelsio.com>,
       Casey Leedom <leedom@chelsio.com>,
       linux-scsi <linux-scsi@vger.kernel.org>,
       LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC][PATCH 1/1] cxgb3i: cxgb3 iSCSI initiator
References: <200807300019.m6U0JkdY012558@localhost.localdomain> <4890C287.60508@pobox.com> <8A71B368A89016469F72CD08050AD334032EC7F5@maui.asicdesigners.com>
In-Reply-To: <8A71B368A89016469F72CD08050AD334032EC7F5@maui.asicdesigners.com>
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Karen Xie wrote:
>> Comments:
>>
>> * SCSI drivers should be submitted via the linux-scsi@vger.kernel.org 
>> mailing list.
> 
> Will do that. Thanks.
> 
>> * The driver is clean and readable, well done
>>
>> * From a networking standpoint, our main concern becomes how this 
>> interacts with the networking stack.  In particular, I'm concerned
> based 
>> on reading the source that this driver uses "TCP port stealing" rather 
>> than using a totally separate MAC address (and IP).
>>
>> Stealing a TCP port on an IP/interface already assigned is a common 
>> solution in this space, but also a flawed one.  Precisely because the 
>> kernel and applications are unaware of this "special, magic TCP port" 
>> you open the potential for application problems that are very difficult
> 
>> for an admin to diagnose based on observed behavior.
> 
> The collisions between the host stack and iSCSI offload are unlikely
> because the iSCSI target server's port is unique (nailed down as 3260).
> If an offload card is plugged in, all iSCSI connections to a given
> target (i.e., destination/port) are offloaded. There is precedence for
> this approach such as RDMA/iWarp.
> 

Please note that all SW iscsi targets I know, let you change the default
3260 port to whatever you want. Is that supported?

Jeff is there a way for the user-mode demon to reserve the port beforehand
so it will appear to be taken.

>> So, additional information on your TCP port usage would be greatly 
>> appreciated.  Also, how does this interact with IPv6?  Clearly it 
>> interacts with IPv4...
> 
> Currently, IPv6 connection request will not be honored, I will make sure
> the checking is added in the resubmission.
> 
> 
Boaz

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