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<TITLE>RE: [openib-general] mthca FMR correctness (and memory windows)</TITLE>
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<P><FONT SIZE=2>> ></FONT>
<BR><FONT SIZE=2>> >Can you elaborate on the issue of fungibility? If one entity has two</FONT>
<BR><FONT SIZE=2>> >QPs, one of which it's using for traffic and one of which it's using</FONT>
<BR><FONT SIZE=2>> >for MW binds, I don't see any security issue (beyond the fact that</FONT>
<BR><FONT SIZE=2>> >you've now given up ordering of operations between the QPs).</FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> If I can snoop or guess rkeys (not a huge challenge with 32 bits), and</FONT>
<BR><FONT SIZE=2>> if I can use them on an arbitrary queuepair, then I can handily peek and</FONT>
<BR><FONT SIZE=2>> poke at memory that does not belong to me.</FONT>
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<P><FONT SIZE=2>No. You can't get to the Window from an arbitrary QP. Only from those QPs that belong to the same PD.</FONT>
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<P><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> For this reason, iWARP requires its steering tags to be scoped to a single</FONT>
<BR><FONT SIZE=2>> connection. This leverages the IP security model and provides correctness.</FONT>
<BR><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> It is true that IB implementations generally don't do this. They should.</FONT>
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<P><FONT SIZE=2>IB allows the 2 flavors (PD bound Windows aka type 1, and QP bound Windows aka type 2).</FONT>
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<P><FONT SIZE=2>> </FONT>
<BR><FONT SIZE=2>> Tom.</FONT>
<BR><FONT SIZE=2>> </FONT>
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<BR><FONT SIZE=2>> general</FONT>
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