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<p class="MsoNormal"><span style="font-size:11.0pt">Hi All,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">In current OAI implementation, we found that there are cases SPGW is out-of-sync with MME, because of the delete_session_request is not received by the SPGW because of some errors, however MME has cleared
the state of that session. Then when the UE re-attaches, a new create_session_request is sent to SPGW; and because we try to allocate the same IP for the same IMSI (local change), the SPGW will result out in trying to update an existing GTP tunnel.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">According to <a href="http://lxr.free-electrons.com/source/drivers/net/gtp.c#L937">
http://lxr.free-electrons.com/source/drivers/net/gtp.c#L937</a> and <a href="https://github.com/RoadRunnr/osmo-ggsn/blob/master/libgtnl/src/gtp-genl.c#L73">
https://github.com/RoadRunnr/osmo-ggsn/blob/master/libgtnl/src/gtp-genl.c#L73</a>, the NLM_F_EXCL flag is used to prevent updating an existing tunnel. I’m is wondering what is the reason of preventing updating?<br>
<br>
While we are actively investigating sending delete_session_request properly, as temporary workaround, I’m thinking to recovery from the out-of-sync problem, we can allow the new GTP tunnel to overwrite the old one in libgtpnl. Your suggestions are welcomed.
Thanks.</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt"> </span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">Regards,</span><o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt">-Jiannan</span><o:p></o:p></p>
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