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<p class="MsoNormal">Hi All,<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">A problem was observed in gianfar driver when the interface MTU was modified to a small value.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">FYI Kernel Version : 2.6.32 on PPC.<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Like if we change the interface mtu to say 100, ping traffic with size greater than 450 is failing.<o:p></o:p></p>
<p class="MsoNormal">It was observed that packets ( ping requests) going out of that interface are getting properly fragmented, but the return packets ( ping replies ) are getting dropped by the interface.
<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">To fix this issue the function <b>gfar_change_mtu() in gianfar.c
</b>was modified as below<b>:<o:p></o:p></b></p>
<p class="MsoNormal"><b><o:p> </o:p></b></p>
<p class="MsoNormal"><b>rx_buffer_size is restored to DEFAULT_RX_BUFFER_SIZE as indicated in
<span style="color:red">RED </span>in the code snippet below<o:p></o:p></b></p>
<p class="MsoNormal"><b><o:p> </o:p></b></p>
<p class="MsoNormal">------------------------- CODE SNIPPET BEGIN ----------------------------------<o:p></o:p></p>
<p class="MsoNormal"> tempsize =<o:p></o:p></p>
<p class="MsoNormal"> (frame_size & ~(INCREMENTAL_BUFFER_SIZE - 1)) +<o:p></o:p></p>
<p class="MsoNormal"> INCREMENTAL_BUFFER_SIZE;<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><b><span style="color:red"> if (tempsize < DEFAULT_RX_BUFFER_SIZE )<o:p></o:p></span></b></p>
<p class="MsoNormal"><b><span style="color:red"> tempsize = DEFAULT_RX_BUFFER_SIZE;<o:p></o:p></span></b></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> /* Only stop and start the controller if it isn't already<o:p></o:p></p>
<p class="MsoNormal"> * stopped, and we changed something */<o:p></o:p></p>
<p class="MsoNormal"> if ((oldsize != tempsize) && (dev->flags & IFF_UP))<o:p></o:p></p>
<p class="MsoNormal"> stop_gfar(dev);<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> priv->rx_buffer_size = tempsize;<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"> dev->mtu = new_mtu;<o:p></o:p></p>
<p class="MsoNormal">------------------------- CODE SNIPPET END----------------------------------<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">If this fix OK? What is the impact of this change on overall behavior?<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Best Regards,<o:p></o:p></p>
<p class="MsoNormal">- Suresh<o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
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