3) Find another RADIUS dictionary file that includes this attribute
(then add this dictionary via another $INCLUDE line).

For item 3 above you might want to take a look at CDRTool.
This product has the Canonical-URI attribute defined in the following
dictionary: CDRTool/setup/radius/OpenSER/dictionary.ser

i copied from CDRtool dictionary.ser to /usr/local/share/freeradius/

and add that line in in dictionary

now i see another error

0(0) INFO:xl_parse_name: using hdr type (21) instead of <event>
0(0) ERROR: acc: can't get code for the Sip-User-Realm attribute
0(0) ERROR:acc:mod_init: failed to init radius
0(0) init_mod(): Error while initializing module acc
ERROR: error while initializing modules
0(0) XLOG: destroy module ...
0(0) DEBUG: tm_shutdown : start

I have searched this Dictionary all the Dictionary files

i dont see this exists any where.

ram