Wireshark has support for the Ceph protocol and it will be shipped in the 1.12.1 release.
The Ceph dissector lives in Wireshark git at
epan/dissectors/packet-ceph.c. At the top of that file there are some
comments explaining how to insert new functionality or to update the encoding
of existing types.
Before you start hacking on Wireshark code you should look at the
doc/README.dissector documents as they explain
the basics of writing dissectors. After reading those two documents you should
be prepared to work on the Ceph dissector. The Wireshark
developers guide also contains a lot of useful information but it is less
directed and is more useful as a reference then an introduction.