Add Wireshark configuration steps

This commit adds information about configuring Wireshark for analyzing
QUIC traffic.

README.rst

@@ -139,6 +139,44 @@ The library file is built for a particular TLS backend.  At the
 moment, libngtcp2_crypto_openssl which uses OpenSSL as TLS backend is
 provided.
 
+
+Configuring Wireshark for QUIC
+------------------------------
+`Wireshark <https://www.wireshark.org/download.html>`_ can be configured to
+analyze QUIC traffic using the following steps:
+
+**1.** Set *SSLKEYLOGFILE* environment variable:
+
+   .. code-block:: text
+
+        $ export SSLKEYLOGFILE=quic_keylog_file
+
+**2.** Set the port that QUIC uses
+
+   Go to *Preferences->Protocols->QUIC* and set the port the program listens to.
+   In the case of the example application this would be the port specified on the
+   command line.
+
+**3.** Set Pre-Master-Secret logfile
+
+   Go to *Preferences->Protocols->TLS* add set the *Pre-Master-Secret log file*
+   to the same value that was specified for *SSLKEYLOGFILE*.
+
+**4.** Choose the correct network interface for capturing
+
+   Make sure you choose the correct network interface for capturing. For example,
+   if using localhost choose the *loopback* network inteface on macos.
+
+**5.** Create a filter
+
+   Create A filter for the udp.port and set the port to the port the application
+   is listening to. For example:
+
+   .. code-block:: text
+
+        udp.port == 7777
+
+
 License
 -------