The vpp pcap dispatch trace dissector has been merged into the wireshark main branch, so the process is simple. Download wireshark, compile it, and install it.
The wireshark git repo is large, so it takes a while to clone.
git clone https://code.wireshark.org/review/wireshark
Here is a list of prerequisite packages which must be present in order to compile wireshark, beyond what's typically installed on an Ubuntu 18.04 system:
libgcrypt11-dev flex bison qtbase5-dev qttools5-dev-tools qttools5-dev
qtmultimedia5-dev libqt5svg5-dev libpcap-dev qt5-default
Mercifully, Wireshark uses cmake, so it's relatively easy to build, at least on Ubuntu 18.04.
$ cd wireshark
$ mkdir build
$ cd build
$ cmake -G Ninja ../
$ ninja -j 8
$ sudo ninja install
Configure vpp to pass traffic in some fashion or other, and then:
vpp# pcap dispatch trace on max 10000 file vppcapture buffer-trace dpdk-input 1000
or similar. Run traffic for long enough to capture some data. Save the dispatch trace capture like so:
vpp# pcap dispatch trace off
Display /tmp/vppcapture in the vpp-enabled version of wireshark. With any luck, normal version of wireshark will refuse to process vpp dispatch trace pcap files because they won't understand the encap type.
Set wireshark to filter on vpp.bufferindex to watch a single packet traverse the forwarding graph. Otherwise, you'll see a vector of packets in e.g. ip4-lookup, then a vector of packets in ip4-rewrite, etc.