data rate formatting possible? [SOLVED]

edit

Save the Lua script below to a file ending in .lua in the
Help->About Wireshark->Folders: Personal Lua Plugins folder.
Start Wireshark or if Wireshark is already running, do Analyze->Reload Lua Plugins. It creates a new field (my_ppi.rate) formatted like the field in the Packet Details.

-- my_ppi.lua
-- https://ask.wireshark.org/question/26798/data-rate-formatting-possible/
-- Grab and format fields as needed

-- Step 1 - document as you go. See header above and set_plugin_info().
local my_ppi_info =
{
    version = "1.0.0",
    author = "Chuck Craft",
    description = "Copy ppi.80211-common.rate with custom format",
}

set_plugin_info(my_ppi_info)

-- Step 2 - create a protocol to attach new fields to
local my_ppi_p = Proto.new("my_ppi","Custom formatted ppi fields")

-- Step 3 - add some field(s) to Step 2 protocol
local pf = { rate = ProtoField.string("my_ppi.rate", "ppi.80211-common.rate with units") }

my_ppi_p.fields = pf

-- Step 4 - grab existing field(s) that will have different output format
ppi_rate_f = Field.new("ppi.80211-common.rate")

-- Step 5 - create the postdissector function that will run on each frame/packet
function my_ppi_p.dissector(tvb,pinfo,root)
    local tree = nil

    finfo = ppi_rate_f()

    if not (finfo == nil) then
        if not tree then
            tree = root:add(my_ppi_p)
        end
        local field_data = string.format("%.1f Mbps", finfo() / 1000.0)
        tree:add(pf.rate, field_data)
    end
end

-- Step 6 - register the new protocol as a postdissector
register_postdissector(my_ppi_p)

The “Packet List” Pane

Add a new (not custom) column with type "IEEE 802.11 TX rate". The format is 24.0 without the Mbps.

Looking at the code (packet-ppi.c) it seems the units should be there but its not.

    rate_kbps = rate_raw * 500;
    ti = proto_tree_add_uint_format(ftree, hf_80211_common_rate, tvb,
                                    ptvcursor_current_offset(csr), 2, rate_kbps, "Rate: %.1f Mbps",
                                    rate_kbps / 1000.0);
    if (rate_kbps == 0)
        proto_item_append_text(ti, " [invalid]");
    col_add_fstr(pinfo->cinfo, COL_TX_RATE, "%.1f Mbps", rate_kbps / 1000.0);

There is a sample capture on the Wireshark wiki:

File: http_PPI.cap

Description: 802.11n capture with PPI encapsulation containing HTTP data.

It looks like packet-ieee80211-radio.c or packet-ieee80211-radiotap.c comes along later and overwrites the column string without the units:

    col_add_fstr(pinfo->cinfo, COL_TX_RATE, "%.1f", data_rate);

Your other options would be to make your own fields with MATE or Lua.

Edit/Note: disabling protocol 802.11 Radio in the sample capture results in the TX Rate column having the format that was set in packet-ppi.c: 24.0 Mbps.