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local ffi = require('ffi')
local bit = require('bit')
local condition = require('cqueues.condition')
-- Buffer selected record information to a table
local function add_selected_records(dst, records)
for _, rec in ipairs(records) do
local rank = rec.rank
-- Separate the referral chain verified flag
local verified = bit.band(rec.rank, kres.rank.AUTH)
if verified then
rank = bit.band(rank, bit.bnot(kres.rank.AUTH))
end
local rank_name = kres.tostring.rank[rank] or tostring(rank)
-- Write out each individual RR
for rr in tostring(rec.rr):gmatch('[^\n]+\n?') do
local row = string.format('cached: %s, rank: %s, record: %s',
rec.cached, rank_name:lower(), rr)
table.insert(dst, row)
end
end
end
local function format_selected_records(header, records)
if #records == 0 then return '' end
return string.format('%s\n%s\n', header, string.rep('-', #header))
.. table.concat(records, '') .. '\n'
end
-- Trace execution of DNS queries
local function serve_trace(h, _)
local path = h:get(':path')
local qname, qtype_str = path:match('/trace/([^/]+)/?([^/]*)')
if not qname then
return 400, 'expected /trace/<query name>/<query type>'
end
-- Parse query type (or default to A)
if not qtype_str or #qtype_str == 0 then
qtype_str = 'A'
end
local qtype = kres.type[qtype_str]
if not qtype then
return 400, string.format('unexpected query type: %s', qtype_str)
end
-- Create logging handler callback
local buffer = {}
local buffer_log_cb = ffi.cast('trace_log_f', function (query, source, msg)
local message = string.format('[%5s] [%s] %s',
query.id, ffi.string(source), ffi.string(msg))
table.insert(buffer, message)
end)
-- Wait for the result of the query
-- Note: We can't do non-blocking write to stream directly from resolve callbacks
-- because they don't run inside cqueue.
local answers, authority = {}, {}
local cond = condition.new()
local waiting, done = false, false
local finish_cb = ffi.cast('trace_callback_f', function (req)
req = kres.request_t(req)
add_selected_records(answers, req.answ_selected)
add_selected_records(authority, req.auth_selected)
if waiting then
cond:signal()
end
done = true
end)
-- Resolve query and buffer logs into table
resolve {
name = qname,
type = qtype,
options = {'TRACE'},
init = function (req)
req = kres.request_t(req)
req.trace_log = buffer_log_cb
req.trace_finish = finish_cb
end
}
-- Wait for asynchronous query and free callbacks
if not done then
waiting = true
cond:wait()
end
buffer_log_cb:free()
finish_cb:free()
-- Build the result
local result = table.concat(buffer, '') .. '\n'
.. format_selected_records('Used records from answer:', answers)
.. format_selected_records('Used records from authority:', authority)
-- Return buffered data
if not done then
return 504, result
end
return result
end
-- Export endpoints
return {
endpoints = {
['/trace'] = {'text/plain', serve_trace},
}
}
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