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-- SPDX-License-Identifier: GPL-3.0-or-later
local ffi = require('ffi')
local condition = require('cqueues.condition')
-- 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 (_, msg)
jit.off(true, true) -- JIT for (C -> lua)^2 nesting isn't allowed
table.insert(buffer, ffi.string(msg))
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 cond = condition.new()
local waiting, done = false, false
local finish_cb = ffi.cast('trace_callback_f', function (req)
jit.off(true, true) -- JIT for (C -> lua)^2 nesting isn't allowed
table.insert(buffer, req:selected_tostring())
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:trace_chain_callbacks(buffer_log_cb, 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, '')
-- 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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