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http/websocket: fix mid-size frames sometimes failing to be received #197

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http/websocket: fix mid-size frames sometimes failing to be received #197

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2 changes: 1 addition & 1 deletion http/websocket.lua
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Original file line number Diff line number Diff line change
Expand Up @@ -241,7 +241,7 @@ local function read_frame(sock, deadline)
if frame.length == 126 then
extra_fill_unget = assert(sock:xread(2, "b", 0))
frame.length = sunpack(">I2", extra_fill_unget)
fill_length = fill_length - 2
fill_length = fill_length - 2 + frame.length
elseif frame.length == 127 then
extra_fill_unget = assert(sock:xread(8, "b", 0))
frame.length = sunpack(">I8", extra_fill_unget)
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71 changes: 55 additions & 16 deletions spec/websocket_spec.lua
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Expand Up @@ -243,23 +243,62 @@ describe("http.websocket module two sided tests", function()
assert.truthy(cq:empty())
end)
local function send_receive_test(name, data, data_type)
it(name, function()
data_type = data_type or "text"
local cq = cqueues.new()
local c, s = new_pair()
cq:wrap(function()
assert(c:send(data, data_type))
assert.same({data, data_type}, {assert(c:receive())})
assert(c:close())
local function do_test(bad_connection)
local bname = name
if bad_connection then
bname = bname .. ", even if the connection is really bad"
end
it(bname, function()
data_type = data_type or "text"
if bad_connection then
local real_xwrite
local fragments = 100
local delay = 1 / fragments -- Aim for 1s.
real_xwrite = cs.interpose("xwrite", function(self, str, mode, timeout)
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@daurnimator daurnimator Jan 17, 2022 •
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You don't need to interpose the whole library: you should be able to overwrite just the specific instance:

local c, s = new_pair()
local real_xwrite = s.socket.xwrite
s.socket.xwrite = ffunction(self, str, mode, timeout)

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It just seemed like the intended way to do it, but sure, I could do that.

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Ah never mind, I remember now why I did it like this. CQS sockets are userdata, you can't just override their methods like that.

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I'm open to alternatives.

if mode ~= "bn" then -- Not interesting, don't throttle.
return real_xwrite(self, str, mode, timeout)
end
local deadline
if timeout then
deadline = cqueues.monotime() + timeout
end
local ok, op, why
local nbytes = math.ceil(#str / fragments)
local before_first = 0
repeat
-- Test range at the end to ensure that real_xwrite is called at least once.
-- We rely on the fact here that :sub sanitizes the input range.
ok, op, why = real_xwrite(self, str:sub(before_first + 1, before_first + nbytes), mode, deadline and (deadline - cqueues.monotime()))
if not ok then
break
end
before_first = before_first + nbytes
cqueues.sleep(delay)
until before_first > #str
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Should probably be >=. > works because xwriting an empty string happens to be ok.

return ok, op, why
end)
finally(function()
cs.interpose("xwrite", real_xwrite)
end)
end
local cq = cqueues.new()
local c, s = new_pair()
cq:wrap(function()
assert(c:send(data, data_type))
assert.same({data, data_type}, {assert(c:receive())})
assert(c:close())
end)
cq:wrap(function()
assert.same({data, data_type}, {assert(s:receive())})
assert(s:send(data, data_type))
assert(s:close())
end)
assert_loop(cq, TEST_TIMEOUT)
assert.truthy(cq:empty())
end)
cq:wrap(function()
assert.same({data, data_type}, {assert(s:receive())})
assert(s:send(data, data_type))
assert(s:close())
end)
assert_loop(cq, TEST_TIMEOUT)
assert.truthy(cq:empty())
end)
end
do_test(false)
do_test(true)
end
send_receive_test("works with small size frames", "f")
send_receive_test("works with medium size frames", ("f"):rep(200))
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