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Fix response byte accounting after partial TCP writes #509

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Merged
mathieucarbou merged 5 commits into from
Nov 11, 2026
Merged

Fix response byte accounting after partial TCP writes #509

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f345b29
fix: count partially accepted response bytes
labodj Nov 10, 2026
b39a135
Merge branch 'main' into codex/fix-partial-response-accounting
mathieucarbou Nov 11, 2026
8ebaf4a
Cleanup PR
mathieucarbou Nov 11, 2026
dd43e1d
Removing unused _writtenLength
mathieucarbou Nov 11, 2026
cdfb5ee
ci(pre-commit): Apply automatic fixes
pre-commit-ci-lite[bot] Nov 11, 2026
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2 changes: 0 additions & 2 deletions src/ESPAsyncWebServer.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1717,8 +1717,6 @@ class AsyncWebServerResponse {
// amount of data sent for content part of the response (excluding all headers)
size_t _sentLength;
size_t _ackedLength;
// amount of response bytes (including all headers) written to sockbuff for delivery
size_t _writtenLength;
WebResponseState _state;

static bool headerMustBePresentOnce(const String &name);
Expand Down
12 changes: 4 additions & 8 deletions src/WebResponses.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -74,7 +74,7 @@ STR_RETURN_TYPE AsyncWebServerResponse::responseCodeToString(int code) {
}

AsyncWebServerResponse::AsyncWebServerResponse()
: _code(0), _contentType(), _contentLength(0), _sendContentLength(true), _chunked(false), _headLength(0), _sentLength(0), _ackedLength(0), _writtenLength(0),
: _code(0), _contentType(), _contentLength(0), _sendContentLength(true), _chunked(false), _headLength(0), _sentLength(0), _ackedLength(0),
_state(RESPONSE_SETUP) {
for (const auto &header : DefaultHeaders::Instance()) {
_headers.emplace_back(header);
Expand Down Expand Up @@ -303,7 +303,6 @@ size_t AsyncBasicResponse::write_send_buffs(AsyncWebServerRequest *request, size
if (_state == RESPONSE_HEADERS) {
// copy headers buffer to sock buffer
size_t const pcb_written = request->client()->add(_assembled_headers.c_str() + _writtenHeadersLength, _assembled_headers.length() - _writtenHeadersLength);
_writtenLength += pcb_written;
_writtenHeadersLength += pcb_written;
if (_writtenHeadersLength < _assembled_headers.length()) {
// we were not able to fit all headers in current buff, send this part here and return later for the rest
Expand All @@ -322,9 +321,8 @@ size_t AsyncBasicResponse::write_send_buffs(AsyncWebServerRequest *request, size

if (_state == RESPONSE_CONTENT) {
size_t const pcb_written = request->client()->write(_content.c_str() + _sentLength, _content.length() - _sentLength);
_writtenLength += pcb_written; // total written data (hdrs + body)
_sentLength += pcb_written; // body written data
payloadlen += pcb_written; // data writtent in current buff
_sentLength += pcb_written; // body written data
payloadlen += pcb_written; // data writtent in current buff
if (_sentLength >= _content.length()) {
// we've just sent all the (remainder) data in current buff, complete the response
_state = RESPONSE_END;
Expand Down Expand Up @@ -404,7 +402,6 @@ size_t AsyncAbstractResponse::write_send_buffs(AsyncWebServerRequest *request, s
if (_state == RESPONSE_HEADERS) {
// copy headers buffer to sock buffer
size_t const pcb_written = request->client()->add(_assembled_headers.c_str() + _writtenHeadersLength, _assembled_headers.length() - _writtenHeadersLength);
_writtenLength += pcb_written;
_writtenHeadersLength += pcb_written;
if (_writtenHeadersLength < _assembled_headers.length()) {
// we were not able to fit all headers in current buff, send this part here and return later for the rest
Expand Down Expand Up @@ -437,6 +434,7 @@ size_t AsyncAbstractResponse::write_send_buffs(AsyncWebServerRequest *request, s
// data is pending in buffer from a previous call or previous iteration; attempt to send it
size_t const added_len =
request->client()->add(reinterpret_cast<char *>(_send_buffer->data() + _send_buffer_offset), _send_buffer_len - _send_buffer_offset);
payloadlen += added_len;
if (added_len != _send_buffer_len - _send_buffer_offset) {
// we were not able to add entire buffer's content to tcp buffs, leave it for later
// (this should not happen normally unless connection's TCP window suddenly changed from remote or mem pressure)
Expand All @@ -445,7 +443,6 @@ size_t AsyncAbstractResponse::write_send_buffs(AsyncWebServerRequest *request, s
} else {
_send_buffer_len = _send_buffer_offset = 0; // consider buffer empty
}
payloadlen += added_len;
tcp_win -= added_len;
}

Expand Down Expand Up @@ -519,7 +516,6 @@ size_t AsyncAbstractResponse::write_send_buffs(AsyncWebServerRequest *request, s

// execute sending whatever we have in sock buffs now
request->client()->send();
_writtenLength += payloadlen;
#if ASYNCWEBSERVER_USE_CHUNK_INFLIGHT
// Take a credit only for data actually put in flight. When the source
// had nothing yet (RESPONSE_TRY_AGAIN), nothing will be acked to return
Expand Down
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