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client writer: handle pause before deocding

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Adds a "cw-pause" client writer in the PROTOCOL phase that buffers
output when the client paused the transfer. This prevents content
decoding from blowing the buffer in the "cw-out" writer.

Added test_02_35 that downloads 2 100MB gzip bombs in parallel and
pauses after 1MB of decoded 0's.

This is a solution to issue #16280, with some limitations:
- cw-out still needs buffering of its own, since it can be paused
  "in the middle" of a write that started with some KB of gzipped
  zeros and exploded into several MB of calls to cw-out.
- cw-pause will then start buffering on its own *after* the write
  that caused the pause. cw-pause has no buffer limits, but the
  data it buffers is still content-encoded.
  Protocols like http/1.1 stop receiving, h2/h3 have window sizes,
  so the cw-pause buffer should not grow out of control, at least
  for these protocols.
- the current limit on cw-out's buffer is ~75MB (for whatever
  historical reason). A potential content-encoding that blows 16KB
  (the common h2 chunk size) into > 75MB would still blow the buffer,
  making the transfer fail. A gzip of 0's makes 16KB into ~16MB, so
  that still works.

A better solution would be to allow CURLE_AGAIN handling in the client
writer chain and make all content encoders handle that. This would stop
explosion of encoding on a pause right away. But this is a large change
of the deocoder operations.

Reported-by: lf- on github
Fixes #16280
Closes #16296
This commit is contained in:
Stefan Eissing 2025-02-10 17:40:11 +01:00 • committed by Daniel Stenberg
parent 279a4772ae
commit f78700814d
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GPG key ID: 5CC908FDB71E12C2
14 changed files with 468 additions and 55 deletions
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31
lib/http2.c
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@ -219,6 +219,7 @@ struct h2_stream_ctx {
BIT(bodystarted);
BIT(body_eos); /* the complete body has been added to `sendbuf` and
* is being/has been processed from there. */
BIT(write_paused); /* stream write is paused */
};
#define H2_STREAM_CTX(ctx,data) ((struct h2_stream_ctx *)(\
@ -289,14 +290,14 @@ static int32_t cf_h2_get_desired_local_win(struct Curl_cfilter *cf,
static CURLcode cf_h2_update_local_win(struct Curl_cfilter *cf,
struct Curl_easy *data,
struct h2_stream_ctx *stream,
bool paused)
struct h2_stream_ctx *stream)
{
struct cf_h2_ctx *ctx = cf->ctx;
int32_t dwsize;
int rv;
dwsize = paused ? 0 : cf_h2_get_desired_local_win(cf, data);
dwsize = (stream->write_paused || stream->xfer_result) ?
0 : cf_h2_get_desired_local_win(cf, data);
if(dwsize != stream->local_window_size) {
int32_t wsize = nghttp2_session_get_stream_effective_local_window_size(
ctx->h2, stream->id);
@ -332,13 +333,11 @@ static CURLcode cf_h2_update_local_win(struct Curl_cfilter *cf,
static CURLcode cf_h2_update_local_win(struct Curl_cfilter *cf,
struct Curl_easy *data,
struct h2_stream_ctx *stream,
bool paused)
struct h2_stream_ctx *stream)
{
(void)cf;
(void)data;
(void)stream;
(void)paused;
return CURLE_OK;
}
#endif /* !NGHTTP2_HAS_SET_LOCAL_WINDOW_SIZE */
@ -1058,7 +1057,7 @@ static void h2_xfer_write_resp_hd(struct Curl_cfilter *cf,
if(!stream->xfer_result) {
stream->xfer_result = Curl_xfer_write_resp_hd(data, buf, blen, eos);
if(!stream->xfer_result && !eos)
stream->xfer_result = cf_h2_update_local_win(cf, data, stream, FALSE);
stream->xfer_result = cf_h2_update_local_win(cf, data, stream);
if(stream->xfer_result)
CURL_TRC_CF(data, cf, "[%d] error %d writing %zu bytes of headers",
stream->id, stream->xfer_result, blen);
@ -1074,8 +1073,6 @@ static void h2_xfer_write_resp(struct Curl_cfilter *cf,
/* If we already encountered an error, skip further writes */
if(!stream->xfer_result)
stream->xfer_result = Curl_xfer_write_resp(data, buf, blen, eos);
if(!stream->xfer_result && !eos)
stream->xfer_result = cf_h2_update_local_win(cf, data, stream, FALSE);
/* If the transfer write is errored, we do not want any more data */
if(stream->xfer_result) {
struct cf_h2_ctx *ctx = cf->ctx;
@ -1085,6 +1082,17 @@ static void h2_xfer_write_resp(struct Curl_cfilter *cf,
nghttp2_submit_rst_stream(ctx->h2, 0, stream->id,
(uint32_t)NGHTTP2_ERR_CALLBACK_FAILURE);
}
else if(!stream->write_paused && Curl_xfer_write_is_paused(data)) {
CURL_TRC_CF(data, cf, "[%d] stream output paused", stream->id);
stream->write_paused = TRUE;
}
else if(stream->write_paused && !Curl_xfer_write_is_paused(data)) {
CURL_TRC_CF(data, cf, "[%d] stream output unpaused", stream->id);
stream->write_paused = FALSE;
}
if(!stream->xfer_result && !eos)
stream->xfer_result = cf_h2_update_local_win(cf, data, stream);
}
static CURLcode on_stream_frame(struct Curl_cfilter *cf,
@ -2579,7 +2587,10 @@ static CURLcode http2_data_pause(struct Curl_cfilter *cf,
DEBUGASSERT(data);
if(ctx && ctx->h2 && stream) {
CURLcode result = cf_h2_update_local_win(cf, data, stream, pause);
CURLcode result;
stream->write_paused = pause;
result = cf_h2_update_local_win(cf, data, stream);
if(result)
return result;