[FFmpeg-devel] [PATCH v2] avformat/http: Add max_request_size option
Zhao Zhili
quinkblack at foxmail.com
Thu Jan 2 17:22:24 EET 2025
> 在 2025年1月2日，上午5:52，Nicolas Frattaroli <ffmpeg at fratti.ch> 写道：
>
> In some cases, webservers may return content more quickly if one
> sends many small requests rather than one big request. Clients may
> wish to opt-in to this workaround.
>
> For this purpose, add a max_request_size AVOption, which returns
> EOF if max_request_size is exceeded, causing a new request with
> an offset to be issued.
>
> In particular, this hack is useful for mpv, where it can be used to
> bypass YouTube's throttling.
I’m afraid it can be treated as a DDOS attack tools. And once we did this, the server may do something else to make this hack useless. I’m not work on the server side and I don’t have strong opinions on this, just some random thoughts.
>
> Signed-off-by: Nicolas Frattaroli <ffmpeg at fratti.ch>
> ---
> Changes in v2:
> - Fix the request hanging if s->filesize < max_request_size
> ---
> libavformat/http.c | 43 +++++++++++++++++++++++++++++++------------
> 1 file changed, 31 insertions(+), 12 deletions(-)
>
> diff --git a/libavformat/http.c b/libavformat/http.c
> index ec60bc0b17..977cc8df7e 100644
> --- a/libavformat/http.c
> +++ b/libavformat/http.c
> @@ -75,7 +75,7 @@ typedef struct HTTPContext {
> /* Used if "Transfer-Encoding: chunked" otherwise -1. */
> uint64_t chunksize;
> int chunkend;
> - uint64_t off, end_off, filesize;
> + uint64_t off, end_off, filesize, max_request_size, range_end;
> char *uri;
> char *location;
> HTTPAuthState auth_state;
> @@ -174,6 +174,7 @@ static const AVOption options[] = {
> { "location", "The actual location of the data received", OFFSET(location), AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, D | E },
> { "offset", "initial byte offset", OFFSET(off), AV_OPT_TYPE_INT64, { .i64 = 0 }, 0, INT64_MAX, D },
> { "end_offset", "try to limit the request to bytes preceding this offset", OFFSET(end_off), AV_OPT_TYPE_INT64, { .i64 = 0 }, 0, INT64_MAX, D },
> + { "max_request_size", "try to limit the request to this many bytes, then reconnect", OFFSET(max_request_size), AV_OPT_TYPE_INT64, { .i64 = 0 }, 0, INT64_MAX, D },
> { "method", "Override the HTTP method or set the expected HTTP method from a client", OFFSET(method), AV_OPT_TYPE_STRING, { .str = NULL }, 0, 0, D | E },
> { "reconnect", "auto reconnect after disconnect before EOF", OFFSET(reconnect), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, D },
> { "reconnect_at_eof", "auto reconnect at EOF", OFFSET(reconnect_at_eof), AV_OPT_TYPE_BOOL, { .i64 = 0 }, 0, 1, D },
> @@ -1522,10 +1523,16 @@ static int http_connect(URLContext *h, const char *path, const char *local_path,
> // Note: we send the Range header on purpose, even when we're probing,
> // since it allows us to detect more reliably if a (non-conforming)
> // server supports seeking by analysing the reply headers.
> - if (!has_header(s->headers, "\r\nRange: ") && !post && (s->off > 0 || s->end_off || s->seekable != 0)) {
> + if (!has_header(s->headers, "\r\nRange: ") && !post && (s->off > 0 || s->end_off || s->seekable != 0 || s->max_request_size)) {
> av_bprintf(&request, "Range: bytes=%"PRIu64"-", s->off);
> - if (s->end_off)
> - av_bprintf(&request, "%"PRId64, s->end_off - 1);
> + if (s->end_off || s->max_request_size) {
> + if (s->end_off && s->max_request_size) {
> + s->range_end = FFMIN(s->end_off, s->off + s->max_request_size);
> + } else {
> + s->range_end = FFMAX(s->end_off, s->off + s->max_request_size);
> + }
> + av_bprintf(&request, "%"PRId64, s->range_end - 1);
> + }
> av_bprintf(&request, "\r\n");
> }
> if (send_expect_100 && !has_header(s->headers, "\r\nExpect: "))
> @@ -1664,7 +1671,16 @@ static int http_buf_read(URLContext *h, uint8_t *buf, int size)
> memcpy(buf, s->buf_ptr, len);
> s->buf_ptr += len;
> } else {
> - uint64_t target_end = s->end_off ? s->end_off : s->filesize;
> + uint64_t target_end = s->filesize;
> + if (s->end_off || s->max_request_size) {
> + if (s->end_off && s->max_request_size) {
> + target_end = FFMIN(s->end_off, s->range_end);
> + } else {
> + target_end = FFMAX(s->end_off, s->range_end);
> + }
> + target_end = FFMIN(target_end, s->filesize);
> + }
> +
> if ((!s->willclose || s->chunksize == UINT64_MAX) && s->off >= target_end)
> return AVERROR_EOF;
> len = ffurl_read(s->hd, buf, size);
> @@ -1762,13 +1778,16 @@ static int http_read_stream(URLContext *h, uint8_t *buf, int size)
> reconnect_delay_total > s->reconnect_delay_total_max)
> return AVERROR(EIO);
>
> - av_log(h, AV_LOG_WARNING, "Will reconnect at %"PRIu64" in %d second(s), error=%s.\n", s->off, reconnect_delay, av_err2str(read_ret));
> - err = ff_network_sleep_interruptible(1000U*1000*reconnect_delay, &h->interrupt_callback);
> - if (err != AVERROR(ETIMEDOUT))
> - return err;
> - reconnect_delay_total += reconnect_delay;
> - reconnect_delay = 1 + 2*reconnect_delay;
> - conn_attempts++;
> + if (!(s->max_request_size > 0 && read_ret == AVERROR_EOF)) {
> + av_log(h, AV_LOG_WARNING, "Will reconnect at %"PRIu64" in %d second(s), error=%s.\n",
> + s->off, reconnect_delay, av_err2str(read_ret));
> + err = ff_network_sleep_interruptible(1000U*1000*reconnect_delay, &h->interrupt_callback);
> + if (err != AVERROR(ETIMEDOUT))
> + return err;
> + reconnect_delay_total += reconnect_delay;
> + reconnect_delay = 1 + 2*reconnect_delay;
> + conn_attempts++;
> + }
> seek_ret = http_seek_internal(h, target, SEEK_SET, 1);
> if (seek_ret >= 0 && seek_ret != target) {
> av_log(h, AV_LOG_ERROR, "Failed to reconnect at %"PRIu64".\n", target);
> --
> 2.47.1
>
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