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Update doc

This commit is contained in:
Tatsuhiro Tsujikawa 2014-02-09 16:49:24 +09:00
parent 945c57c335
commit dffa078c11
2 changed files with 53 additions and 1 deletions
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3
lib/nghttp2_frame.c
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@ -696,7 +696,8 @@ ssize_t nghttp2_frame_add_pad(uint8_t **buf_ptr, size_t *buflen_ptr,
if(rv != 0) {
return rv;
}
/* We have to zero out padding bytes so that we won't reveal the
possible internal data to the remote peer */
memset((*buf_ptr) + trail_padoff, 0, trail_padlen);
return padlen;

51
lib/nghttp2_frame.h
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@ -519,6 +519,57 @@ int nghttp2_iv_check(const nghttp2_settings_entry *iv, size_t niv);
* The |*buf_ptr| and |*buflen_ptr| may be extended to include padding
* bytes.
*
* The padding specifier PAD_HIGH and PAD_LOW are located right after
* the frame header. But they may not be there depending of the length
* of the padding. To save the additional buffer copy, we allocate
* buffer size as if these 2 bytes always exist. Depending of the
* length of the padding, we move the location of frame header and
* adjust |*bufoff_ptr|. If more than or equal to 256 padding is made,
* the |*bufoff_ptr| is 0 and the content of the |*buf_ptr| looks like
* this:
*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Frame header ...
* +---------------------------------------------------------------+
* . Frame header |
* +---------------+---------------+-------------------------------+
* | Pad high | Pad low | Payload ...
* +---------------+---------------+-------------------------------+
*
*
* If padding is less than 256 but strictly more than 0, the
* |*bufoff_ptr| is 1 and the |*buf_ptr| looks like this:
*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Unused | Frame header ...
* +---------------+-----------------------------------------------+
* . Frame header ...
* +---------------+---------------+-------------------------------+
* . Frame Header | Pad low | Payload ...
* +---------------+---------------+-------------------------------+
*
* If no padding is added, the |*bufoff_ptr| is 2 and the |*buf_ptr|
* looks like this:
*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | Unused | Frame header ...
* +-------------------------------+-------------------------------+
* . Frame header ...
* +-------------------------------+-------------------------------+
* . Frame Header | Payload ...
* +-------------------------------+-------------------------------+
*
* Notice that the position of payload does not change. This way, we
* can set PAD_HIGH and PAD_LOW after payload was serialized and no
* additional copy operation is required (if the |*buf_ptr| is large
* enough to account the additional padding, of course).
*
* This function returns the number of padding added to the payload
* including PAD_HIGH and PAD_LOW if it succeeds, or one of the
* following negative error codes: