tree 7efde5d111ec574350f52e10bd1be5679e04e8cd
parent 6cc85a5abba4892b0b3596f4f37828cf44ccff2e
author Willy Tarreau <w@1wt.eu> 1546454294 +0100
committer Willy Tarreau <w@1wt.eu> 1546537538 +0100
encoding latin1

BUG/MEDIUM: mux-h2: decode trailers in HEADERS frames

This is not exactly a bug but a long-time design limitation. We used not
to decode trailers in H2, resulting in broken connections each time a
trailer was sent, since it was impossible to keep the HPACK decompressor
synchronized. Now that the sequencing of operations permits it, we must
make sure to at least properly decode them.

What we try to do is to identify if a HEADERS frame was already seen and
use this indication to know if it's a headers or a trailers. For this,
h2c_decode_headers() checks if the stream indicates that a HEADERS frame
was already received. If so, it decodes it and emits the trailing
0 CRLF CRLF in case of H1, or the HTX_EOD + HTX_EOM blocks in case of HTX,
to terminate the data stream.

The trailers contents are still deleted for now but the request works, and
the connection remains synchronized and usable for subsequent streams.

The correctness may be tested using a simple config and h2spec :

    h2spec -o 1000 -v -t -S -k -h 127.0.0.1 -p 4443 generic/4/4

This should definitely be backported to 1.9 given the low impact for the
benefit. However it cannot be backported to 1.8 since the operations cannot
be resumed. The following patches are also needed with this one :

   MINOR: mux-h2: make h2c_decode_headers() return a status, not a count
   MINOR: mux-h2: add a new dummy stream : h2_error_stream
   MEDIUM: mux-h2: make h2c_decode_headers() support recoverable errors
   BUG/MINOR: mux-h2: detect when the HTX EOM block cannot be added after headers
   MINOR: mux-h2: check for too many streams only for idle streams
   MINOR: mux-h2: set H2_SF_HEADERS_RCVD when a HEADERS frame was decoded