During the H1 message parsing, the Upgrade header values are checked to
detect "h2c" and "h2" tokens and skip them. To do so, we rely on
H1_MF_UPG_H2C flag, set during the parsing. And during the request
post-parsing, if this flag was set, all Upgrade headers are removed.
This was fixed by the commit 7b89aa5b1 ("BUG/MINOR: h1: do not forward h2c
upgrade header token").
However, there are two issues here and the commit above must be refined.
First, the flag is reset for each new Upgrade header. So "h2c" or "h2"
tokens will be properly detected if all tokens are set on the same Upgrade
header. But if splitted on several headers, previously detected tokens will
be hidden by a next ones.
Concretly, the following will be properly caught
Connection: upgrade
Upgrade: foo, h2c, bar
But then following not:
Connection: upgrade:
Upgrade: foo, h2c
Upgrade: bar
Then, when a "h2c" or "h2" token is finally reported, all Upgrade headers
are removed, regardless other tokens.
So, to fix the both issues, everything is now handled during the message
parsing by skipping "h2c" and "h2" tokens, rebuilding the Upgrade header
value without then offending tokens. The same was already performed for the
Connection header, to skip "keep-alive" and "close" value. So it is not a so
fancy change.
Thanks to this change, it is no longer necessary to handle H1_MF_UPG_H2C
during the request post-parsing. And in fact, this flag is no longer
necessary. So let's remove it too.
Thanks to Vincent55 for finding and reporting this.
This patch must be backported as far as 2.4.
8dd49dfaba