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MINOR: h2: clarify the rules for how to convert an H2 request to HTX

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The H2 request parsing is not trivial given that we have multiple
possible syntaxes. Mainly we can have :authority or not, and when
a CONNECT method is seen, :scheme and :path are missing. This mostly
updates the functions' comments and header index assignments to make
them less confusing. Functionally there is no change.
This commit is contained in:
Willy Tarreau 2019-10-08 11:59:37 +02:00 committed by Christopher Faulet
parent 35efbe2cda
commit 2be362c937
1 changed files with 38 additions and 4 deletions
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42
src/h2.c
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@ -122,10 +122,37 @@ int h2_parse_cont_len_header(unsigned int *msgf, struct ist *value, unsigned lon
* no general header field was found yet. Returns the created start line on
* success, or NULL on failure. Upon success, <msgf> is updated with a few
* H2_MSGF_* flags indicating what was found while parsing.
*
* The rules below deserve a bit of explanation. There tends to be some
* confusion regarding H2's authority vs the Host header. They are different
* though may sometimes be exchanged. In H2, the request line is broken into :
* - :method
* - :scheme
* - :authority
* - :path
*
* An equivalent HTTP/1.x absolute-form request would then look like :
* <:method> <:scheme>://<:authority><:path> HTTP/x.y
*
* Except for CONNECT which doesn't have scheme nor path and looks like :
* <:method> <:authority> HTTP/x.y
*
* It's worth noting that H2 still supports an encoding to map H1 origin-form
* and asterisk-form requests. These ones do not specify the authority. However
* in H2 they must still specify the scheme, which is not present in H1. Also,
* when encoding an absolute-form H1 request without a path, the path
* automatically becomes "/" except for the OPTIONS method where it
* becomes "*".
*
* As such it is explicitly permitted for an H2 client to send a request
* featuring a Host header and no :authority, though it's not the recommended
* way to use H2 for a client. It is however the only permitted way to encode
* an origin-form H1 request over H2. Thus we need to respect such differences
* as much as possible when re-encoding the H2 request into HTX.
*/
static struct htx_sl *h2_prepare_htx_reqline(uint32_t fields, struct ist *phdr, struct htx *htx, unsigned int *msgf)
{
int uri_idx = H2_PHDR_IDX_PATH;
int uri_idx;
unsigned int flags = HTX_SL_F_NONE;
struct htx_sl *sl;
size_t i;
@ -147,7 +174,8 @@ static struct htx_sl *h2_prepare_htx_reqline(uint32_t fields, struct ist *phdr,
/* missing authority */
goto fail;
}
// otherwise OK ; let's use the authority instead of the URI
// otherwise OK ; the URI is only made of the authority here
uri_idx = H2_PHDR_IDX_AUTH;
*msgf |= H2_MSGF_BODY_TUNNEL;
}
@ -170,12 +198,18 @@ static struct htx_sl *h2_prepare_htx_reqline(uint32_t fields, struct ist *phdr,
goto fail;
}
}
else { /* regular methods */
/* origin-form requests are made only of the path */
uri_idx = H2_PHDR_IDX_PATH;
}
/* 7540#8.1.2.3: :path must not be empty */
/* make sure the final URI isn't empty. Note that 7540#8.1.2.3 states
* that :path must not be empty.
*/
if (!phdr[uri_idx].len)
goto fail;
/* make sure :path doesn't contain LWS nor CTL characters */
/* The final URI must not contain LWS nor CTL characters */
for (i = 0; i < phdr[uri_idx].len; i++) {
unsigned char c = phdr[uri_idx].ptr[i];
if (HTTP_IS_LWS(c) || HTTP_IS_CTL(c))