haproxy/doc/internals/http-parsing.txt

--- Relevant portions of RFC2616 ---

OCTET               = <any 8-bit sequence of data>
CHAR                = <any US-ASCII character (octets 0 - 127)>
UPALPHA             = <any US-ASCII uppercase letter "A".."Z">
LOALPHA             = <any US-ASCII lowercase letter "a".."z">
ALPHA               = UPALPHA | LOALPHA
DIGIT               = <any US-ASCII digit "0".."9">
CTL                 = <any US-ASCII control character (octets 0 - 31) and DEL (127)>
CR                  = <US-ASCII CR, carriage return (13)>
LF                  = <US-ASCII LF, linefeed (10)>
SP                  = <US-ASCII SP, space (32)>
HT                  = <US-ASCII HT, horizontal-tab (9)>
<">                 = <US-ASCII double-quote mark (34)>
CRLF                = CR LF
LWS                 = [CRLF] 1*( SP | HT )
TEXT                = <any OCTET except CTLs, but including LWS>
HEX                 = "A" | "B" | "C" | "D" | "E" | "F"
                      | "a" | "b" | "c" | "d" | "e" | "f" | DIGIT
separators          = "(" | ")" | "<" | ">" | "@"
                    | "," | ";" | ":" | "\" | <">
                    | "/" | "[" | "]" | "?" | "="
                    | "{" | "}" | SP | HT
token               = 1*<any CHAR except CTLs or separators>

quoted-pair         = "\" CHAR
ctext               = <any TEXT excluding "(" and ")">
qdtext              = <any TEXT except <">>
quoted-string       = ( <"> *(qdtext | quoted-pair ) <"> )
comment             = "(" *( ctext | quoted-pair | comment ) ")"





4 HTTP Message
4.1 Message Types

HTTP messages consist of requests from client to server and responses from
server to client. Request (section 5) and Response (section 6) messages use the
generic message format of RFC 822 [9] for transferring entities (the payload of
the message). Both types of message consist of :

  - a start-line
  - zero or more header fields (also known as "headers")
  - an empty line (i.e., a line with nothing preceding the CRLF) indicating the
    end of the header fields
  - and possibly a message-body.


HTTP-message        = Request | Response

start-line          = Request-Line | Status-Line
generic-message     = start-line
                      *(message-header CRLF)
                      CRLF
                      [ message-body ]

In the interest of robustness, servers SHOULD ignore any empty line(s) received
where a Request-Line is expected. In other words, if the server is reading the
protocol stream at the beginning of a message and receives a CRLF first, it
should ignore the CRLF.


4.2 Message headers

- Each header field consists of a name followed by a colon (":") and the field
  value.
- Field names are case-insensitive.
- The field value MAY be preceded by any amount of LWS, though a single SP is
  preferred.
- Header fields can be extended over multiple lines by preceding each extra
  line with at least one SP or HT.


message-header      = field-name ":" [ field-value ]
field-name          = token
field-value         = *( field-content | LWS )
field-content       = <the OCTETs making up the field-value and consisting of
                       either *TEXT or combinations of token, separators, and
                       quoted-string>


The field-content does not include any leading or trailing LWS occurring before
the first non-whitespace character of the field-value or after the last
non-whitespace character of the field-value. Such leading or trailing LWS MAY
be removed without changing the semantics of the field value. Any LWS that
occurs between field-content MAY be replaced with a single SP before
interpreting the field value or forwarding the message downstream.


=> format des headers = 1*(CHAR & !ctl & !sep) ":" *(OCTET & (!ctl | LWS))
=> les regex de matching de headers s'appliquent sur field-content, et peuvent
   utiliser field-value comme espace de travail (mais de pr<70>f<EFBFBD>rence apr<70>s le
   premier SP).

(19.3) The line terminator for message-header fields is the sequence CRLF.
However, we recommend that applications, when parsing such headers, recognize
a single LF as a line terminator and ignore the leading CR.





message-body    = entity-body
                | <entity-body encoded as per Transfer-Encoding>



5 Request

Request         = Request-Line
                  *(( general-header
                    | request-header
                    | entity-header ) CRLF)
                  CRLF
                  [ message-body ]



5.1 Request line

The elements are separated by SP characters. No CR or LF is allowed except in
the final CRLF sequence.

Request-Line = Method SP Request-URI SP HTTP-Version CRLF

(19.3) Clients SHOULD be tolerant in parsing the Status-Line and servers
tolerant when parsing the Request-Line. In particular, they SHOULD accept any
amount of SP or HT characters between fields, even though only a single SP is
required.

4.5 General headers
Apply to MESSAGE.

general-header  = Cache-Control
                | Connection
                | Date
                | Pragma
                | Trailer
                | Transfer-Encoding
                | Upgrade
                | Via
                | Warning

General-header field names can be extended reliably only in combination with a
change in the protocol version. However, new or experimental header fields may
be given the semantics of general header fields if all parties in the
communication recognize them to be general-header fields. Unrecognized header
fields are treated as entity-header fields.




5.3 Request Header Fields

The request-header fields allow the client to pass additional information about
the request, and about the client itself, to the server. These fields act as
request modifiers, with semantics equivalent to the parameters on a programming
language method invocation.

request-header  = Accept
                | Accept-Charset
                | Accept-Encoding
                | Accept-Language
                | Authorization
                | Expect
                | From
                | Host
                | If-Match
                | If-Modified-Since
                | If-None-Match
                | If-Range
                | If-Unmodified-Since
                | Max-Forwards
                | Proxy-Authorization
                | Range
                | Referer
                | TE
                | User-Agent

Request-header field names can be extended reliably only in combination with a
change in the protocol version. However, new or experimental header fields MAY
be given the semantics of request-header fields if all parties in the
communication recognize them to be request-header fields. Unrecognized header
fields are treated as entity-header fields.



7.1 Entity header fields

Entity-header fields define metainformation about the entity-body or, if no
body is present, about the resource identified by the request. Some of this
metainformation is OPTIONAL; some might be REQUIRED by portions of this
specification.

entity-header   = Allow
                | Content-Encoding
                | Content-Language
                | Content-Length
                | Content-Location
                | Content-MD5
                | Content-Range
                | Content-Type
                | Expires
                | Last-Modified
                | extension-header
extension-header = message-header

The extension-header mechanism allows additional entity-header fields to be
defined without changing the protocol, but these fields cannot be assumed to be
recognizable by the recipient. Unrecognized header fields SHOULD be ignored by
the recipient and MUST be forwarded by transparent proxies.

---- The correct way to do it ----

- one http_session
  It is basically any transport session on which we talk HTTP. It may be TCP,
  SSL over TCP, etc... It knows a way to talk to the client, either the socket
  file descriptor or a direct access to the client-side buffer. It should hold
  information about the last accessed server so that we can guarantee that the
  same server can be used during a whole session if needed. A first version
  without optimal support for HTTP pipelining will have the client buffers tied
  to the http_session. It may be possible that it is not sufficient for full
  pipelining, but this will need further study. The link from the buffers to
  the backend should be managed by the http transaction (http_txn), provided
  that they are serialized. Each http_session, has 0 to N http_txn. Each
  http_txn belongs to one and only one http_session.

- each http_txn has 1 request message (http_req), and 0 or 1 response message
  (http_rtr). Each of them has 1 and only one http_txn. An http_txn holds
  informations such as the HTTP method, the URI, the HTTP version, the
  transfer-encoding, the HTTP status, the authorization, the req and rtr
  content-length, the timers, logs, etc... The backend and server which process
  the request are also known from the http_txn.

- both request and response messages hold header and parsing informations, such
  as the parsing state, start of headers, start of message, captures, etc...