Commit eb2a6180 authored by Daniel Stenberg's avatar Daniel Stenberg
Browse files

README.http2: refreshed and added TODO items

parent 7b223a3a
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+24 −14
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HTTP2 with libcurl

 Spec: http://tools.ietf.org/html/draft-ietf-httpbis-http2

 Document explaining it: http://daniel.haxx.se/http2/

 Build prerequisites
  - nghttp2
  - OpenSSL, NSS, GnutTLS or PolarSSL with a new enough version
@@ -10,8 +11,8 @@ HTTP2 with libcurl
 nghttp2 (https://github.com/tatsuhiro-t/nghttp2)

  libcurl uses this 3rd party library for the low level protocol handling
  parts. The reason for this is that HTTP2 is much more complex at that layer
  than HTTP1.1 (which we implement on our own) and that nghttp2 is an already
  parts. The reason for this is that HTTP/2 is much more complex at that layer
  than HTTP/1.1 (which we implement on our own) and that nghttp2 is an already
  existing and well functional library.

  Right now, nghttp2 implements http2 draft-14
@@ -20,9 +21,9 @@ HTTP2 with libcurl

 Over an http:// URL

  If CURLOPT_HTTP_VERSION is set to CURL_HTTP_VERSION_2, libcurl will include
  an upgrade header in the initial request to the host to allow upgrading to
  http2.
  If CURLOPT_HTTP_VERSION is set to CURL_HTTP_VERSION_2_0, libcurl will
  include an upgrade header in the initial request to the host to allow
  upgrading to http2.

  Possibly we can later introduce an option that will cause libcurl to fail if
  not possible to upgrade. Possibly we introduce an option that makes libcurl
@@ -30,10 +31,10 @@ HTTP2 with libcurl

 Over an https:// URL

  If CURLOPT_HTTP_VERSION is set to CURL_HTTP_VERSION_2, libcurl will use ALPN
  (or NPN) to negotiate which protocol to continue with. Possibly introduce an
  option that will cause libcurl to fail if not possible to use http2.
  Consider options to explicitly disable ALPN and/or NPN.
  If CURLOPT_HTTP_VERSION is set to CURL_HTTP_VERSION_2_0, libcurl will use
  ALPN (or NPN) to negotiate which protocol to continue with. Possibly
  introduce an option that will cause libcurl to fail if not possible to use
  http2.  Consider options to explicitly disable ALPN and/or NPN.

  ALPN is the TLS extension that http2 is expected to use. The NPN extension
  is for a similar purpose, was made prior to ALPN and is used for SPDY so
@@ -51,15 +52,16 @@ SSL libs
    GnuTLS:   ALPN
    PolarSSL: ALPN

Alt-Svc
HTTP Alternative Services

  Alt-Svc is a suggested new header with a corresponding frame (ALTSVC) in
  Alt-Svc is a suggested extension with a corresponding frame (ALTSVC) in
  http2 that tells the client about an alternative "route" to the same content
  for the same origin server that you get the response from. A browser or
  long-living client can use that hint to create a new connection
  asynchronously.  For libcurl, we may introduce a way to bring such clues to
  the applicaton and/or let a subsequent request use the alternate route
  automatically.
  automatically. Spec:
  http://tools.ietf.org/html/draft-ietf-httpbis-alt-svc-05

Applications

@@ -70,8 +72,16 @@ curl tool

  curl offers the --http2 command line option to enable use of http2

To consider:
TODO:

  - Implement multiplexing

  - How to tell libcurl when using the multi interface that all or some of the
    handles are allowed to re-use the same physical connection. Can we just
    re-use existing pipelining logic?

  - Provide API to set priorities / dependencies of individual streams

  - Implement "prior-knowledge" HTTP/2 connecitons over clear text so that
    curl can connect with HTTP/2 at once without 1.1+Upgrade.