1.
20202020
DanielStenberg–curlup-May5th
,2020
in curl

2.
Daniel Stenberg
@bagderhttps://daniel.haxx.se

3.
How HTTP/3 differs from 1 and 2How HTTP/3 differs from 1 and 2
Build curl to enable HTTP/3Build curl to enable HTTP/3
The TLS situationThe TLS situation
HTTP/3 with the curl toolHTTP/3 with the curl tool
HTTP/3 with libcurlHTTP/3 with libcurl
Remaining issuesRemaining issues
WhenWhen
@bagder@bagder

4.
This is not my HTTP/3 explanation talk
HTTP/3 for everyone (FOSDEM 2020)
https://daniel.haxx.se/videos/
@bagder@bagder

5.
@bagder@bagder

6.
Improvements in QUICImprovements in QUIC
TCP head of line blockingTCP head of line blocking
Faster handshakesFaster handshakes
Earlier dataEarlier data
More encryption, alwaysMore encryption, always
Future developmentFuture development
@bagder@bagder

7.
QUIC on top of UDP
TCP and UDP remain “the ones”TCP and UDP remain “the ones”
Use UDP instead of IPUse UDP instead of IP
Reliable transport protocol - inReliable transport protocol - in
user-spaceuser-space
A little like TCP + TLSA little like TCP + TLS
@bagder@bagder

8.
Streams!
QUIC provides streamsQUIC provides streams
Many logical flows within a single connectionMany logical flows within a single connection
Similar to HTTP/2 but in the transport layerSimilar to HTTP/2 but in the transport layer
IndependentIndependent streamsstreams
@bagder@bagder

9.
@bagder@bagder
HTTP/3 = HTTP over QUIC
@bagder@bagder

10.
Stacks: old vs new
TCP
TLS 1.2+
HTTP/2
UDP
HTTP/3
QUIC
TLS 1.3
IP
HTTP/1
@bagder@bagder
streams
@bagder@bagder

11.
HTTPS is TCP?
HTTPS:// URLs are everywhereHTTPS:// URLs are everywhere
TCP (and TLS) on TCP port 443TCP (and TLS) on TCP port 443
@bagder@bagder

12.
This service - over there!
The Alt-Svc: response header
Another host, protocol or port number is the
same “origin”
This site also runs on HTTP/3 “over there”, for
the next NNNN seconds
@bagder@bagder

13.
HTTP/3 challenges
3-7% something of all QUIC attempts fail
Clients need “fall back” algorithms
CPU intensive
Unoptimized UDP stacks
“Funny” TLS layer
All QUIC stacks are user-land
No standard QUIC API
Lack of tooling
@bagder@bagder

14.
Ship date
@bagder@bagder
2020?2020?

15.
curl runs in all your devices
@bagder@bagder

16.
Work in progress
Early days – your help is appreciated
HTTP/3 and QUIC support is experimental
Things might will change
Code is in git master and shipped
Only HTTP/3 (not QUIC) is exposed in curl
@bagder@bagder

17.
@bagder@bagder
Build
@bagder@bagder

18.
Build curl
Early support aids the protocol community
Requires 3rd party libraries for low level
Selectable backend, use one out of several choices
Quiche or ngtcp2 for now
- Different TLS requirements
- Very different APIs
@bagder@bagder

19.
@bagder@bagder
Build curl with quiche
https://github.com/cloudflare/quiche
Uses BoringSSL
(Look at docs/HTTP3.md)
You want alt-svc support as well
@bagder@bagder

20.
@bagder@bagder
Build curl with ngtcp2 (and nghttp3)
https://github.com/ngtcp2/ngtcp2
https://github.com/ngtcp2/nghttp3
Uses a patched OpenSSL or GnuTLS from git
(Look at docs/HTTP3.md)
You want alt-svc support as well
@bagder@bagder

21.
@bagder@bagder
Why is it called ngtcp2?
Jana Iyengar (then at Google) did a QUIC presentation in the HTTP
Workshop Stockholm in July 2016
In that presentation, he showed...

22.
@bagder@bagder
The TLS situation

23.
The TLS situation (1/2)
TLS was made for TCP
TLS is sent over TCP as records containing
individual messages
QUIC uses TLS messages
No TLS library support(ed) TLS messages
QUIC also needs additional secrets
@bagder@bagder

24.
The TLS situation (2/2)
@bagder@bagder
Frame 0
Message 0 Message 1
Frame 1
Message 2 Message 3TCPTCP
Message 0 Message 1 Message 2 Message 3
QUICQUIC

25.
@bagder@bagder
BoringSSL
Supports QUIC already
BoringSSL is really hard for non-Google products to use
Quiche uses BoringSSL
… and so does Chrome/Edge and some other
implementations
@bagder@bagder

26.
@bagder@bagder
OpenSSL
No support in any release, nor git
“once the 3.0 release is done, QUIC will become a significant
focus of our effort” + “final [3.0] release in early Q4 2020”
PR #8797 OpenSSL offers an API similar to the BoringSSL one.
https://github.com/openssl/openssl/pull/8797
ngtcp2 uses OpenSSL+8797
… and so does msquic, node.js and more
@bagder@bagder

27.
@bagder@bagder
GnuTLS
Has initial support landed in git
ngtcp2 can be built to use it
@bagder@bagder

28.
@bagder@bagder
Other libraries
The other TLS libraries curl supports lack the necessary APIs
for QUIC
@bagder@bagder

29.
@bagder@bagder
curl uses a single TLS lib
When built to support QUIC, the same library is used for
“normal” TLS.

30.
Use
@bagder@bagder

31.
It looks like HTTP/1
As for HTTP/2, HTTP/3 in curl is made to lookmade to look
like HTTP/1like HTTP/1 when curl shows requests,
headers and similar. For consistency and easy
of use.
@bagder@bagder

32.
Run curl
--http3
Forces curl to try QUIC and HTTP/3 on the given host name
No fallback!
--alt-svc <filename>
Bootstraps into HTTP/3 the “standard way”
Requires alt-svc: response headers (several dev servers don’t do those)
Takes an additional round-trip
Makes the initial request HTTP/1 or HTTP/2 the “usual way”
The alt-svc file format: https://curl.haxx.se/docs/alt-svc.html
@bagder@bagder

33.
Run curl
$ curl –-http3 https://quic.tech:8443/ -v
$ curl –-alt-svc alt.txt https://quic.tech:8443/ -v
$ curl --version
…
Features: alt-svc ... HTTP3 ...
@bagder@bagder

34.
Works now with HTTP/3
@bagder@bagder
HTTP/3 draft-27
Connecting over IPv4 and IPv6 and “Happy eyeballs”
Direct or via alt-svc
Funny host name/DNS tricks like --resolve and friends
HTTP GET and POST requests
HTTP header parsing, adding and removing headers
Cookies, connection caching, connection re-use etc
SSLKEYLOGFILE

35.
HTTP/3 in the curl CI
We verify the HTTP/3 builds in every curl commit
and PR
Both quiche and ngtcp2
Builds only, they don’t run tests yet
@bagder@bagder

36.
libcurllibcurl
@bagder@bagder

37.
curl is powered by libcurl
Previously mentioned features are in libcurl
… with a few more knobs to tweak
@bagder@bagder

38.
“Force” HTTP/3
@bagder@bagder

39.
Alt-Svc style
@bagder@bagder

40.
Check for support
@bagder@bagder

41.
Remaining issues right now
@bagder@bagder

42.
HTTP/3 is still “experimental” in curl
Fallback
(happy
eyeballs?)
https://github.com/curl/curl/wiki/HTTP3
Multiplexing Certificates
Trailers Stability Tests
Push
qlog
@bagder@bagder

43.
Upgrading to h3 - long term
Tricky
HTTP/2 reuses the same
connection - easier
alt-svc needs cache on disk to be
effective
Happy eyeballs...
@bagder@bagder

44.
When
@bagder@bagder

45.
Specifications
Ship curl HTTP/3-enabled?Ship curl HTTP/3-enabled?
Deployed servers
Browser support
libcurl
TLS libraries
QUIC and HTTP/3 libraries
@bagder@bagder

46.
@bagder@bagder
It will take a while
@bagder@bagder

47.
48
You can help!You can help!
@bagder@bagder

48.
December 6, 2019December 6, 2019
@bagder@bagder

49.
HTTP/3 Explained
https://http3-explained.haxx.se
@bagder@bagder

50.
Daniel Stenberg
@bagder
https://daniel.haxx.se/
Thank you!Thank you!
Questions?Questions?