A quick overview of new features related to 'networking' in Go lang 1.8

1. Go 1.8 新 联网 features
सैफी खान
saifi@ACM.org
New Networking

2. Warm up
package main
import "net/http"
func main() {
_, err := http.Get(`https://graph.facebook.com//v2.4/oauth/access_token`)
if err != nil {
panic(err.Error())
}
}
(22 hrs ago) https://github.com/golang/go/issues/19103

3. Warm up
package main
import "net/http"
func main() {
_, err := http.Get(`https://graph.facebook.com//v2.4/oauth/access_token`)
if err != nil {
panic(err.Error())
}
}
(22 hrs ago) https://github.com/golang/go/issues/19103
x/net/http2: requests with absolute URIs in URL.Opaque produce incorrect :path header
#16847 (2016-08-16)

5. setup

6. SYN attack

7. tear-down

8. TLS exchange

10. socket
message
response
Server Client

11. Packets via intermediate device

12. Ataleoftwoprotocols

13. One TCP connection.
Request → Stream
Streams are multiplexed
Streams are prioritized
Binary Framing Layer
Prioritization
Flow Control
Server Push
Header Compression

14. HTTP/2 Server Push

15. What does all this mean for Go ?
● You got to make “changes” in the library.
● Lots of “small” changes
– Tools
– Libraries
–
● “Context” is critical.

16. Context
● A Context carries
– a deadline
– a cancelation signal
– and other values across API boundaries.
● Context's methods may be called by multiple
goroutines simultaneously.

17. Fix
● The fix tool has a new “context” fix to change
imports from “golang.org/x/net/context” to
“context”.

18. Pprof
● The pprof tool can now profile TLS servers and
skip certificate validation by using the
“https+insecure” URL scheme.

19. Vet
● Vet now checks for copying an array of locks,
duplicate JSON and XML struct field tags, non-
space-separated struct tags, deferred calls to
HTTP Response.Body.Close before
checking errors, and indexed arguments in
Printf.

20. HTTP Server Graceful Shutdown
● The HTTP Server now has support for
– graceful shutdown using the new
Server.Shutdown method
– abrupt shutdown using the new Server.Close
method.

21. HTTP/2 Push
● The net/http package now includes a
mechanism to send HTTP/2 server pushes from
a Handler.
● Similar to the existing Flusher and Hijacker
interfaces, an HTTP/2 ResponseWriter now
implements the new Pusher interface.

22. Context is gonna be HUGE
● new Server.Shutdown takes a context
argument.
● significant additions to the database/sql package
with context support.
● All nine of the new Lookup methods on the new
net.Resolver now take a context.
●

23. crypto/tls
● Conn.CloseWrite allows TLS connections to be
half closed
● Config.Clone clones a TLS configuration.
● Config.GetClientCertificate callback allows
selecting a client certificate based on the
server's TLS CertificateRequest message,
represented by the new CertificateRequestInfo
● Config.KeyLogWriter allows debugging TLS
connections in WireShark
● … more

24. crypto/x509
● PSS signatures are now supported.
● UnknownAuthorityError now has a Cert
field, reporting the untrusted certificate.
● Certificate validation is more permissive in a few
cases and stricter in a few other cases.
● Root certificates will now also be looked for at
/etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem
on Linux, to support RHEL and CentOS.

25. expvar
● Package expvar provides a standardized
interface to public variables
● operation counters in servers.
● exposed via HTTP at /debug/vars in JSON
format.
● new Handler function returns the package's
HTTP handler, to enable installing it in non-
standard locations.
func Handler() http.Handler

26. net
● The new Buffers type permits writing to the
network more efficiently from multiple
discontiguous buffers in memory
● cf. writev
● Scatter – gather
https://linux.die.net/man/2/writev
●

27. net/http/httptrace
● support for tracing a client request's TLS
handshakes
– ClientTrace.TLSHandshakeStart
– ClientTrace.TLSHandshakeDone

28. net/http
● graceful shutdown support
● Server adds configuration options
– ReadHeaderTimeout
– IdleTimeout
– and documents WriteTimeout
● FileServer and ServeContent now support HTTP
If-Match conditional requests (RFC 7232)

29. net/http … server .. Handler
● Context returned by Request.Context is
canceled if the underlying net.Conn closes. For
instance, if the user closes their browser in the
middle of a slow request
● Handler can now detect that the user is gone.
This complements the existing CloseNotifier
support.
● Handler can now abort a response by panicking
with the error ErrAbortHandler.

30. net/http … server .. Handler
● To serve trailers produced after the header has
already been written, see the new TrailerPrefix
mechanism.
● Write of zero bytes to a ResponseWriter is now
defined as a way to test whether a
ResponseWriter has been hijacked
● If so, the Write returns ErrHijacked without
printing an error to the server's error log.

31. net/http … Client
● Client now copies most request headers on
redirect.
● Client now supports 301, 307, and 308 redirects.
● Client.Post now follows 301 redirects, converting
them to GET requests without bodies
● If the redirect requires resending the request
body, the request must have the new
Request.GetBody field defined.
● NewRequest sets Request.GetBody
automatically for common body types.

32. net/http … Transport
● Transport now supports international domain
names.
● Get and other helpers.
● Transport now rejects requests for URLs with
ports containing non-digit characters.
● DefaultTransport.Dialer now enables DualStack
● Transport no longer reads a byte of a non-nil
Request.Body when the Request.ContentLength
is zero to determine whether the ContentLength
is actually zero or just undefined.

33. empty interface
● interface {} may hold values of ANY type

34. References {URL}
● Go 1.8 release notes
https://tip.golang.org/doc/go1.8
● HTTP/2 spec
http://http2.github.io/http2-spec/index.html
● RSA PSS (Probabilistic Signature Scheme)
https://www.emc.com/emc-plus/rsa-labs/historical/ra
●

35. Legal { Attribution(s) }
● The usage of images is purely educational. The
copyright for the images resides with their
respective authros.
● Released under Creative Commons 4.0 Non-
Commercial Share-Alike

36. we use
4.0

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