New feature of go1.18: introduce new netip Network Library

Hello everyone , I'm fried fish .

Writing this article is the first day of the new year , I originally wanted to say that it would be released this month Go1.18 了 . however , good heavens ,Go1.18 beta2 Released , The official informs the community Go1.18 To be dragged to 3 Month. , Cuckoo ...

Here's the picture ：

So we still have to continue to learn new features , Today the fried fish will be combined Brad Fitzpatrick Written 《netaddr.IP: a new IP address type for Go》 Let's get to know Go1.18 New network library net/netip Reason .

background

The big man left

Original Go In the development team Brad Fitzpatrick, stay 2010~2020 All year round Go Team work , stay 2021 The company has changed since .

The following tweets ：

The reason for leaving is ： I have done the same thing for too long , A little bored , Don't want to fall into a comfortable dilemma .

Now it's time to change to Tailscale, do WireGuard Related work , Always deal with network libraries .

Demand is born

Written by big guy company Tailscale, It's essentially a web application , Deal with the Internet , Again Go Written , It will involve the standard library net：

In a single IP Use... In type net.IP.
Use on network presentation net.IPNet.

Sample code ：

import (
    "fmt"
    "net"
)

func main() {
    fmt.Println(net.IPv4(8, 8, 8, 8))
}

Output results ：

8.8.8.8

Brad Fitzpatrick When actually writing and using , Find out net There are many problems with the type of standard library , It's not easy to use .

What's the problem now

Brad Fitzpatrick For the standard library net.IP The problem of , Listed directly in the article , The argument is full .

common 7 A big question ：

It's variable .
net.IP The bottom type of is []byte, This means that anything you pass on to it can change it .
It is not comparable . because Go Medium slice It's not comparable , It means net.IP I won't support it Go Of == Comparison of operators , Can not act as map Of key To use .
It has two kinds of IP Address type , To tangle with net.IP, still net.IPAddr, It's annoying to choose .
It's big .Go Of net.IP contain 2 Parts of , Namely 24 Bytes of slice header and 4/6 Bytes of IP Address . If it is net.IPAddr It also includes Zone Field .
It allocates memory on the heap .Go Of net Packages are distributed everywhere , Put more work on GC On .
It cannot be parsed . Parse from string form IP when ,Go Of IP Type cannot be distinguished IPv4 The mapping of IPv6 Address and IPv4 Address .
It is transparent （transparent type）,net.IP Is defined as ：type IP []byte, Is its public API Part of , Non modifiable .

Brad It was also mentioned that some of them were early designs , I was inexperienced at the time , Or did not consider well .

Now limited by Go1 Compatibility promise , It can't be changed （ Compatibility guarantee double-edged sword ？）.

This is a real version “Eating your own dog food”, So in Tailscale He made another wheel inetaf/netaddr, Want to contribute , Put it into the standard library .

What you want in the future

The comparison table is as follows ：

characteristic	Old scheme net.IP	New scheme
constant	, slice
Comparable	, slice
Small footprint	,28~56 byte	, Fix 24 byte
Do not allocate on the heap
Support IPv4 and IPv6
distinguish IPv4 and IPv6
Support IPv6 Area
Opaque type
Interworking with the standard library		, Adaptation method required

What you want , It's actually Brad Demands from business practice , Is to support the above mentioned 7 spot .

Solution

Current progress

The result of implementation , That is, the new plan has been made , He is inetaf/netaddr This library （ Of course , It does not rule out that it is the result inversion theory ）. And in Go issues To initiate issues and proposal.

Russ Cox Initiated a discussion on the new proposal 《proposal: net/netaddr: add new IP address type, netaddr package (discussion)")》, And be accepted , Into the Go1.18 Among the new features of .

Remanufacture process

new net/netip Every consideration point of the Library ,Brad Are explained in detail in the article .

Limited by length , Let's share two of them , Interested friends can read the analysis part of the original .

Interface type combination

In the matter of comparability ,Go The interface of （interface） Actually, it supports comparison , That is to say, it can be used as map Of key Conduct == Operator comparison .

The first version of the following scheme is implemented , Designed a new netaddr.IP type ：

type IP struct {
  ipImpl
}

type ipImpl interface {
  is4() bool
  is6() bool
  String() string
}

type v4Addr [4]byte
type v6Addr [16]byte
type v6AddrZone struct {
  v6Addr
  zone string
}

The above code , stay IP Added in the structure ipImpl Interface , It can support comparison , You can also avoid exposure （ Opaque type ）, And can support IPv6.

The new problem is , Although it is more original net The small , But I still haven't achieved my goal , There is still the disadvantage of allocating on the heap .

Free of distribution 24 byte

If you continue to use the interface , Is unable to solve the fundamental goal （Brad The goal is 24 byte ） Of .

Because of the interface （interface） Occupy 16 byte , The remaining 8 Bytes can be used , Put the following things ：

Address family （v4、v6, Or neither , Such as ：IP Zero value of ）, Need at least 2 position .
IPv6 Of zone Information .

We should also be able to compare , Obviously, the interface cannot be implemented , Because address +zone Information count bytes , Display is not enough .

There is no way to be formal and explicit ,Brad Thought of using packaging ：

type IP struct {
   addr          [16]byte
   zoneAndFamily uint64
}

But to do so , Means zoneAndFamily The number of digits in the field needs to be calculated , Then push the corresponding value accordingly , But it may not be too much trouble .

Final Brad Think of the , You can use pointers ：

type IP struct {
    addr          [16]byte
    zoneAndFamily *T
}

Redefine 3 The corresponding sentinel values are applied ：

var (
     z0    *intern.Value        //  Indicates a zero value .
     z4    = new(intern.Value)  //  Express  IPv4  Sentinel value of 
     z6noz = new(intern.Value)  //  Express  IPv6  Sentinel value of （ No,  zone）.
)

So we can take IP The type is fixed in 24 byte .

summary

This network address Library , Generally, they are used less . however Brad Fitzpatrick A lot of energy and research have been invested here , Achieved the ultimate goal .

In addition to the functions of the Library , There are many technical optimization points worthy of our study and reference , Interested in further optimization , You can read ：https://tailscale.com/blog/netaddr-new-ip-type-for-go/

This article introduces the new net/netip The library will be in Go1.18 As a new feature , Welcome to study and exchange together ：）

If you have any questions, you are welcome to feedback and exchange in the comments area , The best relationship is mutual achievement , Everyone give the thumbs-up Namely Fried fish The greatest power of creation , Thank you for your support .

Articles are constantly updated , You can search through wechat 【 I have fried fish in my head 】 read , this paper GitHubgithub.com/eddycjy/blog Included , Study Go Language can be seen Go Learn maps and routes , welcome Star Hurry up .