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net: add (*Resolver).ResolveIPAddr #30452

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iangudger opened this issue Feb 28, 2019 · 17 comments
Closed

net: add (*Resolver).ResolveIPAddr #30452

iangudger opened this issue Feb 28, 2019 · 17 comments

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@iangudger
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@iangudger iangudger commented Feb 28, 2019

In the net package, there are two classes of DNS functions: LookupXxx and ResolveXxx. The net.Resolver type implements the LookupXxx functions as methods, but not the ResolveXxx functions. The ResolveXxx functions are similar to LookupHost, except they allow specifying a network. Adding the ResolveXxx functions as methods will allow a net.Resolver to fully replace the global DNS functions.

@gopherbot gopherbot added this to the Proposal milestone Feb 28, 2019
@gopherbot gopherbot added the Proposal label Feb 28, 2019
@bcmills
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@bcmills bcmills commented Feb 28, 2019

@bradfitz
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@bradfitz bradfitz commented Feb 28, 2019

I'm fine with that on principle. I'd never noticed you couldn't do IPv4- vs IPv6-specific lookups on Resolver before. That is, you can't do the equivalent of this today on Resolver:

func main() {
        fmt.Println(net.ResolveIPAddr("ip4", "google.com"))
        fmt.Println(net.ResolveIPAddr("ip6", "google.com"))
}

The name Resolver.ResolveIPAddr is a bit stuttery but probably best for consistency. But I'd also be fine with Resolver.LookupNetIPAddr or something.

@rsc
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@rsc rsc commented Mar 6, 2019

It's unclear why we should add net.Resolver.ResolveIPAddr; why not just use LookupIPAddr and filter out what you want? ResolveIPAddr is just LookupIPAddr plus client-side filtering anyway. It's not any fewer bits on the wire.

@iangudger
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@iangudger iangudger commented Mar 6, 2019

Sure, it can be done, but it would be nice to not make everyone who wants it re-implement it.

@bradfitz
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@bradfitz bradfitz commented Mar 27, 2019

I'm inclined to add this. @rsc, it is fewer bytes on the wire, in both directions: only asking for A or AAAA instead of both, and only getting answers for what we asked for.

@rsc
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@rsc rsc commented Apr 24, 2019

Today we have:

func (r *Resolver) LookupIPAddr(ctx context.Context, host string) ([]IPAddr, error)

We need a new name for the function that takes a network. It would be good to keep the Lookup prefix common to all the other methods.

Maybe it would be enough to shorten to "LookupIP":

func (r *Resolver) LookupIP(ctx context.Context, net, host string) ([]IPAddr, error)

where net is either "ip4" or "ip6".

Do we really need IPAddr in the return type vs plain IP? Can DNS return a zone?

@rsc
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@rsc rsc commented May 7, 2019

@iangudger, any thoughts on the questions in the previous comment? If that API is OK then I think we're close to accepting the proposal. Thanks for your help and your patience.

@iangudger
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@iangudger iangudger commented May 7, 2019

Sounds good to me.

@andybons andybons changed the title proposal: net: add (*Resolver).ResolveIPAddr net: add (*Resolver).ResolveIPAddr May 14, 2019
@andybons andybons modified the milestones: Proposal, Go1.14 May 14, 2019
@rsc rsc modified the milestones: Go1.14, Backlog Oct 9, 2019
@odeke-em
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@odeke-em odeke-em commented Apr 9, 2020

Howdy @iangudger, kindly pinging you as this proposal was approved almost a year ago. The Go tree closes in 3 weeks so if we’d like to see this for Go1.15, we’ve got a window of opportunity. Thank you!

@gopherbot
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@gopherbot gopherbot commented Apr 17, 2020

Change https://golang.org/cl/228641 mentions this issue: net: add (*Resolver).LookupIP

@odeke-em
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@odeke-em odeke-em commented Apr 17, 2020

@rsc, @iangudger @bradfitz @andybons and @golang/proposal-review, I just gave @iangudger a code review in https://go-review.googlesource.com/c/go/+/228641/ and I realized that perhaps the name that we
considered has a couple of problems:
a) There already exists a package level LookuIP; by convention we previously had package level functions that invoked the respectively named methods on the DefaultResolveer
b) The package level ResolveIPAddr(network, address string) (*IPAddr, error) has a signature that returns only a single IPAddr pointer so even a Resolver based ResolveIPAddr of signature (r *Resolver) LookupIP(ctx context.Context, network, host string) ([]IPAddr, error) would be inconsistent, and the name is also stuttery as @bradfitz pointed out

I think @bradfitz's suggestion in #30452 (comment) of

Resolver.LookupNetIPAddr(ctx context.Context, network, host string) ([]IPAddr, error)

might be the best suited, or

Resolver.LookupIPAddrByNetwork(ctx context.Context, network, host string) ([]IPAddr, error)

would suffice. The code otherwise LGTM, but I think that the name will make or break us and inconsistencies might make it harder later on for users to navigate through the net package.

Thank you.

@iangudger
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@iangudger iangudger commented Apr 28, 2020

Ping @rsc, @bradfitz, @andybons and @golang/proposal-review.

@bradfitz
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@bradfitz bradfitz commented Apr 28, 2020

We never got an answer on @rsc's question:

Do we really need IPAddr in the return type vs plain IP? Can DNS return a zone?

If not, then we could just return []IP instead of []IPAddr and then its name LookupIP matches func LookupIP(host string) ([]IP, error) except for the addition of context + network which seems fine.

@iangudger
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@iangudger iangudger commented Apr 28, 2020

AAAA records cannot contain a zone, so I think []IP should be fine.

@bradfitz
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@bradfitz bradfitz commented Apr 28, 2020

Phew. That's what I thought & hoped. (Was worried I missed some RFC.)

Let's go with []IP then.

gopherbot pushed a commit that referenced this issue Apr 28, 2020
Previously, looking up only IPv4 or IPv6 addresses was only possible
with DefaultResolver via ResolveIPAddr. Add this functionality to the
Resolver type with a new method, LookupIP. This largely brings Resolver
functionally to parity with the global functions. The name LookupIP is
used over ResolveIPAddr to be consistent with the other Resolver
methods.

There are two main benefits to (*Resolver).LookupIP over
(*Resolver).LookupHost. First is an ergonomic benefit. Wanting a
specific family of address is common enough to justify a method, evident
by the existence of ResolveIPAddr. Second, this opens the possibility of
not performing unnecessary DNS requests when only a specific family of
addresses are needed. This optimization is left to follow up work.

Updates #30452

Change-Id: I241f61019588022a39738f8920b0ddba900cecdd
Reviewed-on: https://go-review.googlesource.com/c/go/+/228641
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
xujianhai666 added a commit to xujianhai666/go-1 that referenced this issue May 21, 2020
Previously, looking up only IPv4 or IPv6 addresses was only possible
with DefaultResolver via ResolveIPAddr. Add this functionality to the
Resolver type with a new method, LookupIP. This largely brings Resolver
functionally to parity with the global functions. The name LookupIP is
used over ResolveIPAddr to be consistent with the other Resolver
methods.

There are two main benefits to (*Resolver).LookupIP over
(*Resolver).LookupHost. First is an ergonomic benefit. Wanting a
specific family of address is common enough to justify a method, evident
by the existence of ResolveIPAddr. Second, this opens the possibility of
not performing unnecessary DNS requests when only a specific family of
addresses are needed. This optimization is left to follow up work.

Updates golang#30452

Change-Id: I241f61019588022a39738f8920b0ddba900cecdd
Reviewed-on: https://go-review.googlesource.com/c/go/+/228641
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
@tmthrgd
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@tmthrgd tmthrgd commented May 24, 2020

Should CL 228641 have closed this issue?

@ianlancetaylor ianlancetaylor mentioned this issue Jun 12, 2020
133 of 133 tasks complete
@ianlancetaylor
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@ianlancetaylor ianlancetaylor commented Jun 19, 2020

As far as I can tell, this is done. Thanks.

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