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mdlayher opened this issue Apr 10, 2017 · 9 comments
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x/net/bpf: add Setter interface #19912

mdlayher opened this issue Apr 10, 2017 · 9 comments
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FrozenDueToAge NeedsFix The path to resolution is known, but the work has not been done. Proposal Proposal-Accepted
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@mdlayher
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In order to standardize BPF filter attachment in Go, I propose an interface which mimics the most popular signature used in the wild:

package bpf

// A Setter is a type which can attach a compiled BPF filter to itself.
type Setter interface {
    SetBPF(filter []bpf.RawInstruction) error
}

I believe this pattern was first used in x/net/ipv{4,6}:

https://godoc.org/golang.org/x/net/ipv4#PacketConn.SetBPF
https://godoc.org/golang.org/x/net/ipv6#PacketConn.SetBPF

I've used it in a couple of my own repositories as well:

https://godoc.org/github.com/mdlayher/raw#Conn.SetBPF
https://godoc.org/github.com/mdlayher/netlink#Conn.SetBPF

Finally, on at least two occasions, I have defined an unexported interface that contains a method using this proposed interface:

https://github.com/coreos/torus/blob/master/block/aoe/aoe.go#L106-L111
https://github.com/mdlayher/netlink/blob/master/conn.go#L230-L234

For simplicity and standardization, I'd like to add the proposed interface to x/net/bpf's API, in order to ensure consistency between types that can attach a BPF filter to themselves.

/cc @danderson, @mikioh, @breml
@mdlayher mdlayher added this to the Proposal milestone Apr 10, 2017
@rsc
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rsc commented Apr 17, 2017

Given that this interface is already implemented by x/net/ipv4 and x/net/ipv6, it seems fine to add the interface definition too. Any thoughts, @danderson, @mikioh?

@mikioh
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mikioh commented Apr 18, 2017

I'll leave it up to @danderson.

@mikioh
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mikioh commented Jun 2, 2017

ping @danderson

@danderson
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The interface definition seems fine, however: what benefit does it provide? I don't understand what benefit this definition provides, given that the package itself doesn't make use of it. My first instinct is that this is an attempt to define a java-style interface that other packages can implements... Except that this isn't needed in Go. So, I'm just confused :)

What am I missing?

@danderson
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To be clear: if the intent is just to try and steer implementors to standardize on using that method signature to attach BPF programs, sure, I'm happy to go along with it. It just makes me feel a bit strange to have a package define an interface exclusively as a "serving suggestion" for other packages. If I'm alone in feeling weird about that, then definitely let's do it :)

@mdlayher
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mdlayher commented Jun 6, 2017

Hmmm, not sure how I missed this notification, sorry!

To be clear: if the intent is just to try and steer implementors to standardize on using that method signature to attach BPF programs, sure, I'm happy to go along with it.

That's exactly it. Think of it like the interfaces defined in: https://golang.org/pkg/encoding/.

@gopherbot
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CL https://golang.org/cl/44972 mentions this issue.

@rsc
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rsc commented Jun 12, 2017

@danderson, OK to accept this proposal?

@danderson
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LGTM, ship it.

@bradfitz bradfitz changed the title proposal: x/net/bpf: add Setter interface x/net/bpf: add Setter interface Jun 12, 2017
@bradfitz bradfitz added the NeedsFix The path to resolution is known, but the work has not been done. label Jun 12, 2017
@bradfitz bradfitz modified the milestones: Unreleased, Proposal Jun 12, 2017
@golang golang locked and limited conversation to collaborators Jun 13, 2018
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