Setting SO_BINDTODEVICE to a TCPConn

[Elazar Leibovich]

Some socket options must be set before calling "connect" on the socket.

How can I produce a TCPConn whose socket options are set.

For example, how can I create a TCPConn whose socket have SO_BINDTODEVICE set? Since TCPConn is private, I cannot produce it on my own, and the only way to do that (without reimplementing the interface), is to use Dial(), which will already connect the socket to its destination.

What's the best way to solve this issue?

[C Banning]

extend Mike Andrews hack: https://groups.google.com/forum/#!topic/golang-nuts/4J-B29Fnb00

[Elazar Leibovich]

Thanks, but I'd rather not patch Go if possible.

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[Kyle Lemons]

I think you should be able to make all of the syscalls yourself to set up the socket and then when you want it to become a net.Conn you call http://godoc.org/net/#FileConn

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[Elazar Leibovich]

This is a good idea, thanks.

Though, I'll have to replicate the logic in Dial.

[Mikio Hara]

On Wed, Mar 5, 2014 at 6:37 AM, Elazar Leibovich <ela...@gmail.com> wrote:

> Though, I'll have to replicate the logic in Dial.

Unfortunately, but SO_BINDTODEVICE (via syscall.BindToDeivice) is
Linux-specific stuff and also the behavior is a bit strange; different
btw IPv4 and IPv6, trying to override source/destination address
selection on IP packet routing. I have no clue how we can bring this
sort of feature into package net without unnecessary confusion.

[Elazar Leibovich]

Very simply, allow a callback accepting fd to the dialer struct.

Dialer{FDCallback:func(fd int){}}.Dial(...)

[Mikio Hara]

a nit. ;)

On Wed, Mar 5, 2014 at 6:49 AM, Elazar Leibovich <ela...@gmail.com> wrote:

> Dialer{FDCallback:func(fd int){}}.Dial(...)

We cannot drop windows support, and are not keen on exposing raw
socket descriptor or windows handle.

[amba...@defend7.com]

Hi Elazar,

     I just ran into this problem. Used introspection to get access to private variables....

Here is quick writeup I did about how I did the setsockopt.....

http://funwithandroid.blogspot.com/2014/08/doing-setsockopt-in-go.html

Do let me know if this helps.

Ambarish

[Elazar Leibovich]

Thanks,

This would work, but is obviously due to breakage in any Go release. Reminds me this story about Facebook app using a similar "solution":

[0] https://www.facebook.com/notes/facebook-engineering/under-the-hood-dalvik-patch-for-facebook-for-android/10151345597798920

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