Re: [boost] Need cancel() on async_resolve() to callback the resolve handler immediately

On 8/25/21 11:27 AM, Richard Hodges via Boost wrote:

There are a couple of convoluted ways to build cancellation into the linux resolve() activity. The problem is that the sockets and timers used for this are entirely embedded in the OS-shipped library layer and not accessible to user code. It's a bit of a mess that has never been cleaned up. There isn't much that Asio can do about it.

At present the "cleanest" way is to fork a child process to do the resolve call for you and async_wait on a pipe from that child. If you want to cancel it, send the child a SIGKILL which will result in the wait on the pipe completing with an error.

Ghastly I know...

On Linux, there is also getaddrinfo_a: https://man7.org/linux/man-pages/man3/getaddrinfo_a.3.html which allows to perform name resolution asynchronously, with cancellation. It's a GNU extension. I wonder if it can be incorporated into Boost.ASIO. PS: Please, don't top-post.

On Wed, 25 Aug 2021 at 08:30, sandeep m.v wrote:

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Thank you for the response.

We build our application for multiple platforms, Windows, Linux, Android and iOS. If it is not possible to cancel, is there a way to close internal socket, so that it wont callback resolve handler? By that way, we can at least go ahead with our processing after our internal timeout assuming callback never happen later. Is that something possible?

On Wed, Aug 25, 2021 at 1:29 AM Richard Hodges via Boost < boost@lists.boost.org> wrote:

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On Linux async_resolve is currently implemented in terms of a spawned thread which calls a synchronous function. It has a 30s timeout and can’t be cancelled.

On Tue, 24 Aug 2021 at 21:56, Vinnie Falco via Boost < boost@lists.boost.org> wrote:

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On Tue, Aug 24, 2021 at 12:09 PM sandeep m.v via Boost wrote:

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Can someone please help me with this?

Are you by chance using Windows? What version?

Thanks

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