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Sending data and file descriptors at the same time #541

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#562
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Sending data and file descriptors at the same time#541
#562

Description

@chris-martin
chris-martin
opened on Mar 18, 2023

From my brief experimentation with Wayland, it has seemed like the Wayland server expects that when you send a message with a file descriptor parameter, it expects the message and the fd to be sent together in a single sendmsg call. The network library presently does not have any explicit support for doing this.

Currently, in my own code I have a copy of NullSocketAddress, which is internally defined in the network package but not exported.

data NullSocketAddress = NullSocketAddress

instance SocketAddress NullSocketAddress where
    sizeOfSocketAddress _ = 0
    peekSocketAddress _ = return NullSocketAddress
    pokeSocketAddress _ _ = return ()

So then I can use sendBufMsg the way the network package does internally...

Network.Socket.Address.sendBufMsg socket NullSocketAddress datas controls mempty

... where datas contains the wayland message and controls contains the file descriptor.

Proposal one (nearly no effort): It would be nice if the network library simply exported the NullSocketAddress type so that I could use it instead of duplicating it.

Proposal two (slightly more work): Some explicit support for sending data and file descriptors in a single call?

sendWithFds :: Socket -> [ByteString] -> [Fd] -> IO ()

Activity

  1. kazu-yamamoto commented on Mar 20, 2023

    @kazu-yamamoto
    kazu-yamamoto
    on Mar 20, 2023
    Collaborator

    I'm sorry but I don't understand this proposal a bit. Where can I find NullSocketAddress?

  2. chris-martin commented on Mar 20, 2023

    @chris-martin
    chris-martin
    on Mar 20, 2023
    ContributorAuthor

    I apologize, I forgot the words aren't completely spelled. I was attempting to refer to NullSockAddr.

  3. kazu-yamamoto commented on Mar 21, 2023

    @kazu-yamamoto
    kazu-yamamoto
    on Mar 21, 2023
    Collaborator

    OK. I understand.

    Which do you prefer:

    1. Exporting NullSockAddr only
    2. Defining sendWithFds with NullSockAddr hidden

  4. chris-martin commented on Mar 21, 2023

    @chris-martin
    chris-martin
    on Mar 21, 2023
    ContributorAuthor

    If I could only choose one, I'd prefer the second.

  5. kazu-yamamoto commented on Mar 22, 2023

    @kazu-yamamoto
    kazu-yamamoto
    on Mar 22, 2023
    Collaborator

    OK. Would you make a PR including the followings?

    • Implementing sendWithFds
    • Exporting NullSockAddr from Internal

  6. chris-martin commented on Mar 22, 2023

    @chris-martin
    chris-martin
    on Mar 22, 2023
    ContributorAuthor

    Sounds good, will do when I find some time.

  7. kazu-yamamoto commented on May 17, 2023

    @kazu-yamamoto
    kazu-yamamoto
    on May 17, 2023
    Collaborator

    @chris-martin Gentle ping.

  8. chris-martin
    added a commit that references this issue on Jun 27, 2023

    expose NullSockAddr, add send-with-fds functions

    12aaeec
  9. kazu-yamamoto
    closed this as completedin 12aaeecon Jun 28, 2023
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