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LibIPC+LibWeb: Add an IPC helper to transfer an IPC message buffer
This large block of code is repeated nearly verbatim in LibWeb. Move it to a helper function that both LibIPC and LibWeb can defer to. This will let us make changes to this method in a singular location going forward. Note this is a bit of a regression for the MessagePort. It now suffers from the same performance issue that IPC messages face - we prepend the meessage size to the message buffer. This degredation is very temporary though, as a fix is imminent, and this change makes that fix easier.
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6 changed files with 72 additions and 91 deletions
62
Userland/Libraries/LibIPC/Message.cpp
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62
Userland/Libraries/LibIPC/Message.cpp
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/*
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* Copyright (c) 2024, Tim Flynn <trflynn89@serenityos.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <LibCore/Socket.h>
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#include <LibIPC/Message.h>
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#include <sched.h>
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namespace IPC {
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using MessageSizeType = u32;
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ErrorOr<void> MessageBuffer::transfer_message(Core::LocalSocket& fd_passing_socket, Core::LocalSocket& data_socket)
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{
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MessageSizeType message_size = data.size();
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TRY(data.try_prepend(reinterpret_cast<u8 const*>(&message_size), sizeof(message_size)));
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for (auto const& fd : fds)
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TRY(fd_passing_socket.send_fd(fd->value()));
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ReadonlyBytes bytes_to_write { data.span() };
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size_t writes_done = 0;
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while (!bytes_to_write.is_empty()) {
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auto maybe_nwritten = data_socket.write_some(bytes_to_write);
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++writes_done;
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if (maybe_nwritten.is_error()) {
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if (auto error = maybe_nwritten.release_error(); error.is_errno()) {
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// FIXME: This is a hacky way to at least not crash on large messages
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// The limit of 100 writes is arbitrary, and there to prevent indefinite spinning on the EventLoop
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if (error.code() == EAGAIN && writes_done < 100) {
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sched_yield();
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continue;
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}
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switch (error.code()) {
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case EPIPE:
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return Error::from_string_literal("IPC::transfer_message: Disconnected from peer");
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case EAGAIN:
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return Error::from_string_literal("IPC::transfer_message: Peer buffer overflowed");
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default:
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return Error::from_syscall("IPC::transfer_message write"sv, -error.code());
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}
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} else {
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return error;
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}
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}
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bytes_to_write = bytes_to_write.slice(maybe_nwritten.value());
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}
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if (writes_done > 1) {
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dbgln("LibIPC::transfer_message FIXME Warning, needed {} writes needed to send message of size {}B, this is pretty bad, as it spins on the EventLoop", writes_done, data.size());
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}
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return {};
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}
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}
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