| 1 | // Copyright (C) Microsoft Corporation. All rights reserved. |
| 2 | // SPDX-License-Identifier: MIT |
| 3 | #pragma once |
| 4 | |
| 5 | #include <poll.h> |
| 6 | #include <signal.h> |
| 7 | #include <sys/signalfd.h> |
| 8 | #include "lxwil.h" |
| 9 | #include "Forwarder.h" |
| 10 | #include "Packet.h" |
| 11 | #include "Syscall.h" |
| 12 | |
| 13 | #include <stdio.h> |
| 14 | |
| 15 | #define _countof(a) (sizeof(a) / sizeof(*(a))) |
| 16 | |
| 17 | template <typename ProcessingFunction, typename ExceptionHandler> |
| 18 | Forwarder<ProcessingFunction, ExceptionHandler>::Forwarder(int SourceFd, int DestinationFd, ProcessingFunction Handler, ExceptionHandler exceptionHandler) |
| 19 | { |
| 20 | // Create a pipe to signal the thread to stop. |
| 21 | int pipes[2]; |
| 22 | Syscall(pipe2, pipes, 0); |
| 23 | TerminateFd = pipes[1]; |
| 24 | |
| 25 | Worker = std::thread([=]() { |
| 26 | try |
| 27 | { |
| 28 | wil::unique_fd terminate = pipes[0]; |
| 29 | auto wait_for_fd = [&terminate](int fd, int event) -> bool { |
| 30 | struct pollfd poll_fds[2]; |
| 31 | poll_fds[0] = {.fd = fd, .events = event, .revents = 0}; |
| 32 | poll_fds[1] = {.fd = terminate.get(), .events = POLLIN, .revents = 0}; |
| 33 | for (;;) |
| 34 | { |
| 35 | const int return_value = poll(poll_fds, _countof(poll_fds), -1); |
| 36 | if (return_value < 0) |
| 37 | { |
| 38 | if (errno == EINTR) |
| 39 | { |
| 40 | continue; |
| 41 | } |
| 42 | |
| 43 | throw std::runtime_error(std::string("poll returned ") + std::string(strerror(errno))); |
| 44 | } |
| 45 | else if (return_value == 0) |
| 46 | { |
| 47 | continue; |
| 48 | } |
| 49 | else if (poll_fds[1].revents) |
| 50 | { |
| 51 | return false; |
| 52 | } |
| 53 | else if (poll_fds[0].revents & event) |
| 54 | { |
| 55 | return true; |
| 56 | } |
| 57 | } |
| 58 | }; |
| 59 | |
| 60 | Packet packet; |
| 61 | for (;;) |
| 62 | { |
| 63 | packet.reset(); |
| 64 | |
| 65 | // Grow the packet to provide space. |
| 66 | packet.adjust_tail(Packet::InitialPacketSize); |
| 67 | if (!wait_for_fd(SourceFd, POLLIN)) |
| 68 | { |
| 69 | break; |
| 70 | } |
| 71 | |
| 72 | int bytes_read = Syscall(read, SourceFd, packet.data(), packet.data_end() - packet.data()); |
| 73 | |
| 74 | // Shrink packet to size of data read. |
| 75 | packet.adjust_tail(bytes_read - (packet.data_end() - packet.data())); |
| 76 | |
| 77 | // If the handler returns true, write the packet to the destination fd. |
| 78 | if (Handler(packet)) |
| 79 | { |
| 80 | if (!wait_for_fd(DestinationFd, POLLOUT)) |
| 81 | { |
| 82 | break; |
| 83 | } |
| 84 | |
| 85 | Syscall(write, DestinationFd, packet.data(), packet.data_end() - packet.data()); |
| 86 | } |
| 87 | } |
| 88 | } |
| 89 | catch (std::exception& e) |
| 90 | { |
| 91 | if (!exceptionHandler(e)) |
| 92 | { |
| 93 | throw; |
| 94 | } |
| 95 | } |
| 96 | }); |
| 97 | } |
| 98 | |
| 99 | template <typename ProcessingFunction, typename ExceptionHandler> |
| 100 | Forwarder<ProcessingFunction, ExceptionHandler>::~Forwarder() |
| 101 | { |
| 102 | // Close the write end of the pipe to signal the thread to stop. |
| 103 | close(TerminateFd); |
| 104 | if (Worker.joinable()) |
| 105 | { |
| 106 | Worker.join(); |
| 107 | } |
| 108 | } |