IpcServer.cpp

/******************************************************************************
IPC - Simple cross-platform C++ IPC library
Copyright (c) 2024, Marcus Tomlinson

BSD 2-Clause License

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

1. Redistributions of source code must retain the above copyright notice, this
   list of conditions and the following disclaimer.

2. Redistributions in binary form must reproduce the above copyright notice,
   this list of conditions and the following disclaimer in the documentation
   and/or other materials provided with the distribution.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
******************************************************************************/

#include <IpcServer.h>

#include <IpcCommon.h>
#include <IpcMessage.h>

using namespace Ipc;

namespace Ipc::Private
{

class ServerImpl final
{
public:
    explicit ServerImpl( const std::filesystem::path& path )
        : socketPath( path.string() )
    {
        std::error_code err;
        std::filesystem::create_directories( path.parent_path(), err );

#ifdef _WIN32
        WSADATA wsd;
        if ( WSAStartup( WINSOCK_VERSION, &wsd ) != 0 )
        {
            initError = "WSAStartup() failed";
            return;
        }
#endif

        if ( socketPath.length() > sizeof( sockaddr_un::sun_path ) )
        {
            initError = "socket path too long: " + socketPath;
            return;
        }

        // Create a AF_UNIX stream server socket
        serverSocket = socket( AF_UNIX, SOCK_STREAM, 0 );
        if ( serverSocket == INVALID_SOCKET )
        {
            initError = "socket() failed (error: " + std::to_string( lastError() ) + ")";
            return;
        }

        memset( &socketAddr, 0, sizeof( socketAddr ) );
        socketAddr.sun_family = AF_UNIX;
        strncpy( socketAddr.sun_path, socketPath.c_str(), socketPath.length() );

#ifdef _WIN32
        int timeout = 2000;
        setsockopt( serverSocket, SOL_SOCKET, SO_SNDTIMEO, reinterpret_cast<const char*>( &timeout ),
                    sizeof( timeout ) );
        setsockopt( serverSocket, SOL_SOCKET, SO_RCVTIMEO, reinterpret_cast<const char*>( &timeout ),
                    sizeof( timeout ) );
#else
        struct timeval timeout;
        timeout.tv_sec = 2;
        timeout.tv_usec = 0;
        setsockopt( serverSocket, SOL_SOCKET, SO_SNDTIMEO, static_cast<const void*>( &timeout ), sizeof( timeout ) );
        setsockopt( serverSocket, SOL_SOCKET, SO_RCVTIMEO, static_cast<const void*>( &timeout ), sizeof( timeout ) );
#endif

        // Bind the socket to the path
        remove( socketPath.c_str() );
        if ( bind( serverSocket, reinterpret_cast<const sockaddr*>( &socketAddr ), sizeof( socketAddr ) ) ==
             SOCKET_ERROR )
        {
            initError = "bind() failed (error: " + std::to_string( lastError() ) + ")";
            closesocket( serverSocket );
            serverSocket = INVALID_SOCKET;
            return;
        }

        // Listen to start accepting connections
        if ( listen( serverSocket, SOMAXCONN ) == SOCKET_ERROR )
        {
            initError = "listen() failed (error: " + std::to_string( lastError() ) + ")";
            closesocket( serverSocket );
            serverSocket = INVALID_SOCKET;
            return;
        }
    }

    ~ServerImpl()
    {
        if ( serverSocket != INVALID_SOCKET )
        {
            closesocket( serverSocket );
        }

        remove( socketPath.c_str() );
#ifdef _WIN32
        WSACleanup();
#endif
    }

    Message Listen( const std::function<Message( const Message& header, const Message& message )>& callback )
    {
        if ( serverSocket == INVALID_SOCKET )
        {
            return Message( initError, true );
        }

        // Accept a connection
        fd_set fd;
        FD_ZERO( &fd );
        FD_SET( serverSocket, &fd );

        if ( select( (int)serverSocket + 1, &fd, nullptr, nullptr, nullptr ) <= 0 )
        {
            return Message( "select() failed (error: " + std::to_string( lastError() ) + ")", true );
        }

        SOCKET clientSocket = accept( serverSocket, NULL, NULL );
        if ( clientSocket == INVALID_SOCKET )
        {
            return Message( "accept() failed (error: " + std::to_string( lastError() ) + ")", true );
        }

#ifdef _WIN32
        int timeoutMs = 2000;

        setsockopt( clientSocket, SOL_SOCKET, SO_SNDTIMEO, reinterpret_cast<const char*>( &timeoutMs ),
                    sizeof( timeoutMs ) );
        setsockopt( clientSocket, SOL_SOCKET, SO_RCVTIMEO, reinterpret_cast<const char*>( &timeoutMs ),
                    sizeof( timeoutMs ) );
#else
        struct timeval timeout;
        timeout.tv_sec = 2;
        timeout.tv_usec = 0;

        setsockopt( clientSocket, SOL_SOCKET, SO_SNDTIMEO, static_cast<const void*>( &timeout ), sizeof( timeout ) );
        setsockopt( clientSocket, SOL_SOCKET, SO_RCVTIMEO, static_cast<const void*>( &timeout ), sizeof( timeout ) );
#endif

        // Receive header data
        auto recvHeaderBytes = Receive( clientSocket );
        if ( recvHeaderBytes.empty() )
        {
            if ( lastError() == 0 || lastError() == EINVAL )
            {
                closesocket( clientSocket );
                return Message( "" );
            }

            closesocket( clientSocket );
            return Message( "header recv() failed (error: " + std::to_string( lastError() ) + ")", true );
        }

        // Send ack
        if ( !Send( clientSocket, std::vector<unsigned char>{ 1 } ) )
        {
            closesocket( clientSocket );
            return Message( "ack send() failed (error: " + std::to_string( lastError() ) + ")", true );
        }

        // Receive message data
        auto recvMessageBytes = Receive( clientSocket );
        if ( recvMessageBytes.empty() )
        {
            closesocket( clientSocket );
            return Message( "message recv() failed (error: " + std::to_string( lastError() ) + ")", true );
        }

        // Send some data
        auto sendMessage = callback( recvHeaderBytes, recvMessageBytes );
        if ( !Send( clientSocket, sendMessage ) )
        {
            closesocket( clientSocket );
            return Message( "response send() failed (error: " + std::to_string( lastError() ) + ")", true );
        }

        closesocket( clientSocket );
        return Message( "" );
    }

    Message StopListening() const
    {
        SOCKET clientSocket = socket( AF_UNIX, SOCK_STREAM, PF_UNSPEC );
        if ( clientSocket == INVALID_SOCKET )
        {
            return Message( "socket() failed (error: " + std::to_string( lastError() ) + ")", true );
        }

        if ( connect( clientSocket, reinterpret_cast<const sockaddr*>( &socketAddr ), sizeof( socketAddr ) ) ==
             SOCKET_ERROR )
        {
            closesocket( clientSocket );
            return Message( "connect() failed (error: " + std::to_string( lastError() ) + ")", true );
        }

        closesocket( clientSocket );
        return Message( "" );
    }

    static bool Send( SOCKET clientSocket, const Message& message )
    {
        int sendResult = send( clientSocket, reinterpret_cast<const char*>( message.AsRaw() ), (int)message.Size(), 0 );
        if ( sendResult == SOCKET_ERROR )
        {
            return false;
        }
        return true;
    }

    std::vector<unsigned char> Receive( SOCKET clientSocket )
    {
        std::vector<unsigned char> result;

        int recvResult = 0;
        int recvFlags = 0;
        do
        {
            recvResult = recv( clientSocket, reinterpret_cast<char*>( recvBytes ), c_recvBufferSize, recvFlags );
            if ( recvResult > 0 )
            {
                result.insert( result.end(), recvBytes, recvBytes + recvResult );
#ifdef _WIN32
                u_long opt = 1;
                ioctlsocket( clientSocket, FIONBIO, &opt );
#else
                recvFlags = MSG_DONTWAIT;
#endif
            }
            else if ( recvResult < 0 )
            {
                auto const errCode = lastError();
#ifdef _WIN32
                if ( errCode != WSAEWOULDBLOCK )
#else
                if ( errCode != EWOULDBLOCK )
#endif
                {
                    result.clear();
                }
            }
        } while ( recvResult > 0 );

#ifdef _WIN32
        u_long opt = 0;
        ioctlsocket( clientSocket, FIONBIO, &opt );
#endif

        return result;
    }

    std::string initError;
    SOCKET serverSocket = INVALID_SOCKET;
    std::string socketPath = "";
    sockaddr_un socketAddr;
    unsigned char recvBytes[c_recvBufferSize] = {};
};

}  // namespace Ipc::Private

Server::Server( const std::filesystem::path& socketPath )
    : p( std::make_unique<Private::ServerImpl>( socketPath ) )
{
}

Server::~Server() = default;

Message Server::Listen( const std::function<Message( const Message& header, const Message& message )>& callback )
{
    return p->Listen( callback );
}

Message Server::StopListening()
{
    return p->StopListening();
}