Add a http server proxy for better youtube downloading (bypassing rate limit cased by http range header). Fix youtube live streams

1 files changed, 733 insertions, 0 deletions

diff --git a/src/plugins/youtube/YoutubeMediaProxy.cpp b/src/plugins/youtube/YoutubeMediaProxy.cpp
new file mode 100644
index 0000000..e8d0383
--- /dev/null
+++ b/src/plugins/youtube/YoutubeMediaProxy.cpp
@@ -0,0 +1,733 @@
+#include "../../../plugins/youtube/YoutubeMediaProxy.hpp"
+#include "../../../include/NetUtils.hpp"
+
+#include <vector>
+#include <stdio.h>
+#include <string.h>
+#include <errno.h>
+#include <signal.h>
+#include <assert.h>
+
+#include <unistd.h>
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <fcntl.h>
+
+// TODO: What if the client sends a new header without reconnecting? is that even allowed by http standard?
+// TODO: Detect when download has finished (and close connection).
+
+namespace QuickMedia {
+    static const int MAX_BUFFER_SIZE = 65536;
+    static const int RANGE = 524287;
+    static const char download_error_response_msg[] = 
+        "HTTP/1.1 500 Internal Server Error\r\n"
+        "Content-Length: 0\r\n\r\n";
+
+    static bool set_non_blocking(int fd) {
+        const int flags = fcntl(fd, F_GETFL, 0);
+        if(fd == -1 || fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1)
+            return false;
+        return true;
+    }
+
+    // TODO: Restrict range end to remote file size (content-length which we have saved).
+    // TODO: Check if custom youtube redirect code is needed
+    bool YoutubeMediaProxy::start_download(const std::string &media_url, ReadProgram &read_program, int range_start, bool include_header, bool is_livestream, int livestream_sequence) {
+        std::string r = std::to_string(range_start) + "-" + std::to_string(range_start + RANGE);
+
+        std::string url = media_url + "&rn=" + std::to_string(rn) + "&rbuf=" + std::to_string(rbuf);
+        std::vector<const char*> args = { "curl",
+            //"-H", "Accept-Language: en-US,en;q=0.5", "-H", "Connection: keep-alive",
+            //"-H", "user-agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/81.0.4044.138 Safari/537.36",
+            "-g", "-s", "-L", "-f" };
+
+        if(is_livestream) {
+            if(livestream_sequence != -1)
+                url += "&sq=" + std::to_string(livestream_sequence);
+        } else {
+            args.insert(args.end(), { "-r", r.c_str() });
+        }
+
+        if(include_header)
+            args.push_back("-i");
+
+        //fprintf(stderr, "url: %s\n", url.c_str());
+
+        args.insert(args.end(), { "--", url.c_str(), nullptr });
+
+        if(exec_program_pipe(args.data(), &read_program) != 0)
+            return false;
+
+        if(!set_non_blocking(read_program.read_fd)) {
+            perror("start_download: failed to set curl pipe non blocking mode");
+            close(read_program.read_fd);
+            kill(read_program.pid, SIGTERM);
+            read_program.read_fd = -1;
+            read_program.pid = -1;
+            return false;
+        }
+
+        ++rn;
+        rbuf += 3000;
+        if(rbuf > 75000) rbuf = 75000;
+        return true;
+    }
+
+    YoutubeStaticMediaProxy::~YoutubeStaticMediaProxy() {
+        stop();
+    }
+
+    bool YoutubeStaticMediaProxy::start(const std::string &youtube_media_url, int content_length) {
+        if(socket_fd != -1)
+            return false;
+
+        socket_fd = socket(AF_INET, SOCK_STREAM, 0);
+        if(socket_fd == -1) {
+            perror("YoutubeStaticMediaProxy::start: socket failed");
+            return false;
+        }
+
+        socklen_t response_sock_addr_len;
+        struct sockaddr_in server_addr;
+        memset(&server_addr, 0, sizeof(server_addr));
+        server_addr.sin_family = AF_INET;
+        server_addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
+        server_addr.sin_port = htons(0);
+
+        if(bind(socket_fd, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
+            perror("YoutubeStaticMediaProxy::start: bind failed");
+            goto err;
+        }
+
+        if(listen(socket_fd, 2) == -1) {
+            perror("YoutubeStaticMediaProxy::start: listen failed");
+            goto err;
+        }
+
+        if(!set_non_blocking(socket_fd)) {
+            perror("YoutubeStaticMediaProxy::start: failed to set socket non blocking mode");
+            goto err;
+        }
+
+        struct sockaddr_in response_sock_addr;
+        response_sock_addr_len = sizeof(response_sock_addr);
+        if(getsockname(socket_fd, (struct sockaddr*)&response_sock_addr, &response_sock_addr_len) == -1) {
+            perror("YoutubeStaticMediaProxy::start: getsockname failed");
+            goto err;
+        }
+
+        port = ntohs(response_sock_addr.sin_port);
+        this->youtube_media_url = youtube_media_url;
+        this->content_length = content_length;
+        return true;
+
+        err:
+        if(downloader_read_program.read_fd != -1)
+            close(downloader_read_program.read_fd);
+        if(downloader_read_program.pid != -1)
+            kill(downloader_read_program.pid, SIGTERM);
+        close(socket_fd);
+        socket_fd = -1;
+        return false;
+    }
+
+    void YoutubeStaticMediaProxy::stop() {
+        if(downloader_read_program.read_fd != -1) {
+            close(downloader_read_program.read_fd);
+            downloader_read_program.read_fd = -1;
+        }
+
+        if(downloader_read_program.pid != -1) {
+            kill(downloader_read_program.pid, SIGTERM);
+            wait_program(downloader_read_program.pid);
+            downloader_read_program.pid = -1;
+        }
+
+        if(client_fd != -1) {
+            close(client_fd);
+            client_fd = -1;
+        }
+
+        if(socket_fd != -1) {
+            close(socket_fd);
+            socket_fd = -1;
+        }
+
+        clear_download_state();
+        client_request_buffer.clear();
+        client_request_finished = false;
+    }
+
+    YoutubeStaticMediaProxy::Error YoutubeStaticMediaProxy::update() {
+        if(socket_fd == -1)
+            return Error::OK;
+
+        if(client_fd == -1) {
+            client_fd = accept_client();
+            if(client_fd == -1)
+                return Error::OK;
+        } else {
+            const int new_client_fd = accept_client();
+            if(new_client_fd != -1) {
+                on_client_disconnect();
+                client_fd = new_client_fd;
+            }
+        }
+
+        Error err = read_client_data();
+        if(err != Error::OK || !client_request_finished)
+            return err;
+        if(downloader_read_program.pid == -1)
+            return Error::ERROR;
+        return handle_download();
+    }
+
+    bool YoutubeStaticMediaProxy::get_address(std::string &address) {
+        if(socket_fd == -1)
+            return false;
+
+        address = "http://127.0.0.1:" + std::to_string(port);
+        return true;
+    }
+
+    void YoutubeStaticMediaProxy::on_client_disconnect() {
+        client_request_buffer.clear();
+        client_request_finished = false;
+
+        if(client_fd != -1) {
+            close(client_fd);
+            client_fd = -1;
+        }
+
+        if(downloader_read_program.pid != -1)
+            kill(downloader_read_program.pid, SIGTERM);
+
+        update_download_program_status(true);
+    }
+
+    // Returns 0 if start range is not found
+    static int header_extract_start_range(const std::string &header) {
+        std::string range = header_extract_value(header, "range");
+        if(range.empty())
+            return 0;
+
+        int start_range = 0;
+        if(sscanf(range.c_str(), " bytes=%d", &start_range) != 1)
+            return 0;
+
+        return start_range;
+    }
+
+    // TODO: What about hls (live streams)? need to test with that. There may not be a need to use YoutubeMediaProxy for that case (in that case document it).
+    YoutubeStaticMediaProxy::Error YoutubeStaticMediaProxy::read_client_data() {
+        if(client_request_finished)
+            return Error::OK;
+
+        char read_buffer[4096];
+        const ssize_t num_bytes_read = read(client_fd, read_buffer, sizeof(read_buffer));
+        if(num_bytes_read == -1) {
+            const int err = errno;
+            if(err == EAGAIN || err == EWOULDBLOCK) {
+                return Error::OK;
+            } else if(err == EPIPE || err == ECONNRESET) {
+                //fprintf(stderr, "YoutubeStaticMediaProxy::read_client_data: client disconnected\n");
+                on_client_disconnect();
+                return Error::ERROR;
+            } else {
+                perror("YoutubeStaticMediaProxy::read_client_data: read failed");
+                return Error::ERROR;
+            }
+        } else if(num_bytes_read == 0) {
+            //fprintf(stderr, "YoutubeStaticMediaProxy::read_client_data: client disconnected\n");
+            on_client_disconnect();
+            return Error::ERROR;
+        }
+
+        client_request_buffer.append(read_buffer, num_bytes_read);
+        const size_t header_end = client_request_buffer.find("\r\n\r\n");
+        if(header_end != std::string::npos) {
+            client_request_buffer.erase(header_end + 4);
+            client_request_finished = true;
+
+            int new_start_range = header_extract_start_range(client_request_buffer);
+            //fprintf(stderr, "got new range from client: %d\n", new_start_range);
+            if(new_start_range >= 0) {
+                if(downloader_read_program.pid != -1) {
+                    kill(downloader_read_program.pid, SIGTERM);
+                    wait_program(downloader_read_program.pid);
+                    downloader_read_program.pid = -1;
+                }
+                clear_download_state();
+                update_download_program_status(false, new_start_range, true);
+            }
+        } else {
+            if(client_request_buffer.size() > MAX_BUFFER_SIZE) {
+                client_request_finished = true;
+                fprintf(stderr, "YoutubeStaticMediaProxy::read_client_data: buffer is full (malicious client?)\n");
+                return Error::ERROR;
+            }
+        }
+        return Error::OK;
+    }
+
+    void YoutubeStaticMediaProxy::clear_download_state() {
+        download_header.clear();
+        download_header_finished = false;
+        download_header_sent = false;
+        download_header_remaining_sent = false;
+        download_header_written_offset = 0;
+    }
+
+    YoutubeStaticMediaProxy::Error YoutubeStaticMediaProxy::update_download_program_status(bool client_disconnected, int new_range_start, bool restart_download) {
+        int program_status = 0;
+        if(downloader_read_program.pid != -1) {
+            if(client_disconnected) {
+                wait_program(downloader_read_program.pid);
+            } else {
+                if(!wait_program_non_blocking(downloader_read_program.pid, &program_status))
+                    return Error::OK;
+            }
+            downloader_read_program.pid = -1;
+        }
+        
+        if(downloader_read_program.read_fd != -1) {
+            close(downloader_read_program.read_fd);
+            downloader_read_program.read_fd = -1;
+        }
+
+        // TODO: Why is this not 0 when download finishes?
+        if(program_status != 0) {
+            //fprintf(stderr, "YoutubeStaticMediaProxy::update_download_program_status: download failed, exit status: %d\n", program_status);
+            if(client_fd != -1) {
+                write(client_fd, download_error_response_msg, sizeof(download_error_response_msg) - 1);
+                close(client_fd);
+                client_fd = -1;
+                client_request_buffer.clear();
+                client_request_finished = false;
+            }
+            return Error::ERROR;
+        }
+
+        if(client_disconnected) {
+            current_download_range = 0;
+        } else {
+            current_download_range += RANGE + 1;
+        }
+
+        if(new_range_start != -1) {
+            download_range_start = new_range_start;
+            current_download_range = download_range_start;
+        }
+
+        if(new_range_start == -1) {
+            download_header_finished = true;
+            download_header_sent = true;
+            download_header_remaining_sent = true;
+        } else {
+            clear_download_state();
+        }
+
+        if(client_disconnected) {
+            clear_download_state();
+            return Error::ERROR;
+        }
+
+        if(!restart_download)
+            return Error::OK;
+
+        const bool start_download_success = start_download(youtube_media_url, downloader_read_program, current_download_range, new_range_start != -1);
+        if(!start_download_success) {
+            fprintf(stderr, "YoutubeStaticMediaProxy::update_download_program_status: failed to start download\n");
+            if(client_fd != -1) {
+                write(client_fd, download_error_response_msg, sizeof(download_error_response_msg) - 1);
+                close(client_fd);
+                client_fd = -1;
+                client_request_buffer.clear();
+                client_request_finished = false;
+            }
+
+            clear_download_state();
+            return Error::ERROR;
+        }
+
+        return Error::OK;
+    }
+
+    static void header_replace_content_length(std::string &header, size_t header_size, int new_content_length) {
+        if(new_content_length < 0)
+            new_content_length = 0;
+
+        const char *content_length_p = strcasestr(header.c_str(), "content-length:");
+        if(!content_length_p)
+            return;
+
+        const size_t content_length_start = (content_length_p + 15) - header.c_str();
+        if(content_length_start >= header_size)
+            return;
+        const size_t line_end = header.find("\r\n", content_length_start);
+        header.replace(content_length_start, line_end - content_length_start, std::to_string(new_content_length));
+    }
+
+    YoutubeStaticMediaProxy::Error YoutubeStaticMediaProxy::continue_send(const char *buffer_start, size_t total_bytes_to_write, int &buffer_offset) {
+        int num_bytes_to_write = total_bytes_to_write - buffer_offset;
+        //assert(num_bytes_to_write >= 0);
+        if(num_bytes_to_write < 0) num_bytes_to_write = 0;
+        if(num_bytes_to_write == 0) {
+            buffer_offset = 0;
+            return Error::OK;
+        }
+
+        const ssize_t num_bytes_written = write(client_fd, buffer_start + buffer_offset, num_bytes_to_write);
+        if(num_bytes_written == -1) {
+            const int err = errno;
+            if(err == EAGAIN || err == EWOULDBLOCK) {
+                return Error::OK;
+            } else if(err == EPIPE || err == ECONNRESET) {
+                //fprintf(stderr, "YoutubeStaticMediaProxy::continue_send: client disconnected\n");
+                on_client_disconnect();
+                return Error::ERROR;
+            } else {
+                perror("YoutubeStaticMediaProxy::continue_send: write failed");
+                return Error::ERROR;
+            }
+        } else if(num_bytes_written == 0) {
+            //fprintf(stderr, "YoutubeStaticMediaProxy::continue_send: client disconnected\n");
+            on_client_disconnect();
+            return Error::ERROR;
+        } else if(num_bytes_written != num_bytes_to_write) {
+            buffer_offset += num_bytes_written;
+        } else {
+            buffer_offset = 0;
+        }
+        return Error::OK;
+    }
+
+    static bool http_is_redirect(const char *header, size_t size) {
+        const void *end_of_first_line_p = memmem(header, size, "\r\n", 2);
+        if(!end_of_first_line_p)
+            return false;
+        return memmem(header, (const char*)end_of_first_line_p - header, " 30", 3) != nullptr;
+    }
+
+    static size_t find_start_of_first_non_redirect_header(const char *headers, size_t size, size_t &header_end) {
+        const char *start = headers;
+        while(size > 0) {
+            const void *end_of_header = memmem(headers, size, "\r\n\r\n", 4);
+            if(!end_of_header)
+                return std::string::npos;
+
+            const size_t offset_to_end_of_headers = ((const char*)end_of_header + 4) - headers;
+            if(!http_is_redirect(headers, offset_to_end_of_headers)) {
+                header_end = (headers - start) + offset_to_end_of_headers;
+                return headers - start;
+            }
+
+            headers += offset_to_end_of_headers;
+            size -= offset_to_end_of_headers;
+        }
+        return std::string::npos;
+    }
+
+    YoutubeStaticMediaProxy::Error YoutubeStaticMediaProxy::handle_download() {
+        // TODO: Maybe read even if write is being slow and failing?
+        if(download_read_buffer_offset == 0) {
+            downloader_num_read_bytes = read(downloader_read_program.read_fd, download_read_buffer, sizeof(download_read_buffer));
+            if(downloader_num_read_bytes == -1) {
+                const int err = errno;
+                if(err == EAGAIN || err == EWOULDBLOCK) {
+                    return Error::OK;
+                } else {
+                    perror("YoutubeStaticMediaProxy::handle_download: curl read failed");
+                    return Error::ERROR;
+                }
+            } else if(downloader_num_read_bytes == 0) {
+                Error err = update_download_program_status(false, -1, true);
+                if(err != Error::OK)
+                    return err;
+            }
+        }
+
+        if(!download_header_finished) {
+            download_header.append(download_read_buffer, downloader_num_read_bytes);
+            size_t header_end = std::string::npos;
+            const size_t offset_to_start_of_header = find_start_of_first_non_redirect_header(download_header.c_str(), download_header.size(), header_end);
+            if(header_end != std::string::npos) {
+                download_header.erase(0, offset_to_start_of_header);
+                header_end -= offset_to_start_of_header;
+
+                download_header_finished = true;
+                download_header_sent = false;
+                download_header_remaining_sent = false;
+                download_header_written_offset = 0;
+                download_header_offset_to_end_of_header = header_end;
+                download_read_buffer_offset = -1;
+
+                header_replace_content_length(download_header, header_end, content_length - download_range_start);
+            } else {
+                if(download_header.size() > MAX_BUFFER_SIZE) {
+                    fprintf(stderr, "YoutubeStaticMediaProxy::handle_download: buffer is full (malicious server?)\n");
+                    if(downloader_read_program.pid != -1) {
+                        kill(downloader_read_program.pid, SIGTERM);
+                        wait_program(downloader_read_program.pid);
+                        downloader_read_program.pid = -1;
+                    }
+                    clear_download_state();
+                    update_download_program_status(false, 0, false);
+                    return Error::ERROR;
+                }
+            }
+        }
+
+        if(download_header_finished && !download_header_sent) {
+            Error err = continue_send(download_header.data(), download_header_offset_to_end_of_header, download_header_written_offset);
+            if(err != Error::OK)
+                return err;
+
+            if(download_header_written_offset == 0) {
+                download_header_sent = true;
+                download_header_written_offset = download_header_offset_to_end_of_header;
+            }
+        }
+
+        if(download_header_finished && !download_header_remaining_sent) {
+            Error err = continue_send(download_header.data(), download_header.size(), download_header_written_offset);
+            if(err != Error::OK)
+                return err;
+
+            if(download_header_written_offset == 0) {
+                download_header_remaining_sent = true;
+                download_read_buffer_offset = 0;
+                return Error::OK;
+            }
+        }
+
+        if(download_header_remaining_sent)
+            return continue_send(download_read_buffer, downloader_num_read_bytes, download_read_buffer_offset);
+
+        return Error::OK;
+    }
+
+    int YoutubeStaticMediaProxy::accept_client() {
+        struct sockaddr_in client_addr;
+        socklen_t client_addr_len = sizeof(client_addr);
+        int new_client_fd = accept(socket_fd, (struct sockaddr*)&client_addr, &client_addr_len);
+        if(new_client_fd == -1) {
+            const int err = errno;
+            if(err == EAGAIN || err == EWOULDBLOCK) {
+                return -1;
+            } else {
+                perror("YoutubeStaticMediaProxy::accept_client accept failed");
+                return -1;
+            }
+        }
+
+        if(!set_non_blocking(new_client_fd)) {
+            perror("YoutubeStaticMediaProxy::accept_client: failed to set client socket non blocking mode");
+            close(new_client_fd);
+            return -1;
+        }
+
+        //fprintf(stderr, "YoutubeStaticMediaProxy::accept_client: client connected!\n");
+        return new_client_fd;
+    }
+
+    YoutubeLiveStreamMediaProxy::~YoutubeLiveStreamMediaProxy() {
+        stop();
+    }
+
+    bool YoutubeLiveStreamMediaProxy::start(const std::string &youtube_media_url, int) {
+        fd[0] = -1;
+        fd[1] = -1;
+        if(pipe(fd) == -1) {
+            perror("YoutubeLiveStreamMediaProxy::start: failed to open pipe");
+            return false;
+        }
+
+       //if(socketpair(AF_UNIX, SOCK_STREAM, 0, fd) == -1) {
+       //    perror("YoutubeLiveStreamMediaProxy::start: failed to open pipe");
+       //    return false;
+       //}
+
+        for(int i = 0; i < 2; ++i) {
+            if(!set_non_blocking(fd[i])) {
+                stop();
+                return false;
+            }
+        }
+
+        if(!start_download(youtube_media_url, downloader_read_program, 0, true, true)) {
+            stop();
+            return false;
+        }
+
+        this->youtube_media_url = youtube_media_url;
+        return true;
+    }
+
+    void YoutubeLiveStreamMediaProxy::stop() {
+        for(int i = 0; i < 2; ++i) {
+            if(fd[i] != -1) {
+                close(fd[i]);
+                fd[i] = -1;
+            }
+        }
+
+        if(downloader_read_program.read_fd != -1) {
+            close(downloader_read_program.read_fd);
+            downloader_read_program.read_fd = -1;
+        }
+
+        if(downloader_read_program.pid != -1) {
+            kill(downloader_read_program.pid, SIGTERM);
+            wait_program(downloader_read_program.pid);
+            downloader_read_program.pid = -1;
+        }
+    }
+
+    YoutubeMediaProxy::Error YoutubeLiveStreamMediaProxy::update_download_program_status() {
+        int program_status = 0;
+        if(!wait_program_non_blocking(downloader_read_program.pid, &program_status))
+            return Error::OK;
+
+        downloader_read_program.pid = -1;
+        if(downloader_read_program.read_fd != -1) {
+            close(downloader_read_program.read_fd);
+            downloader_read_program.read_fd = -1;
+        }
+
+        // TODO: Why is this not 0 when download finishes?
+        if(program_status != 0) {
+            //fprintf(stderr, "YoutubeLiveStreamMediaProxy::update_download_program_status: download failed, exit status: %d\n", program_status);
+            stop();
+            return Error::ERROR;
+        }
+
+        ++livestream_sequence_num;
+        const bool start_download_success = start_download(youtube_media_url, downloader_read_program, 0, false, true, livestream_sequence_num);
+        if(!start_download_success) {
+            fprintf(stderr, "YoutubeLiveStreamMediaProxy::update_download_program_status: failed to start download\n");
+            stop();
+            return Error::ERROR;
+        }
+
+        return Error::OK;
+    }
+
+    YoutubeMediaProxy::Error YoutubeLiveStreamMediaProxy::continue_send(const char *buffer_start, size_t total_bytes_to_write, int &buffer_offset) {
+        int num_bytes_to_write = total_bytes_to_write - buffer_offset;
+        //assert(num_bytes_to_write >= 0);
+        if(num_bytes_to_write < 0) num_bytes_to_write = 0;
+        if(num_bytes_to_write == 0) {
+            buffer_offset = 0;
+            return Error::OK;
+        }
+
+        const ssize_t num_bytes_written = write(fd[1], buffer_start + buffer_offset, num_bytes_to_write);
+        if(num_bytes_written == -1) {
+            const int err = errno;
+            if(err == EAGAIN || err == EWOULDBLOCK) {
+                return Error::OK;
+            } else if(err == EPIPE || err == ECONNRESET) {
+                //fprintf(stderr, "YoutubeLiveStreamMediaProxy::continue_send: client disconnected\n");
+                stop();
+                return Error::ERROR;
+            } else {
+                perror("YoutubeLiveStreamMediaProxy::continue_send: write failed");
+                return Error::ERROR;
+            }
+        } else if(num_bytes_written == 0) {
+            //fprintf(stderr, "YoutubeLiveStreamMediaProxy::continue_send: client disconnected\n");
+            stop();
+            return Error::ERROR;
+        } else if(num_bytes_written != num_bytes_to_write) {
+            buffer_offset += num_bytes_written;
+        } else {
+            buffer_offset = 0;
+        }
+        return Error::OK;
+    }
+
+    YoutubeMediaProxy::Error YoutubeLiveStreamMediaProxy::update() {
+        if(fd[1] == -1 || downloader_read_program.read_fd == -1)
+            return Error::OK;
+
+        if(download_read_buffer_offset == 0) {
+            downloader_num_read_bytes = read(downloader_read_program.read_fd, download_read_buffer, sizeof(download_read_buffer));
+            if(downloader_num_read_bytes == -1) {
+                const int err = errno;
+                if(err == EAGAIN || err == EWOULDBLOCK) {
+                    return Error::OK;
+                } else {
+                    perror("YoutubeLiveStreamMediaProxy::update: curl read failed");
+                    return Error::ERROR;
+                }
+            } else if(downloader_num_read_bytes == 0) {
+                Error err = update_download_program_status();
+                if(err != Error::OK)
+                    return err;
+            }
+        }
+
+        if(!download_header_finished) {
+            download_header.append(download_read_buffer, downloader_num_read_bytes);
+            size_t header_end = std::string::npos;
+            const size_t offset_to_start_of_header = find_start_of_first_non_redirect_header(download_header.c_str(), download_header.size(), header_end);
+            if(header_end != std::string::npos) {
+                download_header.erase(0, offset_to_start_of_header);
+                header_end -= offset_to_start_of_header;
+
+                download_header_finished = true;
+                download_header_remaining_sent = false;
+                download_header_written_offset = header_end;
+                download_read_buffer_offset = -1;
+                fprintf(stderr, "header: |%.*s|\n", download_header_written_offset, download_header.c_str());
+
+                if(livestream_sequence_num == -1) {
+                    // TODO: What about |header_end|?
+                    std::string sequence_num = header_extract_value(download_header, "x-sequence-num");
+                    fprintf(stderr, "server sequence num: |%s|\n", sequence_num.c_str());
+                    if(sequence_num.empty())
+                        fprintf(stderr, "YoutubeLiveStreamMediaProxy::handle_download: missing sequence num from server\n");
+                    else
+                        livestream_sequence_num = strtol(sequence_num.c_str(), nullptr, 10);
+                }
+            } else {
+                if(download_header.size() > MAX_BUFFER_SIZE) {
+                    fprintf(stderr, "YoutubeLiveStreamMediaProxy::handle_download: buffer is full (malicious server?)\n");
+                    if(downloader_read_program.pid != -1) {
+                        kill(downloader_read_program.pid, SIGTERM);
+                        wait_program(downloader_read_program.pid);
+                        downloader_read_program.pid = -1;
+                    }
+                    download_header_finished = true;
+                    return Error::ERROR;
+                }
+            }
+        }
+
+        if(download_header_finished && !download_header_remaining_sent) {
+            Error err = continue_send(download_header.data(), download_header.size(), download_header_written_offset);
+            if(err != Error::OK)
+                return err;
+
+            if(download_header_written_offset == 0) {
+                download_header_remaining_sent = true;
+                download_read_buffer_offset = 0;
+                return Error::OK;
+            }
+        }
+
+        if(download_header_remaining_sent)
+            return continue_send(download_read_buffer, downloader_num_read_bytes, download_read_buffer_offset);
+
+        return Error::OK;
+    }
+
+    bool YoutubeLiveStreamMediaProxy::get_address(std::string &address) {
+        if(fd[0] == -1)
+            return false;
+
+        address = "fd://" + std::to_string(fd[0]);
+        return true;
+    }
+}
\ No newline at end of file