Fix rpc file getting deleted when launching gsr-ui twice. Use unix domain socket instead

src/Rpc.cpp

@@ -5,11 +5,12 @@
 #include <limits.h>
 #include <string.h>
 #include <errno.h>
-#include <sys/stat.h>
-#include <fcntl.h>
+#include <poll.h>
+#include <sys/socket.h>
+#include <sys/un.h>
 
 namespace gsr {
-    static void get_runtime_filepath(char *buffer, size_t buffer_size, const char *filename) {
+    static void get_socket_filepath(char *buffer, size_t buffer_size, const char *filename) {
         char dir[PATH_MAX];
 
         const char *runtime_dir = getenv("XDG_RUNTIME_DIR");
@@ -24,79 +25,117 @@ namespace gsr {
         snprintf(buffer, buffer_size, "%s/%s", dir, filename);
     }
 
+    static int create_socket(const char *name, struct sockaddr_un *addr, std::string &socket_filepath) {
+        char socket_filepath_tmp[PATH_MAX];
+        get_socket_filepath(socket_filepath_tmp, sizeof(socket_filepath_tmp), name);
+        socket_filepath = socket_filepath_tmp;
+
+        memset(addr, 0, sizeof(*addr));
+        if(strlen(name) > sizeof(addr->sun_path))
+            return false;
+
+        addr->sun_family = AF_UNIX;
+        snprintf(addr->sun_path, sizeof(addr->sun_path), "%s", socket_filepath.c_str());
+
+        return socket(AF_UNIX, SOCK_STREAM | SOCK_NONBLOCK, 0);
+    }
+
+    Rpc::Rpc() {
+        num_polls = 0;
+    }
+
     Rpc::~Rpc() {
-        if(fd > 0)
-            close(fd);
+        if(socket_fd > 0)
+            close(socket_fd);
 
-        if(file)
-            fclose(file);
-
-        if(!fifo_filepath.empty())
-            unlink(fifo_filepath.c_str());
+        if(!socket_filepath.empty())
+            unlink(socket_filepath.c_str());
     }
 
     bool Rpc::create(const char *name) {
-        if(file) {
+        if(socket_fd > 0) {
             fprintf(stderr, "Error: Rpc::create: already created/opened\n");
             return false;
         }
 
-        char fifo_filepath_tmp[PATH_MAX];
-        get_runtime_filepath(fifo_filepath_tmp, sizeof(fifo_filepath_tmp), name);
-        fifo_filepath = fifo_filepath_tmp;
-        unlink(fifo_filepath.c_str());
-
-        if(mkfifo(fifo_filepath.c_str(), 0600) != 0) {
-            fprintf(stderr, "Error: mkfifo failed, error: %s, %s\n", strerror(errno), fifo_filepath.c_str());
-            fifo_filepath.clear();
+        struct sockaddr_un addr;
+        socket_fd = create_socket(name, &addr, socket_filepath);
+        if(socket_fd <= 0) {
+            fprintf(stderr, "Error: Rpc::create: failed to create socket, error: %s\n", strerror(errno));
             return false;
         }
 
-        if(!open_filepath(fifo_filepath.c_str())) {
-            unlink(fifo_filepath.c_str());
-            fifo_filepath.clear();
+        unlink(socket_filepath.c_str());
+
+        if(bind(socket_fd, (struct sockaddr*)&addr, sizeof(addr)) == -1) {
+            const int err = errno;
+            close(socket_fd);
+            socket_fd = 0;
+
+            fprintf(stderr, "Error: Rpc::create: failed to bind, error: %s\n", strerror(err));
             return false;
         }
 
+        if(listen(socket_fd, GSR_RPC_MAX_CONNECTIONS) == -1) {
+            const int err = errno;
+            close(socket_fd);
+            socket_fd = 0;
+
+            fprintf(stderr, "Error: Rpc::create: failed to listen, error: %s\n", strerror(err));
+            return false;
+        }
+
+        polls[0].fd = socket_fd;
+        polls[0].events = POLLIN;
+        polls[0].revents = 0;
+        ++num_polls;
+
         return true;
     }
 
-    bool Rpc::open(const char *name) {
-        if(file) {
+    RpcOpenResult Rpc::open(const char *name) {
+        if(socket_fd > 0) {
             fprintf(stderr, "Error: Rpc::open: already created/opened\n");
-            return false;
+            return RpcOpenResult::ERROR;
         }
 
-        char fifo_filepath_tmp[PATH_MAX];
-        get_runtime_filepath(fifo_filepath_tmp, sizeof(fifo_filepath_tmp), name);
-        return open_filepath(fifo_filepath_tmp);
-    }
-
-    bool Rpc::open_filepath(const char *filepath) {
-        fd = ::open(filepath, O_RDWR | O_NONBLOCK);
-        if(fd <= 0)
-            return false;
-
-        file = fdopen(fd, "r+");
-        if(!file) {
-            close(fd);
-            fd = 0;
-            return false;
+        struct sockaddr_un addr;
+        socket_fd = create_socket(name, &addr, socket_filepath);
+        socket_filepath.clear(); /* We dont want to delete the socket on exit as the client */
+        if(socket_fd <= 0) {
+            fprintf(stderr, "Error: Rpc::open: failed to create socket, error: %s\n", strerror(errno));
+            return RpcOpenResult::ERROR;
         }
-        fd = 0;
-        return true;
+
+        while(true) {
+            if(connect(socket_fd, (struct sockaddr*)&addr, sizeof(addr)) == -1) {
+                const int err = errno;
+                if(err == EWOULDBLOCK) {
+                    usleep(10 * 1000);
+                } else {
+                    close(socket_fd);
+                    socket_fd = 0;
+                    if(err != ENOENT && err != ECONNREFUSED)
+                        fprintf(stderr, "Error: Rpc::create: failed to connect, error: %s\n", strerror(err));
+                    return RpcOpenResult::ERROR;
+                }
+            } else {
+                break;
+            }
+        }
+
+        return RpcOpenResult::OK;
     }
 
     bool Rpc::write(const char *str, size_t size) {
-        if(!file) {
-            fprintf(stderr, "Error: Rpc::write: fifo not created/opened yet\n");
+        if(socket_fd <= 0) {
+            fprintf(stderr, "Error: Rpc::write: unix domain socket not created/opened yet\n");
             return false;
         }
 
         ssize_t offset = 0;
         while(offset < (ssize_t)size) {
-            const ssize_t bytes_written = fwrite(str + offset, 1, size - offset, file);
-            fflush(file);
+            const ssize_t bytes_written = ::write(socket_fd, str + offset, size - offset);
             if(bytes_written > 0)
                 offset += bytes_written;
         }
@@ -104,30 +143,73 @@ namespace gsr {
     }
 
     void Rpc::poll() {
-        if(!file) {
-            //fprintf(stderr, "Error: Rpc::poll: fifo not created/opened yet\n");
+        if(socket_fd <= 0) {
+            //fprintf(stderr, "Error: Rpc::poll: unix domain socket not created/opened yet\n");
             return;
         }
 
         std::string name;
-        char line[1024];
-        while(fgets(line, sizeof(line), file)) {
-            int line_len = strlen(line);
-            if(line_len == 0)
-                continue;
+        while(::poll(polls, num_polls, 0) > 0) {
+            for(int i = 0; i < num_polls; ++i) {
+                if(polls[i].fd == socket_fd) {
+                    if(polls[i].revents & (POLLERR|POLLHUP)) {
+                        close(socket_fd);
+                        socket_fd = 0;
+                        return;
+                    }
 
-            if(line[line_len - 1] == '\n') {
-                line[line_len - 1] = '\0';
-                --line_len;
+                    const int client_fd = accept(socket_fd, NULL, NULL);
+                    if(num_polls >= GSR_RPC_MAX_POLLS) {
+                        if(errno != EWOULDBLOCK)
+                            fprintf(stderr, "Error: Rpc::poll: unable to accept more clients, error: %s\n", strerror(errno));
+                    } else {
+                        polls[num_polls].fd = client_fd;
+                        polls[num_polls].events = POLLIN;
+                        polls[num_polls].revents = 0;
+                        ++num_polls;
+                    }
+                    continue;
+                }
+
+                if(polls[i].revents & POLLIN)
+                    handle_client_data(polls[i].fd, polls_data[i]);
+
+                if(polls[i].revents & (POLLERR|POLLHUP)) {
+                    close(polls[i].fd);
+                    polls[i] = polls[num_polls - 1];
+
+                    memcpy(polls_data[i].buffer, polls_data[num_polls - 1].buffer, polls_data[num_polls - 1].buffer_size);
+                    polls_data[i].buffer_size = polls_data[num_polls - 1].buffer_size;
+
+                    --num_polls;
+                    --i;
+                }
             }
-
-            name = line;
-            auto it = handlers_by_name.find(name);
-            if(it != handlers_by_name.end())
-                it->second(name);
         }
     }
 
+    void Rpc::handle_client_data(int client_fd, PollData &poll_data) {
+        char *write_buffer = poll_data.buffer + poll_data.buffer_size;
+        const ssize_t num_bytes_read = read(client_fd, write_buffer, sizeof(poll_data.buffer) - poll_data.buffer_size);
+        if(num_bytes_read <= 0)
+            return;
+
+        poll_data.buffer_size += num_bytes_read;
+        const char *newline_p = (const char*)memchr(write_buffer, '\n', num_bytes_read);
+        if(!newline_p)
+            return;
+
+        const size_t command_size = newline_p - poll_data.buffer;
+        std::string name;
+        name.assign(poll_data.buffer, command_size);
+        memmove(poll_data.buffer, newline_p + 1, poll_data.buffer_size - (command_size + 1));
+        poll_data.buffer_size -= (command_size + 1);
+
+        auto it = handlers_by_name.find(name);
+        if(it != handlers_by_name.end())
+            it->second(name);
+    }
+
     bool Rpc::add_handler(const std::string &name, RpcCallback callback) {
         return handlers_by_name.insert(std::make_pair(name, std::move(callback))).second;
     }