libxl: Introduce a QMP client

QMP stands for QEMU Monitor Protocol and it is used to query information
from QEMU or to control QEMU.

This implementation will ask QEMU the list of chardevice and store the
path to serial ports in xenstored. So we will be able to use xl console
with QEMU upstream.

In order to connect to the QMP server, a socket file is created in
/var/run/xen/qmp-libxl-$(domid).

Signed-off-by: Anthony PERARD <anthony.perard@citrix.com>
Committed-by: Ian Jackson <ian.jackson@eu.citrix.com>

1 files changed, 595 insertions, 0 deletions

diff --git a/tools/libxl/libxl_qmp.c b/tools/libxl/libxl_qmp.c
new file mode 100644
index 0000000000..8cda29d300
--- /dev/null
+++ b/tools/libxl/libxl_qmp.c
@@ -0,0 +1,595 @@
+/*
+ * Copyright (C) 2011      Citrix Ltd.
+ * Author Anthony PERARD <anthony.perard@citrix.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ */
+
+/*
+ * This file implement a client for QMP (QEMU Monitor Protocol). For the
+ * Specification, see in the QEMU repository.
+ */
+
+#include <unistd.h>
+#include <sys/un.h>
+#include <sys/queue.h>
+#include <fcntl.h>
+
+#include <yajl/yajl_gen.h>
+
+#include "libxl_internal.h"
+
+/* #define DEBUG_RECEIVED */
+
+#ifdef DEBUG_RECEIVED
+#  define DEBUG_REPORT_RECEIVED(buf, len) \
+    LIBXL__LOG(qmp->ctx, LIBXL__LOG_DEBUG, "received: '%.*s'", len, buf)
+#else
+#  define DEBUG_REPORT_RECEIVED(buf, len) ((void)0)
+#endif
+
+/*
+ * QMP types & constant
+ */
+
+#define QMP_RECEIVE_BUFFER_SIZE 4096
+
+typedef int (*qmp_callback_t)(libxl__qmp_handler *qmp,
+                              const libxl__json_object *tree);
+
+typedef struct callback_id_pair {
+    int id;
+    qmp_callback_t callback;
+    SIMPLEQ_ENTRY(callback_id_pair) next;
+} callback_id_pair;
+
+struct libxl__qmp_handler {
+    struct sockaddr_un addr;
+    int qmp_fd;
+    bool connected;
+    time_t timeout;
+    /* wait_for_id will be used by the synchronous send function */
+    int wait_for_id;
+
+    char buffer[QMP_RECEIVE_BUFFER_SIZE];
+    libxl__yajl_ctx *yajl_ctx;
+
+    libxl_ctx *ctx;
+    uint32_t domid;
+
+    int last_id_used;
+    SIMPLEQ_HEAD(callback_list, callback_id_pair) callback_list;
+};
+
+static int qmp_send(libxl__qmp_handler *qmp,
+                    const char *cmd, qmp_callback_t callback);
+
+static const int QMP_SOCKET_CONNECT_TIMEOUT = 5;
+
+/*
+ * QMP callbacks functions
+ */
+
+static int store_serial_port_info(libxl__qmp_handler *qmp,
+                                  const char *chardev,
+                                  int port)
+{
+    libxl__gc gc = LIBXL_INIT_GC(qmp->ctx);
+    char *path = NULL;
+    int ret = 0;
+
+    if (!(chardev && strncmp("pty:", chardev, 4) == 0)) {
+        return -1;
+    }
+
+    path = libxl__xs_get_dompath(&gc, qmp->domid);
+    path = libxl__sprintf(&gc, "%s/serial/%d/tty", path, port);
+
+    ret = libxl__xs_write(&gc, XBT_NULL, path, "%s", chardev + 4);
+
+    libxl__free_all(&gc);
+    return ret;
+}
+
+static int register_serials_chardev_callback(libxl__qmp_handler *qmp,
+                                             const libxl__json_object *o)
+{
+    const libxl__json_object *obj = NULL;
+    const libxl__json_object *label = NULL;
+    const char *s = NULL;
+    int i = 0;
+    const char *chardev = NULL;
+    int ret = 0;
+
+    for (i = 0; (obj = libxl__json_array_get(o, i)); i++) {
+        if (!libxl__json_object_is_map(obj))
+            continue;
+        label = libxl__json_map_get("label", obj, JSON_STRING);
+        s = libxl__json_object_get_string(label);
+
+        if (s && strncmp("serial", s, strlen("serial")) == 0) {
+            const libxl__json_object *filename = NULL;
+            char *endptr = NULL;
+            int port_number;
+
+            filename = libxl__json_map_get("filename", obj, JSON_STRING);
+            chardev = libxl__json_object_get_string(filename);
+
+            s += strlen("serial");
+            port_number = strtol(s, &endptr, 10);
+            if (*s == 0 || *endptr != 0) {
+                LIBXL__LOG(qmp->ctx, LIBXL__LOG_ERROR,
+                           "Invalid serial port number: %s", s);
+                return -1;
+            }
+            ret = store_serial_port_info(qmp, chardev, port_number);
+            if (ret) {
+                LIBXL__LOG_ERRNO(qmp->ctx, LIBXL__LOG_ERROR,
+                                 "Failed to store serial port information"
+                                 " in xenstore");
+                return ret;
+            }
+        }
+    };
+
+    return ret;
+}
+
+static int qmp_capabilities_callback(libxl__qmp_handler *qmp,
+                                     const libxl__json_object *o)
+{
+    qmp->connected = true;
+
+    return 0;
+}
+
+/*
+ * QMP commands
+ */
+
+static int enable_qmp_capabilities(libxl__qmp_handler *qmp)
+{
+    return qmp_send(qmp, "qmp_capabilities", qmp_capabilities_callback);
+}
+
+/*
+ * Helpers
+ */
+
+static libxl__qmp_message_type qmp_response_type(libxl__qmp_handler *qmp,
+                                                 const libxl__json_object *o)
+{
+    libxl__qmp_message_type type;
+    libxl__json_map_node *node = NULL;
+    int i = 0;
+
+    for (i = 0; (node = libxl__json_map_node_get(o, i)); i++) {
+        if (libxl__qmp_message_type_from_string(node->map_key, &type) == 0)
+            return type;
+    }
+
+    return LIBXL__QMP_MESSAGE_TYPE_INVALID;
+}
+
+static callback_id_pair *qmp_get_callback_from_id(libxl__qmp_handler *qmp,
+                                                  const libxl__json_object *o)
+{
+    const libxl__json_object *id_object = libxl__json_map_get("id", o,
+                                                              JSON_INTEGER);
+    int id = -1;
+    callback_id_pair *pp = NULL;
+
+    if (id_object) {
+        id = libxl__json_object_get_integer(id_object);
+
+        SIMPLEQ_FOREACH(pp, &qmp->callback_list, next) {
+            if (pp->id == id) {
+                return pp;
+            }
+        }
+    }
+    return NULL;
+}
+
+static void qmp_handle_error_response(libxl__qmp_handler *qmp,
+                                      const libxl__json_object *resp)
+{
+    callback_id_pair *pp = qmp_get_callback_from_id(qmp, resp);
+
+    resp = libxl__json_map_get("error", resp, JSON_MAP);
+    resp = libxl__json_map_get("desc", resp, JSON_STRING);
+
+    if (pp) {
+        pp->callback(qmp, NULL);
+        if (pp->id == qmp->wait_for_id) {
+            /* tell that the id have been processed */
+            qmp->wait_for_id = 0;
+        }
+        SIMPLEQ_REMOVE(&qmp->callback_list, pp, callback_id_pair, next);
+        free(pp);
+    }
+
+    LIBXL__LOG(qmp->ctx, LIBXL__LOG_ERROR,
+               "received an error message from QMP server: %s",
+               libxl__json_object_get_string(resp));
+}
+
+static int qmp_handle_response(libxl__qmp_handler *qmp,
+                               const libxl__json_object *resp)
+{
+    libxl__qmp_message_type type = LIBXL__QMP_MESSAGE_TYPE_INVALID;
+
+    type = qmp_response_type(qmp, resp);
+    LIBXL__LOG(qmp->ctx, LIBXL__LOG_DEBUG,
+               "message type: %s", libxl__qmp_message_type_to_string(type));
+
+    switch (type) {
+    case LIBXL__QMP_MESSAGE_TYPE_QMP:
+        /* On the greeting message from the server, enable QMP capabilities */
+        enable_qmp_capabilities(qmp);
+        break;
+    case LIBXL__QMP_MESSAGE_TYPE_RETURN: {
+        callback_id_pair *pp = qmp_get_callback_from_id(qmp, resp);
+
+        if (pp) {
+            pp->callback(qmp,
+                         libxl__json_map_get("return", resp, JSON_ANY));
+            if (pp->id == qmp->wait_for_id) {
+                /* tell that the id have been processed */
+                qmp->wait_for_id = 0;
+            }
+            SIMPLEQ_REMOVE(&qmp->callback_list, pp, callback_id_pair, next);
+            free(pp);
+        }
+        break;
+    }
+    case LIBXL__QMP_MESSAGE_TYPE_ERROR:
+        qmp_handle_error_response(qmp, resp);
+        break;
+    case LIBXL__QMP_MESSAGE_TYPE_EVENT:
+        break;
+    case LIBXL__QMP_MESSAGE_TYPE_INVALID:
+        return -1;
+    }
+    return 0;
+}
+
+/*
+ * Handler functions
+ */
+
+static libxl__qmp_handler *qmp_init_handler(libxl_ctx *ctx, uint32_t domid)
+{
+    libxl__qmp_handler *qmp = NULL;
+
+    qmp = calloc(1, sizeof (libxl__qmp_handler));
+    if (qmp == NULL) {
+        LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR,
+                         "Failed to allocate qmp_handler");
+        return NULL;
+    }
+    qmp->ctx = ctx;
+    qmp->domid = domid;
+    qmp->timeout = 5;
+
+    SIMPLEQ_INIT(&qmp->callback_list);
+
+    return qmp;
+}
+
+static int qmp_open(libxl__qmp_handler *qmp, const char *qmp_socket_path,
+                    int timeout)
+{
+    int ret;
+    int flags = 0;
+    int i = 0;
+
+    qmp->qmp_fd = socket(AF_UNIX, SOCK_STREAM, 0);
+    if (qmp->qmp_fd < 0) {
+        return -1;
+    }
+    if ((flags = fcntl(qmp->qmp_fd, F_GETFL)) == 1) {
+        flags = 0;
+    }
+    if (fcntl(qmp->qmp_fd, F_SETFL, flags | O_NONBLOCK) == -1) {
+        return -1;
+    }
+
+    memset(&qmp->addr, 0, sizeof (&qmp->addr));
+    qmp->addr.sun_family = AF_UNIX;
+    strncpy(qmp->addr.sun_path, qmp_socket_path,
+            sizeof (qmp->addr.sun_path));
+
+    do {
+        ret = connect(qmp->qmp_fd, (struct sockaddr *) &qmp->addr,
+                      sizeof (qmp->addr));
+        if (ret == 0)
+            break;
+        if (errno == ENOENT || errno == ECONNREFUSED) {
+            /* ENOENT       : Socket may not have shown up yet
+             * ECONNREFUSED : Leftover socket hasn't been removed yet */
+            continue;
+        }
+        return -1;
+    } while ((++i / 5 <= timeout) && (usleep(200 * 1000) <= 0));
+
+    return ret;
+}
+
+static void qmp_close(libxl__qmp_handler *qmp)
+{
+    callback_id_pair *pp = NULL;
+    callback_id_pair *tmp = NULL;
+
+    close(qmp->qmp_fd);
+    SIMPLEQ_FOREACH(pp, &qmp->callback_list, next) {
+        if (tmp)
+            free(tmp);
+        tmp = pp;
+    }
+    if (tmp)
+        free(tmp);
+}
+
+static int qmp_next(libxl__gc *gc, libxl__qmp_handler *qmp)
+{
+    ssize_t rd;
+    char *s = NULL;
+    char *s_end = NULL;
+
+    char *incomplete = NULL;
+    size_t incomplete_size = 0;
+
+    do {
+        fd_set rfds;
+        int ret = 0;
+        struct timeval timeout = {
+            .tv_sec = qmp->timeout,
+            .tv_usec = 0,
+        };
+
+        FD_ZERO(&rfds);
+        FD_SET(qmp->qmp_fd, &rfds);
+
+        ret = select(qmp->qmp_fd + 1, &rfds, NULL, NULL, &timeout);
+        if (ret == 0) {
+            LIBXL__LOG(qmp->ctx, LIBXL__LOG_ERROR, "timeout");
+            return -1;
+        } else if (ret < 0) {
+            LIBXL__LOG_ERRNO(qmp->ctx, LIBXL__LOG_ERROR, "Select error");
+            return -1;
+        }
+
+        rd = read(qmp->qmp_fd, qmp->buffer, QMP_RECEIVE_BUFFER_SIZE);
+        if (rd == 0) {
+            continue;
+        } else if (rd < 0) {
+            LIBXL__LOG_ERRNO(qmp->ctx, LIBXL__LOG_ERROR, "Socket read error");
+            return rd;
+        }
+
+        DEBUG_REPORT_RECEIVED(qmp->buffer, rd);
+
+        do {
+            char *end = NULL;
+            if (incomplete) {
+                size_t current_pos = s - incomplete;
+                incomplete_size += rd;
+                incomplete = libxl__realloc(gc, incomplete,
+                                            incomplete_size + 1);
+                incomplete = strncat(incomplete, qmp->buffer, rd);
+                s = incomplete + current_pos;
+                s_end = incomplete + incomplete_size;
+            } else {
+                incomplete = libxl__strndup(gc, qmp->buffer, rd);
+                incomplete_size = rd;
+                s = incomplete;
+                s_end = s + rd;
+            }
+
+            end = strstr(s, "\r\n");
+            if (end) {
+                libxl__json_object *o = NULL;
+
+                *end = '\0';
+
+                o = libxl__json_parse(gc, s);
+                s = end + 2;
+
+                if (o) {
+                    qmp_handle_response(qmp, o);
+                    libxl__json_object_free(gc, o);
+                } else {
+                    LIBXL__LOG(qmp->ctx, LIBXL__LOG_ERROR,
+                               "Parse error of : %s\n", s);
+                    return -1;
+                }
+            } else {
+                break;
+            }
+        } while (s < s_end);
+   } while (s < s_end);
+
+    return 1;
+}
+
+static int qmp_send(libxl__qmp_handler *qmp,
+                    const char *cmd, qmp_callback_t callback)
+{
+    yajl_gen_config conf = { 0, NULL };
+    const unsigned char *buf;
+    unsigned int len = 0;
+    yajl_gen_status s;
+    yajl_gen hand;
+
+    hand = yajl_gen_alloc(&conf, NULL);
+    if (!hand) {
+        return -1;
+    }
+
+    yajl_gen_map_open(hand);
+    libxl__yajl_gen_asciiz(hand, "execute");
+    libxl__yajl_gen_asciiz(hand, cmd);
+    libxl__yajl_gen_asciiz(hand, "id");
+    yajl_gen_integer(hand, ++qmp->last_id_used);
+    yajl_gen_map_close(hand);
+
+    s = yajl_gen_get_buf(hand, &buf, &len);
+
+    if (s) {
+        LIBXL__LOG(qmp->ctx, LIBXL__LOG_ERROR,
+                   "Failed to generate a qmp command");
+        return -1;
+    }
+
+    if (callback) {
+        callback_id_pair *elm = malloc(sizeof (callback_id_pair));
+        if (elm == NULL) {
+            LIBXL__LOG_ERRNO(qmp->ctx, LIBXL__LOG_ERROR,
+                             "Failed to allocate a QMP callback");
+            yajl_gen_free(hand);
+            return -1;
+        }
+        elm->id = qmp->last_id_used;
+        elm->callback = callback;
+        SIMPLEQ_INSERT_TAIL(&qmp->callback_list, elm, next);
+    }
+
+    LIBXL__LOG(qmp->ctx, LIBXL__LOG_DEBUG, "next qmp command: '%s'", buf);
+
+    if (libxl_write_exactly(qmp->ctx, qmp->qmp_fd, buf, len,
+                            "QMP command", "QMP socket"))
+        goto error;
+    if (libxl_write_exactly(qmp->ctx, qmp->qmp_fd, "\r\n", 2,
+                            "CRLF", "QMP socket"))
+        goto error;
+
+    yajl_gen_free(hand);
+
+    return qmp->last_id_used;
+
+error:
+    yajl_gen_free(hand);
+    return -1;
+}
+
+static int qmp_synchronous_send(libxl__qmp_handler *qmp, const char *cmd,
+                                qmp_callback_t callback, int ask_timeout)
+{
+    int id = 0;
+    int ret = 0;
+    libxl__gc gc = LIBXL_INIT_GC(qmp->ctx);
+
+    id = qmp_send(qmp, cmd, callback);
+    if (id <= 0) {
+        return -1;
+    }
+    qmp->wait_for_id = id;
+
+    while (qmp->wait_for_id == id) {
+        if ((ret = qmp_next(&gc, qmp)) < 0) {
+            return ret;
+        }
+    }
+
+    libxl__free_all(&gc);
+
+    return 0;
+}
+
+static void qmp_free_handler(libxl__qmp_handler *qmp)
+{
+    free(qmp);
+}
+
+/*
+ * API
+ */
+
+libxl__qmp_handler *libxl__qmp_initialize(libxl_ctx *ctx, uint32_t domid)
+{
+    int ret = 0;
+    libxl__qmp_handler *qmp = NULL;
+    char *qmp_socket;
+    libxl__gc gc = LIBXL_INIT_GC(ctx);
+
+    qmp = qmp_init_handler(ctx, domid);
+
+    qmp_socket = libxl__sprintf(&gc, "%s/qmp-libxl-%d",
+                                libxl_run_dir_path(), domid);
+    if ((ret = qmp_open(qmp, qmp_socket, QMP_SOCKET_CONNECT_TIMEOUT)) < 0) {
+        LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR, "Connection error");
+        libxl__free_all(&gc);
+        qmp_free_handler(qmp);
+        return NULL;
+    }
+
+    LIBXL__LOG(qmp->ctx, LIBXL__LOG_DEBUG, "connected to %s", qmp_socket);
+
+    /* Wait for the response to qmp_capabilities */
+    while (!qmp->connected) {
+        if ((ret = qmp_next(&gc, qmp)) < 0) {
+            break;
+        }
+    }
+
+    libxl__free_all(&gc);
+    if (!qmp->connected) {
+        LIBXL__LOG(ctx, LIBXL__LOG_ERROR, "Failed to connect to QMP");
+        libxl__qmp_close(qmp);
+        return NULL;
+    }
+    return qmp;
+}
+
+void libxl__qmp_close(libxl__qmp_handler *qmp)
+{
+    if (!qmp)
+        return;
+    qmp_close(qmp);
+    qmp_free_handler(qmp);
+}
+
+void libxl__qmp_cleanup(libxl__gc *gc, uint32_t domid)
+{
+    libxl_ctx *ctx = libxl__gc_owner(gc);
+    char *qmp_socket;
+
+    qmp_socket = libxl__sprintf(gc, "%s/qmp-libxl-%d",
+                                libxl_run_dir_path(), domid);
+    if (unlink(qmp_socket) == -1) {
+        if (errno != ENOENT) {
+            LIBXL__LOG_ERRNO(ctx, LIBXL__LOG_ERROR,
+                             "Failed to remove QMP socket file %s",
+                             qmp_socket);
+        }
+    }
+}
+
+int libxl__qmp_query_serial(libxl__qmp_handler *qmp)
+{
+    return qmp_synchronous_send(qmp, "query-chardev",
+                                register_serials_chardev_callback,
+                                qmp->timeout);
+}
+
+int libxl__qmp_initializations(libxl_ctx *ctx, uint32_t domid)
+{
+    libxl__qmp_handler *qmp = NULL;
+    int ret = 0;
+
+    qmp = libxl__qmp_initialize(ctx, domid);
+    if (!qmp)
+        return -1;
+    ret = libxl__qmp_query_serial(qmp);
+    libxl__qmp_close(qmp);
+    return ret;
+}