[libvirt] [PATCH v4 3/7] qapi: Add pass-fd QMP command

This patch adds the pass-fd QMP command using the QAPI framework. Like the getfd command, it is used to pass a file descriptor via SCM_RIGHTS and associate it with a name. However, the pass-fd command also returns the received file descriptor, which is a difference in behavior from the getfd command, which returns nothing. pass-fd also supports a boolean "force" argument that can be used to specify that an existing file descriptor is associated with the specified name, and that it should become a copy of the newly passed file descriptor. The closefd command can be used to close a file descriptor that was passed with the pass-fd command. Note that when using getfd or pass-fd, there are some commands (e.g. migrate with fd:name) that implicitly close the named fd. When this is not the case, closefd must be used to avoid fd leaks. Signed-off-by: Corey Bryant <coreyb(a)linux.vnet.ibm.com&gt; --- v2: -Introduce new QMP command to pass/return fd (lcapitulino(a)redhat.com) -Use passfd as command name (berrange(a)redhat.com) v3: -Use pass-fd as command name (lcapitulino(a)redhat.com) -Fail pass-fd if fdname already exists (lcapitulino(a)redhat.com) -Add notes to QMP command describing behavior in more detail (lcapitulino(a)redhat.com, eblake(a)redhat.com) -Add note about fd leakage (eblake(a)redhat.com) v4: -Don't return same error class twice (lcapitulino(a)redhat.com) -Share code for qmp_gefd and qmp_pass_fd (lcapitulino(a)redhat.com) -Update qmp_closefd to call monitor_get_fd -Add support for "force" argument to pass-fd (eblake(a)redhat.com) dump.c | 3 +- migration-fd.c | 2 +- monitor.c | 96 +++++++++++++++++++++++++++++++++++------------------- monitor.h | 2 +- net.c | 6 ++-- qapi-schema.json | 36 ++++++++++++++++++++ qmp-commands.hx | 42 +++++++++++++++++++++++- 7 files changed, 146 insertions(+), 41 deletions(-) diff --git a/dump.c b/dump.c index 4412d7a..2fd8ced 100644 --- a/dump.c +++ b/dump.c @@ -836,9 +836,8 @@ void qmp_dump_guest_memory(bool paging, const char *file, bool has_begin, #if !defined(WIN32) if (strstart(file, "fd:", &p)) { - fd = monitor_get_fd(cur_mon, p); + fd = monitor_get_fd(cur_mon, p, errp); if (fd == -1) { - error_set(errp, QERR_FD_NOT_FOUND, p); return; } } diff --git a/migration-fd.c b/migration-fd.c index 50138ed..7335167 100644 --- a/migration-fd.c +++ b/migration-fd.c @@ -75,7 +75,7 @@ static int fd_close(MigrationState *s) int fd_start_outgoing_migration(MigrationState *s, const char *fdname) { - s->fd = monitor_get_fd(cur_mon, fdname); + s->fd = monitor_get_fd(cur_mon, fdname, NULL); if (s->fd == -1) { DPRINTF("fd_migration: invalid file descriptor identifier\n"); goto err_after_get_fd; diff --git a/monitor.c b/monitor.c index 1a7f7e7..3433c06 100644 --- a/monitor.c +++ b/monitor.c @@ -814,7 +814,7 @@ static int add_graphics_client(Monitor *mon, const QDict *qdict, QObject **ret_d CharDriverState *s; if (strcmp(protocol, "spice") == 0) { - int fd = monitor_get_fd(mon, fdname); + int fd = monitor_get_fd(mon, fdname, NULL); int skipauth = qdict_get_try_bool(qdict, "skipauth", 0); int tls = qdict_get_try_bool(qdict, "tls", 0); if (!using_spice) { @@ -828,18 +828,18 @@ static int add_graphics_client(Monitor *mon, const QDict *qdict, QObject **ret_d return 0; #ifdef CONFIG_VNC } else if (strcmp(protocol, "vnc") == 0) { - int fd = monitor_get_fd(mon, fdname); + int fd = monitor_get_fd(mon, fdname, NULL); int skipauth = qdict_get_try_bool(qdict, "skipauth", 0); - vnc_display_add_client(NULL, fd, skipauth); - return 0; + vnc_display_add_client(NULL, fd, skipauth); + return 0; #endif } else if ((s = qemu_chr_find(protocol)) != NULL) { - int fd = monitor_get_fd(mon, fdname); - if (qemu_chr_add_client(s, fd) < 0) { - qerror_report(QERR_ADD_CLIENT_FAILED); - return -1; - } - return 0; + int fd = monitor_get_fd(mon, fdname, NULL); + if (qemu_chr_add_client(s, fd) < 0) { + qerror_report(QERR_ADD_CLIENT_FAILED); + return -1; + } + return 0; } qerror_report(QERR_INVALID_PARAMETER, "protocol"); @@ -2182,57 +2182,69 @@ static void do_inject_mce(Monitor *mon, const QDict *qdict) } #endif -void qmp_getfd(const char *fdname, Error **errp) +static int monitor_put_fd(Monitor *mon, const char *fdname, bool replace, + bool copy, Error **errp) { mon_fd_t *monfd; int fd; - fd = qemu_chr_fe_get_msgfd(cur_mon->chr); + fd = qemu_chr_fe_get_msgfd(mon->chr); if (fd == -1) { error_set(errp, QERR_FD_NOT_SUPPLIED); - return; + return -1; } if (qemu_isdigit(fdname[0])) { error_set(errp, QERR_INVALID_PARAMETER_VALUE, "fdname", "a name not starting with a digit"); - return; + return -1; } - QLIST_FOREACH(monfd, &cur_mon->fds, next) { + QLIST_FOREACH(monfd, &mon->fds, next) { if (strcmp(monfd->name, fdname) != 0) { continue; } - close(monfd->fd); - monfd->fd = fd; - return; + if (replace) { + /* the existing fd is replaced with the new fd */ + close(monfd->fd); + monfd->fd = fd; + return fd; + } + + if (copy) { + /* the existing fd becomes a copy of the new fd */ + if (dup2(fd, monfd->fd) == -1) { + error_set(errp, QERR_UNDEFINED_ERROR); + return -1; + } + close(fd); + return monfd->fd; + } + + error_set(errp, QERR_INVALID_PARAMETER, "fdname"); + return -1; + } + + if (copy) { + error_set(errp, QERR_INVALID_PARAMETER, "fdname"); + return -1; } monfd = g_malloc0(sizeof(mon_fd_t)); monfd->name = g_strdup(fdname); monfd->fd = fd; - QLIST_INSERT_HEAD(&cur_mon->fds, monfd, next); + QLIST_INSERT_HEAD(&mon->fds, monfd, next); + return fd; } void qmp_closefd(const char *fdname, Error **errp) { - mon_fd_t *monfd; - - QLIST_FOREACH(monfd, &cur_mon->fds, next) { - if (strcmp(monfd->name, fdname) != 0) { - continue; - } - - QLIST_REMOVE(monfd, next); - close(monfd->fd); - g_free(monfd->name); - g_free(monfd); - return; + int fd = monitor_get_fd(cur_mon, fdname, errp); + if (fd != -1) { + close(fd); } - - error_set(errp, QERR_FD_NOT_FOUND, fdname); } static void do_loadvm(Monitor *mon, const QDict *qdict) @@ -2247,7 +2259,7 @@ static void do_loadvm(Monitor *mon, const QDict *qdict) } } -int monitor_get_fd(Monitor *mon, const char *fdname) +int monitor_get_fd(Monitor *mon, const char *fdname, Error **errp) { mon_fd_t *monfd; @@ -2268,9 +2280,25 @@ int monitor_get_fd(Monitor *mon, const char *fdname) return fd; } + error_set(errp, QERR_FD_NOT_FOUND, fdname); return -1; } +int64_t qmp_pass_fd(const char *fdname, bool has_force, bool force, + Error **errp) +{ + bool replace = false; + bool copy = has_force ? force : false; + return monitor_put_fd(cur_mon, fdname, replace, copy, errp); +} + +void qmp_getfd(const char *fdname, Error **errp) +{ + bool replace = true; + bool copy = false; + monitor_put_fd(cur_mon, fdname, replace, copy, errp); +} + /* mon_cmds and info_cmds would be sorted at runtime */ static mon_cmd_t mon_cmds[] = { #include "hmp-commands.h" diff --git a/monitor.h b/monitor.h index cd1d878..8fa515d 100644 --- a/monitor.h +++ b/monitor.h @@ -63,7 +63,7 @@ int monitor_read_block_device_key(Monitor *mon, const char *device, BlockDriverCompletionFunc *completion_cb, void *opaque); -int monitor_get_fd(Monitor *mon, const char *fdname); +int monitor_get_fd(Monitor *mon, const char *fdname, Error **errp); void monitor_vprintf(Monitor *mon, const char *fmt, va_list ap) GCC_FMT_ATTR(2, 0); diff --git a/net.c b/net.c index 4aa416c..28860b8 100644 --- a/net.c +++ b/net.c @@ -730,12 +730,14 @@ int qemu_find_nic_model(NICInfo *nd, const char * const *models, int net_handle_fd_param(Monitor *mon, const char *param) { int fd; + Error *local_err = NULL; if (!qemu_isdigit(param[0]) && mon) { - fd = monitor_get_fd(mon, param); + fd = monitor_get_fd(mon, param, &local_err); if (fd == -1) { - error_report("No file descriptor named %s found", param); + qerror_report_err(local_err); + error_free(local_err); return -1; } } else { diff --git a/qapi-schema.json b/qapi-schema.json index 26a6b84..2ac1261 100644 --- a/qapi-schema.json +++ b/qapi-schema.json @@ -1864,6 +1864,41 @@ { 'command': 'netdev_del', 'data': {'id': 'str'} } ## +# @pass-fd: +# +# Pass a file descriptor via SCM rights and assign it a name +# +# @fdname: file descriptor name +# +# @force: #optional true specifies that an existing file descriptor is +# associated with @fdname, and that it should become a copy of the +# newly passed file descriptor. +# +# Returns: The QEMU file descriptor that is assigned to @fdname +# If file descriptor was not received, FdNotSupplied +# If @fdname is not valid, InvalidParameterValue +# If @fdname already exists, and @force is not true, InvalidParameter +# If @fdname does not already exist, and @force is true, +# InvalidParameter +# If @force fails to copy the passed file descriptor, +# UndefinedError +# +# Since: 1.2.0 +# +# Notes: If @fdname already exists, and @force is not true, the +# command will fail. +# +# If @fdname already exists, and @force is true, the value of +# the existing file descriptor is returned when the command is +# successful. +# +# The 'closefd' command can be used to explicitly close the +# file descriptor when it is no longer needed. +## +{ 'command': 'pass-fd', 'data': {'fdname': 'str', '*force': 'bool'}, + 'returns': 'int' } + +## # @getfd: # # Receive a file descriptor via SCM rights and assign it a name @@ -1879,6 +1914,7 @@ # Notes: If @fdname already exists, the file descriptor assigned to # it will be closed and replaced by the received file # descriptor. +# # The 'closefd' command can be used to explicitly close the # file descriptor when it is no longer needed. ## diff --git a/qmp-commands.hx b/qmp-commands.hx index e3cf3c5..7e3c07e 100644 --- a/qmp-commands.hx +++ b/qmp-commands.hx @@ -869,9 +869,49 @@ Example: EQMP { + .name = "pass-fd", + .args_type = "fdname:s,force:b?", + .params = "pass-fd fdname force", + .help = "pass a file descriptor via SCM rights and assign it a name", + .mhandler.cmd_new = qmp_marshal_input_pass_fd, + }, + +SQMP +pass-fd +------- + +Pass a file descriptor via SCM rights and assign it a name. + +Arguments: + +- "fdname": file descriptor name (json-string) +- "force": true specifies that an existing file descriptor is associated + with "fdname", and that it should become a copy of the newly + passed file descriptor. (json-bool, optional) + +Return a json-int with the QEMU file descriptor that is assigned to "fdname". + +Example: + +-> { "execute": "pass-fd", "arguments": { "fdname": "fd1" } } +<- { "return": 42 } + +Notes: + +(1) If the name specified by the "fdname" argument already exists, and + "force" is not true, the command will fail. +(2) If the name specified by the "fdname" argument already exists, and + "force" is true, the value of the existing file descriptor is + returned when the command is successful. +(3) The 'closefd' command can be used to explicitly close the file + descriptor when it is no longer needed. + +EQMP + + { .name = "getfd", .args_type = "fdname:s", - .params = "getfd name", + .params = "getfd fdname", .help = "receive a file descriptor via SCM rights and assign it a name", .mhandler.cmd_new = qmp_marshal_input_getfd, }, -- 1.7.10.2