io: add QIOChannelCommand class

Add a QIOChannel subclass that is capable of performing I/O
to/from a separate process, via a pair of pipes. The command
can be used for unidirectional or bi-directional I/O.
Signed-off-by: NDaniel P. Berrange <berrange@redhat.com>

include/io/channel-command.h

+/*
+ * QEMU I/O channels external command driver
+ *
+ * Copyright (c) 2015 Red Hat, Inc.
+ *
+ * This library 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; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef QIO_CHANNEL_COMMAND_H__
+#define QIO_CHANNEL_COMMAND_H__
+
+#include "io/channel.h"
+
+#define TYPE_QIO_CHANNEL_COMMAND "qio-channel-command"
+#define QIO_CHANNEL_COMMAND(obj)                                     \
+    OBJECT_CHECK(QIOChannelCommand, (obj), TYPE_QIO_CHANNEL_COMMAND)
+
+typedef struct QIOChannelCommand QIOChannelCommand;
+
+
+/**
+ * QIOChannelCommand:
+ *
+ * The QIOChannelCommand class provides a channel implementation
+ * that can transport data with an externally running command
+ * via its stdio streams.
+ */
+
+struct QIOChannelCommand {
+    QIOChannel parent;
+    int writefd;
+    int readfd;
+    pid_t pid;
+};
+
+
+/**
+ * qio_channel_command_new_pid:
+ * @writefd: the FD connected to the command's stdin
+ * @readfd: the FD connected to the command's stdout
+ * @pid: the PID of the running child command
+ * @errp: pointer to an uninitialized error object
+ *
+ * Create a channel for performing I/O with the
+ * previously spawned command identified by @pid.
+ * The two file descriptors provide the connection
+ * to command's stdio streams, either one or which
+ * may be -1 to indicate that stream is not open.
+ *
+ * The channel will take ownership of the process
+ * @pid and will kill it when closing the channel.
+ * Similarly it will take responsibility for
+ * closing the file descriptors @writefd and @readfd.
+ *
+ * Returns: the command channel object, or NULL on error
+ */
+QIOChannelCommand *
+qio_channel_command_new_pid(int writefd,
+                            int readfd,
+                            pid_t pid);
+
+/**
+ * qio_channel_command_new_spawn:
+ * @argv: the NULL terminated list of command arguments
+ * @flags: the I/O mode, one of O_RDONLY, O_WRONLY, O_RDWR
+ * @errp: pointer to an uninitialized error object
+ *
+ * Create a channel for performing I/O with the
+ * command to be spawned with arguments @argv.
+ *
+ * Returns: the command channel object, or NULL on error
+ */
+QIOChannelCommand *
+qio_channel_command_new_spawn(const char *const argv[],
+                              int flags,
+                              Error **errp);
+
+
+#endif /* QIO_CHANNEL_COMMAND_H__ */

io/Makefile.objs

 io-obj-y = channel.o
+io-obj-y += channel-command.o
 io-obj-y += channel-file.o
 io-obj-y += channel-socket.o
 io-obj-y += channel-tls.o

io/channel-command.c

+/*
+ * QEMU I/O channels external command driver
+ *
+ * Copyright (c) 2015 Red Hat, Inc.
+ *
+ * This library 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; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "io/channel-command.h"
+#include "io/channel-watch.h"
+#include "qemu/sockets.h"
+#include "trace.h"
+
+
+QIOChannelCommand *
+qio_channel_command_new_pid(int writefd,
+                            int readfd,
+                            pid_t pid)
+{
+    QIOChannelCommand *ioc;
+
+    ioc = QIO_CHANNEL_COMMAND(object_new(TYPE_QIO_CHANNEL_COMMAND));
+
+    ioc->readfd = readfd;
+    ioc->writefd = writefd;
+    ioc->pid = pid;
+
+    trace_qio_channel_command_new_pid(ioc, writefd, readfd, pid);
+    return ioc;
+}
+
+
+#ifndef WIN32
+QIOChannelCommand *
+qio_channel_command_new_spawn(const char *const argv[],
+                              int flags,
+                              Error **errp)
+{
+    pid_t pid = -1;
+    int stdinfd[2] = { -1, -1 };
+    int stdoutfd[2] = { -1, -1 };
+    int devnull = -1;
+    bool stdinnull = false, stdoutnull = false;
+    QIOChannelCommand *ioc;
+
+    flags = flags & O_ACCMODE;
+
+    if (flags == O_RDONLY) {
+        stdinnull = true;
+    }
+    if (flags == O_WRONLY) {
+        stdoutnull = true;
+    }
+
+    if (stdinnull || stdoutnull) {
+        devnull = open("/dev/null", O_RDWR);
+        if (!devnull) {
+            error_setg_errno(errp, errno,
+                             "Unable to open /dev/null");
+            goto error;
+        }
+    }
+
+    if ((!stdinnull && pipe(stdinfd) < 0) ||
+        (!stdoutnull && pipe(stdoutfd) < 0)) {
+        error_setg_errno(errp, errno,
+                         "Unable to open pipe");
+        goto error;
+    }
+
+    pid = qemu_fork(errp);
+    if (pid < 0) {
+        goto error;
+    }
+
+    if (pid == 0) { /* child */
+        dup2(stdinnull ? devnull : stdinfd[0], STDIN_FILENO);
+        dup2(stdoutnull ? devnull : stdoutfd[1], STDOUT_FILENO);
+        /* Leave stderr connected to qemu's stderr */
+
+        if (!stdinnull) {
+            close(stdinfd[0]);
+            close(stdinfd[1]);
+        }
+        if (!stdoutnull) {
+            close(stdoutfd[0]);
+            close(stdoutfd[1]);
+        }
+
+        execv(argv[0], (char * const *)argv);
+        _exit(1);
+    }
+
+    if (!stdinnull) {
+        close(stdinfd[0]);
+    }
+    if (!stdoutnull) {
+        close(stdoutfd[1]);
+    }
+
+    ioc = qio_channel_command_new_pid(stdinnull ? devnull : stdinfd[1],
+                                      stdoutnull ? devnull : stdoutfd[0],
+                                      pid);
+    trace_qio_channel_command_new_spawn(ioc, argv[0], flags);
+    return ioc;
+
+ error:
+    if (stdinfd[0] != -1) {
+        close(stdinfd[0]);
+    }
+    if (stdinfd[1] != -1) {
+        close(stdinfd[1]);
+    }
+    if (stdoutfd[0] != -1) {
+        close(stdoutfd[0]);
+    }
+    if (stdoutfd[1] != -1) {
+        close(stdoutfd[1]);
+    }
+    return NULL;
+}
+
+#else /* WIN32 */
+QIOChannelCommand *
+qio_channel_command_new_spawn(const char *const argv[],
+                              int flags,
+                              Error **errp)
+{
+    error_setg_errno(errp, ENOSYS,
+                     "Command spawn not supported on this platform");
+    return NULL;
+}
+#endif /* WIN32 */
+
+#ifndef WIN32
+static int qio_channel_command_abort(QIOChannelCommand *ioc,
+                                     Error **errp)
+{
+    pid_t ret;
+    int status;
+    int step = 0;
+
+    /* See if intermediate process has exited; if not, try a nice
+     * SIGTERM followed by a more severe SIGKILL.
+     */
+ rewait:
+    trace_qio_channel_command_abort(ioc, ioc->pid);
+    ret = waitpid(ioc->pid, &status, WNOHANG);
+    trace_qio_channel_command_wait(ioc, ioc->pid, ret, status);
+    if (ret == (pid_t)-1) {
+        if (errno == EINTR) {
+            goto rewait;
+        } else {
+            error_setg_errno(errp, errno,
+                             "Cannot wait on pid %llu",
+                             (unsigned long long)ioc->pid);
+            return -1;
+        }
+    } else if (ret == 0) {
+        if (step == 0) {
+            kill(ioc->pid, SIGTERM);
+        } else if (step == 1) {
+            kill(ioc->pid, SIGKILL);
+        } else {
+            error_setg(errp,
+                       "Process %llu refused to die",
+                       (unsigned long long)ioc->pid);
+            return -1;
+        }
+        usleep(10 * 1000);
+        goto rewait;
+    }
+
+    return 0;
+}
+#endif /* ! WIN32 */
+
+
+static void qio_channel_command_init(Object *obj)
+{
+    QIOChannelCommand *ioc = QIO_CHANNEL_COMMAND(obj);
+    ioc->readfd = -1;
+    ioc->writefd = -1;
+    ioc->pid = -1;
+}
+
+static void qio_channel_command_finalize(Object *obj)
+{
+    QIOChannelCommand *ioc = QIO_CHANNEL_COMMAND(obj);
+    if (ioc->readfd != -1) {
+        close(ioc->readfd);
+        ioc->readfd = -1;
+    }
+    if (ioc->writefd != -1) {
+        close(ioc->writefd);
+        ioc->writefd = -1;
+    }
+    if (ioc->pid > 0) {
+#ifndef WIN32
+        qio_channel_command_abort(ioc, NULL);
+#endif
+    }
+}
+
+
+static ssize_t qio_channel_command_readv(QIOChannel *ioc,
+                                         const struct iovec *iov,
+                                         size_t niov,
+                                         int **fds,
+                                         size_t *nfds,
+                                         Error **errp)
+{
+    QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
+    ssize_t ret;
+
+ retry:
+    ret = readv(cioc->readfd, iov, niov);
+    if (ret < 0) {
+        if (errno == EAGAIN ||
+            errno == EWOULDBLOCK) {
+            return QIO_CHANNEL_ERR_BLOCK;
+        }
+        if (errno == EINTR) {
+            goto retry;
+        }
+
+        error_setg_errno(errp, errno,
+                         "Unable to read from command");
+        return -1;
+    }
+
+    return ret;
+}
+
+static ssize_t qio_channel_command_writev(QIOChannel *ioc,
+                                          const struct iovec *iov,
+                                          size_t niov,
+                                          int *fds,
+                                          size_t nfds,
+                                          Error **errp)
+{
+    QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
+    ssize_t ret;
+
+ retry:
+    ret = writev(cioc->writefd, iov, niov);
+    if (ret <= 0) {
+        if (errno == EAGAIN ||
+            errno == EWOULDBLOCK) {
+            return QIO_CHANNEL_ERR_BLOCK;
+        }
+        if (errno == EINTR) {
+            goto retry;
+        }
+        error_setg_errno(errp, errno, "%s",
+                         "Unable to write to command");
+        return -1;
+    }
+    return ret;
+}
+
+static int qio_channel_command_set_blocking(QIOChannel *ioc,
+                                            bool enabled,
+                                            Error **errp)
+{
+    QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
+
+    if (enabled) {
+        qemu_set_block(cioc->writefd);
+        qemu_set_block(cioc->readfd);
+    } else {
+        qemu_set_nonblock(cioc->writefd);
+        qemu_set_nonblock(cioc->readfd);
+    }
+
+    return 0;
+}
+
+
+static int qio_channel_command_close(QIOChannel *ioc,
+                                     Error **errp)
+{
+    QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
+    int rv = 0;
+
+    /* We close FDs before killing, because that
+     * gives a better chance of clean shutdown
+     */
+    if (close(cioc->writefd) < 0) {
+        rv = -1;
+    }
+    if (close(cioc->readfd) < 0) {
+        rv = -1;
+    }
+#ifndef WIN32
+    if (qio_channel_command_abort(cioc, errp) < 0) {
+        return -1;
+    }
+#endif
+    if (rv < 0) {
+        error_setg_errno(errp, errno, "%s",
+                         "Unable to close command");
+    }
+    return rv;
+}
+
+
+static GSource *qio_channel_command_create_watch(QIOChannel *ioc,
+                                                 GIOCondition condition)
+{
+    QIOChannelCommand *cioc = QIO_CHANNEL_COMMAND(ioc);
+    return qio_channel_create_fd_pair_watch(ioc,
+                                            cioc->readfd,
+                                            cioc->writefd,
+                                            condition);
+}
+
+
+static void qio_channel_command_class_init(ObjectClass *klass,
+                                           void *class_data G_GNUC_UNUSED)
+{
+    QIOChannelClass *ioc_klass = QIO_CHANNEL_CLASS(klass);
+
+    ioc_klass->io_writev = qio_channel_command_writev;
+    ioc_klass->io_readv = qio_channel_command_readv;
+    ioc_klass->io_set_blocking = qio_channel_command_set_blocking;
+    ioc_klass->io_close = qio_channel_command_close;
+    ioc_klass->io_create_watch = qio_channel_command_create_watch;
+}
+
+static const TypeInfo qio_channel_command_info = {
+    .parent = TYPE_QIO_CHANNEL,
+    .name = TYPE_QIO_CHANNEL_COMMAND,
+    .instance_size = sizeof(QIOChannelCommand),
+    .instance_init = qio_channel_command_init,
+    .instance_finalize = qio_channel_command_finalize,
+    .class_init = qio_channel_command_class_init,
+};
+
+static void qio_channel_command_register_types(void)
+{
+    type_register_static(&qio_channel_command_info);
+}
+
+type_init(qio_channel_command_register_types);

tests/.gitignore

@@ -24,6 +24,8 @@ test-cutils
 test-hbitmap
 test-int128
 test-iov
+test-io-channel-command
+test-io-channel-command.fifo
 test-io-channel-file
 test-io-channel-file.txt
 test-io-channel-socket

tests/Makefile

@@ -88,6 +88,7 @@ check-unit-y += tests/test-io-task$(EXESUF)
 check-unit-y += tests/test-io-channel-socket$(EXESUF)
 check-unit-y += tests/test-io-channel-file$(EXESUF)
 check-unit-$(CONFIG_GNUTLS) += tests/test-io-channel-tls$(EXESUF)
+check-unit-y += tests/test-io-channel-command$(EXESUF)
 
 check-block-$(CONFIG_POSIX) += tests/qemu-iotests-quick.sh
 
@@ -482,6 +483,8 @@ tests/test-io-channel-file$(EXESUF): tests/test-io-channel-file.o \
 tests/test-io-channel-tls$(EXESUF): tests/test-io-channel-tls.o \
 	tests/crypto-tls-x509-helpers.o tests/pkix_asn1_tab.o \
 	tests/io-channel-helpers.o $(test-io-obj-y)
+tests/test-io-channel-command$(EXESUF): tests/test-io-channel-command.o \
+        tests/io-channel-helpers.o $(test-io-obj-y)
 
 libqos-obj-y = tests/libqos/pci.o tests/libqos/fw_cfg.o tests/libqos/malloc.o
 libqos-obj-y += tests/libqos/i2c.o tests/libqos/libqos.o

tests/test-io-channel-command.c

+/*
+ * QEMU I/O channel command test
+ *
+ * Copyright (c) 2015 Red Hat, Inc.
+ *
+ * This library 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; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library 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.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "io/channel-command.h"
+#include "io-channel-helpers.h"
+
+#ifndef WIN32
+static void test_io_channel_command_fifo(bool async)
+{
+#define TEST_FIFO "tests/test-io-channel-command.fifo"
+    QIOChannel *src, *dst;
+    QIOChannelTest *test;
+    char *srcfifo = g_strdup_printf("PIPE:%s,wronly", TEST_FIFO);
+    char *dstfifo = g_strdup_printf("PIPE:%s,rdonly", TEST_FIFO);
+    const char *srcargv[] = {
+        "/bin/socat", "-", srcfifo, NULL,
+    };
+    const char *dstargv[] = {
+        "/bin/socat", dstfifo, "-", NULL,
+    };
+
+    unlink(TEST_FIFO);
+    if (access("/bin/socat", X_OK) < 0) {
+        return; /* Pretend success if socat is not present */
+    }
+    if (mkfifo(TEST_FIFO, 0600) < 0) {
+        abort();
+    }
+    src = QIO_CHANNEL(qio_channel_command_new_spawn(srcargv,
+                                                    O_WRONLY,
+                                                    &error_abort));
+    dst = QIO_CHANNEL(qio_channel_command_new_spawn(dstargv,
+                                                    O_RDONLY,
+                                                    &error_abort));
+
+    test = qio_channel_test_new();
+    qio_channel_test_run_threads(test, async, src, dst);
+    qio_channel_test_validate(test);
+
+    object_unref(OBJECT(src));
+    object_unref(OBJECT(dst));
+
+    g_free(srcfifo);
+    g_free(dstfifo);
+    unlink(TEST_FIFO);
+}
+
+
+static void test_io_channel_command_fifo_async(void)
+{
+    test_io_channel_command_fifo(true);
+}
+
+static void test_io_channel_command_fifo_sync(void)
+{
+    test_io_channel_command_fifo(false);
+}
+
+
+static void test_io_channel_command_echo(bool async)
+{
+    QIOChannel *ioc;
+    QIOChannelTest *test;
+    const char *socatargv[] = {
+        "/bin/socat", "-", "-", NULL,
+    };
+
+    if (access("/bin/socat", X_OK) < 0) {
+        return; /* Pretend success if socat is not present */
+    }
+
+    ioc = QIO_CHANNEL(qio_channel_command_new_spawn(socatargv,
+                                                    O_RDWR,
+                                                    &error_abort));
+    test = qio_channel_test_new();
+    qio_channel_test_run_threads(test, async, ioc, ioc);
+    qio_channel_test_validate(test);
+
+    object_unref(OBJECT(ioc));
+}
+
+
+static void test_io_channel_command_echo_async(void)
+{
+    test_io_channel_command_echo(true);
+}
+
+static void test_io_channel_command_echo_sync(void)
+{
+    test_io_channel_command_echo(false);
+}
+#endif
+
+int main(int argc, char **argv)
+{
+    module_call_init(MODULE_INIT_QOM);
+
+    g_test_init(&argc, &argv, NULL);
+
+#ifndef WIN32
+    g_test_add_func("/io/channel/command/fifo/sync",
+                    test_io_channel_command_fifo_sync);
+    g_test_add_func("/io/channel/command/fifo/async",
+                    test_io_channel_command_fifo_async);
+    g_test_add_func("/io/channel/command/echo/sync",
+                    test_io_channel_command_echo_sync);
+    g_test_add_func("/io/channel/command/echo/async",
+                    test_io_channel_command_echo_async);
+#endif
+
+    return g_test_run();
+}

trace-events

@@ -1858,3 +1858,9 @@ qio_channel_websock_handshake_pending(void *ioc, int status) "Websock handshake
 qio_channel_websock_handshake_reply(void *ioc) "Websock handshake reply ioc=%p"
 qio_channel_websock_handshake_fail(void *ioc) "Websock handshake fail ioc=%p"
 qio_channel_websock_handshake_complete(void *ioc) "Websock handshake complete ioc=%p"
+
+# io/channel-command.c
+qio_channel_command_new_pid(void *ioc, int writefd, int readfd, int pid) "Command new pid ioc=%p writefd=%d readfd=%d pid=%d"
+qio_channel_command_new_spawn(void *ioc, const char *binary, int flags) "Command new spawn ioc=%p binary=%s flags=%d"
+qio_channel_command_abort(void *ioc, int pid) "Command abort ioc=%p pid=%d"
+qio_channel_command_wait(void *ioc, int pid, int ret, int status) "Command abort ioc=%p pid=%d ret=%d status=%d"