qemu: add slirp helper unit

The unit provides the functions associated with a slirp-helper:
- probing / checking capabilities
- opening the socketpair
- starting / stoping the helper
- registering for dbus-vmstate migration
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>
Reviewed-by: NMichal Privoznik <mprivozn@redhat.com>

src/qemu/Makefile.inc.am

@@ -58,6 +58,8 @@ QEMU_DRIVER_SOURCES = \
 	qemu/qemu_security.h \
 	qemu/qemu_qapi.c \
 	qemu/qemu_qapi.h \
+	qemu/qemu_slirp.c \
+	qemu/qemu_slirp.h \
 	qemu/qemu_tpm.c \
 	qemu/qemu_tpm.h \
 	$(NULL)

src/qemu/qemu_slirp.c

+/*
+ * qemu_slirp.c: QEMU Slirp support
+ *
+ * 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 2.1 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 <config.h>
+
+#include "qemu_dbus.h"
+#include "qemu_extdevice.h"
+#include "qemu_security.h"
+#include "qemu_slirp.h"
+#include "viralloc.h"
+#include "virenum.h"
+#include "virerror.h"
+#include "virjson.h"
+#include "virlog.h"
+#include "virpidfile.h"
+#include "virstring.h"
+#include "virtime.h"
+
+#define VIR_FROM_THIS VIR_FROM_NONE
+
+VIR_LOG_INIT("qemu.slirp");
+
+VIR_ENUM_IMPL(qemuSlirpFeature,
+              QEMU_SLIRP_FEATURE_LAST,
+              "",
+              "ipv4",
+              "ipv6",
+              "tftp",
+              "dbus-address",
+              "dbus-p2p",
+              "migrate",
+              "restrict",
+              "exit-with-parent",
+);
+
+
+void
+qemuSlirpFree(qemuSlirpPtr slirp)
+{
+    if (!slirp)
+        return;
+
+    VIR_FORCE_CLOSE(slirp->fd[0]);
+    VIR_FORCE_CLOSE(slirp->fd[1]);
+    virBitmapFree(slirp->features);
+    VIR_FREE(slirp);
+}
+
+
+void
+qemuSlirpSetFeature(qemuSlirpPtr slirp,
+                    qemuSlirpFeature feature)
+{
+    ignore_value(virBitmapSetBit(slirp->features, feature));
+}
+
+
+bool
+qemuSlirpHasFeature(const qemuSlirp *slirp,
+                    qemuSlirpFeature feature)
+{
+    return virBitmapIsBitSet(slirp->features, feature);
+}
+
+
+qemuSlirpPtr
+qemuSlirpNew(void)
+{
+    VIR_AUTOPTR(qemuSlirp) slirp = NULL;
+
+    if (VIR_ALLOC(slirp) < 0 ||
+        !(slirp->features = virBitmapNew(QEMU_SLIRP_FEATURE_LAST)))
+        return NULL;
+
+    slirp->pid = (pid_t)-1;
+    slirp->fd[0] = slirp->fd[1] = -1;
+
+    VIR_RETURN_PTR(slirp);
+}
+
+
+qemuSlirpPtr
+qemuSlirpNewForHelper(const char *helper)
+{
+    VIR_AUTOPTR(qemuSlirp) slirp = NULL;
+    VIR_AUTOPTR(virCommand) cmd = NULL;
+    VIR_AUTOFREE(char *) output = NULL;
+    VIR_AUTOPTR(virJSONValue) doc = NULL;
+    virJSONValuePtr featuresJSON;
+    size_t i, nfeatures;
+
+    if (!helper)
+        return NULL;
+
+    slirp = qemuSlirpNew();
+    if (!slirp) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Failed to allocate slirp for '%s'"), helper);
+        return NULL;
+    }
+
+    cmd = virCommandNewArgList(helper, "--print-capabilities", NULL);
+    virCommandSetOutputBuffer(cmd, &output);
+    if (virCommandRun(cmd, NULL) < 0)
+        return NULL;
+
+    if (!(doc = virJSONValueFromString(output)) ||
+        !(featuresJSON = virJSONValueObjectGetArray(doc, "features"))) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("unable to parse json capabilities '%s'"),
+                       helper);
+        return NULL;
+    }
+
+    nfeatures = virJSONValueArraySize(featuresJSON);
+    for (i = 0; i < nfeatures; i++) {
+        virJSONValuePtr item = virJSONValueArrayGet(featuresJSON, i);
+        const char *tmpStr = virJSONValueGetString(item);
+        int tmp;
+
+        if ((tmp = qemuSlirpFeatureTypeFromString(tmpStr)) <= 0) {
+            VIR_WARN("unknown slirp feature %s", tmpStr);
+            continue;
+        }
+
+        qemuSlirpSetFeature(slirp, tmp);
+    }
+
+    VIR_RETURN_PTR(slirp);
+}
+
+
+static char *
+qemuSlirpCreatePidFilename(virQEMUDriverConfigPtr cfg,
+                           const virDomainDef *def,
+                           const char *alias)
+{
+    VIR_AUTOFREE(char *) shortName = NULL;
+    VIR_AUTOFREE(char *) name = NULL;
+
+    if (!(shortName = virDomainDefGetShortName(def)) ||
+        virAsprintf(&name, "%s-%s-slirp", shortName, alias) < 0)
+        return NULL;
+
+    return virPidFileBuildPath(cfg->slirpStateDir, name);
+}
+
+
+int
+qemuSlirpOpen(qemuSlirpPtr slirp,
+              virQEMUDriverPtr driver,
+              virDomainDefPtr def)
+{
+    int rc, pair[2] = { -1, -1 };
+
+    if (qemuSecuritySetSocketLabel(driver->securityManager, def) < 0)
+        goto error;
+
+    rc = socketpair(AF_UNIX, SOCK_DGRAM, 0, pair);
+
+    if (qemuSecurityClearSocketLabel(driver->securityManager, def) < 0)
+        goto error;
+
+    if (rc < 0) {
+        virReportSystemError(errno, "%s", _("failed to create socketpair"));
+        goto error;
+    }
+
+    slirp->fd[0] = pair[0];
+    slirp->fd[1] = pair[1];
+
+    return 0;
+
+ error:
+    VIR_FORCE_CLOSE(pair[0]);
+    VIR_FORCE_CLOSE(pair[1]);
+    return -1;
+}
+
+
+int
+qemuSlirpGetFD(qemuSlirpPtr slirp)
+{
+    int fd = slirp->fd[0];
+    slirp->fd[0] = -1;
+    return fd;
+}
+
+
+static char *
+qemuSlirpGetDBusVMStateId(virDomainNetDefPtr net)
+{
+    char macstr[VIR_MAC_STRING_BUFLEN] = "";
+    char *id = NULL;
+
+    /* can't use alias, because it's not stable across restarts */
+    if (virAsprintf(&id, "slirp-%s", virMacAddrFormat(&net->mac, macstr)) < 0)
+        return NULL;
+
+    return id;
+}
+
+
+static char *
+qemuSlirpGetDBusPath(virQEMUDriverConfigPtr cfg,
+                     const virDomainDef *def,
+                     const char *alias)
+{
+    VIR_AUTOFREE(char *) shortName = NULL;
+    char *path = NULL;
+
+    if (!(shortName = virDomainDefGetShortName(def)) ||
+        virAsprintf(&path, "%s/%s-%s-slirp",
+                    cfg->slirpStateDir, shortName, alias) < 0)
+        return NULL;
+
+    return path;
+}
+
+
+void
+qemuSlirpStop(qemuSlirpPtr slirp,
+              virDomainObjPtr vm,
+              virQEMUDriverPtr driver,
+              virDomainNetDefPtr net,
+              bool hot)
+{
+    VIR_AUTOUNREF(virQEMUDriverConfigPtr) cfg = virQEMUDriverGetConfig(driver);
+    VIR_AUTOFREE(char *) pidfile = NULL;
+    VIR_AUTOFREE(char *) dbus_path = NULL;
+    VIR_AUTOFREE(char *) id = qemuSlirpGetDBusVMStateId(net);
+    virErrorPtr orig_err;
+    pid_t pid;
+    int rc;
+
+    if (!(pidfile = qemuSlirpCreatePidFilename(cfg, vm->def, net->info.alias))) {
+        VIR_WARN("Unable to construct slirp pidfile path");
+        return;
+    }
+
+    if (id) {
+        qemuDBusVMStateRemove(driver, vm, id, hot);
+    } else {
+        VIR_WARN("Unable to construct vmstate id");
+    }
+
+    virErrorPreserveLast(&orig_err);
+    rc = virPidFileReadPathIfAlive(pidfile, &pid, cfg->slirpHelperName);
+    if (rc >= 0 && pid != (pid_t) -1)
+        virProcessKillPainfully(pid, true);
+
+    if (unlink(pidfile) < 0 &&
+        errno != ENOENT) {
+        virReportSystemError(errno,
+                             _("Unable to remove stale pidfile %s"),
+                             pidfile);
+    }
+    slirp->pid = 0;
+
+    dbus_path = qemuSlirpGetDBusPath(cfg, vm->def, net->info.alias);
+    if (dbus_path) {
+        if (unlink(dbus_path) < 0 &&
+            errno != ENOENT) {
+            virReportSystemError(errno,
+                                 _("Unable to remove stale dbus socket %s"),
+                                 dbus_path);
+        }
+    } else {
+        VIR_WARN("Unable to construct dbus socket path");
+    }
+
+    virErrorRestore(&orig_err);
+}
+
+
+int
+qemuSlirpStart(qemuSlirpPtr slirp,
+               virDomainObjPtr vm,
+               virQEMUDriverPtr driver,
+               virDomainNetDefPtr net,
+               bool hotplug,
+               bool incoming)
+{
+    VIR_AUTOUNREF(virQEMUDriverConfigPtr) cfg = virQEMUDriverGetConfig(driver);
+    VIR_AUTOPTR(virCommand) cmd = NULL;
+    VIR_AUTOFREE(char *) cmdstr = NULL;
+    VIR_AUTOFREE(char *) pidfile = NULL;
+    VIR_AUTOFREE(char *) dbus_path = NULL;
+    VIR_AUTOFREE(char *) dbus_addr = NULL;
+    VIR_AUTOFREE(char *) id = NULL;
+    size_t i;
+    const unsigned long long timeout = 5 * 1000; /* ms */
+    pid_t pid = (pid_t) -1;
+    int rc;
+    int exitstatus = 0;
+    int cmdret = 0;
+    VIR_AUTOCLOSE errfd = -1;
+
+    if (incoming &&
+        !qemuSlirpHasFeature(slirp, QEMU_SLIRP_FEATURE_MIGRATE)) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("The slirp-helper doesn't support migration"));
+    }
+
+    if (!(pidfile = qemuSlirpCreatePidFilename(cfg, vm->def, net->info.alias)))
+        return -1;
+
+    if (!(cmd = virCommandNew(cfg->slirpHelperName)))
+        return -1;
+
+    virCommandClearCaps(cmd);
+    virCommandSetPidFile(cmd, pidfile);
+    virCommandSetErrorFD(cmd, &errfd);
+    virCommandDaemonize(cmd);
+
+    virCommandAddArgFormat(cmd, "--fd=%d", slirp->fd[1]);
+    virCommandPassFD(cmd, slirp->fd[1],
+                     VIR_COMMAND_PASS_FD_CLOSE_PARENT);
+    slirp->fd[1] = -1;
+
+    for (i = 0; i < net->guestIP.nips; i++) {
+        const virNetDevIPAddr *ip = net->guestIP.ips[i];
+        VIR_AUTOFREE(char *) addr = NULL;
+        const char *opt = "";
+
+        if (!(addr = virSocketAddrFormat(&ip->address)))
+            return -1;
+
+        if (VIR_SOCKET_ADDR_IS_FAMILY(&ip->address, AF_INET))
+            opt = "--net";
+        if (VIR_SOCKET_ADDR_IS_FAMILY(&ip->address, AF_INET6))
+            opt = "--prefix-ipv6";
+
+        virCommandAddArgFormat(cmd, "%s=%s", opt, addr);
+
+        if (ip->prefix) {
+            if (VIR_SOCKET_ADDR_IS_FAMILY(&ip->address, AF_INET)) {
+                virSocketAddr netmask;
+                VIR_AUTOFREE(char *) netmaskStr = NULL;
+
+                if (virSocketAddrPrefixToNetmask(ip->prefix, &netmask, AF_INET) < 0) {
+                    virReportError(VIR_ERR_INTERNAL_ERROR,
+                                   _("Failed to translate prefix %d to netmask"),
+                                   ip->prefix);
+                    return -1;
+                }
+                if (!(netmaskStr = virSocketAddrFormat(&netmask)))
+                    return -1;
+                virCommandAddArgFormat(cmd, "--mask=%s", netmaskStr);
+            }
+            if (VIR_SOCKET_ADDR_IS_FAMILY(&ip->address, AF_INET6))
+                virCommandAddArgFormat(cmd, "--prefix-length-ipv6=%u", ip->prefix);
+        }
+    }
+
+    if (qemuSlirpHasFeature(slirp, QEMU_SLIRP_FEATURE_DBUS_P2P)) {
+        if (!(id = qemuSlirpGetDBusVMStateId(net)))
+            return -1;
+
+        if (!(dbus_path = qemuSlirpGetDBusPath(cfg, vm->def, net->info.alias)))
+            return -1;
+
+        if (unlink(dbus_path) < 0 && errno != ENOENT) {
+            virReportSystemError(errno, _("Unable to unlink %s"), dbus_path);
+            return -1;
+        }
+
+        if (virAsprintf(&dbus_addr, "unix:path=%s", dbus_path) < 0)
+            return -1;
+
+        virCommandAddArgFormat(cmd, "--dbus-id=%s", id);
+
+        virCommandAddArgFormat(cmd, "--dbus-p2p=%s", dbus_addr);
+
+        if (incoming &&
+            qemuSlirpHasFeature(slirp, QEMU_SLIRP_FEATURE_MIGRATE))
+            virCommandAddArg(cmd, "--dbus-incoming");
+    }
+
+    if (qemuSlirpHasFeature(slirp, QEMU_SLIRP_FEATURE_EXIT_WITH_PARENT))
+        virCommandAddArg(cmd, "--exit-with-parent");
+
+    if (qemuExtDeviceLogCommand(driver, vm, cmd, "slirp") < 0)
+        return -1;
+
+    if (qemuSecurityCommandRun(driver, vm, cmd, -1, -1, &exitstatus, &cmdret) < 0)
+        return -1;
+
+    if (cmdret < 0 || exitstatus != 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR,
+                       _("Could not start 'slirp'. exitstatus: %d"), exitstatus);
+        goto error;
+    }
+
+    rc = virPidFileReadPath(pidfile, &pid);
+    if (rc < 0) {
+        virReportSystemError(-rc,
+                             _("Unable to read slirp pidfile '%s'"),
+                             pidfile);
+        goto error;
+    }
+
+    if (dbus_path) {
+        virTimeBackOffVar timebackoff;
+
+        if (virTimeBackOffStart(&timebackoff, 1, timeout) < 0)
+            goto error;
+
+        while (virTimeBackOffWait(&timebackoff)) {
+            char errbuf[1024] = { 0 };
+
+            if (virFileExists(dbus_path))
+                break;
+
+            if (virProcessKill(pid, 0) == 0)
+                continue;
+
+            if (saferead(errfd, errbuf, sizeof(errbuf) - 1) < 0) {
+                virReportSystemError(errno,
+                                     _("slirp helper %s died unexpectedly"),
+                                     cfg->prHelperName);
+            } else {
+                virReportError(VIR_ERR_OPERATION_FAILED,
+                               _("slirp helper died and reported: %s"), errbuf);
+            }
+            goto error;
+        }
+
+        if (!virFileExists(dbus_path)) {
+            virReportError(VIR_ERR_OPERATION_TIMEOUT, "%s",
+                           _("slirp dbus socket did not show up"));
+            goto error;
+        }
+    }
+
+    if (qemuSlirpHasFeature(slirp, QEMU_SLIRP_FEATURE_MIGRATE) &&
+        qemuDBusVMStateAdd(driver, vm, id, dbus_addr, hotplug) < 0) {
+        virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
+                       _("Failed to register slirp migration"));
+        goto error;
+    }
+
+    slirp->pid = pid;
+    return 0;
+
+ error:
+    if (pid != -1)
+        virProcessKillPainfully(pid, true);
+    if (pidfile)
+        unlink(pidfile);
+    if (dbus_path)
+        unlink(dbus_path);
+    return -1;
+}

src/qemu/qemu_slirp.h

+/*
+ * qemu_slirp.h: QEMU Slirp support
+ *
+ * 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 2.1 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/>.
+ */
+
+#pragma once
+
+#include "qemu_conf.h"
+#include "virbitmap.h"
+#include "virenum.h"
+
+typedef enum {
+    QEMU_SLIRP_FEATURE_NONE = 0,
+    QEMU_SLIRP_FEATURE_IPV4,
+    QEMU_SLIRP_FEATURE_IPV6,
+    QEMU_SLIRP_FEATURE_TFTP,
+    QEMU_SLIRP_FEATURE_DBUS_ADDRESS,
+    QEMU_SLIRP_FEATURE_DBUS_P2P,
+    QEMU_SLIRP_FEATURE_MIGRATE,
+    QEMU_SLIRP_FEATURE_RESTRICT,
+    QEMU_SLIRP_FEATURE_EXIT_WITH_PARENT,
+
+    QEMU_SLIRP_FEATURE_LAST,
+} qemuSlirpFeature;
+
+VIR_ENUM_DECL(qemuSlirpFeature);
+
+typedef struct _qemuSlirp qemuSlirp;
+typedef qemuSlirp *qemuSlirpPtr;
+struct _qemuSlirp {
+    int fd[2];
+    virBitmapPtr features;
+    pid_t pid;
+};
+
+qemuSlirpPtr qemuSlirpNew(void);
+
+qemuSlirpPtr qemuSlirpNewForHelper(const char *helper);
+
+void qemuSlirpFree(qemuSlirpPtr slirp);
+
+void qemuSlirpSetFeature(qemuSlirpPtr slirp,
+                         qemuSlirpFeature feature);
+
+bool qemuSlirpHasFeature(const qemuSlirp *slirp,
+                         qemuSlirpFeature feature);
+
+int qemuSlirpOpen(qemuSlirpPtr slirp,
+                  virQEMUDriverPtr driver,
+                  virDomainDefPtr def);
+
+int qemuSlirpStart(qemuSlirpPtr slirp,
+                   virDomainObjPtr vm,
+                   virQEMUDriverPtr driver,
+                   virDomainNetDefPtr net,
+                   bool hot,
+                   bool incoming);
+
+void qemuSlirpStop(qemuSlirpPtr slirp,
+                   virDomainObjPtr vm,
+                   virQEMUDriverPtr driver,
+                   virDomainNetDefPtr net,
+                   bool hot);
+
+int qemuSlirpGetFD(qemuSlirpPtr slirp);
+
+VIR_DEFINE_AUTOPTR_FUNC(qemuSlirp, qemuSlirpFree);