On Wed, 15 Feb 2023 18:04:56 +0100 Michal Prívozník <mprivozn(a)redhat.com> wrote:On 2/15/23 08:50, Laine Stump wrote:That doesn't need to be the case (--log-file and --stderr being mutually exclusive)... if you have a use case for it, let's change that in passt. I just wanted to keep it simple for users ("give a log file, and be sure it won't spam"). Also mind that Laine's series: https://archives.passt.top/passt-dev/20230215082437.110151-1-laine@redhat.c… *should* already cover all the cases where libvirt is interested in relaying "early" errors back to the user. By the way, the one below is pretty much the patch I would have proposed for libvirt. I prepared it earlier today and didn't have a chance to test it yet, it's compile-tested only, and doesn't take cgroups into account (which, it seems, is needed no matter the lifecycle). So I'm sharing it here as reference (that's how simple I wanted it to be -- minus cgroups), or if it's convenient for you to copy and paste something. --- diff --git a/src/qemu/qemu_extdevice.c b/src/qemu/qemu_extdevice.c index fdefe59215..23d25c134a 100644 --- a/src/qemu/qemu_extdevice.c +++ b/src/qemu/qemu_extdevice.c @@ -337,12 +337,6 @@ qemuExtDevicesSetupCgroup(virQEMUDriver *driver, if (slirp && qemuSlirpSetupCgroup(slirp, cgroup) < 0) return -1; - - if (net->type == VIR_DOMAIN_NET_TYPE_USER && - net->backend.type == VIR_DOMAIN_NET_BACKEND_PASST && - qemuPasstSetupCgroup(vm, net, cgroup) < 0) { - return -1; - } } for (i = 0; i < def->ntpms; i++) { diff --git a/src/qemu/qemu_passt.c b/src/qemu/qemu_passt.c index f640a69c00..2327b3e25e 100644 --- a/src/qemu/qemu_passt.c +++ b/src/qemu/qemu_passt.c @@ -28,29 +28,12 @@ #include "virerror.h" #include "virjson.h" #include "virlog.h" -#include "virpidfile.h" #define VIR_FROM_THIS VIR_FROM_NONE VIR_LOG_INIT("qemu.passt"); -static char * -qemuPasstCreatePidFilename(virDomainObj *vm, - virDomainNetDef *net) -{ - qemuDomainObjPrivate *priv = vm->privateData; - virQEMUDriver *driver = priv->driver; - g_autofree char *shortName = virDomainDefGetShortName(vm->def); - g_autoptr(virQEMUDriverConfig) cfg = virQEMUDriverGetConfig(driver); - g_autofree char *name = NULL; - - name = g_strdup_printf("%s-%s-passt", shortName, net->info.alias); - - return virPidFileBuildPath(cfg->passtStateDir, name); -} - - static char * qemuPasstCreateSocketPath(virDomainObj *vm, virDomainNetDef *net) @@ -65,17 +48,6 @@ qemuPasstCreateSocketPath(virDomainObj *vm, } -static int -qemuPasstGetPid(virDomainObj *vm, - virDomainNetDef *net, - pid_t *pid) -{ - g_autofree char *pidfile = qemuPasstCreatePidFilename(vm, net); - - return virPidFileReadPathIfLocked(pidfile, pid); -} - - int qemuPasstAddNetProps(virDomainObj *vm, virDomainNetDef *net, @@ -106,29 +78,32 @@ void qemuPasstStop(virDomainObj *vm, virDomainNetDef *net) { - g_autofree char *pidfile = qemuPasstCreatePidFilename(vm, net); - virErrorPtr orig_err; - - virErrorPreserveLast(&orig_err); - - if (virPidFileForceCleanupPath(pidfile) < 0) - VIR_WARN("Unable to kill passt process"); - - virErrorRestore(&orig_err); -} - + g_autofree char *passtSocketName = qemuPasstCreateSocketPath(vm, net); + struct sockaddr_un addr = { .sun_family = AF_UNIX }; + int fd; + + fd = socket(AF_UNIX, SOCK_STREAM, 0); + if (fd < 0) { + virReportError(errno, + "%s", _("Unable to open socket to connect to passt")); + return; + } -int -qemuPasstSetupCgroup(virDomainObj *vm, - virDomainNetDef *net, - virCgroup *cgroup) -{ - pid_t pid = (pid_t) -1; + if (virStrcpyStatic(addr.sun_path, passtSocketName) < 0) { + virReportError(VIR_ERR_INTERNAL_ERROR, + _("Socket path %s too big for destination"), + passtSocketName); + goto out; + } - if (qemuPasstGetPid(vm, net, &pid) < 0 || pid <= 0) - return -1; + if (connect(fd, (struct sockaddr *)&addr, sizeof(addr)) < 0) { + if (errno != ECONNREFUSED && errno != ENOENT) + virReportError(errno, + "%s", _("Unable to connect to passt to terminate it")); + } - return virCgroupAddProcess(cgroup, pid); + out: + VIR_FORCE_CLOSE(fd); } @@ -140,13 +115,9 @@ qemuPasstStart(virDomainObj *vm, virQEMUDriver *driver = priv->driver; g_autofree char *passtSocketName = qemuPasstCreateSocketPath(vm, net); g_autoptr(virCommand) cmd = NULL; - g_autofree char *pidfile = qemuPasstCreatePidFilename(vm, net); g_autofree char *errbuf = NULL; char macaddr[VIR_MAC_STRING_BUFLEN]; size_t i; - pid_t pid = (pid_t) -1; - int exitstatus = 0; - int cmdret = 0; cmd = virCommandNew(PASST); @@ -157,7 +128,6 @@ qemuPasstStart(virDomainObj *vm, "--one-off", "--socket", passtSocketName, "--mac-addr", virMacAddrFormat(&net->mac, macaddr), - "--pid", pidfile, NULL); if (net->mtu) { @@ -254,26 +224,15 @@ qemuPasstStart(virDomainObj *vm, virCommandAddArg(cmd, virBufferCurrentContent(&buf)); } - if (qemuExtDeviceLogCommand(driver, vm, cmd, "passt") < 0) return -1; - if (qemuSecurityCommandRun(driver, vm, cmd, -1, -1, &exitstatus, &cmdret) < 0) - goto error; - - if (cmdret < 0 || exitstatus != 0) { + /* passt forks once it's ready, terminates on connection closure */ + if (virCommandRun(cmd, NULL) < 0) { virReportError(VIR_ERR_INTERNAL_ERROR, _("Could not start 'passt': %s"), errbuf); - goto error; + return -1; } return 0; - - error: - ignore_value(virPidFileReadPathIfLocked(pidfile, &pid)); - if (pid != -1) - virProcessKillPainfully(pid, true); - unlink(pidfile); - - return -1; } -- StefanoOn 2/14/23 8:02 AM, Stefano Brivio wrote:Alright. I think I have a solution that would please everybody involved. I'll post it tomorrow though. I need to test it thoroughly. We would be able to get passt's PID (which is needed not only for killing it, but also for CGroup placement), NOT use --foreground and still pass errors from it to users (that is unless logfile was specified, because unfortunately, --log-file and --stderr are mutually exclusive).On Tue, 14 Feb 2023 12:51:22 +0100 Michal Privoznik <mprivozn(a)redhat.com> wrote:When passt starts it tries to do some security measures to restrict itself. For instance, it creates its own namespaces, umounts basically everything, drops capabilities, forks off to further restrict itself (the child is where all interesting work takes place now). This is sound, except it's causing two problems: 1) the PID file FD, which we leak into the passt process, gets closed (and thus our virPidFile*() helpers see unlocked PID file, which makes them think the process is gone),I didn't realise this was the case, but giving passt write (unless I'm missing something) access to a file created by libvirtd doesn't look desirable to me.> 2) the PID file no longer reflects true PID of the process. > > Worse, the child calls setsid() so we can't even kill the whole > process group. I mean, we can but it won't be any good.I think that (incorrect PID in the pidfile) is happening because Michal is using the original version of my patches that were pushed - I had mimicked the behavior of slirp, where libvirt deamonizes the new process. If that process then daemonizes itself, we have some sort of "double daemon"; libvirt has saved off the pid of what it thinks is going to be the final process, but then that process further forks and exits from the process whose pid libvirt saved. But because passt was cleaning up after itself I hadn't noticed the discrepancy in pids when testing. Without going into all the details of the pidfile and locking and etc, I just want to say that if we can fork/exec dnsmasq and let it daemonize itself and create its own pidfile, then certainly we can do the same thing for passt. (and if there's a fundamental problem, then it's a fundamental problem for dnsmasq as well).