nsresourced: add client-side helpers around nsresourced APIs

This adds simple functions that wrap the Varlink IPC calls.

src/shared/meson.build

@@ -126,6 +126,7 @@ shared_sources = files(
         'netif-sriov.c',
         'netif-util.c',
         'nsflags.c',
+        'nsresource.c',
         'numa-util.c',
         'open-file.c',
         'openssl-util.c',

src/shared/nsresource.c

@@ -0,0 +1,329 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <sys/prctl.h>
+
+#include "fd-util.h"
+#include "format-util.h"
+#include "missing_sched.h"
+#include "namespace-util.h"
+#include "nsresource.h"
+#include "process-util.h"
+#include "varlink.h"
+
+static int make_pid_name(char **ret) {
+        char comm[TASK_COMM_LEN];
+
+        assert(ret);
+
+        if (prctl(PR_GET_NAME, comm) < 0)
+                return -errno;
+
+        /* So the namespace name should be 16 chars at max (because we want that it is usable in usernames,
+         * which have a limit of 31 chars effectively, and the nsresourced service wants to prefix/suffix
+         * some bits). But it also should be unique if we are called multiple times in a row. Hence we take
+         * the "comm" name (which is 15 chars), and suffix it with the UID, possibly overriding the end. */
+        assert_cc(TASK_COMM_LEN == 15 + 1);
+
+        char spid[DECIMAL_STR_MAX(pid_t)];
+        xsprintf(spid, PID_FMT, getpid_cached());
+
+        assert(strlen(spid) <= 16);
+        strshorten(comm, 16 - strlen(spid));
+
+        _cleanup_free_ char *s = strjoin(comm, spid);
+        if (!s)
+                return -ENOMEM;
+
+        *ret = TAKE_PTR(s);
+        return 0;
+}
+
+int nsresource_allocate_userns(const char *name, uint64_t size) {
+        _cleanup_(varlink_unrefp) Varlink *vl = NULL;
+        _cleanup_close_ int userns_fd = -EBADF;
+        _cleanup_free_ char *_name = NULL;
+        const char *error_id;
+        int r, userns_fd_idx;
+
+        /* Allocate a new dynamic user namespace via the userdb registry logic */
+
+        if (!name) {
+                r = make_pid_name(&_name);
+                if (r < 0)
+                        return r;
+
+                name = _name;
+        }
+
+        if (size <= 0 || size > UINT64_C(0x100000000)) /* Note: the server actually only allows allocating 1 or 64K right now */
+                return -EINVAL;
+
+        r = varlink_connect_address(&vl, "/run/systemd/io.systemd.NamespaceResource");
+        if (r < 0)
+                return log_debug_errno(r, "Failed to connect to namespace resource manager: %m");
+
+        r = varlink_set_allow_fd_passing_output(vl, true);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to enable varlink fd passing for write: %m");
+
+        userns_fd = userns_acquire_empty();
+        if (userns_fd < 0)
+                return log_debug_errno(userns_fd, "Failed to acquire empty user namespace: %m");
+
+        userns_fd_idx = varlink_push_dup_fd(vl, userns_fd);
+        if (userns_fd_idx < 0)
+                return log_debug_errno(userns_fd_idx, "Failed to push userns fd into varlink connection: %m");
+
+        JsonVariant *reply = NULL;
+        r = varlink_callb(vl,
+                          "io.systemd.NamespaceResource.AllocateUserRange",
+                          &reply,
+                          &error_id,
+                          JSON_BUILD_OBJECT(
+                                          JSON_BUILD_PAIR("name", JSON_BUILD_STRING(name)),
+                                          JSON_BUILD_PAIR("size", JSON_BUILD_UNSIGNED(size)),
+                                          JSON_BUILD_PAIR("userNamespaceFileDescriptor", JSON_BUILD_UNSIGNED(userns_fd_idx))));
+        if (r < 0)
+                return log_debug_errno(r, "Failed to call AllocateUserRange() varlink call: %m");
+        if (error_id)
+                return log_debug_errno(varlink_error_to_errno(error_id, reply), "Failed to allocate user namespace with %" PRIu64 " users: %s", size, error_id);
+
+        return TAKE_FD(userns_fd);
+}
+
+int nsresource_register_userns(const char *name, int userns_fd) {
+        _cleanup_(varlink_unrefp) Varlink *vl = NULL;
+        _cleanup_close_ int _userns_fd = -EBADF;
+        _cleanup_free_ char *_name = NULL;
+        const char *error_id;
+        int r, userns_fd_idx;
+
+        /* Register the specified user namespace with userbd. */
+
+        if (!name) {
+                r = make_pid_name(&_name);
+                if (r < 0)
+                        return r;
+
+                name = _name;
+        }
+
+        if (userns_fd < 0) {
+                _userns_fd = namespace_open_by_type(NAMESPACE_USER);
+                if (_userns_fd < 0)
+                        return -errno;
+
+                userns_fd = _userns_fd;
+        }
+
+        r = varlink_connect_address(&vl, "/run/systemd/io.systemd.NamespaceResource");
+        if (r < 0)
+                return log_debug_errno(r, "Failed to connect to namespace resource manager: %m");
+
+        r = varlink_set_allow_fd_passing_output(vl, true);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to enable varlink fd passing for write: %m");
+
+        userns_fd_idx = varlink_push_dup_fd(vl, userns_fd);
+        if (userns_fd_idx < 0)
+                return log_debug_errno(userns_fd_idx, "Failed to push userns fd into varlink connection: %m");
+
+        JsonVariant *reply = NULL;
+        r = varlink_callb(vl,
+                          "io.systemd.NamespaceResource.RegisterUserNamespace",
+                          &reply,
+                          &error_id,
+                          JSON_BUILD_OBJECT(
+                                          JSON_BUILD_PAIR("name", JSON_BUILD_STRING(name)),
+                                          JSON_BUILD_PAIR("userNamespaceFileDescriptor", JSON_BUILD_UNSIGNED(userns_fd_idx))));
+        if (r < 0)
+                return log_debug_errno(r, "Failed to call RegisterUserNamespace() varlink call: %m");
+        if (error_id)
+                return log_debug_errno(varlink_error_to_errno(error_id, reply), "Failed to register user namespace: %s", error_id);
+
+        return 0;
+}
+
+int nsresource_add_mount(int userns_fd, int mount_fd) {
+        _cleanup_(varlink_unrefp) Varlink *vl = NULL;
+        int r, userns_fd_idx, mount_fd_idx;
+        const char *error_id;
+
+        assert(mount_fd >= 0);
+
+        if (userns_fd < 0) {
+                int _userns_fd = namespace_open_by_type(NAMESPACE_USER);
+                if (_userns_fd < 0)
+                        return -errno;
+
+                userns_fd = _userns_fd;
+        }
+
+        r = varlink_connect_address(&vl, "/run/systemd/io.systemd.NamespaceResource");
+        if (r < 0)
+                return log_error_errno(r, "Failed to connect to namespace resource manager: %m");
+
+        r = varlink_set_allow_fd_passing_output(vl, true);
+        if (r < 0)
+                return log_error_errno(r, "Failed to enable varlink fd passing for write: %m");
+
+        userns_fd_idx = varlink_push_dup_fd(vl, userns_fd);
+        if (userns_fd_idx < 0)
+                return log_error_errno(userns_fd_idx, "Failed to push userns fd into varlink connection: %m");
+
+        mount_fd_idx = varlink_push_dup_fd(vl, mount_fd);
+        if (mount_fd_idx < 0)
+                return log_error_errno(mount_fd_idx, "Failed to push mount fd into varlink connection: %m");
+
+        JsonVariant *reply = NULL;
+        r = varlink_callb(vl,
+                          "io.systemd.NamespaceResource.AddMountToUserNamespace",
+                          &reply,
+                          &error_id,
+                          JSON_BUILD_OBJECT(
+                                          JSON_BUILD_PAIR("userNamespaceFileDescriptor", JSON_BUILD_UNSIGNED(userns_fd_idx)),
+                                          JSON_BUILD_PAIR("mountFileDescriptor", JSON_BUILD_UNSIGNED(mount_fd_idx))));
+        if (r < 0)
+                return log_error_errno(r, "Failed to call AddMountToUserNamespace() varlink call: %m");
+        if (streq_ptr(error_id, "io.systemd.NamespaceResource.UserNamespaceNotRegistered")) {
+                log_notice("User namespace has not been allocated via namespace resource registry, not adding mount to registration.");
+                return 0;
+        }
+        if (error_id)
+                return log_error_errno(varlink_error_to_errno(error_id, reply), "Failed to mount image: %s", error_id);
+
+        return 1;
+}
+
+int nsresource_add_cgroup(int userns_fd, int cgroup_fd) {
+        _cleanup_(varlink_unrefp) Varlink *vl = NULL;
+        _cleanup_close_ int _userns_fd = -EBADF;
+        int r, userns_fd_idx, cgroup_fd_idx;
+        const char *error_id;
+
+        assert(cgroup_fd >= 0);
+
+        if (userns_fd < 0) {
+                _userns_fd = namespace_open_by_type(NAMESPACE_USER);
+                if (_userns_fd < 0)
+                        return -errno;
+
+                userns_fd = _userns_fd;
+        }
+
+        r = varlink_connect_address(&vl, "/run/systemd/io.systemd.NamespaceResource");
+        if (r < 0)
+                return log_debug_errno(r, "Failed to connect to namespace resource manager: %m");
+
+        r = varlink_set_allow_fd_passing_output(vl, true);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to enable varlink fd passing for write: %m");
+
+        userns_fd_idx = varlink_push_dup_fd(vl, userns_fd);
+        if (userns_fd_idx < 0)
+                return log_debug_errno(userns_fd_idx, "Failed to push userns fd into varlink connection: %m");
+
+        cgroup_fd_idx = varlink_push_dup_fd(vl, cgroup_fd);
+        if (cgroup_fd_idx < 0)
+                return log_debug_errno(userns_fd_idx, "Failed to push cgroup fd into varlink connection: %m");
+
+        JsonVariant *reply = NULL;
+        r = varlink_callb(vl,
+                          "io.systemd.NamespaceResource.AddControlGroupToUserNamespace",
+                          &reply,
+                          &error_id,
+                          JSON_BUILD_OBJECT(
+                                          JSON_BUILD_PAIR("userNamespaceFileDescriptor", JSON_BUILD_UNSIGNED(userns_fd_idx)),
+                                          JSON_BUILD_PAIR("controlGroupFileDescriptor", JSON_BUILD_UNSIGNED(cgroup_fd_idx))));
+        if (r < 0)
+                return log_debug_errno(r, "Failed to call AddControlGroupToUserNamespace() varlink call: %m");
+        if (streq_ptr(error_id, "io.systemd.NamespaceResource.UserNamespaceNotRegistered")) {
+                log_notice("User namespace has not been allocated via namespace resource registry, not adding cgroup to registration.");
+                return 0;
+        }
+        if (error_id)
+                return log_debug_errno(varlink_error_to_errno(error_id, reply), "Failed to add cgroup to user namespace: %s", error_id);
+
+        return 1;
+}
+
+int nsresource_add_netif(
+                int userns_fd,
+                int netns_fd,
+                const char *namespace_ifname,
+                char **ret_host_ifname,
+                char **ret_namespace_ifname) {
+
+        _cleanup_close_ int _userns_fd = -EBADF, _netns_fd = -EBADF;
+        _cleanup_(varlink_unrefp) Varlink *vl = NULL;
+        int r, userns_fd_idx, netns_fd_idx;
+        const char *error_id;
+
+        if (userns_fd < 0) {
+                _userns_fd = namespace_open_by_type(NAMESPACE_USER);
+                if (_userns_fd < 0)
+                        return -errno;
+
+                userns_fd = _userns_fd;
+        }
+
+        if (netns_fd < 0) {
+                _netns_fd = namespace_open_by_type(NAMESPACE_NET);
+                if (_netns_fd < 0)
+                        return -errno;
+
+                netns_fd = _netns_fd;
+        }
+
+        r = varlink_connect_address(&vl, "/run/systemd/io.systemd.NamespaceResource");
+        if (r < 0)
+                return log_debug_errno(r, "Failed to connect to namespace resource manager: %m");
+
+        r = varlink_set_allow_fd_passing_output(vl, true);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to enable varlink fd passing for write: %m");
+
+        userns_fd_idx = varlink_push_dup_fd(vl, userns_fd);
+        if (userns_fd_idx < 0)
+                return log_debug_errno(userns_fd_idx, "Failed to push userns fd into varlink connection: %m");
+
+        netns_fd_idx = varlink_push_dup_fd(vl, netns_fd);
+        if (netns_fd_idx < 0)
+                return log_debug_errno(netns_fd_idx, "Failed to push netns fd into varlink connection: %m");
+
+        JsonVariant *reply = NULL;
+        r = varlink_callb(vl,
+                          "io.systemd.NamespaceResource.AddNetworkToUserNamespace",
+                          &reply,
+                          &error_id,
+                          JSON_BUILD_OBJECT(
+                                          JSON_BUILD_PAIR("userNamespaceFileDescriptor", JSON_BUILD_UNSIGNED(userns_fd_idx)),
+                                          JSON_BUILD_PAIR("networkNamespaceFileDescriptor", JSON_BUILD_UNSIGNED(netns_fd_idx)),
+                                          JSON_BUILD_PAIR("mode", JSON_BUILD_CONST_STRING("veth")),
+                                          JSON_BUILD_PAIR_CONDITION(namespace_ifname, "namespaceInterfaceName", JSON_BUILD_STRING(namespace_ifname))));
+        if (r < 0)
+                return log_debug_errno(r, "Failed to call AddNetworkToUserNamespace() varlink call: %m");
+        if (streq_ptr(error_id, "io.systemd.NamespaceResource.UserNamespaceNotRegistered")) {
+                log_notice("User namespace has not been allocated via namespace resource registry, not adding network to registration.");
+                return 0;
+        }
+        if (error_id)
+                return log_debug_errno(varlink_error_to_errno(error_id, reply), "Failed to add network to user namespace: %s", error_id);
+
+        _cleanup_free_ char *host_interface_name = NULL, *namespace_interface_name = NULL;
+        r = json_dispatch(
+                        reply,
+                        (const JsonDispatch[]) {
+                                { "hostInterfaceName",      JSON_VARIANT_STRING, json_dispatch_string, PTR_TO_SIZE(&host_interface_name)      },
+                                { "namespaceInterfaceName", JSON_VARIANT_STRING, json_dispatch_string, PTR_TO_SIZE(&namespace_interface_name) },
+                        },
+                        JSON_ALLOW_EXTENSIONS,
+                        /* userdata= */ NULL);
+
+        if (ret_host_ifname)
+                *ret_host_ifname = TAKE_PTR(host_interface_name);
+        if (ret_namespace_ifname)
+                *ret_namespace_ifname = TAKE_PTR(namespace_interface_name);
+
+        return 1;
+}

src/shared/nsresource.h

@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#pragma once
+
+#include <inttypes.h>
+
+int nsresource_allocate_userns(const char *name, uint64_t size);
+int nsresource_register_userns(const char *name, int userns_fd);
+int nsresource_add_mount(int userns_fd, int mount_fd);
+int nsresource_add_cgroup(int userns_fd, int cgroup_fd);
+int nsresource_add_netif(int userns_fd, int netns_fd, const char *namespace_ifname, char **ret_host_ifname, char **ret_namespace_ifname);