diff options
Diffstat (limited to 'src/core/restrict-ifaces.c')
| -rw-r--r-- | src/core/restrict-ifaces.c | 200 |
1 files changed, 200 insertions, 0 deletions
diff --git a/src/core/restrict-ifaces.c b/src/core/restrict-ifaces.c new file mode 100644 index 0000000..4dd8656 --- /dev/null +++ b/src/core/restrict-ifaces.c @@ -0,0 +1,200 @@ +/* SPDX-License-Identifier: LGPL-2.1-or-later */ + +#include "fd-util.h" +#include "restrict-ifaces.h" +#include "netlink-util.h" + +#if BPF_FRAMEWORK +/* libbpf, clang and llc compile time dependencies are satisfied */ + +#include "bpf-dlopen.h" +#include "bpf-link.h" +#include "bpf-util.h" +#include "bpf/restrict_ifaces/restrict-ifaces-skel.h" + +static struct restrict_ifaces_bpf *restrict_ifaces_bpf_free(struct restrict_ifaces_bpf *obj) { + restrict_ifaces_bpf__destroy(obj); + return NULL; +} + +DEFINE_TRIVIAL_CLEANUP_FUNC(struct restrict_ifaces_bpf *, restrict_ifaces_bpf_free); + +static int prepare_restrict_ifaces_bpf( + Unit* u, + bool is_allow_list, + const Set *restrict_network_interfaces, + struct restrict_ifaces_bpf **ret_object) { + + _cleanup_(restrict_ifaces_bpf_freep) struct restrict_ifaces_bpf *obj = NULL; + _cleanup_(sd_netlink_unrefp) sd_netlink *rtnl = NULL; + char *iface; + int r, map_fd; + + assert(ret_object); + + obj = restrict_ifaces_bpf__open(); + if (!obj) + return log_unit_full_errno(u, u ? LOG_ERR : LOG_DEBUG, errno, "restrict-interfaces: Failed to open BPF object: %m"); + + r = sym_bpf_map__set_max_entries(obj->maps.sd_restrictif, MAX(set_size(restrict_network_interfaces), 1u)); + if (r != 0) + return log_unit_full_errno(u, u ? LOG_ERR : LOG_WARNING, r, + "restrict-interfaces: Failed to resize BPF map '%s': %m", + sym_bpf_map__name(obj->maps.sd_restrictif)); + + obj->rodata->is_allow_list = is_allow_list; + + r = restrict_ifaces_bpf__load(obj); + if (r != 0) + return log_unit_full_errno(u, u ? LOG_ERR : LOG_DEBUG, r, "restrict-interfaces: Failed to load BPF object: %m"); + + map_fd = sym_bpf_map__fd(obj->maps.sd_restrictif); + + SET_FOREACH(iface, restrict_network_interfaces) { + uint8_t dummy = 0; + int ifindex; + + ifindex = rtnl_resolve_interface(&rtnl, iface); + if (ifindex < 0) { + log_unit_warning_errno(u, ifindex, + "restrict-interfaces: Couldn't find index of network interface '%s', ignoring: %m", + iface); + continue; + } + + if (sym_bpf_map_update_elem(map_fd, &ifindex, &dummy, BPF_ANY)) + return log_unit_full_errno(u, u ? LOG_ERR : LOG_WARNING, errno, + "restrict-interfaces: Failed to update BPF map '%s' fd: %m", + sym_bpf_map__name(obj->maps.sd_restrictif)); + } + + *ret_object = TAKE_PTR(obj); + return 0; +} + +int restrict_network_interfaces_supported(void) { + _cleanup_(restrict_ifaces_bpf_freep) struct restrict_ifaces_bpf *obj = NULL; + static int supported = -1; + int r; + + if (supported >= 0) + return supported; + + if (!cgroup_bpf_supported()) + return (supported = false); + + if (!compat_libbpf_probe_bpf_prog_type(BPF_PROG_TYPE_CGROUP_SKB, /*opts=*/NULL)) { + log_debug("restrict-interfaces: BPF program type cgroup_skb is not supported"); + return (supported = false); + } + + r = prepare_restrict_ifaces_bpf(NULL, true, NULL, &obj); + if (r < 0) { + log_debug_errno(r, "restrict-interfaces: Failed to load BPF object: %m"); + return (supported = false); + } + + return (supported = bpf_can_link_program(obj->progs.sd_restrictif_i)); +} + +static int restrict_network_interfaces_install_impl(Unit *u) { + _cleanup_(bpf_link_freep) struct bpf_link *egress_link = NULL, *ingress_link = NULL; + _cleanup_(restrict_ifaces_bpf_freep) struct restrict_ifaces_bpf *obj = NULL; + _cleanup_free_ char *cgroup_path = NULL; + _cleanup_close_ int cgroup_fd = -EBADF; + CGroupContext *cc; + int r; + + cc = unit_get_cgroup_context(u); + if (!cc) + return 0; + + r = cg_get_path(SYSTEMD_CGROUP_CONTROLLER, u->cgroup_path, NULL, &cgroup_path); + if (r < 0) + return log_unit_error_errno(u, r, "restrict-interfaces: Failed to get cgroup path: %m"); + + if (!cc->restrict_network_interfaces) + return 0; + + r = prepare_restrict_ifaces_bpf(u, + cc->restrict_network_interfaces_is_allow_list, + cc->restrict_network_interfaces, + &obj); + if (r < 0) + return r; + + cgroup_fd = open(cgroup_path, O_RDONLY | O_CLOEXEC | O_DIRECTORY, 0); + if (cgroup_fd < 0) + return -errno; + + ingress_link = sym_bpf_program__attach_cgroup(obj->progs.sd_restrictif_i, cgroup_fd); + r = sym_libbpf_get_error(ingress_link); + if (r != 0) + return log_unit_error_errno(u, r, "restrict-interfaces: Failed to create ingress cgroup link: %m"); + + egress_link = sym_bpf_program__attach_cgroup(obj->progs.sd_restrictif_e, cgroup_fd); + r = sym_libbpf_get_error(egress_link); + if (r != 0) + return log_unit_error_errno(u, r, "restrict-interfaces: Failed to create egress cgroup link: %m"); + + u->restrict_ifaces_ingress_bpf_link = TAKE_PTR(ingress_link); + u->restrict_ifaces_egress_bpf_link = TAKE_PTR(egress_link); + + return 0; +} + +int restrict_network_interfaces_install(Unit *u) { + int r = restrict_network_interfaces_install_impl(u); + fdset_close(u->initial_restric_ifaces_link_fds); + return r; +} + +int serialize_restrict_network_interfaces(Unit *u, FILE *f, FDSet *fds) { + int r; + + assert(u); + + r = bpf_serialize_link(f, fds, "restrict-ifaces-bpf-fd", u->restrict_ifaces_ingress_bpf_link); + if (r < 0) + return r; + + return bpf_serialize_link(f, fds, "restrict-ifaces-bpf-fd", u->restrict_ifaces_egress_bpf_link); +} + +int restrict_network_interfaces_add_initial_link_fd(Unit *u, int fd) { + int r; + + assert(u); + + if (!u->initial_restric_ifaces_link_fds) { + u->initial_restric_ifaces_link_fds = fdset_new(); + if (!u->initial_restric_ifaces_link_fds) + return log_oom(); + } + + r = fdset_put(u->initial_restric_ifaces_link_fds, fd); + if (r < 0) + return log_unit_error_errno(u, r, + "restrict-interfaces: Failed to put restrict-ifaces-bpf-fd %d to restored fdset: %m", fd); + + return 0; +} + +#else /* ! BPF_FRAMEWORK */ +int restrict_network_interfaces_supported(void) { + return 0; +} + +int restrict_network_interfaces_install(Unit *u) { + return log_unit_debug_errno(u, SYNTHETIC_ERRNO(EOPNOTSUPP), + "restrict-interfaces: Failed to install; BPF programs built from source code are not supported: %m"); +} + +int serialize_restrict_network_interfaces(Unit *u, FILE *f, FDSet *fds) { + return 0; +} + +int restrict_network_interfaces_add_initial_link_fd(Unit *u, int fd) { + return 0; +} +#endif |