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/* 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
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