core: add bpf-foreign to fragment parser

- Parse a string for bpf attach type
- Simplify bpffs path
- Add foreign bpf program to cgroup context

src/core/load-fragment-gperf.gperf.m4

@@ -234,7 +234,8 @@ $1.ManagedOOMSwap,                       config_parse_managed_oom_mode,
 $1.ManagedOOMMemoryPressure,             config_parse_managed_oom_mode,               0,                                  offsetof($1, cgroup_context.moom_mem_pressure)
 $1.ManagedOOMMemoryPressureLimit,        config_parse_managed_oom_mem_pressure_limit, 0,                                  offsetof($1, cgroup_context.moom_mem_pressure_limit)
 $1.ManagedOOMPreference,                 config_parse_managed_oom_preference,         0,                                  offsetof($1, cgroup_context.moom_preference)
-$1.NetClass,                             config_parse_warn_compat,                    DISABLED_LEGACY,                    0'
+$1.NetClass,                             config_parse_warn_compat,                    DISABLED_LEGACY,                    0
+$1.BPFProgram,                           config_parse_bpf_foreign_program,            0,                                  offsetof($1, cgroup_context)'
 )m4_dnl
 Unit.Description,                        config_parse_unit_string_printf,             0,                                  offsetof(Unit, description)
 Unit.Documentation,                      config_parse_documentation,                  0,                                  offsetof(Unit, documentation)

src/core/load-fragment.c

@@ -19,6 +19,7 @@
 #include "all-units.h"
 #include "alloc-util.h"
 #include "bpf-firewall.h"
+#include "bpf-program.h"
 #include "bus-error.h"
 #include "bus-internal.h"
 #include "bus-util.h"
@@ -5581,6 +5582,64 @@ int config_parse_ip_filter_bpf_progs(
         return 0;
 }
 
+int config_parse_bpf_foreign_program(
+                const char *unit,
+                const char *filename,
+                unsigned line,
+                const char *section,
+                unsigned section_line,
+                const char *lvalue,
+                int ltype,
+                const char *rvalue,
+                void *data,
+                void *userdata) {
+        _cleanup_free_ char *resolved = NULL, *word = NULL;
+        CGroupContext *c = data;
+        Unit *u = userdata;
+        int attach_type, r;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+
+        if (isempty(rvalue)) {
+                while (c->bpf_foreign_programs)
+                        cgroup_context_remove_bpf_foreign_program(c, c->bpf_foreign_programs);
+
+                return 0;
+        }
+
+        r = extract_first_word(&rvalue, &word, ":", 0);
+        if (r == -ENOMEM)
+                return log_oom();
+        if (r < 0) {
+                log_syntax(unit, LOG_WARNING, filename, line, r, "Failed to parse foreign BPF program, ignoring: %s", rvalue);
+                return 0;
+        }
+
+        attach_type = bpf_cgroup_attach_type_from_string(word);
+        if (attach_type < 0) {
+                log_syntax(unit, LOG_WARNING, filename, line, 0, "Unknown BPF attach type=%s, ignoring: %s", word, rvalue);
+                return 0;
+        }
+
+        r = unit_full_printf(u, rvalue, &resolved);
+        if (r < 0) {
+                log_syntax(unit, LOG_WARNING, filename, line, r, "Failed to resolve unit specifiers in '%s', ignoring: %m", rvalue);
+                return 0;
+        }
+
+        r = path_simplify_and_warn(resolved, PATH_CHECK_ABSOLUTE, unit, filename, line, lvalue);
+        if (r < 0)
+                return 0;
+
+        r = cgroup_add_bpf_foreign_program(c, attach_type, resolved);
+        if (r < 0)
+                return log_error_errno(r, "Failed to add foreign BPF program to cgroup context: %m");
+
+        return 0;
+}
+
 static int merge_by_names(Unit **u, Set *names, const char *id) {
         char *k;
         int r;

src/core/load-fragment.h

@@ -140,6 +140,7 @@ CONFIG_PARSER_PROTOTYPE(config_parse_swap_priority);
 CONFIG_PARSER_PROTOTYPE(config_parse_mount_images);
 CONFIG_PARSER_PROTOTYPE(config_parse_socket_timestamping);
 CONFIG_PARSER_PROTOTYPE(config_parse_extension_images);
+CONFIG_PARSER_PROTOTYPE(config_parse_bpf_foreign_program);
 
 /* gperf prototypes */
 const struct ConfigPerfItem* load_fragment_gperf_lookup(const char *key, GPERF_LEN_TYPE length);