Add abstraction model for BPF programs

This object takes a number of bpf_insn members and wraps them together with
the in-kernel reference id. Will be needed by the firewall code.

src/basic/bpf-program.c

@@ -0,0 +1,182 @@
+/***
+  This file is part of systemd.
+
+  Copyright 2016 Daniel Mack
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include <fcntl.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "alloc-util.h"
+#include "bpf-program.h"
+#include "fd-util.h"
+#include "log.h"
+#include "missing.h"
+
+int bpf_program_new(uint32_t prog_type, BPFProgram **ret) {
+        _cleanup_(bpf_program_unrefp) BPFProgram *p = NULL;
+
+        p = new0(BPFProgram, 1);
+        if (!p)
+                return log_oom();
+
+        p->prog_type = prog_type;
+        p->kernel_fd = -1;
+
+        *ret = p;
+        p = NULL;
+        return 0;
+}
+
+BPFProgram *bpf_program_unref(BPFProgram *p) {
+        if (!p)
+                return NULL;
+
+        safe_close(p->kernel_fd);
+        free(p->instructions);
+
+        return mfree(p);
+}
+
+int bpf_program_add_instructions(BPFProgram *p, const struct bpf_insn *instructions, size_t count) {
+
+        assert(p);
+
+        if (!GREEDY_REALLOC(p->instructions, p->allocated, p->n_instructions + count))
+                return -ENOMEM;
+
+        memcpy(p->instructions + p->n_instructions, instructions, sizeof(struct bpf_insn) * count);
+        p->n_instructions += count;
+
+        return 0;
+}
+
+int bpf_program_load_kernel(BPFProgram *p, char *log_buf, size_t log_size) {
+        union bpf_attr attr;
+
+        assert(p);
+
+        if (p->kernel_fd >= 0)
+                return -EBUSY;
+
+        attr = (union bpf_attr) {
+                .prog_type = p->prog_type,
+                .insns = PTR_TO_UINT64(p->instructions),
+                .insn_cnt = p->n_instructions,
+                .license = PTR_TO_UINT64("GPL"),
+                .log_buf = PTR_TO_UINT64(log_buf),
+                .log_level = !!log_buf,
+                .log_size = log_size,
+        };
+
+        p->kernel_fd = bpf(BPF_PROG_LOAD, &attr, sizeof(attr));
+        if (p->kernel_fd < 0)
+                return -errno;
+
+        return 0;
+}
+
+int bpf_program_cgroup_attach(BPFProgram *p, int type, const char *path) {
+        _cleanup_close_ int fd = -1;
+        union bpf_attr attr;
+
+        assert(p);
+        assert(type >= 0);
+        assert(path);
+
+        fd = open(path, O_DIRECTORY|O_RDONLY|O_CLOEXEC);
+        if (fd < 0)
+                return -errno;
+
+        attr = (union bpf_attr) {
+                .attach_type = type,
+                .target_fd = fd,
+                .attach_bpf_fd = p->kernel_fd,
+        };
+
+        if (bpf(BPF_PROG_ATTACH, &attr, sizeof(attr)) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int bpf_program_cgroup_detach(int type, const char *path) {
+        _cleanup_close_ int fd = -1;
+        union bpf_attr attr;
+
+        assert(path);
+
+        fd = open(path, O_DIRECTORY|O_RDONLY|O_CLOEXEC);
+        if (fd < 0)
+                return -errno;
+
+        attr = (union bpf_attr) {
+                .attach_type = type,
+                .target_fd = fd,
+        };
+
+        if (bpf(BPF_PROG_DETACH, &attr, sizeof(attr)) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int bpf_map_new(enum bpf_map_type type, size_t key_size, size_t value_size, size_t max_entries, uint32_t flags) {
+        union bpf_attr attr = {
+                .map_type = type,
+                .key_size = key_size,
+                .value_size = value_size,
+                .max_entries = max_entries,
+                .map_flags = flags,
+        };
+        int fd;
+
+        fd = bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
+        if (fd < 0)
+                return -errno;
+
+        return fd;
+}
+
+int bpf_map_update_element(int fd, const void *key, void *value) {
+
+        union bpf_attr attr = {
+                .map_fd = fd,
+                .key = PTR_TO_UINT64(key),
+                .value = PTR_TO_UINT64(value),
+        };
+
+        if (bpf(BPF_MAP_UPDATE_ELEM, &attr, sizeof(attr)) < 0)
+                return -errno;
+
+        return 0;
+}
+
+int bpf_map_lookup_element(int fd, const void *key, void *value) {
+
+        union bpf_attr attr = {
+                .map_fd = fd,
+                .key = PTR_TO_UINT64(key),
+                .value = PTR_TO_UINT64(value),
+        };
+
+        if (bpf(BPF_MAP_LOOKUP_ELEM, &attr, sizeof(attr)) < 0)
+                return -errno;
+
+        return 0;
+}