1 files changed, 319 insertions, 0 deletions
diff --git a/src/libknot/xdp/bpf-user.c b/src/libknot/xdp/bpf-user.c
new file mode 100644
index 0000000..449dffe
--- /dev/null
+++ b/src/libknot/xdp/bpf-user.c
@@ -0,0 +1,319 @@
+/*  Copyright (C) 2022 CZ.NIC, z.s.p.o. <knot-dns@labs.nic.cz>
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program 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 General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <bpf/bpf.h>
+#include <linux/if_link.h>
+#include <net/if.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+#include "libknot/endian.h"
+#include "libknot/error.h"
+#include "libknot/xdp/bpf-kernel-obj.h"
+#include "libknot/xdp/bpf-user.h"
+#include "libknot/xdp/eth.h"
+#include "contrib/openbsd/strlcpy.h"
+
+#define NO_BPF_MAPS	2
+
+static inline bool IS_ERR_OR_NULL(const void *ptr)
+{
+	return (ptr == NULL) || (unsigned long)ptr >= (unsigned long)-4095;
+}
+
+static int prog_load(struct bpf_object **pobj, int *prog_fd)
+{
+	struct bpf_program *prog, *first_prog = NULL;
+	struct bpf_object *obj;
+
+	obj = bpf_object__open_mem(bpf_kernel_o, bpf_kernel_o_len, NULL);
+	if (IS_ERR_OR_NULL(obj)) {
+		return KNOT_ENOENT;
+	}
+
+	bpf_object__for_each_program(prog, obj) {
+		bpf_program__set_type(prog, BPF_PROG_TYPE_XDP);
+		if (first_prog == NULL) {
+			first_prog = prog;
+		}
+	}
+
+	if (first_prog == NULL) {
+		bpf_object__close(obj);
+		return KNOT_ENOENT;
+	}
+
+	int ret = bpf_object__load(obj);
+	if (ret != 0) {
+		bpf_object__close(obj);
+		return KNOT_EINVAL;
+	}
+
+	*pobj = obj;
+	*prog_fd = bpf_program__fd(first_prog);
+
+	return KNOT_EOK;
+}
+
+static int ensure_prog(struct kxsk_iface *iface, bool overwrite, bool generic_xdp)
+{
+	if (bpf_kernel_o_len < 2) {
+		return KNOT_ENOTSUP;
+	}
+
+	/* Use libbpf for extracting BPF byte-code from BPF-ELF object, and
+	 * loading this into the kernel via bpf-syscall. */
+	int prog_fd;
+	int ret = prog_load(&iface->prog_obj, &prog_fd);
+	if (ret != KNOT_EOK) {
+		return KNOT_EPROGRAM;
+	}
+
+	uint32_t flags = 0;
+	if (!overwrite) {
+		flags |= XDP_FLAGS_UPDATE_IF_NOEXIST;
+	}
+	if (generic_xdp) {
+		flags |= XDP_FLAGS_SKB_MODE;
+	}
+
+#if USE_LIBXDP
+	ret = bpf_xdp_attach(iface->if_index, prog_fd, flags, NULL);
+#else
+	ret = bpf_set_link_xdp_fd(iface->if_index, prog_fd, flags);
+#endif
+	if (ret != 0) {
+		close(prog_fd);
+	}
+	if (ret == -EBUSY && !overwrite) { // We try accepting the present program.
+		uint32_t prog_id = 0;
+#if USE_LIBXDP
+		ret = bpf_xdp_query_id(iface->if_index, 0, &prog_id);
+#else
+		ret = bpf_get_link_xdp_id(iface->if_index, &prog_id, 0);
+#endif
+		if (ret == 0 && prog_id != 0) {
+			ret = prog_fd = bpf_prog_get_fd_by_id(prog_id);
+		}
+	}
+	if (ret < 0) {
+		return KNOT_EFD;
+	} else {
+		return prog_fd;
+	}
+}
+
+static void unget_bpf_maps(struct kxsk_iface *iface)
+{
+	if (iface->opts_map_fd >= 0) {
+		close(iface->opts_map_fd);
+	}
+	if (iface->xsks_map_fd >= 0) {
+		close(iface->xsks_map_fd);
+	}
+	iface->opts_map_fd = iface->xsks_map_fd = -1;
+}
+
+/*!
+ * /brief Get FDs for the two maps and assign them into xsk_info-> fields.
+ *
+ * Inspired by xsk_lookup_bpf_maps() from libbpf before qidconf_map elimination.
+ */
+static int get_bpf_maps(int prog_fd, struct kxsk_iface *iface)
+{
+	uint32_t *map_ids = calloc(NO_BPF_MAPS, sizeof(*map_ids));
+	if (map_ids == NULL) {
+		return KNOT_ENOMEM;
+	}
+
+	struct bpf_prog_info prog_info = {
+		.nr_map_ids = NO_BPF_MAPS,
+		.map_ids = (__u64)(unsigned long)map_ids,
+	};
+
+	uint32_t prog_len = sizeof(struct bpf_prog_info);
+	int ret = bpf_obj_get_info_by_fd(prog_fd, &prog_info, &prog_len);
+	if (ret != 0) {
+		free(map_ids);
+		return ret;
+	}
+
+	for (int i = 0; i < NO_BPF_MAPS; ++i) {
+		int fd = bpf_map_get_fd_by_id(map_ids[i]);
+		if (fd < 0) {
+			continue;
+		}
+
+		struct bpf_map_info map_info = { 0 };
+		uint32_t map_len = sizeof(struct bpf_map_info);
+		ret = bpf_obj_get_info_by_fd(fd, &map_info, &map_len);
+		if (ret != 0) {
+			close(fd);
+			continue;
+		}
+
+		if (strcmp(map_info.name, "opts_map") == 0) {
+			iface->opts_map_fd = fd;
+			continue;
+		}
+
+		if (strcmp(map_info.name, "xsks_map") == 0) {
+			iface->xsks_map_fd = fd;
+			continue;
+		}
+
+		close(fd);
+	}
+
+	if (iface->opts_map_fd < 0 || iface->xsks_map_fd < 0) {
+		unget_bpf_maps(iface);
+		free(map_ids);
+		return KNOT_ENOENT;
+	}
+
+	free(map_ids);
+	return KNOT_EOK;
+}
+
+int kxsk_socket_start(const struct kxsk_iface *iface, knot_xdp_filter_flag_t flags,
+                      uint16_t udp_port, uint16_t quic_port, struct xsk_socket *xsk)
+{
+	if (iface == NULL || xsk == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	int fd = xsk_socket__fd(xsk);
+	int ret = bpf_map_update_elem(iface->xsks_map_fd, &iface->if_queue, &fd, 0);
+	if (ret != 0) {
+		return ret;
+	}
+
+	knot_xdp_opts_t opts = {
+		.flags = flags | KNOT_XDP_FILTER_ON,
+		.udp_port = udp_port,
+		.quic_port = quic_port,
+	};
+
+	ret = bpf_map_update_elem(iface->opts_map_fd, &iface->if_queue, &opts, 0);
+	if (ret != 0) {
+		(void)bpf_map_delete_elem(iface->xsks_map_fd, &iface->if_queue);
+	}
+
+	return ret;
+}
+
+void kxsk_socket_stop(const struct kxsk_iface *iface)
+{
+	if (iface == NULL) {
+		return;
+	}
+
+	knot_xdp_opts_t opts = { 0 };
+
+	(void)bpf_map_update_elem(iface->opts_map_fd, &iface->if_queue, &opts, 0);
+	(void)bpf_map_delete_elem(iface->xsks_map_fd, &iface->if_queue);
+}
+
+int kxsk_iface_new(const char *if_name, unsigned if_queue, knot_xdp_load_bpf_t load_bpf,
+                   bool generic_xdp, struct kxsk_iface **out_iface)
+{
+	if (if_name == NULL || out_iface == NULL) {
+		return KNOT_EINVAL;
+	}
+
+	struct kxsk_iface *iface = calloc(1, sizeof(*iface) + IFNAMSIZ);
+	if (iface == NULL) {
+		return KNOT_ENOMEM;
+	}
+	iface->if_name = (char *)(iface + 1);
+	strlcpy((char *)iface->if_name, if_name, IFNAMSIZ);
+	iface->if_index = if_nametoindex(if_name);
+	if (iface->if_index == 0) {
+		free(iface);
+		return KNOT_EINVAL;
+	}
+	iface->if_queue = if_queue;
+	iface->opts_map_fd = iface->xsks_map_fd = -1;
+
+	int ret;
+	switch (load_bpf) {
+	case KNOT_XDP_LOAD_BPF_NEVER:
+		(void)0;
+		uint32_t prog_id = 0;
+#if USE_LIBXDP
+		ret = bpf_xdp_query_id(iface->if_index, 0, &prog_id);
+#else
+		ret = bpf_get_link_xdp_id(iface->if_index, &prog_id, 0);
+#endif
+		if (ret == 0) {
+			if (prog_id == 0) {
+				ret = KNOT_EPROGRAM;
+			} else {
+				ret = bpf_prog_get_fd_by_id(prog_id);
+			}
+		}
+		break;
+	case KNOT_XDP_LOAD_BPF_ALWAYS_UNLOAD:
+#if USE_LIBXDP
+		(void)bpf_xdp_detach(iface->if_index, 0, NULL);
+#else
+		(void)bpf_set_link_xdp_fd(iface->if_index, -1, 0);
+#endif
+		sleep(1);
+		// FALLTHROUGH
+	case KNOT_XDP_LOAD_BPF_ALWAYS:
+		ret = ensure_prog(iface, true, generic_xdp);
+		break;
+	case KNOT_XDP_LOAD_BPF_MAYBE:
+		ret = ensure_prog(iface, false, generic_xdp);
+		break;
+	default:
+		return KNOT_EINVAL;
+	}
+
+	if (ret >= 0) {
+		ret = get_bpf_maps(ret, iface);
+	}
+	if (ret < 0) {
+		free(iface);
+		return ret;
+	}
+
+	knot_xdp_mode_t mode = knot_eth_xdp_mode(iface->if_index);
+	if (mode == KNOT_XDP_MODE_NONE) {
+		free(iface);
+		return KNOT_ENOTSUP;
+	}
+
+	*out_iface = iface;
+	return KNOT_EOK;
+}
+
+void kxsk_iface_free(struct kxsk_iface *iface)
+{
+	if (iface == NULL) {
+		return;
+	}
+
+	unget_bpf_maps(iface);
+
+	if (iface->prog_obj != NULL) {
+		bpf_object__close(iface->prog_obj);
+	}
+
+	free(iface);
+}