basic04: add a solution for assignment 2

aspsk · aspsk · commit 1da7dbb54286 · 2019-08-01T01:23:05.000Z
Add a solution for the second assignment of the basic04 lesson.  Namely, copy
the xdp_loader program from the basic04 to basic-solutions and add a new flag,
-M or --reuse-maps, which lets the user to reuse existing maps when reloading
the program.

Signed-off-by: Anton Protopopov &lt;a.s.protopopov@gmail.com&gt;
diff --git a/basic-solutions/Makefile b/basic-solutions/Makefile
@@ -1,6 +1,6 @@
 # SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
 
-USER_TARGETS := xdp_stats
+USER_TARGETS := xdp_stats xdp_loader
 
 LIBBPF_DIR = ../libbpf/src/
 COMMON_DIR = ../common/
diff --git a/basic-solutions/README.org b/basic-solutions/README.org
@@ -67,4 +67,4 @@ See the [[file:xdp_stats.c][xdp_stats.c]] program in this directory.
 
 *** Assignment 2: (xdp_loader.c) reuse pinned map
 
-TBD
+See the [[file:xdp_loader.c][xdp_loader.c]] program in this directory.
diff --git a/basic-solutions/xdp_loader.c b/basic-solutions/xdp_loader.c
@@ -0,0 +1,165 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+static const char *__doc__ = "XDP loader\n"
+	" - Allows selecting BPF section --progsec name to XDP-attach to --dev\n";
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <getopt.h>
+
+#include <locale.h>
+#include <unistd.h>
+#include <time.h>
+
+#include <bpf/bpf.h>
+#include <bpf/libbpf.h>
+
+#include <net/if.h>
+#include <linux/if_link.h> /* depend on kernel-headers installed */
+
+#include "../common/common_params.h"
+#include "../common/common_user_bpf_xdp.h"
+#include "../common/common_libbpf.h"
+
+static const char *default_filename = "xdp_prog_kern.o";
+
+static const struct option_wrapper long_options[] = {
+
+	{{"help",        no_argument,		NULL, 'h' },
+	 "Show help", false},
+
+	{{"dev",         required_argument,	NULL, 'd' },
+	 "Operate on device <ifname>", "<ifname>", true},
+
+	{{"skb-mode",    no_argument,		NULL, 'S' },
+	 "Install XDP program in SKB (AKA generic) mode"},
+
+	{{"native-mode", no_argument,		NULL, 'N' },
+	 "Install XDP program in native mode"},
+
+	{{"auto-mode",   no_argument,		NULL, 'A' },
+	 "Auto-detect SKB or native mode"},
+
+	{{"force",       no_argument,		NULL, 'F' },
+	 "Force install, replacing existing program on interface"},
+
+	{{"unload",      no_argument,		NULL, 'U' },
+	 "Unload XDP program instead of loading"},
+
+	{{"reuse-maps",  no_argument,		NULL, 'M' },
+	 "Reuse pinned maps"},
+
+	{{"quiet",       no_argument,		NULL, 'q' },
+	 "Quiet mode (no output)"},
+
+	{{"filename",    required_argument,	NULL,  1  },
+	 "Load program from <file>", "<file>"},
+
+	{{"progsec",    required_argument,	NULL,  2  },
+	 "Load program in <section> of the ELF file", "<section>"},
+
+	{{0, 0, NULL,  0 }, NULL, false}
+};
+
+#ifndef PATH_MAX
+#define PATH_MAX	4096
+#endif
+
+const char *pin_basedir =  "/sys/fs/bpf";
+const char *map_name    =  "xdp_stats_map";
+
+/* Pinning maps under /sys/fs/bpf in subdir */
+int pin_maps_in_bpf_object(struct bpf_object *bpf_obj, struct config *cfg)
+{
+	char map_filename[PATH_MAX];
+	int err, len;
+
+	len = snprintf(map_filename, PATH_MAX, "%s/%s/%s",
+		       pin_basedir, cfg->ifname, map_name);
+	if (len < 0) {
+		fprintf(stderr, "ERR: creating map_name\n");
+		return EXIT_FAIL_OPTION;
+	}
+
+	/* Existing/previous XDP prog might not have cleaned up */
+	if (access(map_filename, F_OK ) != -1 ) {
+		if (verbose)
+			printf(" - Unpinning (remove) prev maps in %s/\n",
+			       cfg->pin_dir);
+
+		/* Basically calls unlink(3) on map_filename */
+		err = bpf_object__unpin_maps(bpf_obj, cfg->pin_dir);
+		if (err) {
+			fprintf(stderr, "ERR: UNpinning maps in %s\n", cfg->pin_dir);
+			return EXIT_FAIL_BPF;
+		}
+	}
+	if (verbose)
+		printf(" - Pinning maps in %s/\n", cfg->pin_dir);
+
+	/* This will pin all maps in our bpf_object */
+	err = bpf_object__pin_maps(bpf_obj, cfg->pin_dir);
+	if (err)
+		return EXIT_FAIL_BPF;
+
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	struct bpf_object *bpf_obj;
+	int err, len;
+
+	struct config cfg = {
+		.xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST | XDP_FLAGS_DRV_MODE,
+		.ifindex   = -1,
+		.do_unload = false,
+	};
+	/* Set default BPF-ELF object file and BPF program name */
+	strncpy(cfg.filename, default_filename, sizeof(cfg.filename));
+	/* Cmdline options can change progsec */
+	parse_cmdline_args(argc, argv, long_options, &cfg, __doc__);
+
+	/* Required option */
+	if (cfg.ifindex == -1) {
+		fprintf(stderr, "ERR: required option --dev missing\n\n");
+		usage(argv[0], __doc__, long_options, (argc == 1));
+		return EXIT_FAIL_OPTION;
+	}
+	if (cfg.do_unload) {
+		if (!cfg.reuse_maps) {
+		/* TODO: Miss unpin of maps on unload */
+		}
+		return xdp_link_detach(cfg.ifindex, cfg.xdp_flags, 0);
+	}
+
+	len = snprintf(cfg.pin_dir, PATH_MAX, "%s/%s", pin_basedir, cfg.ifname);
+	if (len < 0) {
+		fprintf(stderr, "ERR: creating pin dirname\n");
+		return EXIT_FAIL_OPTION;
+	}
+
+
+	bpf_obj = load_bpf_and_xdp_attach(&cfg);
+	if (!bpf_obj)
+		return EXIT_FAIL_BPF;
+
+	if (verbose) {
+		printf("Success: Loaded BPF-object(%s) and used section(%s)\n",
+		       cfg.filename, cfg.progsec);
+		printf(" - XDP prog attached on device:%s(ifindex:%d)\n",
+		       cfg.ifname, cfg.ifindex);
+	}
+
+	/* Use the --dev name as subdir for exporting/pinning maps */
+	if (!cfg.reuse_maps) {
+		err = pin_maps_in_bpf_object(bpf_obj, &cfg);
+		if (err) {
+			fprintf(stderr, "ERR: pinning maps\n");
+			return err;
+		}
+	}
+
+	return EXIT_OK;
+}
diff --git a/common/common_defines.h b/common/common_defines.h
@@ -14,6 +14,8 @@ struct config {
 	char *redirect_ifname;
 	char redirect_ifname_buf[IF_NAMESIZE];
 	bool do_unload;
+	bool reuse_maps;
+	char pin_dir[512];
 	char filename[512];
 	char progsec[32];
 	char src_mac[18];
diff --git a/common/common_params.c b/common/common_params.c
@@ -91,7 +91,7 @@ void parse_cmdline_args(int argc, char **argv,
 	}
 
 	/* Parse commands line args */
-	while ((opt = getopt_long(argc, argv, "hd:r:L:R:ASNFUq",
+	while ((opt = getopt_long(argc, argv, "hd:r:L:R:ASNFUMq",
 				  long_options, &longindex)) != -1) {
 		switch (opt) {
 		case 'd':
@@ -142,6 +142,9 @@ void parse_cmdline_args(int argc, char **argv,
 		case 'F':
 			cfg->xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
 			break;
+		case 'M':
+			cfg->reuse_maps = true;
+			break;
 		case 'U':
 			cfg->do_unload = true;
 			break;
diff --git a/common/common_user_bpf_xdp.c b/common/common_user_bpf_xdp.c
@@ -8,9 +8,14 @@
 #include <bpf/libbpf.h>
 
 #include <linux/if_link.h> /* Need XDP flags */
+#include <linux/err.h>
 
 #include "common_defines.h"
 
+#ifndef PATH_MAX
+#define PATH_MAX	4096
+#endif
+
 int xdp_link_attach(int ifindex, __u32 xdp_flags, int prog_fd)
 {
 	int err;
@@ -124,6 +129,110 @@ struct bpf_object *load_bpf_object_file(const char *filename, int ifindex)
 	return obj;
 }
 
+static struct bpf_object *open_bpf_object(const char *file, int ifindex)
+{
+	int err;
+	struct bpf_object *obj;
+	struct bpf_map *map;
+	struct bpf_program *prog, *first_prog = NULL;
+
+	struct bpf_object_open_attr open_attr = {
+		.file = file,
+		.prog_type = BPF_PROG_TYPE_XDP,
+	};
+
+	obj = bpf_object__open_xattr(&open_attr);
+	if (IS_ERR_OR_NULL(obj)) {
+		err = -PTR_ERR(obj);
+		fprintf(stderr, "ERR: opening BPF-OBJ file(%s) (%d): %s\n",
+			file, err, strerror(-err));
+		return NULL;
+	}
+
+	bpf_object__for_each_program(prog, obj) {
+		bpf_program__set_type(prog, BPF_PROG_TYPE_XDP);
+		bpf_program__set_ifindex(prog, ifindex);
+		if (!first_prog)
+			first_prog = prog;
+	}
+
+	bpf_object__for_each_map(map, obj) {
+		if (!bpf_map__is_offload_neutral(map))
+			bpf_map__set_ifindex(map, ifindex);
+	}
+
+	if (!first_prog) {
+		fprintf(stderr, "ERR: file %s contains no programs\n", file);
+		return NULL;
+	}
+
+	return obj;
+}
+
+static int reuse_maps(struct bpf_object *obj, const char *path)
+{
+	struct bpf_map *map;
+
+	if (!obj)
+		return -ENOENT;
+
+	if (!path)
+		return -EINVAL;
+
+	bpf_object__for_each_map(map, obj) {
+		int len, err;
+		int pinned_map_fd;
+		char buf[PATH_MAX];
+
+		len = snprintf(buf, PATH_MAX, "%s/%s", path, bpf_map__name(map));
+		if (len < 0) {
+			return -EINVAL;
+		} else if (len >= PATH_MAX) {
+			return -ENAMETOOLONG;
+		}
+
+		pinned_map_fd = bpf_obj_get(buf);
+		if (pinned_map_fd < 0)
+			return pinned_map_fd;
+
+		err = bpf_map__reuse_fd(map, pinned_map_fd);
+		if (err)
+			return err;
+	}
+
+	return 0;
+}
+
+struct bpf_object *load_bpf_object_file_reuse_maps(const char *file,
+						   int ifindex,
+						   const char *pin_dir)
+{
+	int err;
+	struct bpf_object *obj;
+
+	obj = open_bpf_object(file, ifindex);
+	if (!obj) {
+		fprintf(stderr, "ERR: failed to open object %s\n", file);
+		return NULL;
+	}
+
+	err = reuse_maps(obj, pin_dir);
+	if (err) {
+		fprintf(stderr, "ERR: failed to reuse maps for object %s, pin_dir=%s\n",
+				file, pin_dir);
+		return NULL;
+	}
+
+	err = bpf_object__load(obj);
+	if (err) {
+		fprintf(stderr, "ERR: loading BPF-OBJ file(%s) (%d): %s\n",
+			file, err, strerror(-err));
+		return NULL;
+	}
+
+	return obj;
+}
+
 struct bpf_object *load_bpf_and_xdp_attach(struct config *cfg)
 {
 	struct bpf_program *bpf_prog;
@@ -137,7 +246,12 @@ struct bpf_object *load_bpf_and_xdp_attach(struct config *cfg)
 		offload_ifindex = cfg->ifindex;
 
 	/* Load the BPF-ELF object file and get back libbpf bpf_object */
-	bpf_obj = load_bpf_object_file(cfg->filename, offload_ifindex);
+	if (cfg->reuse_maps)
+		bpf_obj = load_bpf_object_file_reuse_maps(cfg->filename,
+							  offload_ifindex,
+							  cfg->pin_dir);
+	else
+		bpf_obj = load_bpf_object_file(cfg->filename, offload_ifindex);
 	if (!bpf_obj) {
 		fprintf(stderr, "ERR: loading file: %s\n", cfg->filename);
 		exit(EXIT_FAIL_BPF);

Original file line number	Diff line number	Diff line change
`@@ -67,4 +67,4 @@ See the [[file:xdp_stats.c][xdp_stats.c]] program in this directory.`
`67`	`67`
`68`	`68`	`*** Assignment 2: (xdp_loader.c) reuse pinned map`
`69`	`69`
`70`		`-TBD`
	`70`	`+See the [[file:xdp_loader.c][xdp_loader.c]] program in this directory.`