xref: /openbmc/linux/tools/bpf/bpftool/net.c (revision 50fc8d92) 
1 // SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
2 // Copyright (C) 2018 Facebook
3 
4 #define _GNU_SOURCE
5 #include <errno.h>
6 #include <fcntl.h>
7 #include <stdlib.h>
8 #include <string.h>
9 #include <time.h>
10 #include <unistd.h>
11 #include <bpf/bpf.h>
12 #include <bpf/libbpf.h>
13 #include <net/if.h>
14 #include <linux/if.h>
15 #include <linux/rtnetlink.h>
16 #include <linux/socket.h>
17 #include <linux/tc_act/tc_bpf.h>
18 #include <sys/socket.h>
19 #include <sys/stat.h>
20 #include <sys/types.h>
21 
22 #include "bpf/nlattr.h"
23 #include "main.h"
24 #include "netlink_dumper.h"
25 
26 #ifndef SOL_NETLINK
27 #define SOL_NETLINK 270
28 #endif
29 
30 struct ip_devname_ifindex {
31 	char	devname[64];
32 	int	ifindex;
33 };
34 
35 struct bpf_netdev_t {
36 	struct ip_devname_ifindex *devices;
37 	int	used_len;
38 	int	array_len;
39 	int	filter_idx;
40 };
41 
42 struct tc_kind_handle {
43 	char	kind[64];
44 	int	handle;
45 };
46 
47 struct bpf_tcinfo_t {
48 	struct tc_kind_handle	*handle_array;
49 	int			used_len;
50 	int			array_len;
51 	bool			is_qdisc;
52 };
53 
54 struct bpf_filter_t {
55 	const char	*kind;
56 	const char	*devname;
57 	int		ifindex;
58 };
59 
60 struct bpf_attach_info {
61 	__u32 flow_dissector_id;
62 };
63 
64 enum net_attach_type {
65 	NET_ATTACH_TYPE_XDP,
66 	NET_ATTACH_TYPE_XDP_GENERIC,
67 	NET_ATTACH_TYPE_XDP_DRIVER,
68 	NET_ATTACH_TYPE_XDP_OFFLOAD,
69 };
70 
71 static const char * const attach_type_strings[] = {
72 	[NET_ATTACH_TYPE_XDP]		= "xdp",
73 	[NET_ATTACH_TYPE_XDP_GENERIC]	= "xdpgeneric",
74 	[NET_ATTACH_TYPE_XDP_DRIVER]	= "xdpdrv",
75 	[NET_ATTACH_TYPE_XDP_OFFLOAD]	= "xdpoffload",
76 };
77 
78 const size_t net_attach_type_size = ARRAY_SIZE(attach_type_strings);
79 
80 static enum net_attach_type parse_attach_type(const char *str)
81 {
82 	enum net_attach_type type;
83 
84 	for (type = 0; type < net_attach_type_size; type++) {
85 		if (attach_type_strings[type] &&
86 		    is_prefix(str, attach_type_strings[type]))
87 			return type;
88 	}
89 
90 	return net_attach_type_size;
91 }
92 
93 typedef int (*dump_nlmsg_t)(void *cookie, void *msg, struct nlattr **tb);
94 
95 typedef int (*__dump_nlmsg_t)(struct nlmsghdr *nlmsg, dump_nlmsg_t, void *cookie);
96 
97 static int netlink_open(__u32 *nl_pid)
98 {
99 	struct sockaddr_nl sa;
100 	socklen_t addrlen;
101 	int one = 1, ret;
102 	int sock;
103 
104 	memset(&sa, 0, sizeof(sa));
105 	sa.nl_family = AF_NETLINK;
106 
107 	sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
108 	if (sock < 0)
109 		return -errno;
110 
111 	if (setsockopt(sock, SOL_NETLINK, NETLINK_EXT_ACK,
112 		       &one, sizeof(one)) < 0) {
113 		p_err("Netlink error reporting not supported");
114 	}
115 
116 	if (bind(sock, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
117 		ret = -errno;
118 		goto cleanup;
119 	}
120 
121 	addrlen = sizeof(sa);
122 	if (getsockname(sock, (struct sockaddr *)&sa, &addrlen) < 0) {
123 		ret = -errno;
124 		goto cleanup;
125 	}
126 
127 	if (addrlen != sizeof(sa)) {
128 		ret = -LIBBPF_ERRNO__INTERNAL;
129 		goto cleanup;
130 	}
131 
132 	*nl_pid = sa.nl_pid;
133 	return sock;
134 
135 cleanup:
136 	close(sock);
137 	return ret;
138 }
139 
140 static int netlink_recv(int sock, __u32 nl_pid, __u32 seq,
141 			    __dump_nlmsg_t _fn, dump_nlmsg_t fn,
142 			    void *cookie)
143 {
144 	bool multipart = true;
145 	struct nlmsgerr *err;
146 	struct nlmsghdr *nh;
147 	char buf[4096];
148 	int len, ret;
149 
150 	while (multipart) {
151 		multipart = false;
152 		len = recv(sock, buf, sizeof(buf), 0);
153 		if (len < 0) {
154 			ret = -errno;
155 			goto done;
156 		}
157 
158 		if (len == 0)
159 			break;
160 
161 		for (nh = (struct nlmsghdr *)buf; NLMSG_OK(nh, len);
162 		     nh = NLMSG_NEXT(nh, len)) {
163 			if (nh->nlmsg_pid != nl_pid) {
164 				ret = -LIBBPF_ERRNO__WRNGPID;
165 				goto done;
166 			}
167 			if (nh->nlmsg_seq != seq) {
168 				ret = -LIBBPF_ERRNO__INVSEQ;
169 				goto done;
170 			}
171 			if (nh->nlmsg_flags & NLM_F_MULTI)
172 				multipart = true;
173 			switch (nh->nlmsg_type) {
174 			case NLMSG_ERROR:
175 				err = (struct nlmsgerr *)NLMSG_DATA(nh);
176 				if (!err->error)
177 					continue;
178 				ret = err->error;
179 				libbpf_nla_dump_errormsg(nh);
180 				goto done;
181 			case NLMSG_DONE:
182 				return 0;
183 			default:
184 				break;
185 			}
186 			if (_fn) {
187 				ret = _fn(nh, fn, cookie);
188 				if (ret)
189 					return ret;
190 			}
191 		}
192 	}
193 	ret = 0;
194 done:
195 	return ret;
196 }
197 
198 static int __dump_class_nlmsg(struct nlmsghdr *nlh,
199 			      dump_nlmsg_t dump_class_nlmsg,
200 			      void *cookie)
201 {
202 	struct nlattr *tb[TCA_MAX + 1], *attr;
203 	struct tcmsg *t = NLMSG_DATA(nlh);
204 	int len;
205 
206 	len = nlh->nlmsg_len - NLMSG_LENGTH(sizeof(*t));
207 	attr = (struct nlattr *) ((void *) t + NLMSG_ALIGN(sizeof(*t)));
208 	if (libbpf_nla_parse(tb, TCA_MAX, attr, len, NULL) != 0)
209 		return -LIBBPF_ERRNO__NLPARSE;
210 
211 	return dump_class_nlmsg(cookie, t, tb);
212 }
213 
214 static int netlink_get_class(int sock, unsigned int nl_pid, int ifindex,
215 			     dump_nlmsg_t dump_class_nlmsg, void *cookie)
216 {
217 	struct {
218 		struct nlmsghdr nlh;
219 		struct tcmsg t;
220 	} req = {
221 		.nlh.nlmsg_len = NLMSG_LENGTH(sizeof(struct tcmsg)),
222 		.nlh.nlmsg_type = RTM_GETTCLASS,
223 		.nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
224 		.t.tcm_family = AF_UNSPEC,
225 		.t.tcm_ifindex = ifindex,
226 	};
227 	int seq = time(NULL);
228 
229 	req.nlh.nlmsg_seq = seq;
230 	if (send(sock, &req, req.nlh.nlmsg_len, 0) < 0)
231 		return -errno;
232 
233 	return netlink_recv(sock, nl_pid, seq, __dump_class_nlmsg,
234 			    dump_class_nlmsg, cookie);
235 }
236 
237 static int __dump_qdisc_nlmsg(struct nlmsghdr *nlh,
238 			      dump_nlmsg_t dump_qdisc_nlmsg,
239 			      void *cookie)
240 {
241 	struct nlattr *tb[TCA_MAX + 1], *attr;
242 	struct tcmsg *t = NLMSG_DATA(nlh);
243 	int len;
244 
245 	len = nlh->nlmsg_len - NLMSG_LENGTH(sizeof(*t));
246 	attr = (struct nlattr *) ((void *) t + NLMSG_ALIGN(sizeof(*t)));
247 	if (libbpf_nla_parse(tb, TCA_MAX, attr, len, NULL) != 0)
248 		return -LIBBPF_ERRNO__NLPARSE;
249 
250 	return dump_qdisc_nlmsg(cookie, t, tb);
251 }
252 
253 static int netlink_get_qdisc(int sock, unsigned int nl_pid, int ifindex,
254 			     dump_nlmsg_t dump_qdisc_nlmsg, void *cookie)
255 {
256 	struct {
257 		struct nlmsghdr nlh;
258 		struct tcmsg t;
259 	} req = {
260 		.nlh.nlmsg_len = NLMSG_LENGTH(sizeof(struct tcmsg)),
261 		.nlh.nlmsg_type = RTM_GETQDISC,
262 		.nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
263 		.t.tcm_family = AF_UNSPEC,
264 		.t.tcm_ifindex = ifindex,
265 	};
266 	int seq = time(NULL);
267 
268 	req.nlh.nlmsg_seq = seq;
269 	if (send(sock, &req, req.nlh.nlmsg_len, 0) < 0)
270 		return -errno;
271 
272 	return netlink_recv(sock, nl_pid, seq, __dump_qdisc_nlmsg,
273 			    dump_qdisc_nlmsg, cookie);
274 }
275 
276 static int __dump_filter_nlmsg(struct nlmsghdr *nlh,
277 			       dump_nlmsg_t dump_filter_nlmsg,
278 			       void *cookie)
279 {
280 	struct nlattr *tb[TCA_MAX + 1], *attr;
281 	struct tcmsg *t = NLMSG_DATA(nlh);
282 	int len;
283 
284 	len = nlh->nlmsg_len - NLMSG_LENGTH(sizeof(*t));
285 	attr = (struct nlattr *) ((void *) t + NLMSG_ALIGN(sizeof(*t)));
286 	if (libbpf_nla_parse(tb, TCA_MAX, attr, len, NULL) != 0)
287 		return -LIBBPF_ERRNO__NLPARSE;
288 
289 	return dump_filter_nlmsg(cookie, t, tb);
290 }
291 
292 static int netlink_get_filter(int sock, unsigned int nl_pid, int ifindex, int handle,
293 			      dump_nlmsg_t dump_filter_nlmsg, void *cookie)
294 {
295 	struct {
296 		struct nlmsghdr nlh;
297 		struct tcmsg t;
298 	} req = {
299 		.nlh.nlmsg_len = NLMSG_LENGTH(sizeof(struct tcmsg)),
300 		.nlh.nlmsg_type = RTM_GETTFILTER,
301 		.nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
302 		.t.tcm_family = AF_UNSPEC,
303 		.t.tcm_ifindex = ifindex,
304 		.t.tcm_parent = handle,
305 	};
306 	int seq = time(NULL);
307 
308 	req.nlh.nlmsg_seq = seq;
309 	if (send(sock, &req, req.nlh.nlmsg_len, 0) < 0)
310 		return -errno;
311 
312 	return netlink_recv(sock, nl_pid, seq, __dump_filter_nlmsg,
313 			    dump_filter_nlmsg, cookie);
314 }
315 
316 static int __dump_link_nlmsg(struct nlmsghdr *nlh,
317 			     dump_nlmsg_t dump_link_nlmsg, void *cookie)
318 {
319 	struct nlattr *tb[IFLA_MAX + 1], *attr;
320 	struct ifinfomsg *ifi = NLMSG_DATA(nlh);
321 	int len;
322 
323 	len = nlh->nlmsg_len - NLMSG_LENGTH(sizeof(*ifi));
324 	attr = (struct nlattr *) ((void *) ifi + NLMSG_ALIGN(sizeof(*ifi)));
325 	if (libbpf_nla_parse(tb, IFLA_MAX, attr, len, NULL) != 0)
326 		return -LIBBPF_ERRNO__NLPARSE;
327 
328 	return dump_link_nlmsg(cookie, ifi, tb);
329 }
330 
331 static int netlink_get_link(int sock, unsigned int nl_pid,
332 			    dump_nlmsg_t dump_link_nlmsg, void *cookie)
333 {
334 	struct {
335 		struct nlmsghdr nlh;
336 		struct ifinfomsg ifm;
337 	} req = {
338 		.nlh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg)),
339 		.nlh.nlmsg_type = RTM_GETLINK,
340 		.nlh.nlmsg_flags = NLM_F_DUMP | NLM_F_REQUEST,
341 		.ifm.ifi_family = AF_PACKET,
342 	};
343 	int seq = time(NULL);
344 
345 	req.nlh.nlmsg_seq = seq;
346 	if (send(sock, &req, req.nlh.nlmsg_len, 0) < 0)
347 		return -errno;
348 
349 	return netlink_recv(sock, nl_pid, seq, __dump_link_nlmsg,
350 			    dump_link_nlmsg, cookie);
351 }
352 
353 static int dump_link_nlmsg(void *cookie, void *msg, struct nlattr **tb)
354 {
355 	struct bpf_netdev_t *netinfo = cookie;
356 	struct ifinfomsg *ifinfo = msg;
357 
358 	if (netinfo->filter_idx > 0 && netinfo->filter_idx != ifinfo->ifi_index)
359 		return 0;
360 
361 	if (netinfo->used_len == netinfo->array_len) {
362 		netinfo->devices = realloc(netinfo->devices,
363 			(netinfo->array_len + 16) *
364 			sizeof(struct ip_devname_ifindex));
365 		if (!netinfo->devices)
366 			return -ENOMEM;
367 
368 		netinfo->array_len += 16;
369 	}
370 	netinfo->devices[netinfo->used_len].ifindex = ifinfo->ifi_index;
371 	snprintf(netinfo->devices[netinfo->used_len].devname,
372 		 sizeof(netinfo->devices[netinfo->used_len].devname),
373 		 "%s",
374 		 tb[IFLA_IFNAME]
375 			 ? libbpf_nla_getattr_str(tb[IFLA_IFNAME])
376 			 : "");
377 	netinfo->used_len++;
378 
379 	return do_xdp_dump(ifinfo, tb);
380 }
381 
382 static int dump_class_qdisc_nlmsg(void *cookie, void *msg, struct nlattr **tb)
383 {
384 	struct bpf_tcinfo_t *tcinfo = cookie;
385 	struct tcmsg *info = msg;
386 
387 	if (tcinfo->is_qdisc) {
388 		/* skip clsact qdisc */
389 		if (tb[TCA_KIND] &&
390 		    strcmp(libbpf_nla_data(tb[TCA_KIND]), "clsact") == 0)
391 			return 0;
392 		if (info->tcm_handle == 0)
393 			return 0;
394 	}
395 
396 	if (tcinfo->used_len == tcinfo->array_len) {
397 		tcinfo->handle_array = realloc(tcinfo->handle_array,
398 			(tcinfo->array_len + 16) * sizeof(struct tc_kind_handle));
399 		if (!tcinfo->handle_array)
400 			return -ENOMEM;
401 
402 		tcinfo->array_len += 16;
403 	}
404 	tcinfo->handle_array[tcinfo->used_len].handle = info->tcm_handle;
405 	snprintf(tcinfo->handle_array[tcinfo->used_len].kind,
406 		 sizeof(tcinfo->handle_array[tcinfo->used_len].kind),
407 		 "%s",
408 		 tb[TCA_KIND]
409 			 ? libbpf_nla_getattr_str(tb[TCA_KIND])
410 			 : "unknown");
411 	tcinfo->used_len++;
412 
413 	return 0;
414 }
415 
416 static int dump_filter_nlmsg(void *cookie, void *msg, struct nlattr **tb)
417 {
418 	const struct bpf_filter_t *filter_info = cookie;
419 
420 	return do_filter_dump((struct tcmsg *)msg, tb, filter_info->kind,
421 			      filter_info->devname, filter_info->ifindex);
422 }
423 
424 static int show_dev_tc_bpf(int sock, unsigned int nl_pid,
425 			   struct ip_devname_ifindex *dev)
426 {
427 	struct bpf_filter_t filter_info;
428 	struct bpf_tcinfo_t tcinfo;
429 	int i, handle, ret = 0;
430 
431 	tcinfo.handle_array = NULL;
432 	tcinfo.used_len = 0;
433 	tcinfo.array_len = 0;
434 
435 	tcinfo.is_qdisc = false;
436 	ret = netlink_get_class(sock, nl_pid, dev->ifindex,
437 				dump_class_qdisc_nlmsg, &tcinfo);
438 	if (ret)
439 		goto out;
440 
441 	tcinfo.is_qdisc = true;
442 	ret = netlink_get_qdisc(sock, nl_pid, dev->ifindex,
443 				dump_class_qdisc_nlmsg, &tcinfo);
444 	if (ret)
445 		goto out;
446 
447 	filter_info.devname = dev->devname;
448 	filter_info.ifindex = dev->ifindex;
449 	for (i = 0; i < tcinfo.used_len; i++) {
450 		filter_info.kind = tcinfo.handle_array[i].kind;
451 		ret = netlink_get_filter(sock, nl_pid, dev->ifindex,
452 					 tcinfo.handle_array[i].handle,
453 					 dump_filter_nlmsg, &filter_info);
454 		if (ret)
455 			goto out;
456 	}
457 
458 	/* root, ingress and egress handle */
459 	handle = TC_H_ROOT;
460 	filter_info.kind = "root";
461 	ret = netlink_get_filter(sock, nl_pid, dev->ifindex, handle,
462 				 dump_filter_nlmsg, &filter_info);
463 	if (ret)
464 		goto out;
465 
466 	handle = TC_H_MAKE(TC_H_CLSACT, TC_H_MIN_INGRESS);
467 	filter_info.kind = "clsact/ingress";
468 	ret = netlink_get_filter(sock, nl_pid, dev->ifindex, handle,
469 				 dump_filter_nlmsg, &filter_info);
470 	if (ret)
471 		goto out;
472 
473 	handle = TC_H_MAKE(TC_H_CLSACT, TC_H_MIN_EGRESS);
474 	filter_info.kind = "clsact/egress";
475 	ret = netlink_get_filter(sock, nl_pid, dev->ifindex, handle,
476 				 dump_filter_nlmsg, &filter_info);
477 	if (ret)
478 		goto out;
479 
480 out:
481 	free(tcinfo.handle_array);
482 	return 0;
483 }
484 
485 static int query_flow_dissector(struct bpf_attach_info *attach_info)
486 {
487 	__u32 attach_flags;
488 	__u32 prog_ids[1];
489 	__u32 prog_cnt;
490 	int err;
491 	int fd;
492 
493 	fd = open("/proc/self/ns/net", O_RDONLY);
494 	if (fd < 0) {
495 		p_err("can't open /proc/self/ns/net: %s",
496 		      strerror(errno));
497 		return -1;
498 	}
499 	prog_cnt = ARRAY_SIZE(prog_ids);
500 	err = bpf_prog_query(fd, BPF_FLOW_DISSECTOR, 0,
501 			     &attach_flags, prog_ids, &prog_cnt);
502 	close(fd);
503 	if (err) {
504 		if (errno == EINVAL) {
505 			/* Older kernel's don't support querying
506 			 * flow dissector programs.
507 			 */
508 			errno = 0;
509 			return 0;
510 		}
511 		p_err("can't query prog: %s", strerror(errno));
512 		return -1;
513 	}
514 
515 	if (prog_cnt == 1)
516 		attach_info->flow_dissector_id = prog_ids[0];
517 
518 	return 0;
519 }
520 
521 static int net_parse_dev(int *argc, char ***argv)
522 {
523 	int ifindex;
524 
525 	if (is_prefix(**argv, "dev")) {
526 		NEXT_ARGP();
527 
528 		ifindex = if_nametoindex(**argv);
529 		if (!ifindex)
530 			p_err("invalid devname %s", **argv);
531 
532 		NEXT_ARGP();
533 	} else {
534 		p_err("expected 'dev', got: '%s'?", **argv);
535 		return -1;
536 	}
537 
538 	return ifindex;
539 }
540 
541 static int do_attach_detach_xdp(int progfd, enum net_attach_type attach_type,
542 				int ifindex, bool overwrite)
543 {
544 	__u32 flags = 0;
545 
546 	if (!overwrite)
547 		flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
548 	if (attach_type == NET_ATTACH_TYPE_XDP_GENERIC)
549 		flags |= XDP_FLAGS_SKB_MODE;
550 	if (attach_type == NET_ATTACH_TYPE_XDP_DRIVER)
551 		flags |= XDP_FLAGS_DRV_MODE;
552 	if (attach_type == NET_ATTACH_TYPE_XDP_OFFLOAD)
553 		flags |= XDP_FLAGS_HW_MODE;
554 
555 	return bpf_set_link_xdp_fd(ifindex, progfd, flags);
556 }
557 
558 static int do_attach(int argc, char **argv)
559 {
560 	enum net_attach_type attach_type;
561 	int progfd, ifindex, err = 0;
562 	bool overwrite = false;
563 
564 	/* parse attach args */
565 	if (!REQ_ARGS(5))
566 		return -EINVAL;
567 
568 	attach_type = parse_attach_type(*argv);
569 	if (attach_type == net_attach_type_size) {
570 		p_err("invalid net attach/detach type: %s", *argv);
571 		return -EINVAL;
572 	}
573 	NEXT_ARG();
574 
575 	progfd = prog_parse_fd(&argc, &argv);
576 	if (progfd < 0)
577 		return -EINVAL;
578 
579 	ifindex = net_parse_dev(&argc, &argv);
580 	if (ifindex < 1) {
581 		err = -EINVAL;
582 		goto cleanup;
583 	}
584 
585 	if (argc) {
586 		if (is_prefix(*argv, "overwrite")) {
587 			overwrite = true;
588 		} else {
589 			p_err("expected 'overwrite', got: '%s'?", *argv);
590 			err = -EINVAL;
591 			goto cleanup;
592 		}
593 	}
594 
595 	/* attach xdp prog */
596 	if (is_prefix("xdp", attach_type_strings[attach_type]))
597 		err = do_attach_detach_xdp(progfd, attach_type, ifindex,
598 					   overwrite);
599 	if (err) {
600 		p_err("interface %s attach failed: %s",
601 		      attach_type_strings[attach_type], strerror(-err));
602 		goto cleanup;
603 	}
604 
605 	if (json_output)
606 		jsonw_null(json_wtr);
607 cleanup:
608 	close(progfd);
609 	return err;
610 }
611 
612 static int do_detach(int argc, char **argv)
613 {
614 	enum net_attach_type attach_type;
615 	int progfd, ifindex, err = 0;
616 
617 	/* parse detach args */
618 	if (!REQ_ARGS(3))
619 		return -EINVAL;
620 
621 	attach_type = parse_attach_type(*argv);
622 	if (attach_type == net_attach_type_size) {
623 		p_err("invalid net attach/detach type: %s", *argv);
624 		return -EINVAL;
625 	}
626 	NEXT_ARG();
627 
628 	ifindex = net_parse_dev(&argc, &argv);
629 	if (ifindex < 1)
630 		return -EINVAL;
631 
632 	/* detach xdp prog */
633 	progfd = -1;
634 	if (is_prefix("xdp", attach_type_strings[attach_type]))
635 		err = do_attach_detach_xdp(progfd, attach_type, ifindex, NULL);
636 
637 	if (err < 0) {
638 		p_err("interface %s detach failed: %s",
639 		      attach_type_strings[attach_type], strerror(-err));
640 		return err;
641 	}
642 
643 	if (json_output)
644 		jsonw_null(json_wtr);
645 
646 	return 0;
647 }
648 
649 static int do_show(int argc, char **argv)
650 {
651 	struct bpf_attach_info attach_info = {};
652 	int i, sock, ret, filter_idx = -1;
653 	struct bpf_netdev_t dev_array;
654 	unsigned int nl_pid = 0;
655 	char err_buf[256];
656 
657 	if (argc == 2) {
658 		filter_idx = net_parse_dev(&argc, &argv);
659 		if (filter_idx < 1)
660 			return -1;
661 	} else if (argc != 0) {
662 		usage();
663 	}
664 
665 	ret = query_flow_dissector(&attach_info);
666 	if (ret)
667 		return -1;
668 
669 	sock = netlink_open(&nl_pid);
670 	if (sock < 0) {
671 		fprintf(stderr, "failed to open netlink sock\n");
672 		return -1;
673 	}
674 
675 	dev_array.devices = NULL;
676 	dev_array.used_len = 0;
677 	dev_array.array_len = 0;
678 	dev_array.filter_idx = filter_idx;
679 
680 	if (json_output)
681 		jsonw_start_array(json_wtr);
682 	NET_START_OBJECT;
683 	NET_START_ARRAY("xdp", "%s:\n");
684 	ret = netlink_get_link(sock, nl_pid, dump_link_nlmsg, &dev_array);
685 	NET_END_ARRAY("\n");
686 
687 	if (!ret) {
688 		NET_START_ARRAY("tc", "%s:\n");
689 		for (i = 0; i < dev_array.used_len; i++) {
690 			ret = show_dev_tc_bpf(sock, nl_pid,
691 					      &dev_array.devices[i]);
692 			if (ret)
693 				break;
694 		}
695 		NET_END_ARRAY("\n");
696 	}
697 
698 	NET_START_ARRAY("flow_dissector", "%s:\n");
699 	if (attach_info.flow_dissector_id > 0)
700 		NET_DUMP_UINT("id", "id %u", attach_info.flow_dissector_id);
701 	NET_END_ARRAY("\n");
702 
703 	NET_END_OBJECT;
704 	if (json_output)
705 		jsonw_end_array(json_wtr);
706 
707 	if (ret) {
708 		if (json_output)
709 			jsonw_null(json_wtr);
710 		libbpf_strerror(ret, err_buf, sizeof(err_buf));
711 		fprintf(stderr, "Error: %s\n", err_buf);
712 	}
713 	free(dev_array.devices);
714 	close(sock);
715 	return ret;
716 }
717 
718 static int do_help(int argc, char **argv)
719 {
720 	if (json_output) {
721 		jsonw_null(json_wtr);
722 		return 0;
723 	}
724 
725 	fprintf(stderr,
726 		"Usage: %1$s %2$s { show | list } [dev <devname>]\n"
727 		"       %1$s %2$s attach ATTACH_TYPE PROG dev <devname> [ overwrite ]\n"
728 		"       %1$s %2$s detach ATTACH_TYPE dev <devname>\n"
729 		"       %1$s %2$s help\n"
730 		"\n"
731 		"       " HELP_SPEC_PROGRAM "\n"
732 		"       ATTACH_TYPE := { xdp | xdpgeneric | xdpdrv | xdpoffload }\n"
733 		"\n"
734 		"Note: Only xdp and tc attachments are supported now.\n"
735 		"      For progs attached to cgroups, use \"bpftool cgroup\"\n"
736 		"      to dump program attachments. For program types\n"
737 		"      sk_{filter,skb,msg,reuseport} and lwt/seg6, please\n"
738 		"      consult iproute2.\n"
739 		"",
740 		bin_name, argv[-2]);
741 
742 	return 0;
743 }
744 
745 static const struct cmd cmds[] = {
746 	{ "show",	do_show },
747 	{ "list",	do_show },
748 	{ "attach",	do_attach },
749 	{ "detach",	do_detach },
750 	{ "help",	do_help },
751 	{ 0 }
752 };
753 
754 int do_net(int argc, char **argv)
755 {
756 	return cmd_select(cmds, argc, argv, do_help);
757 }
758