Commit 7f0c57fe authored by Stanislav Fomichev's avatar Stanislav Fomichev Committed by Daniel Borkmann
Browse files

bpftool: show flow_dissector attachment status 



Right now there is no way to query whether BPF flow_dissector program
is attached to a network namespace or not. In previous commit, I added
support for querying that info, show it when doing `bpftool net`:

$ bpftool prog loadall ./bpf_flow.o \
	/sys/fs/bpf/flow type flow_dissector \
	pinmaps /sys/fs/bpf/flow
$ bpftool prog
3: flow_dissector  name _dissect  tag 8c9e917b513dd5cc  gpl
        loaded_at 2019-04-23T16:14:48-0700  uid 0
        xlated 656B  jited 461B  memlock 4096B  map_ids 1,2
        btf_id 1
...

$ bpftool net -j
[{"xdp":[],"tc":[],"flow_dissector":[]}]

$ bpftool prog attach pinned \
	/sys/fs/bpf/flow/flow_dissector flow_dissector
$ bpftool net -j
[{"xdp":[],"tc":[],"flow_dissector":["id":3]}]

Doesn't show up in a different net namespace:
$ ip netns add test
$ ip netns exec test bpftool net -j
[{"xdp":[],"tc":[],"flow_dissector":[]}]

Non-json output:
$ bpftool net
xdp:

tc:

flow_dissector:
id 3

v2:
* initialization order (Jakub Kicinski)
* clear errno for batch mode (Quentin Monnet)

Signed-off-by: default avatarStanislav Fomichev <sdf@google.com>
Reviewed-by: default avatarQuentin Monnet <quentin.monnet@netronome.com>
Reviewed-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 118c8e9a

tools/bpf/bpftool/net.c

+54 −0
Original line number Diff line number Diff line
@@ -3,6 +3,7 @@ 


#define _GNU_SOURCE

#include <errno.h>

#include <fcntl.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>
@@ -12,6 +13,8 @@ 
#include <linux/rtnetlink.h>

#include <linux/tc_act/tc_bpf.h>

#include <sys/socket.h>

#include <sys/stat.h>

#include <sys/types.h>



#include <bpf.h>

#include <nlattr.h>
@@ -48,6 +51,10 @@ struct bpf_filter_t { 
	int		ifindex;

};



struct bpf_attach_info {

	__u32 flow_dissector_id;

};



static int dump_link_nlmsg(void *cookie, void *msg, struct nlattr **tb)

{

	struct bpf_netdev_t *netinfo = cookie;
@@ -180,8 +187,45 @@ out: 
	return 0;

}



static int query_flow_dissector(struct bpf_attach_info *attach_info)

{

	__u32 attach_flags;

	__u32 prog_ids[1];

	__u32 prog_cnt;

	int err;

	int fd;



	fd = open("/proc/self/ns/net", O_RDONLY);

	if (fd < 0) {

		p_err("can't open /proc/self/ns/net: %d",

		      strerror(errno));

		return -1;

	}

	prog_cnt = ARRAY_SIZE(prog_ids);

	err = bpf_prog_query(fd, BPF_FLOW_DISSECTOR, 0,

			     &attach_flags, prog_ids, &prog_cnt);

	close(fd);

	if (err) {

		if (errno == EINVAL) {

			/* Older kernel's don't support querying

			 * flow dissector programs.

			 */

			errno = 0;

			return 0;

		}

		p_err("can't query prog: %s", strerror(errno));

		return -1;

	}



	if (prog_cnt == 1)

		attach_info->flow_dissector_id = prog_ids[0];



	return 0;

}



static int do_show(int argc, char **argv)

{

	struct bpf_attach_info attach_info = {};

	int i, sock, ret, filter_idx = -1;

	struct bpf_netdev_t dev_array;

	unsigned int nl_pid;
@@ -199,6 +243,10 @@ static int do_show(int argc, char **argv) 
		usage();

	}



	ret = query_flow_dissector(&attach_info);

	if (ret)

		return -1;



	sock = libbpf_netlink_open(&nl_pid);

	if (sock < 0) {

		fprintf(stderr, "failed to open netlink sock\n");
@@ -227,6 +275,12 @@ static int do_show(int argc, char **argv) 
		}

		NET_END_ARRAY("\n");

	}



	NET_START_ARRAY("flow_dissector", "%s:\n");

	if (attach_info.flow_dissector_id > 0)

		NET_DUMP_UINT("id", "id %u", attach_info.flow_dissector_id);

	NET_END_ARRAY("\n");



	NET_END_OBJECT;

	if (json_output)

		jsonw_end_array(json_wtr);

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