samples/bpf: Check the prog id before exiting

Check the program id within the signal handler on polling xdp samples
that were previously converted to libbpf usage. Avoid the situation of
unloading the program that was not attached by sample that is exiting.
Handle also the case where bpf_get_link_xdp_id didn't exit with an error
but the xdp program was not found on an interface.

Reported-by: Michal Papaj <michal.papaj@intel.com>
Reported-by: Jakub Spizewski <jakub.spizewski@intel.com>
Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@intel.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 22 insertions, 1 deletions

diff --git a/samples/bpf/xdpsock_user.c b/samples/bpf/xdpsock_user.c
index 188723784768..f73055e0191f 100644
--- a/samples/bpf/xdpsock_user.c
+++ b/samples/bpf/xdpsock_user.c
@@ -76,6 +76,7 @@ static int opt_poll;
 static int opt_shared_packet_buffer;
 static int opt_interval = 1;
 static u32 opt_xdp_bind_flags;
+static __u32 prog_id;
 
 struct xdp_umem_uqueue {
 	u32 cached_prod;
@@ -631,9 +632,20 @@ static void *poller(void *arg)
 
 static void int_exit(int sig)
 {
+	__u32 curr_prog_id = 0;
+
 	(void)sig;
 	dump_stats();
-	bpf_set_link_xdp_fd(opt_ifindex, -1, opt_xdp_flags);
+	if (bpf_get_link_xdp_id(opt_ifindex, &curr_prog_id, opt_xdp_flags)) {
+		printf("bpf_get_link_xdp_id failed\n");
+		exit(EXIT_FAILURE);
+	}
+	if (prog_id == curr_prog_id)
+		bpf_set_link_xdp_fd(opt_ifindex, -1, opt_xdp_flags);
+	else if (!curr_prog_id)
+		printf("couldn't find a prog id on a given interface\n");
+	else
+		printf("program on interface changed, not removing\n");
 	exit(EXIT_SUCCESS);
 }
 
@@ -907,6 +919,8 @@ int main(int argc, char **argv)
 		.prog_type	= BPF_PROG_TYPE_XDP,
 	};
 	int prog_fd, qidconf_map, xsks_map;
+	struct bpf_prog_info info = {};
+	__u32 info_len = sizeof(info);
 	struct bpf_object *obj;
 	char xdp_filename[256];
 	struct bpf_map *map;
@@ -953,6 +967,13 @@ int main(int argc, char **argv)
 		exit(EXIT_FAILURE);
 	}
 
+	ret = bpf_obj_get_info_by_fd(prog_fd, &info, &info_len);
+	if (ret) {
+		printf("can't get prog info - %s\n", strerror(errno));
+		return 1;
+	}
+	prog_id = info.id;
+
 	ret = bpf_map_update_elem(qidconf_map, &key, &opt_queue, 0);
 	if (ret) {
 		fprintf(stderr, "ERROR: bpf_map_update_elem qidconf\n");