linux-kernel - [PATCH v4,bpf-next] samples/bpf: check detach prog exist or not in xdp

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Message-ID: <20220531121804.194901-1-shaozhengchao@huawei.com>
Date:   Tue, 31 May 2022 20:18:04 +0800
From:   Zhengchao Shao <shaozhengchao@...wei.com>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <ast@...nel.org>,
        <daniel@...earbox.net>, <davem@...emloft.net>, <kuba@...nel.org>,
        <hawk@...nel.org>, <john.fastabend@...il.com>, <andrii@...nel.org>,
        <kafai@...com>, <songliubraving@...com>, <yhs@...com>,
        <kpsingh@...nel.org>, <toke@...nel.org>
CC:     <weiyongjun1@...wei.com>, <shaozhengchao@...wei.com>,
        <yuehaibing@...wei.com>
Subject: [PATCH v4,bpf-next] samples/bpf: check detach prog exist or not in xdp_fwd

Before detach the prog, we should check detach prog exist or not.

Signed-off-by: Zhengchao Shao <shaozhengchao@...wei.com>
---
 samples/bpf/xdp_fwd_user.c | 62 ++++++++++++++++++++++++++++++++------
 1 file changed, 53 insertions(+), 9 deletions(-)

diff --git a/samples/bpf/xdp_fwd_user.c b/samples/bpf/xdp_fwd_user.c
index 1828487bae9a..a4ba53891653 100644
--- a/samples/bpf/xdp_fwd_user.c
+++ b/samples/bpf/xdp_fwd_user.c
@@ -47,17 +47,61 @@ static int do_attach(int idx, int prog_fd, int map_fd, const char *name)
 	return err;
 }
 
-static int do_detach(int idx, const char *name)
+static int do_detach(int ifindex, const char *ifname, const char *app_name)
 {
-	int err;
+	LIBBPF_OPTS(bpf_xdp_attach_opts, opts);
+	struct bpf_prog_info prog_info = {};
+	char prog_name[BPF_OBJ_NAME_LEN];
+	__u32 info_len, curr_prog_id;
+	int prog_fd;
+	int err = 1;
+
+	if (bpf_xdp_query_id(ifindex, xdp_flags, &curr_prog_id)) {
+		printf("ERROR: bpf_xdp_query_id failed (%s)\n",
+		       strerror(errno));
+		return -errno;
+	}
+
+	if (!curr_prog_id) {
+		printf("ERROR: flags(0x%x) xdp prog is not attached to %s\n",
+		       xdp_flags, ifname);
+		goto err_out;
+	}
 
-	err = bpf_xdp_detach(idx, xdp_flags, NULL);
-	if (err < 0)
-		printf("ERROR: failed to detach program from %s\n", name);
+	info_len = sizeof(prog_info);
+	prog_fd = bpf_prog_get_fd_by_id(curr_prog_id);
+	if (prog_fd < 0) {
+		printf("ERROR: bpf_prog_get_fd_by_id failed (%s)\n",
+		       strerror(errno));
+		return -errno;
+	}
+
+	err = bpf_obj_get_info_by_fd(prog_fd, &prog_info, &info_len);
+	if (err) {
+		printf("ERROR: bpf_obj_get_info_by_fd failed (%s)\n",
+		       strerror(errno));
+		goto close_out;
+	}
+	snprintf(prog_name, sizeof(prog_name), "%s_prog", app_name);
+	prog_name[BPF_OBJ_NAME_LEN - 1] = '\0';
+
+	if (strcmp(prog_info.name, prog_name)) {
+		printf("ERROR: %s isn't attached to %s\n", app_name, ifname);
+		err = 1;
+	} else {
+		opts.old_prog_fd = prog_fd;
+		err = bpf_xdp_detach(ifindex, xdp_flags, &opts);
+		if (err < 0)
+			printf("ERROR: failed to detach program from %s (%s)\n",
+			       ifname, strerror(errno));
+		/* TODO: Remember to cleanup map, when adding use of shared map
+		 *  bpf_map_delete_elem((map_fd, &idx);
+		 */
+	}
 
-	/* TODO: Remember to cleanup map, when adding use of shared map
-	 *  bpf_map_delete_elem((map_fd, &idx);
-	 */
+close_out:
+	close(prog_fd);
+err_out:
 	return err;
 }
 
@@ -169,7 +213,7 @@ int main(int argc, char **argv)
 			return 1;
 		}
 		if (!attach) {
-			err = do_detach(idx, argv[i]);
+			err = do_detach(idx, argv[i], prog_name);
 			if (err)
 				ret = err;
 		} else {
-- 
2.17.1