[PATCH v3,bpf-next] samples/bpf: check detach prog exist or not in xdp_fwd

[PATCH v3,bpf-next] samples/bpf: check detach prog exist or not in xdp_fwd

[Zhengchao Shao]

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

Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
---
 samples/bpf/xdp_fwd_user.c | 59 ++++++++++++++++++++++++++++++++------
 1 file changed, 50 insertions(+), 9 deletions(-)

diff --git a/samples/bpf/xdp_fwd_user.c b/samples/bpf/xdp_fwd_user.c
index 1828487bae9a..03a50f64e99a 100644
--- a/samples/bpf/xdp_fwd_user.c
+++ b/samples/bpf/xdp_fwd_user.c
@@ -47,17 +47,58 @@ 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 err;
+	}
+
+	if (!curr_prog_id) {
+		printf("ERROR: flags(0x%x) xdp prog is not attached to %s\n",
+		       xdp_flags, ifname);
+		return err;
+	}
 
-	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 err;
+	}
+
+	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));
+		return err;
+	}
+	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);
-	 */
 	return err;
 }
 
@@ -169,7 +210,7 @@ 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

答复: [PATCH v3,bpf-next] samples/bpf: check detach prog exist or not in xdp_fwd

[shaozhengchao]

-----邮件原件-----
发件人: shaozhengchao 
发送时间: 2022年5月21日 12:35
收件人: bpf@vger.kernel.org; netdev@vger.kernel.org; linux-kernel@vger.kernel.org; ast@kernel.org; daniel@iogearbox.net; davem@davemloft.net; kuba@kernel.org; hawk@kernel.org; john.fastabend@gmail.com; andrii@kernel.org; kafai@fb.com; songliubraving@fb.com; yhs@fb.com; kpsingh@kernel.org
抄送: weiyongjun (A) <weiyongjun1@huawei.com>; shaozhengchao <shaozhengchao@huawei.com>; yuehaibing <yuehaibing@huawei.com>
主题: [PATCH v3,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@huawei.com>
---
 samples/bpf/xdp_fwd_user.c | 59 ++++++++++++++++++++++++++++++++------
 1 file changed, 50 insertions(+), 9 deletions(-)

diff --git a/samples/bpf/xdp_fwd_user.c b/samples/bpf/xdp_fwd_user.c index 1828487bae9a..03a50f64e99a 100644
--- a/samples/bpf/xdp_fwd_user.c
+++ b/samples/bpf/xdp_fwd_user.c
@@ -47,17 +47,58 @@ 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 err;
+	}
+
+	if (!curr_prog_id) {
+		printf("ERROR: flags(0x%x) xdp prog is not attached to %s\n",
+		       xdp_flags, ifname);
+		return err;
+	}
 
-	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 err;
+	}
+
+	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));
+		return err;
+	}
+	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);
-	 */
 	return err;
 }
 
@@ -169,7 +210,7 @@ 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


Hi Toke,
Do you have any more feedback? Does it look better to you now?

Re: [PATCH v3,bpf-next] samples/bpf: check detach prog exist or not in xdp_fwd

[Toke Høiland-Jørgensen]

Zhengchao Shao <shaozhengchao@huawei.com> writes:

> Before detach the prog, we should check detach prog exist or not.
>
> Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
> ---
>  samples/bpf/xdp_fwd_user.c | 59 ++++++++++++++++++++++++++++++++------
>  1 file changed, 50 insertions(+), 9 deletions(-)
>
> diff --git a/samples/bpf/xdp_fwd_user.c b/samples/bpf/xdp_fwd_user.c
> index 1828487bae9a..03a50f64e99a 100644
> --- a/samples/bpf/xdp_fwd_user.c
> +++ b/samples/bpf/xdp_fwd_user.c
> @@ -47,17 +47,58 @@ 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 err;
> +	}
> +
> +	if (!curr_prog_id) {
> +		printf("ERROR: flags(0x%x) xdp prog is not attached to %s\n",
> +		       xdp_flags, ifname);
> +		return err;
> +	}
>  
> -	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);

This fd is never closed again; you'll need to replace the 'return err'
statement below with a 'goto err' and add a label at the end that closes
the fd before returning - see comments below.

> +	if (prog_fd < 0) {
> +		printf("ERROR: bpf_prog_get_fd_by_id failed (%s)\n",
> +		       strerror(errno));
> +		return err;

err is not actually set here; you could either 'return prog_fd' or
'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));
> +		return err;

make this 'goto err'...
> +	}
> +	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);
> -	 */
...and add something like:

err:
        close(prog_fd);
>  	return err;
>  }
>  
> @@ -169,7 +210,7 @@ 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

Re: 答复: [PATCH v3,bpf-next] samples/bpf: check detach prog exist or not in xdp_fwd

[Toke Høiland-Jørgensen]

> Hi Toke,
> Do you have any more feedback? Does it look better to you now?

Ah, sorry, missed your v3; replied now. Please make sure to add me
directly to Cc on any follow-ups to make sure I don't miss them :)

-Toke