[PATCH bpf-next] samples/bpf: detach xdp prog when program exits unexpectedly in xdp_rxq_info_user

[PATCH bpf-next] samples/bpf: detach xdp prog when program exits unexpectedly in xdp_rxq_info_user

[Zhengchao Shao]

When xdp_rxq_info_user program exits unexpectedly, it doesn't detach xdp
prog of device, and other xdp prog can't be attached to the device. So
call init_exit() to detach xdp prog when program exits unexpectedly.

Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
---
 samples/bpf/xdp_rxq_info_user.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

diff --git a/samples/bpf/xdp_rxq_info_user.c b/samples/bpf/xdp_rxq_info_user.c
index f2d90cba5164..6378007e085a 100644
--- a/samples/bpf/xdp_rxq_info_user.c
+++ b/samples/bpf/xdp_rxq_info_user.c
@@ -18,7 +18,7 @@ static const char *__doc__ = " XDP RX-queue info extract example\n\n"
 #include <getopt.h>
 #include <net/if.h>
 #include <time.h>
-
+#include <limits.h>
 #include <arpa/inet.h>
 #include <linux/if_link.h>
 
@@ -44,6 +44,9 @@ static struct bpf_map *rx_queue_index_map;
 #define EXIT_FAIL_BPF		4
 #define EXIT_FAIL_MEM		5
 
+#define FAIL_MEM_SIG		INT_MAX
+#define FAIL_STAT_SIG		(INT_MAX - 1)
+
 static const struct option long_options[] = {
 	{"help",	no_argument,		NULL, 'h' },
 	{"dev",		required_argument,	NULL, 'd' },
@@ -77,6 +80,12 @@ static void int_exit(int sig)
 			printf("program on interface changed, not removing\n");
 		}
 	}
+
+	if (sig == FAIL_MEM_SIG)
+		exit(EXIT_FAIL_MEM);
+	else if (sig == FAIL_STAT_SIG)
+		exit(EXIT_FAIL);
+
 	exit(EXIT_OK);
 }
 
@@ -141,7 +150,7 @@ static char* options2str(enum cfg_options_flags flag)
 	if (flag & READ_MEM)
 		return "read";
 	fprintf(stderr, "ERR: Unknown config option flags");
-	exit(EXIT_FAIL);
+	int_exit(FAIL_STAT_SIG);
 }
 
 static void usage(char *argv[])
@@ -174,7 +183,7 @@ static __u64 gettime(void)
 	res = clock_gettime(CLOCK_MONOTONIC, &t);
 	if (res < 0) {
 		fprintf(stderr, "Error with gettimeofday! (%i)\n", res);
-		exit(EXIT_FAIL);
+		int_exit(FAIL_STAT_SIG);
 	}
 	return (__u64) t.tv_sec * NANOSEC_PER_SEC + t.tv_nsec;
 }
@@ -202,7 +211,7 @@ static struct datarec *alloc_record_per_cpu(void)
 	array = calloc(nr_cpus, sizeof(struct datarec));
 	if (!array) {
 		fprintf(stderr, "Mem alloc error (nr_cpus:%u)\n", nr_cpus);
-		exit(EXIT_FAIL_MEM);
+		int_exit(FAIL_MEM_SIG);
 	}
 	return array;
 }
@@ -215,7 +224,7 @@ static struct record *alloc_record_per_rxq(void)
 	array = calloc(nr_rxqs, sizeof(struct record));
 	if (!array) {
 		fprintf(stderr, "Mem alloc error (nr_rxqs:%u)\n", nr_rxqs);
-		exit(EXIT_FAIL_MEM);
+		int_exit(FAIL_MEM_SIG);
 	}
 	return array;
 }
@@ -229,7 +238,7 @@ static struct stats_record *alloc_stats_record(void)
 	rec = calloc(1, sizeof(struct stats_record));
 	if (!rec) {
 		fprintf(stderr, "Mem alloc error\n");
-		exit(EXIT_FAIL_MEM);
+		int_exit(FAIL_MEM_SIG);
 	}
 	rec->rxq = alloc_record_per_rxq();
 	for (i = 0; i < nr_rxqs; i++)
-- 
2.17.1

Re: [PATCH bpf-next] samples/bpf: detach xdp prog when program exits unexpectedly in xdp_rxq_info_user

[Andrii Nakryiko]

On Thu, Apr 21, 2022 at 5:07 AM Zhengchao Shao <shaozhengchao@huawei.com> wrote:
>
> When xdp_rxq_info_user program exits unexpectedly, it doesn't detach xdp
> prog of device, and other xdp prog can't be attached to the device. So
> call init_exit() to detach xdp prog when program exits unexpectedly.
>
> Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
> ---
>  samples/bpf/xdp_rxq_info_user.c | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)
>

you are introducing a new compilation warning, please fix it


/data/users/andriin/linux/samples/bpf/xdp_rxq_info_user.c: In function
‘options2str’:
/data/users/andriin/linux/samples/bpf/xdp_rxq_info_user.c:153:1:
warning: control reaches end of non-void function [-Wreturn-type]
  153 | }
      | ^

It also would be good to instead use bpf_link-based XDP attachment
that would be auto-detached automatically on process crash
(bpf_link_create() FTW). Please consider also converting this sample
to skeleton (and then bpf_program__attach_xdp() as high-level
alternative to bpf_link_create()).

> diff --git a/samples/bpf/xdp_rxq_info_user.c b/samples/bpf/xdp_rxq_info_user.c
> index f2d90cba5164..6378007e085a 100644
> --- a/samples/bpf/xdp_rxq_info_user.c
> +++ b/samples/bpf/xdp_rxq_info_user.c
> @@ -18,7 +18,7 @@ static const char *__doc__ = " XDP RX-queue info extract example\n\n"
>  #include <getopt.h>
>  #include <net/if.h>
>  #include <time.h>

[...]

答复: [PATCH bpf-next] samples/bpf: detach xdp prog when program exits unexpectedly in xdp_rxq_info_user

[shaozhengchao]

Thank you for your reply.

I will fix the compilation warning firstly, and then convert this sample to skeleton. Thank you very much.

-----邮件原件-----
发件人: Andrii Nakryiko [mailto:andrii.nakryiko@gmail.com] 
发送时间: 2022年4月26日 12:35
收件人: shaozhengchao <shaozhengchao@huawei.com>
抄送: bpf <bpf@vger.kernel.org>; Networking <netdev@vger.kernel.org>; open list <linux-kernel@vger.kernel.org>; Alexei Starovoitov <ast@kernel.org>; Daniel Borkmann <daniel@iogearbox.net>; David S. Miller <davem@davemloft.net>; Jakub Kicinski <kuba@kernel.org>; Jesper Dangaard Brouer <hawk@kernel.org>; john fastabend <john.fastabend@gmail.com>; Andrii Nakryiko <andrii@kernel.org>; Martin Lau <kafai@fb.com>; Song Liu <songliubraving@fb.com>; Yonghong Song <yhs@fb.com>; KP Singh <kpsingh@kernel.org>; weiyongjun (A) <weiyongjun1@huawei.com>; yuehaibing <yuehaibing@huawei.com>
主题: Re: [PATCH bpf-next] samples/bpf: detach xdp prog when program exits unexpectedly in xdp_rxq_info_user

On Thu, Apr 21, 2022 at 5:07 AM Zhengchao Shao <shaozhengchao@huawei.com> wrote:
>
> When xdp_rxq_info_user program exits unexpectedly, it doesn't detach 
> xdp prog of device, and other xdp prog can't be attached to the 
> device. So call init_exit() to detach xdp prog when program exits unexpectedly.
>
> Signed-off-by: Zhengchao Shao <shaozhengchao@huawei.com>
> ---
>  samples/bpf/xdp_rxq_info_user.c | 21 +++++++++++++++------
>  1 file changed, 15 insertions(+), 6 deletions(-)
>

you are introducing a new compilation warning, please fix it


/data/users/andriin/linux/samples/bpf/xdp_rxq_info_user.c: In function
‘options2str’:
/data/users/andriin/linux/samples/bpf/xdp_rxq_info_user.c:153:1:
warning: control reaches end of non-void function [-Wreturn-type]
  153 | }
      | ^

It also would be good to instead use bpf_link-based XDP attachment that would be auto-detached automatically on process crash
(bpf_link_create() FTW). Please consider also converting this sample to skeleton (and then bpf_program__attach_xdp() as high-level alternative to bpf_link_create()).

> diff --git a/samples/bpf/xdp_rxq_info_user.c 
> b/samples/bpf/xdp_rxq_info_user.c index f2d90cba5164..6378007e085a 
> 100644
> --- a/samples/bpf/xdp_rxq_info_user.c
> +++ b/samples/bpf/xdp_rxq_info_user.c
> @@ -18,7 +18,7 @@ static const char *__doc__ = " XDP RX-queue info extract example\n\n"
>  #include <getopt.h>
>  #include <net/if.h>
>  #include <time.h>

[...]