linux-kernel - [PATCH] samples/bpf: Update sockex2: get the expected output results

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Message-Id: <20230726070955.178288-1-guodongtai@kylinos.cn>
Date:   Wed, 26 Jul 2023 15:09:55 +0800
From:   George Guo <guodongtai@...inos.cn>
To:     masahiroy@...nel.org, ndesaulniers@...gle.com, nathan@...nel.org,
        nicolas@...sle.eu
Cc:     linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org,
        bpf@...r.kernel.org
Subject: [PATCH] samples/bpf: Update sockex2: get the expected output results

Running "ping -4 -c5 localhost" only shows 4 times prints not 5:

$ sudo ./samples/bpf/sockex2
ip 127.0.0.1 bytes 392 packets 4
ip 127.0.0.1 bytes 784 packets 8
ip 127.0.0.1 bytes 1176 packets 12
ip 127.0.0.1 bytes 1568 packets 16

debug it with num prints:
$ sudo ./samples/bpf/sockex2
num = 1: ip 127.0.0.1 bytes 392 packets 4
num = 2: ip 127.0.0.1 bytes 784 packets 8
num = 3: ip 127.0.0.1 bytes 1176 packets 12
num = 4: ip 127.0.0.1 bytes 1568 packets 16

The reason is that we check it faster, just put sleep(1) before check
while(bpf_map_get_next_key(map_fd, &key, &next_key) == 0).
Now we get the expected results:

$ sudo ./samples/bpf/sockex2
num = 0: ip 127.0.0.1 bytes 392 packets 4
num = 1: ip 127.0.0.1 bytes 784 packets 8
num = 2: ip 127.0.0.1 bytes 1176 packets 12
num = 3: ip 127.0.0.1 bytes 1568 packets 16
num = 4: ip 127.0.0.1 bytes 1960 packets 20

Signed-off-by: George Guo <guodongtai@...inos.cn>
---
 samples/bpf/sockex2_user.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/samples/bpf/sockex2_user.c b/samples/bpf/sockex2_user.c
index 2c18471336f0..84bf1ab77649 100644
--- a/samples/bpf/sockex2_user.c
+++ b/samples/bpf/sockex2_user.c
@@ -18,8 +18,8 @@ int main(int ac, char **argv)
 	struct bpf_program *prog;
 	struct bpf_object *obj;
 	int map_fd, prog_fd;
-	char filename[256];
-	int i, sock, err;
+	char filename[256], command[64];
+	int i, sock, err, num = 5;
 	FILE *f;
 
 	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
@@ -42,21 +42,22 @@ int main(int ac, char **argv)
 	assert(setsockopt(sock, SOL_SOCKET, SO_ATTACH_BPF, &prog_fd,
 			  sizeof(prog_fd)) == 0);
 
-	f = popen("ping -4 -c5 localhost", "r");
+	snprintf(command, sizeof(command), "ping -4 -c%d localhost", num);
+	f = popen(command, "r");
 	(void) f;
 
-	for (i = 0; i < 5; i++) {
+	for (i = 0; i < num; i++) {
 		int key = 0, next_key;
 		struct pair value;
 
+		sleep(1);
 		while (bpf_map_get_next_key(map_fd, &key, &next_key) == 0) {
 			bpf_map_lookup_elem(map_fd, &next_key, &value);
-			printf("ip %s bytes %lld packets %lld\n",
+			printf("num = %d: ip %s bytes %lld packets %lld\n", i,
 			       inet_ntoa((struct in_addr){htonl(next_key)}),
 			       value.bytes, value.packets);
 			key = next_key;
 		}
-		sleep(1);
 	}
 	return 0;
 }
-- 
2.34.1