[PATCH 6.1 0224/1146] samples/bpf: Fix map iteration in xdp1_user

Greg Kroah-Hartman
2022-12-28T15:27:59Z

From: Gerhard Engleder <gerhard@engleder-embedded.com>

[ Upstream commit 05ee658c654bacda03f7fecef367e62aaf8e1cfe ]

BPF map iteration in xdp1_user results in endless loop without any
output, because the return value of bpf_map_get_next_key() is checked
against the wrong value.

Other call locations of bpf_map_get_next_key() check for equal 0 for
continuing the iteration. xdp1_user checks against unequal -1. This is
wrong for a function which can return arbitrary negative errno values,
because a return value of e.g. -2 results in an endless loop.

With this fix xdp1_user is printing statistics again:
proto 0: 1 pkt/s
proto 0: 1 pkt/s
proto 17: 107383 pkt/s
proto 17: 881655 pkt/s
proto 17: 882083 pkt/s
proto 17: 881758 pkt/s

Fixes: bd054102a8c7 ("libbpf: enforce strict libbpf 1.0 behaviors")
Signed-off-by: Gerhard Engleder <gerhard@engleder-embedded.com>
Acked-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20221013200922.17167-1-gerhard@engleder-embedded.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
samples/bpf/xdp1_user.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/bpf/xdp1_user.c b/samples/bpf/xdp1_user.c
index ac370e638fa3..281dc964de8d 100644
--- a/samples/bpf/xdp1_user.c
+++ b/samples/bpf/xdp1_user.c
@@ -51,7 +51,7 @@ static void poll_stats(int map_fd, int interval)

sleep(interval);

- while (bpf_map_get_next_key(map_fd, &key, &key) != -1) {
+ while (bpf_map_get_next_key(map_fd, &key, &key) == 0) {
__u64 sum = 0;

assert(bpf_map_lookup_elem(map_fd, &key, values) == 0);
--
2.35.1