[PATCH bpf 3/3] bpf, selftests: Adapt cls_redirect to call csum_level helper

[Daniel Borkmann]

Adapt bpf_skb_adjust_room() to pass in BPF_F_ADJ_ROOM_NO_CSUM_RESET flag and
use the new bpf_csum_level() helper to inc/dec the checksum level by one after
the encap/decap.

Signed-off-by: Daniel Borkmann <dan...@iogearbox.net>
---
 tools/testing/selftests/bpf/progs/test_cls_redirect.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/tools/testing/selftests/bpf/progs/test_cls_redirect.c 
b/tools/testing/selftests/bpf/progs/test_cls_redirect.c
index 1668b993eb86..f0b72e86bee5 100644
--- a/tools/testing/selftests/bpf/progs/test_cls_redirect.c
+++ b/tools/testing/selftests/bpf/progs/test_cls_redirect.c
@@ -380,9 +380,10 @@ static ret_t accept_locally(struct __sk_buff *skb, 
encap_headers_t *encap)
        }
 
        if (bpf_skb_adjust_room(skb, -encap_overhead, BPF_ADJ_ROOM_MAC,
-                               BPF_F_ADJ_ROOM_FIXED_GSO)) {
+                               BPF_F_ADJ_ROOM_FIXED_GSO |
+                               BPF_F_ADJ_ROOM_NO_CSUM_RESET) ||
+           bpf_csum_level(skb, BPF_CSUM_LEVEL_DEC))
                return TC_ACT_SHOT;
-       }
 
        return bpf_redirect(skb->ifindex, BPF_F_INGRESS);
 }
@@ -472,7 +473,9 @@ static ret_t forward_with_gre(struct __sk_buff *skb, 
encap_headers_t *encap,
        }
 
        if (bpf_skb_adjust_room(skb, delta, BPF_ADJ_ROOM_NET,
-                               BPF_F_ADJ_ROOM_FIXED_GSO)) {
+                               BPF_F_ADJ_ROOM_FIXED_GSO |
+                               BPF_F_ADJ_ROOM_NO_CSUM_RESET) ||
+           bpf_csum_level(skb, BPF_CSUM_LEVEL_INC)) {
                metrics->errors_total_encap_adjust_failed++;
                return TC_ACT_SHOT;
        }
-- 
2.21.0