Commit 6b8838be authored by Jesper Dangaard Brouer's avatar Jesper Dangaard Brouer Committed by Daniel Borkmann
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selftests/bpf: Use bpf_check_mtu in selftest test_cls_redirect 



This demonstrate how bpf_check_mtu() helper can easily be used together
with bpf_skb_adjust_room() helper, prior to doing size adjustment, as
delta argument is already setup.

Hint: This specific test can be selected like this:
 ./test_progs -t cls_redirect

Signed-off-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/161287791481.790810.4444271170546646080.stgit@firesoul
parent 5f7d5728

tools/testing/selftests/bpf/progs/test_cls_redirect.c

+7 −0
Original line number Diff line number Diff line
@@ -70,6 +70,7 @@ typedef struct { 
	uint64_t errors_total_encap_adjust_failed;

	uint64_t errors_total_encap_buffer_too_small;

	uint64_t errors_total_redirect_loop;

	uint64_t errors_total_encap_mtu_violate;

} metrics_t;



typedef enum {
@@ -407,6 +408,7 @@ static INLINING ret_t forward_with_gre(struct __sk_buff *skb, encap_headers_t *e 
		payload_off - sizeof(struct ethhdr) - sizeof(struct iphdr);

	int32_t delta = sizeof(struct gre_base_hdr) - encap_overhead;

	uint16_t proto = ETH_P_IP;

	uint32_t mtu_len = 0;



	/* Loop protection: the inner packet's TTL is decremented as a safeguard

	 * against any forwarding loop. As the only interesting field is the TTL
@@ -479,6 +481,11 @@ static INLINING ret_t forward_with_gre(struct __sk_buff *skb, encap_headers_t *e 
		}

	}



	if (bpf_check_mtu(skb, skb->ifindex, &mtu_len, delta, 0)) {

		metrics->errors_total_encap_mtu_violate++;

		return TC_ACT_SHOT;

	}



	if (bpf_skb_adjust_room(skb, delta, BPF_ADJ_ROOM_NET,

				BPF_F_ADJ_ROOM_FIXED_GSO |

				BPF_F_ADJ_ROOM_NO_CSUM_RESET) ||