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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: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/161287791481.790810.4444271170546646080.stgit@firesoul
This commit is contained in:
Jesper Dangaard Brouer 2021-02-09 14:38:34 +01:00 committed by Daniel Borkmann
parent 5f7d57280c
commit 6b8838be7e
1 changed files with 7 additions and 0 deletions
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7
tools/testing/selftests/bpf/progs/test_cls_redirect.c
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@ -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) ||