diff options
| -rw-r--r-- | samples/bpf/xdp2skb_meta_kern.c | 8 |
1 files changed, 5 insertions, 3 deletions
diff --git a/samples/bpf/xdp2skb_meta_kern.c b/samples/bpf/xdp2skb_meta_kern.c index 12e1024069c2..0c12048ac79f 100644 --- a/samples/bpf/xdp2skb_meta_kern.c +++ b/samples/bpf/xdp2skb_meta_kern.c @@ -35,15 +35,17 @@ int _xdp_mark(struct xdp_md *ctx) void *data, *data_end; int ret; - /* Reserve space in-front data pointer for our meta info. + /* Reserve space in-front of data pointer for our meta info. * (Notice drivers not supporting data_meta will fail here!) */ ret = bpf_xdp_adjust_meta(ctx, -(int)sizeof(*meta)); if (ret < 0) return XDP_ABORTED; - /* For some unknown reason, these ctx pointers must be read - * after bpf_xdp_adjust_meta, else verifier will reject prog. + /* Notice: Kernel-side verifier requires that loading of + * ctx->data MUST happen _after_ helper bpf_xdp_adjust_meta(), + * as pkt-data pointers are invalidated. Helpers that require + * this are determined/marked by bpf_helper_changes_pkt_data() */ data = (void *)(unsigned long)ctx->data; |