bpf: add helper to invalidate hash

Add a small helper that complements 36bbef5 ("bpf: direct packet write and access for helpers for clsact progs") for invalidating the current skb->hash after mangling on headers via direct packet write. Signed-off-by: Daniel Borkmann <[email protected]> Acked-by: Alexei Starovoitov <[email protected]> Signed-off-by: David S. Miller <[email protected]>
torvalds · Sep 23, 2016 · 7a4b28c · 7a4b28c
1 parent 669dc4d
commit 7a4b28c
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diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
@@ -419,6 +419,13 @@ enum bpf_func_id {
  */
  BPF_FUNC_csum_update,
 
+ /**
+ * bpf_set_hash_invalid(skb)
+ * Invalidate current skb>hash.
+ * @skb: pointer to skb
+ */
+ BPF_FUNC_set_hash_invalid,
+
  __BPF_FUNC_MAX_ID,
 };
 

diff --git a/net/core/filter.c b/net/core/filter.c
@@ -1777,6 +1777,22 @@ static const struct bpf_func_proto bpf_get_hash_recalc_proto = {
  .arg1_type = ARG_PTR_TO_CTX,
 };
 
+BPF_CALL_1(bpf_set_hash_invalid, struct sk_buff *, skb)
+{
+ /* After all direct packet write, this can be used once for
+ * triggering a lazy recalc on next skb_get_hash() invocation.
+ */
+ skb_clear_hash(skb);
+ return 0;
+}
+
+static const struct bpf_func_proto bpf_set_hash_invalid_proto = {
+ .func = bpf_set_hash_invalid,
+ .gpl_only = false,
+ .ret_type = RET_INTEGER,
+ .arg1_type = ARG_PTR_TO_CTX,
+};
+
 BPF_CALL_3(bpf_skb_vlan_push, struct sk_buff *, skb, __be16, vlan_proto,
  u16, vlan_tci)
 {
@@ -2534,6 +2550,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
  return &bpf_get_route_realm_proto;
  case BPF_FUNC_get_hash_recalc:
  return &bpf_get_hash_recalc_proto;
+ case BPF_FUNC_set_hash_invalid:
+ return &bpf_set_hash_invalid_proto;
  case BPF_FUNC_perf_event_output:
  return &bpf_skb_event_output_proto;
  case BPF_FUNC_get_smp_processor_id: