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Commit 13c5c240 authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller
Browse files

bpf: add bpf_get_hash_recalc helper 



If skb_clear_hash() was invoked due to mangling of relevant headers and
BPF program needs skb->hash later on, we can add a helper to trigger hash
recalculation via bpf_get_hash_recalc().

The helper will return the newly retrieved hash directly, but later access
can also be done via skb context again through skb->hash directly (inline)
without needing to call the helper once more.

Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 6fd980ac

include/uapi/linux/bpf.h

+9 −0
Original line number Diff line number Diff line
@@ -348,6 +348,15 @@ enum bpf_func_id { 
	 *    < 0 error

	 */

	BPF_FUNC_skb_in_cgroup,



	/**

	 * bpf_get_hash_recalc(skb)

	 * Retrieve and possibly recalculate skb->hash.

	 * @skb: pointer to skb

	 * Return: hash

	 */

	BPF_FUNC_get_hash_recalc,



	__BPF_FUNC_MAX_ID,

};

net/core/filter.c

+19 −0
Original line number Diff line number Diff line
@@ -1729,6 +1729,23 @@ static const struct bpf_func_proto bpf_get_route_realm_proto = { 
	.arg1_type      = ARG_PTR_TO_CTX,

};



static u64 bpf_get_hash_recalc(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)

{

	/* If skb_clear_hash() was called due to mangling, we can

	 * trigger SW recalculation here. Later access to hash

	 * can then use the inline skb->hash via context directly

	 * instead of calling this helper again.

	 */

	return skb_get_hash((struct sk_buff *) (unsigned long) r1);

}



static const struct bpf_func_proto bpf_get_hash_recalc_proto = {

	.func		= bpf_get_hash_recalc,

	.gpl_only	= false,

	.ret_type	= RET_INTEGER,

	.arg1_type	= ARG_PTR_TO_CTX,

};



static u64 bpf_skb_vlan_push(u64 r1, u64 r2, u64 vlan_tci, u64 r4, u64 r5)

{

	struct sk_buff *skb = (struct sk_buff *) (long) r1;
@@ -2337,6 +2354,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id) 
		return &bpf_redirect_proto;

	case BPF_FUNC_get_route_realm:

		return &bpf_get_route_realm_proto;

	case BPF_FUNC_get_hash_recalc:

		return &bpf_get_hash_recalc_proto;

	case BPF_FUNC_perf_event_output:

		return bpf_get_event_output_proto();

	case BPF_FUNC_get_smp_processor_id: