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Commit d1b662ad authored by Daniel Borkmann's avatar Daniel Borkmann Committed by David S. Miller
Browse files

bpf: allow option for setting bpf_l4_csum_replace from scratch 



When programs need to calculate the csum from scratch for small UDP
packets and use bpf_l4_csum_replace() to feed the result from helpers
like bpf_csum_diff(), then we need a flag besides BPF_F_MARK_MANGLED_0
that would ignore the case of current csum being 0, and which would
still allow for the helper to set the csum and transform when needed
to CSUM_MANGLED_0.

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 2492d3b8

include/uapi/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -522,6 +522,7 @@ enum bpf_func_id { 
/* BPF_FUNC_l4_csum_replace flags. */

#define BPF_F_PSEUDO_HDR		(1ULL << 4)

#define BPF_F_MARK_MANGLED_0		(1ULL << 5)

#define BPF_F_MARK_ENFORCE		(1ULL << 6)



/* BPF_FUNC_clone_redirect and BPF_FUNC_redirect flags. */

#define BPF_F_INGRESS			(1ULL << 0)

net/core/filter.c

+4 −3
Original line number Diff line number Diff line
@@ -1522,10 +1522,11 @@ BPF_CALL_5(bpf_l4_csum_replace, struct sk_buff *, skb, u32, offset, 
{

	bool is_pseudo = flags & BPF_F_PSEUDO_HDR;

	bool is_mmzero = flags & BPF_F_MARK_MANGLED_0;

	bool do_mforce = flags & BPF_F_MARK_ENFORCE;

	__sum16 *ptr;



	if (unlikely(flags & ~(BPF_F_MARK_MANGLED_0 | BPF_F_PSEUDO_HDR |

			       BPF_F_HDR_FIELD_MASK)))

	if (unlikely(flags & ~(BPF_F_MARK_MANGLED_0 | BPF_F_MARK_ENFORCE |

			       BPF_F_PSEUDO_HDR | BPF_F_HDR_FIELD_MASK)))

		return -EINVAL;

	if (unlikely(offset > 0xffff || offset & 1))

		return -EFAULT;
@@ -1533,7 +1534,7 @@ BPF_CALL_5(bpf_l4_csum_replace, struct sk_buff *, skb, u32, offset, 
		return -EFAULT;



	ptr = (__sum16 *)(skb->data + offset);

	if (is_mmzero && !*ptr)

	if (is_mmzero && !do_mforce && !*ptr)

		return 0;



	switch (flags & BPF_F_HDR_FIELD_MASK) {