Commit cf62089b authored by Willem de Bruijn's avatar Willem de Bruijn Committed by Alexei Starovoitov
Browse files

bpf: Add gso_size to __sk_buff 



BPF programs may want to know whether an skb is gso. The canonical
answer is skb_is_gso(skb), which tests that gso_size != 0.

Expose this field in the same manner as gso_segs. That field itself
is not a sufficient signal, as the comment in skb_shared_info makes
clear: gso_segs may be zero, e.g., from dodgy sources.

Also prepare net/bpf/test_run for upcoming BPF_PROG_TEST_RUN tests
of the feature.

Signed-off-by: default avatarWillem de Bruijn <willemb@google.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200303200503.226217-2-willemdebruijn.kernel@gmail.com
parent abbc61a5

include/uapi/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -3176,6 +3176,7 @@ struct __sk_buff { 
	__u32 wire_len;

	__u32 gso_segs;

	__bpf_md_ptr(struct bpf_sock *, sk);

	__u32 gso_size;

};



struct bpf_tunnel_key {

net/bpf/test_run.c

+7 −0
Original line number Diff line number Diff line
@@ -277,6 +277,12 @@ static int convert___skb_to_skb(struct sk_buff *skb, struct __sk_buff *__skb) 
	/* gso_segs is allowed */



	if (!range_is_zero(__skb, offsetofend(struct __sk_buff, gso_segs),

			   offsetof(struct __sk_buff, gso_size)))

		return -EINVAL;



	/* gso_size is allowed */



	if (!range_is_zero(__skb, offsetofend(struct __sk_buff, gso_size),

			   sizeof(struct __sk_buff)))

		return -EINVAL;
@@ -297,6 +303,7 @@ static int convert___skb_to_skb(struct sk_buff *skb, struct __sk_buff *__skb) 
	if (__skb->gso_segs > GSO_MAX_SEGS)

		return -EINVAL;

	skb_shinfo(skb)->gso_segs = __skb->gso_segs;

	skb_shinfo(skb)->gso_size = __skb->gso_size;



	return 0;

}

net/core/filter.c

+30 −14
Original line number Diff line number Diff line
@@ -7139,6 +7139,27 @@ static u32 flow_dissector_convert_ctx_access(enum bpf_access_type type, 
	return insn - insn_buf;

}



static struct bpf_insn *bpf_convert_shinfo_access(const struct bpf_insn *si,

						  struct bpf_insn *insn)

{

	/* si->dst_reg = skb_shinfo(SKB); */

#ifdef NET_SKBUFF_DATA_USES_OFFSET

	*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),

			      BPF_REG_AX, si->src_reg,

			      offsetof(struct sk_buff, end));

	*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, head),

			      si->dst_reg, si->src_reg,

			      offsetof(struct sk_buff, head));

	*insn++ = BPF_ALU64_REG(BPF_ADD, si->dst_reg, BPF_REG_AX);

#else

	*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),

			      si->dst_reg, si->src_reg,

			      offsetof(struct sk_buff, end));

#endif



	return insn;

}



static u32 bpf_convert_ctx_access(enum bpf_access_type type,

				  const struct bpf_insn *si,

				  struct bpf_insn *insn_buf,
@@ -7461,26 +7482,21 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type, 
		break;



	case offsetof(struct __sk_buff, gso_segs):

		/* si->dst_reg = skb_shinfo(SKB); */

#ifdef NET_SKBUFF_DATA_USES_OFFSET

		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),

				      BPF_REG_AX, si->src_reg,

				      offsetof(struct sk_buff, end));

		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, head),

				      si->dst_reg, si->src_reg,

				      offsetof(struct sk_buff, head));

		*insn++ = BPF_ALU64_REG(BPF_ADD, si->dst_reg, BPF_REG_AX);

#else

		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct sk_buff, end),

				      si->dst_reg, si->src_reg,

				      offsetof(struct sk_buff, end));

#endif

		insn = bpf_convert_shinfo_access(si, insn);

		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct skb_shared_info, gso_segs),

				      si->dst_reg, si->dst_reg,

				      bpf_target_off(struct skb_shared_info,

						     gso_segs, 2,

						     target_size));

		break;

	case offsetof(struct __sk_buff, gso_size):

		insn = bpf_convert_shinfo_access(si, insn);

		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(struct skb_shared_info, gso_size),

				      si->dst_reg, si->dst_reg,

				      bpf_target_off(struct skb_shared_info,

						     gso_size, 2,

						     target_size));

		break;

	case offsetof(struct __sk_buff, wire_len):

		BUILD_BUG_ON(sizeof_field(struct qdisc_skb_cb, pkt_len) != 4);

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