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Commit c2497395 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by David S. Miller
Browse files

bpf: allow BPF programs access 'protocol' and 'vlan_tci' fields 



as a follow on to patch 70006af9 ("bpf: allow eBPF access skb fields")
this patch allows 'protocol' and 'vlan_tci' fields to be accessible
from extended BPF programs.

The usage of 'protocol', 'vlan_present' and 'vlan_tci' fields is the same as
corresponding SKF_AD_PROTOCOL, SKF_AD_VLAN_TAG_PRESENT and SKF_AD_VLAN_TAG
accesses in classic BPF.

Signed-off-by: default avatarAlexei Starovoitov <ast@plumgrid.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9cf7867c

include/uapi/linux/bpf.h

+3 −0
Original line number Diff line number Diff line
@@ -178,6 +178,9 @@ struct __sk_buff { 
	__u32 pkt_type;

	__u32 mark;

	__u32 queue_mapping;

	__u32 protocol;

	__u32 vlan_present;

	__u32 vlan_tci;

};



#endif /* _UAPI__LINUX_BPF_H__ */

net/core/filter.c

+50 −22
Original line number Diff line number Diff line
@@ -177,6 +177,35 @@ static u32 convert_skb_access(int skb_field, int dst_reg, int src_reg, 
		*insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,

				      offsetof(struct sk_buff, queue_mapping));

		break;



	case SKF_AD_PROTOCOL:

		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);



		/* dst_reg = *(u16 *) (src_reg + offsetof(protocol)) */

		*insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,

				      offsetof(struct sk_buff, protocol));

		/* dst_reg = ntohs(dst_reg) [emitting a nop or swap16] */

		*insn++ = BPF_ENDIAN(BPF_FROM_BE, dst_reg, 16);

		break;



	case SKF_AD_VLAN_TAG:

	case SKF_AD_VLAN_TAG_PRESENT:

		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);

		BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);



		/* dst_reg = *(u16 *) (src_reg + offsetof(vlan_tci)) */

		*insn++ = BPF_LDX_MEM(BPF_H, dst_reg, src_reg,

				      offsetof(struct sk_buff, vlan_tci));

		if (skb_field == SKF_AD_VLAN_TAG) {

			*insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg,

						~VLAN_TAG_PRESENT);

		} else {

			/* dst_reg >>= 12 */

			*insn++ = BPF_ALU32_IMM(BPF_RSH, dst_reg, 12);

			/* dst_reg &= 1 */

			*insn++ = BPF_ALU32_IMM(BPF_AND, dst_reg, 1);

		}

		break;

	}



	return insn - insn_buf;
@@ -190,13 +219,8 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 


	switch (fp->k) {

	case SKF_AD_OFF + SKF_AD_PROTOCOL:

		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, protocol) != 2);



		/* A = *(u16 *) (CTX + offsetof(protocol)) */

		*insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,

				      offsetof(struct sk_buff, protocol));

		/* A = ntohs(A) [emitting a nop or swap16] */

		*insn = BPF_ENDIAN(BPF_FROM_BE, BPF_REG_A, 16);

		cnt = convert_skb_access(SKF_AD_PROTOCOL, BPF_REG_A, BPF_REG_CTX, insn);

		insn += cnt - 1;

		break;



	case SKF_AD_OFF + SKF_AD_PKTTYPE:
@@ -242,22 +266,15 @@ static bool convert_bpf_extensions(struct sock_filter *fp, 
		break;



	case SKF_AD_OFF + SKF_AD_VLAN_TAG:

	case SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT:

		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, vlan_tci) != 2);

		BUILD_BUG_ON(VLAN_TAG_PRESENT != 0x1000);

		cnt = convert_skb_access(SKF_AD_VLAN_TAG,

					 BPF_REG_A, BPF_REG_CTX, insn);

		insn += cnt - 1;

		break;



		/* A = *(u16 *) (CTX + offsetof(vlan_tci)) */

		*insn++ = BPF_LDX_MEM(BPF_H, BPF_REG_A, BPF_REG_CTX,

				      offsetof(struct sk_buff, vlan_tci));

		if (fp->k == SKF_AD_OFF + SKF_AD_VLAN_TAG) {

			*insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A,

					      ~VLAN_TAG_PRESENT);

		} else {

			/* A >>= 12 */

			*insn++ = BPF_ALU32_IMM(BPF_RSH, BPF_REG_A, 12);

			/* A &= 1 */

			*insn = BPF_ALU32_IMM(BPF_AND, BPF_REG_A, 1);

		}

	case SKF_AD_OFF + SKF_AD_VLAN_TAG_PRESENT:

		cnt = convert_skb_access(SKF_AD_VLAN_TAG_PRESENT,

					 BPF_REG_A, BPF_REG_CTX, insn);

		insn += cnt - 1;

		break;



	case SKF_AD_OFF + SKF_AD_PAY_OFFSET:
@@ -1215,6 +1232,17 @@ static u32 sk_filter_convert_ctx_access(int dst_reg, int src_reg, int ctx_off, 


	case offsetof(struct __sk_buff, queue_mapping):

		return convert_skb_access(SKF_AD_QUEUE, dst_reg, src_reg, insn);



	case offsetof(struct __sk_buff, protocol):

		return convert_skb_access(SKF_AD_PROTOCOL, dst_reg, src_reg, insn);



	case offsetof(struct __sk_buff, vlan_present):

		return convert_skb_access(SKF_AD_VLAN_TAG_PRESENT,

					  dst_reg, src_reg, insn);



	case offsetof(struct __sk_buff, vlan_tci):

		return convert_skb_access(SKF_AD_VLAN_TAG,

					  dst_reg, src_reg, insn);

	}



	return insn - insn_buf;

samples/bpf/test_verifier.c

+9 −0
Original line number Diff line number Diff line
@@ -658,6 +658,15 @@ static struct bpf_test tests[] = { 
			BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,

				    offsetof(struct __sk_buff, queue_mapping)),

			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 0),

			BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,

				    offsetof(struct __sk_buff, protocol)),

			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 0),

			BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,

				    offsetof(struct __sk_buff, vlan_present)),

			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 0),

			BPF_LDX_MEM(BPF_W, BPF_REG_0, BPF_REG_1,

				    offsetof(struct __sk_buff, vlan_tci)),

			BPF_JMP_IMM(BPF_JGE, BPF_REG_0, 0, 0),

			BPF_EXIT_INSN(),

		},

		.result = ACCEPT,