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Commit aa4c1037 authored by David Ahern's avatar David Ahern Committed by David S. Miller
Browse files

bpf: Add support for reading socket family, type, protocol 



Add socket family, type and protocol to bpf_sock allowing bpf programs
read-only access.

Add __sk_flags_offset[0] to struct sock before the bitfield to
programmtically determine the offset of the unsigned int containing
protocol and type.

Signed-off-by: default avatarDavid Ahern <dsa@cumulusnetworks.com>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent ad2805dc

include/net/sock.h

+15 −0
Original line number Diff line number Diff line
@@ -389,6 +389,21 @@ struct sock { 
	 * Because of non atomicity rules, all

	 * changes are protected by socket lock.

	 */

	unsigned int		__sk_flags_offset[0];

#ifdef __BIG_ENDIAN_BITFIELD

#define SK_FL_PROTO_SHIFT  16

#define SK_FL_PROTO_MASK   0x00ff0000



#define SK_FL_TYPE_SHIFT   0

#define SK_FL_TYPE_MASK    0x0000ffff

#else

#define SK_FL_PROTO_SHIFT  8

#define SK_FL_PROTO_MASK   0x0000ff00



#define SK_FL_TYPE_SHIFT   16

#define SK_FL_TYPE_MASK    0xffff0000

#endif



	kmemcheck_bitfield_begin(flags);

	unsigned int		sk_padding : 2,

				sk_no_check_tx : 1,

include/uapi/linux/bpf.h

+3 −0
Original line number Diff line number Diff line
@@ -571,6 +571,9 @@ enum bpf_ret_code { 


struct bpf_sock {

	__u32 bound_dev_if;

	__u32 family;

	__u32 type;

	__u32 protocol;

};



/* User return codes for XDP prog type.

net/core/filter.c

+21 −0
Original line number Diff line number Diff line
@@ -3121,6 +3121,27 @@ static u32 sock_filter_convert_ctx_access(enum bpf_access_type type, 
			*insn++ = BPF_LDX_MEM(BPF_W, dst_reg, src_reg,

				      offsetof(struct sock, sk_bound_dev_if));

		break;



	case offsetof(struct bpf_sock, family):

		BUILD_BUG_ON(FIELD_SIZEOF(struct sock, sk_family) != 2);



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

				      offsetof(struct sock, sk_family));

		break;



	case offsetof(struct bpf_sock, type):

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

				      offsetof(struct sock, __sk_flags_offset));

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

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

		break;



	case offsetof(struct bpf_sock, protocol):

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

				      offsetof(struct sock, __sk_flags_offset));

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

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

		break;

	}



	return insn - insn_buf;