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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: David Ahern <dsa@cumulusnetworks.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David Ahern 2016-12-01 08:48:06 -08:00 committed by David S. Miller
parent ad2805dc79
commit aa4c1037a3
3 changed files with 39 additions and 0 deletions
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15
include/net/sock.h
View File

@ -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,

3
include/uapi/linux/bpf.h
View File

@ -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.

21
net/core/filter.c
View File

@ -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;