bpf: Make SOCK_OPS_GET_TCP struct independent (34d367c5) · Commits · 戴 / test

Changed SOCK_OPS_GET_TCP to SOCK_OPS_GET_FIELD and added 2 arguments so now it can also work with struct sock fields. The first argument is the name of the field in the bpf_sock_ops struct, the 2nd argument is the name of the field in the OBJ struct. Previous: SOCK_OPS_GET_TCP(FIELD_NAME) New: SOCK_OPS_GET_FIELD(BPF_FIELD, OBJ_FIELD, OBJ) Where OBJ is either "struct tcp_sock" or "struct sock" (without quotation). BPF_FIELD is the name of the field in the bpf_sock_ops struct and OBJ_FIELD is the name of the field in the OBJ struct. Although the field names are currently the same, the kernel struct names could change in the future and this change makes it easier to support that. Note that adding access to tcp_sock fields in sock_ops programs does not preclude the tcp_sock fields from being removed as long as we are willing to do one of the following: 1) Return a fixed value (e.x. 0 or 0xffffffff), or 2) Make the verifier fail if that field is accessed (i.e. program fails to load) so the user will know that field is no longer supported. Signed-off-by:

Lawrence Brakmo <brakmo@fb.com> Signed-off-by:

Alexei Starovoitov <ast@kernel.org>

net/core/filter.c

+10 −10

Original line number	Diff line number	Diff line
		@@ -4469,11 +4469,11 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type,
		is_fullsock));
		break;

		/* Helper macro for adding read access to tcp_sock fields. */
		#define SOCK_OPS_GET_TCP(FIELD_NAME) \
		/* Helper macro for adding read access to tcp_sock or sock fields. */
		#define SOCK_OPS_GET_FIELD(BPF_FIELD, OBJ_FIELD, OBJ) \
		do { \
		BUILD_BUG_ON(FIELD_SIZEOF(struct tcp_sock, FIELD_NAME) > \
		FIELD_SIZEOF(struct bpf_sock_ops, FIELD_NAME)); \
		BUILD_BUG_ON(FIELD_SIZEOF(OBJ, OBJ_FIELD) > \
		FIELD_SIZEOF(struct bpf_sock_ops, BPF_FIELD)); \
		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF( \
		struct bpf_sock_ops_kern, \
		is_fullsock), \
		@@ -4485,18 +4485,18 @@ static u32 sock_ops_convert_ctx_access(enum bpf_access_type type,
		struct bpf_sock_ops_kern, sk),\
		si->dst_reg, si->src_reg, \
		offsetof(struct bpf_sock_ops_kern, sk));\
		*insn++ = BPF_LDX_MEM(FIELD_SIZEOF(struct tcp_sock, \
		FIELD_NAME), si->dst_reg, \
		si->dst_reg, \
		offsetof(struct tcp_sock, FIELD_NAME)); \
		*insn++ = BPF_LDX_MEM(BPF_FIELD_SIZEOF(OBJ, \
		OBJ_FIELD), \
		si->dst_reg, si->dst_reg, \
		offsetof(OBJ, OBJ_FIELD)); \
		} while (0)

		case offsetof(struct bpf_sock_ops, snd_cwnd):
		SOCK_OPS_GET_TCP(snd_cwnd);
		SOCK_OPS_GET_FIELD(snd_cwnd, snd_cwnd, struct tcp_sock);
		break;

		case offsetof(struct bpf_sock_ops, srtt_us):
		SOCK_OPS_GET_TCP(srtt_us);
		SOCK_OPS_GET_FIELD(srtt_us, srtt_us, struct tcp_sock);
		break;
		}
		return insn - insn_buf;

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