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Commit f11216b2 authored by Vlad Dumitrescu's avatar Vlad Dumitrescu Committed by Alexei Starovoitov
Browse files

bpf: add skb->tstamp r/w access from tc clsact and cg skb progs 



This could be used to rate limit egress traffic in concert with a qdisc
which supports Earliest Departure Time, such as FQ.

Write access from cg skb progs only with CAP_SYS_ADMIN, since the value
will be used by downstream qdiscs. It might make sense to relax this.

Changes v1 -> v2:
  - allow access from cg skb, write only with CAP_SYS_ADMIN

Signed-off-by: default avatarVlad Dumitrescu <vladum@google.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarWillem de Bruijn <willemb@google.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent ab85b014

include/uapi/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -2468,6 +2468,7 @@ struct __sk_buff { 


	__u32 data_meta;

	struct bpf_flow_keys *flow_keys;

	__u64 tstamp;

};



struct bpf_tunnel_key {

net/core/filter.c

+29 −0
Original line number Diff line number Diff line
@@ -5573,6 +5573,10 @@ static bool bpf_skb_is_valid_access(int off, int size, enum bpf_access_type type 
		if (size != sizeof(struct bpf_flow_keys *))

			return false;

		break;

	case bpf_ctx_range(struct __sk_buff, tstamp):

		if (size != sizeof(__u64))

			return false;

		break;

	default:

		/* Only narrow read access allowed for now. */

		if (type == BPF_WRITE) {
@@ -5600,6 +5604,7 @@ static bool sk_filter_is_valid_access(int off, int size, 
	case bpf_ctx_range(struct __sk_buff, data_end):

	case bpf_ctx_range(struct __sk_buff, flow_keys):

	case bpf_ctx_range_till(struct __sk_buff, family, local_port):

	case bpf_ctx_range(struct __sk_buff, tstamp):

		return false;

	}
@@ -5638,6 +5643,10 @@ static bool cg_skb_is_valid_access(int off, int size, 
		case bpf_ctx_range(struct __sk_buff, priority):

		case bpf_ctx_range_till(struct __sk_buff, cb[0], cb[4]):

			break;

		case bpf_ctx_range(struct __sk_buff, tstamp):

			if (!capable(CAP_SYS_ADMIN))

				return false;

			break;

		default:

			return false;

		}
@@ -5665,6 +5674,7 @@ static bool lwt_is_valid_access(int off, int size, 
	case bpf_ctx_range_till(struct __sk_buff, family, local_port):

	case bpf_ctx_range(struct __sk_buff, data_meta):

	case bpf_ctx_range(struct __sk_buff, flow_keys):

	case bpf_ctx_range(struct __sk_buff, tstamp):

		return false;

	}
@@ -5874,6 +5884,7 @@ static bool tc_cls_act_is_valid_access(int off, int size, 
		case bpf_ctx_range(struct __sk_buff, priority):

		case bpf_ctx_range(struct __sk_buff, tc_classid):

		case bpf_ctx_range_till(struct __sk_buff, cb[0], cb[4]):

		case bpf_ctx_range(struct __sk_buff, tstamp):

			break;

		default:

			return false;
@@ -6093,6 +6104,7 @@ static bool sk_skb_is_valid_access(int off, int size, 
	case bpf_ctx_range(struct __sk_buff, tc_classid):

	case bpf_ctx_range(struct __sk_buff, data_meta):

	case bpf_ctx_range(struct __sk_buff, flow_keys):

	case bpf_ctx_range(struct __sk_buff, tstamp):

		return false;

	}
@@ -6179,6 +6191,7 @@ static bool flow_dissector_is_valid_access(int off, int size, 
	case bpf_ctx_range(struct __sk_buff, tc_classid):

	case bpf_ctx_range(struct __sk_buff, data_meta):

	case bpf_ctx_range_till(struct __sk_buff, family, local_port):

	case bpf_ctx_range(struct __sk_buff, tstamp):

		return false;

	}
@@ -6488,6 +6501,22 @@ static u32 bpf_convert_ctx_access(enum bpf_access_type type, 
		*insn++ = BPF_LDX_MEM(BPF_SIZEOF(void *), si->dst_reg,

				      si->src_reg, off);

		break;



	case offsetof(struct __sk_buff, tstamp):

		BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, tstamp) != 8);



		if (type == BPF_WRITE)

			*insn++ = BPF_STX_MEM(BPF_DW,

					      si->dst_reg, si->src_reg,

					      bpf_target_off(struct sk_buff,

							     tstamp, 8,

							     target_size));

		else

			*insn++ = BPF_LDX_MEM(BPF_DW,

					      si->dst_reg, si->src_reg,

					      bpf_target_off(struct sk_buff,

							     tstamp, 8,

							     target_size));

	}



	return insn - insn_buf;

tools/include/uapi/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -2468,6 +2468,7 @@ struct __sk_buff { 


	__u32 data_meta;

	struct bpf_flow_keys *flow_keys;

	__u64 tstamp;

};



struct bpf_tunnel_key {

tools/testing/selftests/bpf/test_verifier.c

+29 −0
Original line number Diff line number Diff line
@@ -2446,6 +2446,10 @@ static struct bpf_test tests[] = { 
				    offsetof(struct __sk_buff, tc_index)),

			BPF_STX_MEM(BPF_W, BPF_REG_1, BPF_REG_0,

				    offsetof(struct __sk_buff, cb[3])),

			BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1,

				    offsetof(struct __sk_buff, tstamp)),

			BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0,

				    offsetof(struct __sk_buff, tstamp)),

			BPF_EXIT_INSN(),

		},

		.errstr_unpriv = "",
@@ -5297,6 +5301,31 @@ static struct bpf_test tests[] = { 
		.errstr_unpriv = "R2 leaks addr into helper function",

		.prog_type = BPF_PROG_TYPE_CGROUP_SKB,

	},

	{

		"write tstamp from CGROUP_SKB",

		.insns = {

			BPF_MOV64_IMM(BPF_REG_0, 0),

			BPF_STX_MEM(BPF_DW, BPF_REG_1, BPF_REG_0,

				    offsetof(struct __sk_buff, tstamp)),

			BPF_MOV64_IMM(BPF_REG_0, 0),

			BPF_EXIT_INSN(),

		},

		.result = ACCEPT,

		.result_unpriv = REJECT,

		.errstr_unpriv = "invalid bpf_context access off=152 size=8",

		.prog_type = BPF_PROG_TYPE_CGROUP_SKB,

	},

	{

		"read tstamp from CGROUP_SKB",

		.insns = {

			BPF_LDX_MEM(BPF_DW, BPF_REG_0, BPF_REG_1,

				    offsetof(struct __sk_buff, tstamp)),

			BPF_MOV64_IMM(BPF_REG_0, 0),

			BPF_EXIT_INSN(),

		},

		.result = ACCEPT,

		.prog_type = BPF_PROG_TYPE_CGROUP_SKB,

	},

	{

		"multiple registers share map_lookup_elem result",

		.insns = {