From f11216b24219ab26d8d159fbfa12dff886b16e32 Mon Sep 17 00:00:00 2001 From: Vlad Dumitrescu Date: Thu, 22 Nov 2018 14:39:16 -0500 Subject: [PATCH] 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: Vlad Dumitrescu Acked-by: Eric Dumazet Acked-by: Willem de Bruijn Signed-off-by: Alexei Starovoitov --- include/uapi/linux/bpf.h | 1 + net/core/filter.c | 29 +++++++++++++++++++++ tools/include/uapi/linux/bpf.h | 1 + tools/testing/selftests/bpf/test_verifier.c | 29 +++++++++++++++++++++ 4 files changed, 60 insertions(+) diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h index c1554aa07465..23e2031a43d4 100644 --- a/include/uapi/linux/bpf.h +++ b/include/uapi/linux/bpf.h @@ -2468,6 +2468,7 @@ struct __sk_buff { __u32 data_meta; struct bpf_flow_keys *flow_keys; + __u64 tstamp; }; struct bpf_tunnel_key { diff --git a/net/core/filter.c b/net/core/filter.c index f6ca38a7d433..65dc13aeca7c 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -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; diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h index c1554aa07465..23e2031a43d4 100644 --- a/tools/include/uapi/linux/bpf.h +++ b/tools/include/uapi/linux/bpf.h @@ -2468,6 +2468,7 @@ struct __sk_buff { __u32 data_meta; struct bpf_flow_keys *flow_keys; + __u64 tstamp; }; struct bpf_tunnel_key { diff --git a/tools/testing/selftests/bpf/test_verifier.c b/tools/testing/selftests/bpf/test_verifier.c index 54d16fbdef8b..537a8f91af02 100644 --- a/tools/testing/selftests/bpf/test_verifier.c +++ b/tools/testing/selftests/bpf/test_verifier.c @@ -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 = {