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 <vla...@google.com>
---
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 c1554aa074659..23e2031a43d43 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 f6ca38a7d4332..65dc13aeca7c4 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 c1554aa074659..23e2031a43d43 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 54d16fbdef8b9..537a8f91af02d 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 = {
--
2.19.1.1215.g8438c0b245-goog
