Skip to content

Commit

Permalink
bpf: add skb->tstamp r/w access from tc clsact and cg skb progs
Browse files Browse the repository at this point in the history 
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 <vladum@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
  • Loading branch information
Vlad Dumitrescu authored and Alexei Starovoitov committed Nov 22, 2018
1 parent ab85b01 commit f11216b
Show file tree
Hide file tree
Showing 4 changed files with 60 additions and 0 deletions.
1 change: 1 addition & 0 deletions include/uapi/linux/bpf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2468,6 +2468,7 @@ struct __sk_buff {

__u32 data_meta;
struct bpf_flow_keys *flow_keys;
__u64 tstamp;
};

struct bpf_tunnel_key {
Expand Down
29 changes: 29 additions & 0 deletions net/core/filter.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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) {
Expand Down Expand Up @@ -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;
}

Expand Down Expand Up @@ -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;
}
Expand Down Expand Up @@ -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;
}

Expand Down Expand Up @@ -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;
Expand Down Expand Up @@ -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;
}

Expand Down Expand Up @@ -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;
}

Expand Down Expand Up @@ -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;
Expand Down
1 change: 1 addition & 0 deletions tools/include/uapi/linux/bpf.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2468,6 +2468,7 @@ struct __sk_buff {

__u32 data_meta;
struct bpf_flow_keys *flow_keys;
__u64 tstamp;
};

struct bpf_tunnel_key {
Expand Down
29 changes: 29 additions & 0 deletions tools/testing/selftests/bpf/test_verifier.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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 = "",
Expand Down Expand Up @@ -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 = {
Expand Down

0 comments on commit f11216b

Please sign in to comment.