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cgroup: bpf: Add bpf_skb_in_cgroup_proto

Adds a bpf helper, bpf_skb_in_cgroup, to decide if a skb->sk
belongs to a descendant of a cgroup2.  It is similar to the
feature added in netfilter:
commit c38c459 ("netfilter: implement xt_cgroup cgroup2 path match")

The user is expected to populate a BPF_MAP_TYPE_CGROUP_ARRAY
which will be used by the bpf_skb_in_cgroup.

Modifications to the bpf verifier is to ensure BPF_MAP_TYPE_CGROUP_ARRAY
and bpf_skb_in_cgroup() are always used together.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Cc: Alexei Starovoitov <ast@fb.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Tejun Heo <tj@kernel.org>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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iamkafai authored and davem330 committed Jun 30, 2016
1 parent 4ed8ec5 commit 4a482f34afcc162d8456f449b137ec2a95be60d8
Showing with 56 additions and 1 deletion.
  1. +11 −0 include/uapi/linux/bpf.h
  2. +7 −1 kernel/bpf/verifier.c
  3. +38 −0 net/core/filter.c
@@ -337,6 +337,17 @@ enum bpf_func_id {
*/
BPF_FUNC_skb_change_type,
/**
* bpf_skb_in_cgroup(skb, map, index) - Check cgroup2 membership of skb
* @skb: pointer to skb
* @map: pointer to bpf_map in BPF_MAP_TYPE_CGROUP_ARRAY type
* @index: index of the cgroup in the bpf_map
* Return:
* == 0 skb failed the cgroup2 descendant test
* == 1 skb succeeded the cgroup2 descendant test
* < 0 error
*/
BPF_FUNC_skb_in_cgroup,
__BPF_FUNC_MAX_ID,
};
@@ -1036,7 +1036,9 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id)
goto error;
break;
case BPF_MAP_TYPE_CGROUP_ARRAY:
goto error;
if (func_id != BPF_FUNC_skb_in_cgroup)
goto error;
break;
default:
break;
}
@@ -1056,6 +1058,10 @@ static int check_map_func_compatibility(struct bpf_map *map, int func_id)
if (map->map_type != BPF_MAP_TYPE_STACK_TRACE)
goto error;
break;
case BPF_FUNC_skb_in_cgroup:
if (map->map_type != BPF_MAP_TYPE_CGROUP_ARRAY)
goto error;
break;
default:
break;
}
@@ -2239,6 +2239,40 @@ bpf_get_skb_set_tunnel_proto(enum bpf_func_id which)
}
}
#ifdef CONFIG_SOCK_CGROUP_DATA
static u64 bpf_skb_in_cgroup(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
{
struct sk_buff *skb = (struct sk_buff *)(long)r1;
struct bpf_map *map = (struct bpf_map *)(long)r2;
struct bpf_array *array = container_of(map, struct bpf_array, map);
struct cgroup *cgrp;
struct sock *sk;
u32 i = (u32)r3;
sk = skb->sk;
if (!sk || !sk_fullsock(sk))
return -ENOENT;
if (unlikely(i >= array->map.max_entries))
return -E2BIG;
cgrp = READ_ONCE(array->ptrs[i]);
if (unlikely(!cgrp))
return -EAGAIN;
return cgroup_is_descendant(sock_cgroup_ptr(&sk->sk_cgrp_data), cgrp);
}
static const struct bpf_func_proto bpf_skb_in_cgroup_proto = {
.func = bpf_skb_in_cgroup,
.gpl_only = false,
.ret_type = RET_INTEGER,
.arg1_type = ARG_PTR_TO_CTX,
.arg2_type = ARG_CONST_MAP_PTR,
.arg3_type = ARG_ANYTHING,
};
#endif
static const struct bpf_func_proto *
sk_filter_func_proto(enum bpf_func_id func_id)
{
@@ -2307,6 +2341,10 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
return bpf_get_event_output_proto();
case BPF_FUNC_get_smp_processor_id:
return &bpf_get_smp_processor_id_proto;
#ifdef CONFIG_SOCK_CGROUP_DATA
case BPF_FUNC_skb_in_cgroup:
return &bpf_skb_in_cgroup_proto;
#endif
default:
return sk_filter_func_proto(func_id);
}

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