On 08/30/2018 08:22 PM, Petar Penkov wrote:
> From: Petar Penkov <ppen...@google.com>
>
> Adds a hook for programs of type BPF_PROG_TYPE_FLOW_DISSECTOR and
> attach type BPF_FLOW_DISSECTOR that is executed in the flow dissector
> path. The BPF program is per-network namespace.
>
> Signed-off-by: Petar Penkov <ppen...@google.com>
> Signed-off-by: Willem de Bruijn <will...@google.com>
[...]
> + err = check_flow_keys_access(env, off, size);
> + if (!err && t == BPF_READ && value_regno >= 0)
> + mark_reg_unknown(env, regs, value_regno);
> } else {
> verbose(env, "R%d invalid mem access '%s'\n", regno,
> reg_type_str[reg->type]);
> @@ -1925,6 +1954,8 @@ static int check_helper_mem_access(struct
> bpf_verifier_env *env, int regno,
> case PTR_TO_PACKET_META:
> return check_packet_access(env, regno, reg->off, access_size,
> zero_size_allowed);
> + case PTR_TO_FLOW_KEYS:
> + return check_flow_keys_access(env, reg->off, access_size);
> case PTR_TO_MAP_VALUE:
> return check_map_access(env, regno, reg->off, access_size,
> zero_size_allowed);
> @@ -3976,6 +4007,7 @@ static bool may_access_skb(enum bpf_prog_type type)
> case BPF_PROG_TYPE_SOCKET_FILTER:
> case BPF_PROG_TYPE_SCHED_CLS:
> case BPF_PROG_TYPE_SCHED_ACT:
> + case BPF_PROG_TYPE_FLOW_DISSECTOR:
> return true;
This one should not be added here. It would allow for LD_ABS to be used, but
you already have direct packet access as well as bpf_skb_load_bytes() helper
enabled. Downside on LD_ABS is that error path will exit the BPF prog with
return 0 for historical reasons w/o user realizing (here: to BPF_OK mapping).
So we should not encourage use of LD_ABS/IND anymore in eBPF context and
avoid surprises.
> default:
> return false;
> @@ -4451,6 +4483,7 @@ static bool regsafe(struct bpf_reg_state *rold, struct
> bpf_reg_state *rcur,
> case PTR_TO_CTX:
> case CONST_PTR_TO_MAP:
> case PTR_TO_PACKET_END:
> + case PTR_TO_FLOW_KEYS:
> /* Only valid matches are exact, which memcmp() above
> * would have accepted
> */
> diff --git a/net/core/filter.c b/net/core/filter.c
> index c25eb36f1320..0143b9c0c67e 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -5092,6 +5092,17 @@ sk_skb_func_proto(enum bpf_func_id func_id, const
> struct bpf_prog *prog)
> }
> }
>
> +static const struct bpf_func_proto *
> +flow_dissector_func_proto(enum bpf_func_id func_id, const struct bpf_prog
> *prog)
> +{
> + switch (func_id) {
> + case BPF_FUNC_skb_load_bytes:
> + return &bpf_skb_load_bytes_proto;
Probably makes sense to also enable bpf_skb_pull_data helper for direct packet
access use to fetch non-linear data from here once.
> + default:
> + return bpf_base_func_proto(func_id);
> + }
> +}
> +
> static const struct bpf_func_proto *
> lwt_out_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
> {
> @@ -5207,6 +5218,7 @@ static bool bpf_skb_is_valid_access(int off, int size,
> enum bpf_access_type type
> case bpf_ctx_range(struct __sk_buff, data):
> case bpf_ctx_range(struct __sk_buff, data_meta):
> case bpf_ctx_range(struct __sk_buff, data_end):
> + case bpf_ctx_range(struct __sk_buff, flow_keys):
> if (size != size_default)
> return false;
> break;
> @@ -5235,6 +5247,7 @@ static bool sk_filter_is_valid_access(int off, int size,
> case bpf_ctx_range(struct __sk_buff, data):
> case bpf_ctx_range(struct __sk_buff, data_meta):
> 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):
[...]
Thanks,
Daniel
