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Date: Sat, 2 Apr 2016 12:39:45 -0400
From: Tom Herbert <tom@...bertland.com>
To: Brenden Blanco <bblanco@...mgrid.com>
Cc: "David S. Miller" <davem@...emloft.net>,
Linux Kernel Network Developers <netdev@...r.kernel.org>,
Alexei Starovoitov <alexei.starovoitov@...il.com>,
gerlitz@...lanox.com, Daniel Borkmann <daniel@...earbox.net>,
john fastabend <john.fastabend@...il.com>,
Jesper Dangaard Brouer <brouer@...hat.com>
Subject: Re: [RFC PATCH 1/5] bpf: add PHYS_DEV prog type for early driver filter
On Fri, Apr 1, 2016 at 9:21 PM, Brenden Blanco <bblanco@...mgrid.com> wrote:
> Add a new bpf prog type that is intended to run in early stages of the
> packet rx path. Only minimal packet metadata will be available, hence a new
> context type, struct xdp_metadata, is exposed to userspace. So far only
> expose the readable packet length, and only in read mode.
>
This would eventually be a generic abstraction of receive descriptors?
> The PHYS_DEV name is chosen to represent that the program is meant only
> for physical adapters, rather than all netdevs.
>
Is there a hard restriction that this could only work with physical devices?
> While the user visible struct is new, the underlying context must be
> implemented as a minimal skb in order for the packet load_* instructions
> to work. The skb filled in by the driver must have skb->len, skb->head,
> and skb->data set, and skb->data_len == 0.
>
> Signed-off-by: Brenden Blanco <bblanco@...mgrid.com>
> ---
> include/uapi/linux/bpf.h | 5 ++++
> kernel/bpf/verifier.c | 1 +
> net/core/filter.c | 68 ++++++++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 74 insertions(+)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 924f537..b8a4ef2 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -92,6 +92,7 @@ enum bpf_prog_type {
> BPF_PROG_TYPE_KPROBE,
> BPF_PROG_TYPE_SCHED_CLS,
> BPF_PROG_TYPE_SCHED_ACT,
> + BPF_PROG_TYPE_PHYS_DEV,
> };
>
> #define BPF_PSEUDO_MAP_FD 1
> @@ -367,6 +368,10 @@ struct __sk_buff {
> __u32 tc_classid;
> };
>
> +struct xdp_metadata {
> + __u32 len;
> +};
> +
> struct bpf_tunnel_key {
> __u32 tunnel_id;
> union {
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 2e08f8e..804ca70 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -1340,6 +1340,7 @@ 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_PHYS_DEV:
> return true;
> default:
> return false;
> diff --git a/net/core/filter.c b/net/core/filter.c
> index b7177d0..c417db6 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -2018,6 +2018,12 @@ tc_cls_act_func_proto(enum bpf_func_id func_id)
> }
> }
>
> +static const struct bpf_func_proto *
> +phys_dev_func_proto(enum bpf_func_id func_id)
> +{
> + return sk_filter_func_proto(func_id);
> +}
> +
> static bool __is_valid_access(int off, int size, enum bpf_access_type type)
> {
> /* check bounds */
> @@ -2073,6 +2079,36 @@ static bool tc_cls_act_is_valid_access(int off, int size,
> return __is_valid_access(off, size, type);
> }
>
> +static bool __is_valid_xdp_access(int off, int size,
> + enum bpf_access_type type)
> +{
> + if (off < 0 || off >= sizeof(struct xdp_metadata))
> + return false;
> +
> + if (off % size != 0)
> + return false;
> +
> + if (size != 4)
> + return false;
> +
> + return true;
> +}
> +
> +static bool phys_dev_is_valid_access(int off, int size,
> + enum bpf_access_type type)
> +{
> + if (type == BPF_WRITE)
> + return false;
> +
> + switch (off) {
> + case offsetof(struct xdp_metadata, len):
> + break;
> + default:
> + return false;
> + }
> + return __is_valid_xdp_access(off, size, type);
> +}
> +
> static u32 bpf_net_convert_ctx_access(enum bpf_access_type type, int dst_reg,
> int src_reg, int ctx_off,
> struct bpf_insn *insn_buf,
> @@ -2210,6 +2246,26 @@ static u32 bpf_net_convert_ctx_access(enum bpf_access_type type, int dst_reg,
> return insn - insn_buf;
> }
>
> +static u32 bpf_phys_dev_convert_ctx_access(enum bpf_access_type type,
> + int dst_reg, int src_reg,
> + int ctx_off,
> + struct bpf_insn *insn_buf,
> + struct bpf_prog *prog)
> +{
> + struct bpf_insn *insn = insn_buf;
> +
> + switch (ctx_off) {
> + case offsetof(struct xdp_metadata, len):
> + BUILD_BUG_ON(FIELD_SIZEOF(struct sk_buff, len) != 4);
> +
> + *insn++ = BPF_LDX_MEM(BPF_W, dst_reg, src_reg,
> + offsetof(struct sk_buff, len));
> + break;
> + }
> +
> + return insn - insn_buf;
> +}
> +
> static const struct bpf_verifier_ops sk_filter_ops = {
> .get_func_proto = sk_filter_func_proto,
> .is_valid_access = sk_filter_is_valid_access,
> @@ -2222,6 +2278,12 @@ static const struct bpf_verifier_ops tc_cls_act_ops = {
> .convert_ctx_access = bpf_net_convert_ctx_access,
> };
>
> +static const struct bpf_verifier_ops phys_dev_ops = {
> + .get_func_proto = phys_dev_func_proto,
> + .is_valid_access = phys_dev_is_valid_access,
> + .convert_ctx_access = bpf_phys_dev_convert_ctx_access,
> +};
> +
> static struct bpf_prog_type_list sk_filter_type __read_mostly = {
> .ops = &sk_filter_ops,
> .type = BPF_PROG_TYPE_SOCKET_FILTER,
> @@ -2237,11 +2299,17 @@ static struct bpf_prog_type_list sched_act_type __read_mostly = {
> .type = BPF_PROG_TYPE_SCHED_ACT,
> };
>
> +static struct bpf_prog_type_list phys_dev_type __read_mostly = {
> + .ops = &phys_dev_ops,
> + .type = BPF_PROG_TYPE_PHYS_DEV,
> +};
> +
> static int __init register_sk_filter_ops(void)
> {
> bpf_register_prog_type(&sk_filter_type);
> bpf_register_prog_type(&sched_cls_type);
> bpf_register_prog_type(&sched_act_type);
> + bpf_register_prog_type(&phys_dev_type);
>
> return 0;
> }
> --
> 2.8.0
>
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