On Thu, Apr 19, 2018 at 12:58:22AM +0300, Eyal Birger wrote:
> This commit introduces a helper which allows fetching xfrm state
> parameters by eBPF programs attached to TC.
>
> Prototype:
> bpf_skb_get_xfrm_state(skb, index, xfrm_state, size, flags)
>
> skb: pointer to skb
> index: the index in the skb xfrm_state secpath array
> xfrm_state: pointer to 'struct bpf_xfrm_state'
> size: size of 'struct bpf_xfrm_state'
> flags: reserved for future extensions
>
> The helper returns 0 on success. Non zero if no xfrm state at the index
> is found - or non exists at all.
>
> struct bpf_xfrm_state currently includes the SPI, peer IPv4/IPv6
> address and the reqid; it can be further extended by adding elements to
> its end - indicating the populated fields by the 'size' argument -
> keeping backwards compatibility.
>
> Typical usage:
>
> struct bpf_xfrm_state x = {};
> bpf_skb_get_xfrm_state(skb, 0, &x, sizeof(x), 0);
> ...
>
> Signed-off-by: Eyal Birger <eyal.bir...@gmail.com>
> ---
> include/uapi/linux/bpf.h | 25 ++++++++++++++++++++++++-
> net/core/filter.c | 48
> ++++++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 72 insertions(+), 1 deletion(-)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 9a2d1a0..82b407a 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -762,6 +762,15 @@ union bpf_attr {
> * @xdp_md: pointer to xdp_md
> * @delta: A negative integer to be added to xdp_md.data_end
> * Return: 0 on success or negative on error
> + *
> + * int bpf_skb_get_xfrm_state(skb, index, xfrm_state, size, flags)
> + * retrieve XFRM state
> + * @skb: pointer to skb
> + * @index: index of the xfrm state in the secpath
> + * @key: pointer to 'struct bpf_xfrm_state'
> + * @size: size of 'struct bpf_xfrm_state'
> + * @flags: room for future extensions
> + * Return: 0 on success or negative error
> */
> #define __BPF_FUNC_MAPPER(FN) \
> FN(unspec), \
> @@ -829,7 +838,8 @@ union bpf_attr {
> FN(msg_cork_bytes), \
> FN(msg_pull_data), \
> FN(bind), \
> - FN(xdp_adjust_tail),
> + FN(xdp_adjust_tail), \
> + FN(skb_get_xfrm_state),
>
> /* integer value in 'imm' field of BPF_CALL instruction selects which helper
> * function eBPF program intends to call
> @@ -935,6 +945,19 @@ struct bpf_tunnel_key {
> __u32 tunnel_label;
> };
>
> +/* user accessible mirror of in-kernel xfrm_state.
> + * new fields can only be added to the end of this structure
> + */
> +struct bpf_xfrm_state {
> + __u32 reqid;
> + __u32 spi;
> + __u16 family;
> + union {
> + __u32 remote_ipv4;
> + __u32 remote_ipv6[4];
> + };
> +};
> +
> /* Generic BPF return codes which all BPF program types may support.
> * The values are binary compatible with their TC_ACT_* counter-part to
> * provide backwards compatibility with existing SCHED_CLS and SCHED_ACT
> diff --git a/net/core/filter.c b/net/core/filter.c
> index 2931859..489d360 100644
> --- a/net/core/filter.c
> +++ b/net/core/filter.c
> @@ -57,6 +57,7 @@
> #include <net/sock_reuseport.h>
> #include <net/busy_poll.h>
> #include <net/tcp.h>
> +#include <net/xfrm.h>
> #include <linux/bpf_trace.h>
>
> /**
> @@ -3749,6 +3750,49 @@ static const struct bpf_func_proto bpf_bind_proto = {
> .arg3_type = ARG_CONST_SIZE,
> };
>
> +#ifdef CONFIG_XFRM
> +BPF_CALL_5(bpf_skb_get_xfrm_state, struct sk_buff *, skb, u32, index,
> + struct bpf_xfrm_state *, to, u32, size, u64, flags)
> +{
> + const struct sec_path *sp = skb_sec_path(skb);
> + const struct xfrm_state *x;
> +
> + if (!sp || unlikely(index >= sp->len || flags))
> + goto err_clear;
> +
> + x = sp->xvec[index];
> +
> + if (unlikely(size != sizeof(struct bpf_xfrm_state)))
> + goto err_clear;
> +
> + to->reqid = x->props.reqid;
> + to->spi = be32_to_cpu(x->id.spi);
> + to->family = x->props.family;
> + if (to->family == AF_INET6) {
> + memcpy(to->remote_ipv6, x->props.saddr.a6,
> + sizeof(to->remote_ipv6));
> + } else {
> + to->remote_ipv4 = be32_to_cpu(x->props.saddr.a4);
> + }
that looks inconsistent. Why v4 is cpu endian, but v6 not?
Why change endianness of the spi?
