On Mon, Dec 4, 2023 at 12:57 PM Daniel Xu <dxu@xxxxxxxxx> wrote:
>
> This commit adds an unstable kfunc helper to access internal xfrm_state
> associated with an SA. This is intended to be used for the upcoming
> IPsec pcpu work to assign special pcpu SAs to a particular CPU. In other
> words: for custom software RSS.
>
> That being said, the function that this kfunc wraps is fairly generic
> and used for a lot of xfrm tasks. I'm sure people will find uses
> elsewhere over time.
>
> Co-developed-by: Antony Antony <antony.antony@xxxxxxxxxxx>
> Signed-off-by: Antony Antony <antony.antony@xxxxxxxxxxx>
> Signed-off-by: Daniel Xu <dxu@xxxxxxxxx>
> ---
> include/net/xfrm.h | 9 ++++
> net/xfrm/xfrm_bpf.c | 102 +++++++++++++++++++++++++++++++++++++++++
> net/xfrm/xfrm_policy.c | 2 +
> 3 files changed, 113 insertions(+)
>
> diff --git a/include/net/xfrm.h b/include/net/xfrm.h
> index c9bb0f892f55..1d107241b901 100644
> --- a/include/net/xfrm.h
> +++ b/include/net/xfrm.h
> @@ -2190,4 +2190,13 @@ static inline int register_xfrm_interface_bpf(void)
>
> #endif
>
> +#if IS_ENABLED(CONFIG_DEBUG_INFO_BTF)
> +int register_xfrm_state_bpf(void);
> +#else
> +static inline int register_xfrm_state_bpf(void)
> +{
> + return 0;
> +}
> +#endif
> +
> #endif /* _NET_XFRM_H */
> diff --git a/net/xfrm/xfrm_bpf.c b/net/xfrm/xfrm_bpf.c
> index 3d3018b87f96..3d6cac7345ca 100644
> --- a/net/xfrm/xfrm_bpf.c
> +++ b/net/xfrm/xfrm_bpf.c
> @@ -6,9 +6,11 @@
> */
>
> #include <linux/bpf.h>
> +#include <linux/btf.h>
> #include <linux/btf_ids.h>
>
> #include <net/dst_metadata.h>
> +#include <net/xdp.h>
> #include <net/xfrm.h>
>
> #if IS_BUILTIN(CONFIG_XFRM_INTERFACE) || \
> @@ -112,3 +114,103 @@ int __init register_xfrm_interface_bpf(void)
> }
>
> #endif /* xfrm interface */
> +
> +/* bpf_xfrm_state_opts - Options for XFRM state lookup helpers
> + *
> + * Members:
> + * @error - Out parameter, set for any errors encountered
> + * Values:
> + * -EINVAL - netns_id is less than -1
> + * -EINVAL - opts__sz isn't BPF_XFRM_STATE_OPTS_SZ
> + * -ENONET - No network namespace found for netns_id
> + * @netns_id - Specify the network namespace for lookup
> + * Values:
> + * BPF_F_CURRENT_NETNS (-1)
> + * Use namespace associated with ctx
> + * [0, S32_MAX]
> + * Network Namespace ID
> + * @mark - XFRM mark to match on
> + * @daddr - Destination address to match on
> + * @spi - Security parameter index to match on
> + * @proto - L3 protocol to match on
> + * @family - L3 protocol family to match on
> + */
> +struct bpf_xfrm_state_opts {
> + s32 error;
> + s32 netns_id;
> + u32 mark;
> + xfrm_address_t daddr;
> + __be32 spi;
> + u8 proto;
> + u16 family;
> +};
> +
> +enum {
> + BPF_XFRM_STATE_OPTS_SZ = sizeof(struct bpf_xfrm_state_opts),
> +};
> +
> +__bpf_kfunc_start_defs();
> +
> +/* bpf_xdp_get_xfrm_state - Get XFRM state
> + *
> + * Parameters:
> + * @ctx - Pointer to ctx (xdp_md) in XDP program
> + * Cannot be NULL
> + * @opts - Options for lookup (documented above)
> + * Cannot be NULL
> + * @opts__sz - Length of the bpf_xfrm_state_opts structure
> + * Must be BPF_XFRM_STATE_OPTS_SZ
> + */
> +__bpf_kfunc struct xfrm_state *
> +bpf_xdp_get_xfrm_state(struct xdp_md *ctx, struct bpf_xfrm_state_opts *opts, u32 opts__sz)
> +{
> + struct xdp_buff *xdp = (struct xdp_buff *)ctx;
> + struct net *net = dev_net(xdp->rxq->dev);
> + struct xfrm_state *x;
> +
> + if (!opts || opts__sz < sizeof(opts->error))
> + return NULL;
> +
> + if (opts__sz != BPF_XFRM_STATE_OPTS_SZ) {
> + opts->error = -EINVAL;
> + return NULL;
> + }
> +
> + if (unlikely(opts->netns_id < BPF_F_CURRENT_NETNS)) {
> + opts->error = -EINVAL;
> + return NULL;
> + }
> +
> + if (opts->netns_id >= 0) {
> + net = get_net_ns_by_id(net, opts->netns_id);
> + if (unlikely(!net)) {
> + opts->error = -ENONET;
> + return NULL;
> + }
> + }
> +
> + x = xfrm_state_lookup(net, opts->mark, &opts->daddr, opts->spi,
> + opts->proto, opts->family);
> +
> + if (opts->netns_id >= 0)
> + put_net(net);
Maybe opts->error should be set to something like -ENOENT if x == NULL?
> +
> + return x;
> +}
> +
> +__bpf_kfunc_end_defs();
> +
> +BTF_SET8_START(xfrm_state_kfunc_set)
> +BTF_ID_FLAGS(func, bpf_xdp_get_xfrm_state, KF_RET_NULL | KF_ACQUIRE)
> +BTF_SET8_END(xfrm_state_kfunc_set)
> +
> +static const struct btf_kfunc_id_set xfrm_state_xdp_kfunc_set = {
> + .owner = THIS_MODULE,
> + .set = &xfrm_state_kfunc_set,
> +};
> +
> +int __init register_xfrm_state_bpf(void)
> +{
> + return register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP,
> + &xfrm_state_xdp_kfunc_set);
> +}
> diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
> index c13dc3ef7910..1b7e75159727 100644
> --- a/net/xfrm/xfrm_policy.c
> +++ b/net/xfrm/xfrm_policy.c
> @@ -4218,6 +4218,8 @@ void __init xfrm_init(void)
> #ifdef CONFIG_XFRM_ESPINTCP
> espintcp_init();
> #endif
> +
> + register_xfrm_state_bpf();
> }
>
> #ifdef CONFIG_AUDITSYSCALL
> --
> 2.42.1
>
>
