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Date: Wed, 2 Oct 2019 16:50:45 +0100
From: Lorenz Bauer <lmb@...udflare.com>
To: Toke Høiland-Jørgensen <toke@...hat.com>
Cc: Daniel Borkmann <daniel@...earbox.net>,
Alexei Starovoitov <ast@...nel.org>,
Martin KaFai Lau <kafai@...com>,
Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
Marek Majkowski <marek@...udflare.com>,
David Miller <davem@...emloft.net>,
Jesper Dangaard Brouer <brouer@...hat.com>,
Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
kernel-team <kernel-team@...udflare.com>
Subject: Re: [PATCH bpf-next 2/9] xdp: Add new xdp_chain_map type for
specifying XDP call sequences
On Wed, 2 Oct 2019 at 14:30, Toke Høiland-Jørgensen <toke@...hat.com> wrote:
>
> diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c
> index 113e1286e184..ab855095c830 100644
> --- a/kernel/bpf/hashtab.c
> +++ b/kernel/bpf/hashtab.c
> @@ -1510,3 +1510,156 @@ const struct bpf_map_ops htab_of_maps_map_ops = {
> .map_gen_lookup = htab_of_map_gen_lookup,
> .map_check_btf = map_check_no_btf,
> };
> +
> +struct xdp_chain_table {
> + struct bpf_prog *wildcard_act;
> + struct bpf_prog *act[XDP_ACT_MAX];
> +};
> +
> +static int xdp_chain_map_alloc_check(union bpf_attr *attr)
> +{
> + BUILD_BUG_ON(sizeof(struct xdp_chain_table) / sizeof(void *) !=
> + sizeof(struct xdp_chain_acts) / sizeof(u32));
> +
> + if (attr->key_size != sizeof(u32) ||
> + attr->value_size != sizeof(struct xdp_chain_acts))
> + return -EINVAL;
How are we going to extend xdp_chain_acts if a new XDP action is introduced?
> +
> + attr->value_size = sizeof(struct xdp_chain_table);
> + return htab_map_alloc_check(attr);
> +}
> +
> +struct bpf_prog *bpf_xdp_chain_map_get_prog(struct bpf_map *map,
> + u32 prev_id,
> + enum xdp_action action)
> +{
> + struct xdp_chain_table *tab;
> + void *ptr;
> +
> + ptr = htab_map_lookup_elem(map, &prev_id);
> +
> + if (!ptr)
> + return NULL;
> +
> + tab = READ_ONCE(ptr);
> + return tab->act[action - 1] ?: tab->wildcard_act;
> +}
> +EXPORT_SYMBOL_GPL(bpf_xdp_chain_map_get_prog);
> +
> +/* only called from syscall */
> +int bpf_xdp_chain_map_lookup_elem(struct bpf_map *map, void *key, void *value)
> +{
> + struct xdp_chain_acts *act = value;
> + struct xdp_chain_table *tab;
> + void *ptr;
> + u32 *cur;
> + int i;
> +
> + ptr = htab_map_lookup_elem(map, key);
> + if (!ptr)
> + return -ENOENT;
> +
> + tab = READ_ONCE(ptr);
> +
> + if (tab->wildcard_act)
> + act->wildcard_act = tab->wildcard_act->aux->id;
> +
> + cur = &act->drop_act;
> + for (i = 0; i < XDP_ACT_MAX; i++, cur++)
> + if(tab->act[i])
> + *cur = tab->act[i]->aux->id;
For completeness, zero out *cur in the else case?
> +
> + return 0;
> +}
> +
> +static void *xdp_chain_map_get_ptr(int fd)
> +{
> + struct bpf_prog *prog = bpf_prog_get(fd);
> +
> + if (IS_ERR(prog))
> + return prog;
> +
> + if (prog->type != BPF_PROG_TYPE_XDP ||
> + bpf_prog_is_dev_bound(prog->aux)) {
> + bpf_prog_put(prog);
> + return ERR_PTR(-EINVAL);
> + }
> +
> + return prog;
> +}
> +
> +static void xdp_chain_map_put_ptrs(void *value)
> +{
> + struct xdp_chain_table *tab = value;
> + int i;
> +
> + for (i = 0; i < XDP_ACT_MAX; i++)
> + if (tab->act[i])
> + bpf_prog_put(tab->act[i]);
> +
> + if (tab->wildcard_act)
> + bpf_prog_put(tab->wildcard_act);
> +}
> +
> +/* only called from syscall */
> +int bpf_xdp_chain_map_update_elem(struct bpf_map *map, void *key, void *value,
> + u64 map_flags)
Nit: check that map_flags == 0
> +{
> + struct xdp_chain_acts *act = value;
> + struct xdp_chain_table tab = {};
> + u32 lookup_key = *((u32*)key);
> + u32 *cur = &act->drop_act;
> + bool found_val = false;
> + int ret, i;
> + void *ptr;
> +
> + if (!lookup_key)
> + return -EINVAL;
Is it possible to check that this is a valid prog id / fd or whatever it is?
> +
> + if (act->wildcard_act) {
If this is an fd, 0 is a valid value no?
> + ptr = xdp_chain_map_get_ptr(act->wildcard_act);
> + if (IS_ERR(ptr))
> + return PTR_ERR(ptr);
> + tab.wildcard_act = ptr;
> + found_val = true;
> + }
> +
> + for (i = 0; i < XDP_ACT_MAX; i++, cur++) {
> + if (*cur) {
> + ptr = xdp_chain_map_get_ptr(*cur);
> + if (IS_ERR(ptr)) {
> + ret = PTR_ERR(ptr);
> + goto out_err;
> + }
> + tab.act[i] = ptr;
> + found_val = true;
> + }
> + }
> +
> + if (!found_val) {
> + ret = -EINVAL;
> + goto out_err;
> + }
> +
> + ret = htab_map_update_elem(map, key, &tab, map_flags);
> + if (ret)
> + goto out_err;
> +
> + return ret;
> +
> +out_err:
> + xdp_chain_map_put_ptrs(&tab);
> +
> + return ret;
> +}
> +
> +
> +const struct bpf_map_ops xdp_chain_map_ops = {
> + .map_alloc_check = xdp_chain_map_alloc_check,
> + .map_alloc = htab_map_alloc,
> + .map_free = fd_htab_map_free,
> + .map_get_next_key = htab_map_get_next_key,
> + .map_delete_elem = htab_map_delete_elem,
> + .map_fd_put_value = xdp_chain_map_put_ptrs,
> + .map_check_btf = map_check_no_btf,
> +};
--
Lorenz Bauer | Systems Engineer
6th Floor, County Hall/The Riverside Building, SE1 7PB, UK
www.cloudflare.com
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