net/xfrm/xfrm_state_bpf.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Unstable XFRM state BPF helpers.
   3  *
   4  * Note that it is allowed to break compatibility for these functions since the
   5  * interface they are exposed through to BPF programs is explicitly unstable.
   6  */
   7
   8 #include <linux/bpf.h>
   9 #include <linux/btf.h>
  10 #include <linux/btf_ids.h>
  11 #include <net/xdp.h>
  12 #include <net/xfrm.h>
  13
  14 /* bpf_xfrm_state_opts - Options for XFRM state lookup helpers
  15  *
  16  * Members:
  17  * @error      - Out parameter, set for any errors encountered
  18  *               Values:
  19  *                 -EINVAL - netns_id is less than -1
  20  *                 -EINVAL - opts__sz isn't BPF_XFRM_STATE_OPTS_SZ
  21  *                 -ENONET - No network namespace found for netns_id
  22  *                 -ENOENT - No xfrm_state found
  23  * @netns_id    - Specify the network namespace for lookup
  24  *               Values:
  25  *                 BPF_F_CURRENT_NETNS (-1)
  26  *                   Use namespace associated with ctx
  27  *                 [0, S32_MAX]
  28  *                   Network Namespace ID
  29  * @mark        - XFRM mark to match on
  30  * @daddr       - Destination address to match on
  31  * @spi         - Security parameter index to match on
  32  * @proto       - IP protocol to match on (eg. IPPROTO_ESP)
  33  * @family      - Protocol family to match on (AF_INET/AF_INET6)
  34  */
  35 struct bpf_xfrm_state_opts {
  36         s32 error;
  37         s32 netns_id;
  38         u32 mark;
  39         xfrm_address_t daddr;
  40         __be32 spi;
  41         u8 proto;
  42         u16 family;
  43 };
  44
  45 enum {
  46         BPF_XFRM_STATE_OPTS_SZ = sizeof(struct bpf_xfrm_state_opts),
  47 };
  48
  49 __bpf_kfunc_start_defs();
  50
  51 /* bpf_xdp_get_xfrm_state - Get XFRM state
  52  *
  53  * A `struct xfrm_state *`, if found, must be released with a corresponding
  54  * bpf_xdp_xfrm_state_release.
  55  *
  56  * Parameters:
  57  * @ctx - Pointer to ctx (xdp_md) in XDP program
  58  *                  Cannot be NULL
  59  * @opts        - Options for lookup (documented above)
  60  *                  Cannot be NULL
  61  * @opts__sz    - Length of the bpf_xfrm_state_opts structure
  62  *                  Must be BPF_XFRM_STATE_OPTS_SZ
  63  */
  64 __bpf_kfunc struct xfrm_state *
  65 bpf_xdp_get_xfrm_state(struct xdp_md *ctx, struct bpf_xfrm_state_opts *opts, u32 opts__sz)
  66 {
  67         struct xdp_buff *xdp = (struct xdp_buff *)ctx;
  68         struct net *net = dev_net(xdp->rxq->dev);
  69         struct xfrm_state *x;
  70
  71         if (!opts || opts__sz < sizeof(opts->error))
  72                 return NULL;
  73
  74         if (opts__sz != BPF_XFRM_STATE_OPTS_SZ) {
  75                 opts->error = -EINVAL;
  76                 return NULL;
  77         }
  78
  79         if (unlikely(opts->netns_id < BPF_F_CURRENT_NETNS)) {
  80                 opts->error = -EINVAL;
  81                 return NULL;
  82         }
  83
  84         if (opts->netns_id >= 0) {
  85                 net = get_net_ns_by_id(net, opts->netns_id);
  86                 if (unlikely(!net)) {
  87                         opts->error = -ENONET;
  88                         return NULL;
  89                 }
  90         }
  91
  92         x = xfrm_state_lookup(net, opts->mark, &opts->daddr, opts->spi,
  93                               opts->proto, opts->family);
  94
  95         if (opts->netns_id >= 0)
  96                 put_net(net);
  97         if (!x)
  98                 opts->error = -ENOENT;
  99
 100         return x;
 101 }
 102
 103 /* bpf_xdp_xfrm_state_release - Release acquired xfrm_state object
 104  *
 105  * This must be invoked for referenced PTR_TO_BTF_ID, and the verifier rejects
 106  * the program if any references remain in the program in all of the explored
 107  * states.
 108  *
 109  * Parameters:
 110  * @x           - Pointer to referenced xfrm_state object, obtained using
 111  *                bpf_xdp_get_xfrm_state.
 112  */
 113 __bpf_kfunc void bpf_xdp_xfrm_state_release(struct xfrm_state *x)
 114 {
 115         xfrm_state_put(x);
 116 }
 117
 118 __bpf_kfunc_end_defs();
 119
 120 BTF_KFUNCS_START(xfrm_state_kfunc_set)
 121 BTF_ID_FLAGS(func, bpf_xdp_get_xfrm_state, KF_RET_NULL | KF_ACQUIRE)
 122 BTF_ID_FLAGS(func, bpf_xdp_xfrm_state_release, KF_RELEASE)
 123 BTF_KFUNCS_END(xfrm_state_kfunc_set)
 124
 125 static const struct btf_kfunc_id_set xfrm_state_xdp_kfunc_set = {
 126         .owner = THIS_MODULE,
 127         .set   = &xfrm_state_kfunc_set,
 128 };
 129
 130 int __init register_xfrm_state_bpf(void)
 131 {
 132         return register_btf_kfunc_id_set(BPF_PROG_TYPE_XDP,
 133                                          &xfrm_state_xdp_kfunc_set);
 134 }