net/xfrm/xfrm_interface_bpf.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /* Unstable XFRM Helpers for TC-BPF hook
   3  *
   4  * These are called from SCHED_CLS BPF programs. Note that it is
   5  * allowed to break compatibility for these functions since the interface they
   6  * are exposed through to BPF programs is explicitly unstable.
   7  */
   8
   9 #include <linux/bpf.h>
  10 #include <linux/btf_ids.h>
  11
  12 #include <net/dst_metadata.h>
  13 #include <net/xfrm.h>
  14
  15 /* bpf_xfrm_info - XFRM metadata information
  16  *
  17  * Members:
  18  * @if_id       - XFRM if_id:
  19  *                  Transmit: if_id to be used in policy and state lookups
  20  *                  Receive: if_id of the state matched for the incoming packet
  21  * @link        - Underlying device ifindex:
  22  *                  Transmit: used as the underlying device in VRF routing
  23  *                  Receive: the device on which the packet had been received
  24  */
  25 struct bpf_xfrm_info {
  26         u32 if_id;
  27         int link;
  28 };
  29
  30 __bpf_kfunc_start_defs();
  31
  32 /* bpf_skb_get_xfrm_info - Get XFRM metadata
  33  *
  34  * Parameters:
  35  * @skb_ctx     - Pointer to ctx (__sk_buff) in TC program
  36  *                  Cannot be NULL
  37  * @to          - Pointer to memory to which the metadata will be copied
  38  *                  Cannot be NULL
  39  */
  40 __bpf_kfunc int bpf_skb_get_xfrm_info(struct __sk_buff *skb_ctx, struct bpf_xfrm_info *to)
  41 {
  42         struct sk_buff *skb = (struct sk_buff *)skb_ctx;
  43         struct xfrm_md_info *info;
  44
  45         info = skb_xfrm_md_info(skb);
  46         if (!info)
  47                 return -EINVAL;
  48
  49         to->if_id = info->if_id;
  50         to->link = info->link;
  51         return 0;
  52 }
  53
  54 /* bpf_skb_get_xfrm_info - Set XFRM metadata
  55  *
  56  * Parameters:
  57  * @skb_ctx     - Pointer to ctx (__sk_buff) in TC program
  58  *                  Cannot be NULL
  59  * @from        - Pointer to memory from which the metadata will be copied
  60  *                  Cannot be NULL
  61  */
  62 __bpf_kfunc int bpf_skb_set_xfrm_info(struct __sk_buff *skb_ctx, const struct bpf_xfrm_info *from)
  63 {
  64         struct sk_buff *skb = (struct sk_buff *)skb_ctx;
  65         struct metadata_dst *md_dst;
  66         struct xfrm_md_info *info;
  67
  68         if (unlikely(skb_metadata_dst(skb)))
  69                 return -EINVAL;
  70
  71         if (!xfrm_bpf_md_dst) {
  72                 struct metadata_dst __percpu *tmp;
  73
  74                 tmp = metadata_dst_alloc_percpu(0, METADATA_XFRM, GFP_ATOMIC);
  75                 if (!tmp)
  76                         return -ENOMEM;
  77                 if (cmpxchg(&xfrm_bpf_md_dst, NULL, tmp))
  78                         metadata_dst_free_percpu(tmp);
  79         }
  80         md_dst = this_cpu_ptr(xfrm_bpf_md_dst);
  81
  82         info = &md_dst->u.xfrm_info;
  83
  84         info->if_id = from->if_id;
  85         info->link = from->link;
  86         skb_dst_force(skb);
  87         info->dst_orig = skb_dst(skb);
  88
  89         dst_hold((struct dst_entry *)md_dst);
  90         skb_dst_set(skb, (struct dst_entry *)md_dst);
  91         return 0;
  92 }
  93
  94 __bpf_kfunc_end_defs();
  95
  96 BTF_SET8_START(xfrm_ifc_kfunc_set)
  97 BTF_ID_FLAGS(func, bpf_skb_get_xfrm_info)
  98 BTF_ID_FLAGS(func, bpf_skb_set_xfrm_info)
  99 BTF_SET8_END(xfrm_ifc_kfunc_set)
 100
 101 static const struct btf_kfunc_id_set xfrm_interface_kfunc_set = {
 102         .owner = THIS_MODULE,
 103         .set   = &xfrm_ifc_kfunc_set,
 104 };
 105
 106 int __init register_xfrm_interface_bpf(void)
 107 {
 108         return register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS,
 109                                          &xfrm_interface_kfunc_set);
 110 }