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 __diag_push();
  31 __diag_ignore_all("-Wmissing-prototypes",
  32                   "Global functions as their definitions will be in xfrm_interface BTF");
  33
  34 /* bpf_skb_get_xfrm_info - Get XFRM metadata
  35  *
  36  * Parameters:
  37  * @skb_ctx     - Pointer to ctx (__sk_buff) in TC program
  38  *                  Cannot be NULL
  39  * @to          - Pointer to memory to which the metadata will be copied
  40  *                  Cannot be NULL
  41  */
  42 __bpf_kfunc int bpf_skb_get_xfrm_info(struct __sk_buff *skb_ctx, struct bpf_xfrm_info *to)
  43 {
  44         struct sk_buff *skb = (struct sk_buff *)skb_ctx;
  45         struct xfrm_md_info *info;
  46
  47         info = skb_xfrm_md_info(skb);
  48         if (!info)
  49                 return -EINVAL;
  50
  51         to->if_id = info->if_id;
  52         to->link = info->link;
  53         return 0;
  54 }
  55
  56 /* bpf_skb_get_xfrm_info - Set XFRM metadata
  57  *
  58  * Parameters:
  59  * @skb_ctx     - Pointer to ctx (__sk_buff) in TC program
  60  *                  Cannot be NULL
  61  * @from        - Pointer to memory from which the metadata will be copied
  62  *                  Cannot be NULL
  63  */
  64 __bpf_kfunc int bpf_skb_set_xfrm_info(struct __sk_buff *skb_ctx, const struct bpf_xfrm_info *from)
  65 {
  66         struct sk_buff *skb = (struct sk_buff *)skb_ctx;
  67         struct metadata_dst *md_dst;
  68         struct xfrm_md_info *info;
  69
  70         if (unlikely(skb_metadata_dst(skb)))
  71                 return -EINVAL;
  72
  73         if (!xfrm_bpf_md_dst) {
  74                 struct metadata_dst __percpu *tmp;
  75
  76                 tmp = metadata_dst_alloc_percpu(0, METADATA_XFRM, GFP_ATOMIC);
  77                 if (!tmp)
  78                         return -ENOMEM;
  79                 if (cmpxchg(&xfrm_bpf_md_dst, NULL, tmp))
  80                         metadata_dst_free_percpu(tmp);
  81         }
  82         md_dst = this_cpu_ptr(xfrm_bpf_md_dst);
  83
  84         info = &md_dst->u.xfrm_info;
  85
  86         info->if_id = from->if_id;
  87         info->link = from->link;
  88         skb_dst_force(skb);
  89         info->dst_orig = skb_dst(skb);
  90
  91         dst_hold((struct dst_entry *)md_dst);
  92         skb_dst_set(skb, (struct dst_entry *)md_dst);
  93         return 0;
  94 }
  95
  96 __diag_pop()
  97
  98 BTF_SET8_START(xfrm_ifc_kfunc_set)
  99 BTF_ID_FLAGS(func, bpf_skb_get_xfrm_info)
 100 BTF_ID_FLAGS(func, bpf_skb_set_xfrm_info)
 101 BTF_SET8_END(xfrm_ifc_kfunc_set)
 102
 103 static const struct btf_kfunc_id_set xfrm_interface_kfunc_set = {
 104         .owner = THIS_MODULE,
 105         .set   = &xfrm_ifc_kfunc_set,
 106 };
 107
 108 int __init register_xfrm_interface_bpf(void)
 109 {
 110         return register_btf_kfunc_id_set(BPF_PROG_TYPE_SCHED_CLS,
 111                                          &xfrm_interface_kfunc_set);
 112 }