xref: /openbmc/linux/net/xfrm/xfrm_interface_bpf.c (revision 400031e0)
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  */
bpf_skb_get_xfrm_info(struct __sk_buff * skb_ctx,struct bpf_xfrm_info * to)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  */
bpf_skb_set_xfrm_info(struct __sk_buff * skb_ctx,const struct bpf_xfrm_info * from)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 
register_xfrm_interface_bpf(void)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 }
113