1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * 6LoWPAN next header compression
4 *
5 * Authors:
6 * Alexander Aring <aar@pengutronix.de>
7 */
8
9 #include <linux/netdevice.h>
10
11 #include <net/ipv6.h>
12
13 #include "nhc.h"
14
15 static const struct lowpan_nhc *lowpan_nexthdr_nhcs[NEXTHDR_MAX + 1];
16 static DEFINE_SPINLOCK(lowpan_nhc_lock);
17
18 static const struct lowpan_nhc *lowpan_nhc_by_nhcid(struct sk_buff *skb)
19 {
20 const struct lowpan_nhc *nhc;
21 int i;
22 u8 id;
23
24 if (!pskb_may_pull(skb, 1))
25 return NULL;
26
27 id = *skb->data;
28
29 for (i = 0; i < NEXTHDR_MAX + 1; i++) {
30 nhc = lowpan_nexthdr_nhcs[i];
31 if (!nhc)
32 continue;
33
34 if ((id & nhc->idmask) == nhc->id)
35 return nhc;
36 }
37
38 return NULL;
39 }
40
41 int lowpan_nhc_check_compression(struct sk_buff *skb,
42 const struct ipv6hdr *hdr, u8 **hc_ptr)
43 {
44 const struct lowpan_nhc *nhc;
45 int ret = 0;
46
47 spin_lock_bh(&lowpan_nhc_lock);
48
49 nhc = lowpan_nexthdr_nhcs[hdr->nexthdr];
50 if (!(nhc && nhc->compress))
51 ret = -ENOENT;
52
53 spin_unlock_bh(&lowpan_nhc_lock);
54
55 return ret;
56 }
57
58 int lowpan_nhc_do_compression(struct sk_buff *skb, const struct ipv6hdr *hdr,
59 u8 **hc_ptr)
60 {
61 int ret;
62 const struct lowpan_nhc *nhc;
63
64 spin_lock_bh(&lowpan_nhc_lock);
65
66 nhc = lowpan_nexthdr_nhcs[hdr->nexthdr];
67 /* check if the nhc module was removed in unlocked part.
68 * TODO: this is a workaround we should prevent unloading
69 * of nhc modules while unlocked part, this will always drop
70 * the lowpan packet but it's very unlikely.
71 *
72 * Solution isn't easy because we need to decide at
73 * lowpan_nhc_check_compression if we do a compression or not.
74 * Because the inline data which is added to skb, we can't move this
75 * handling.
76 */
77 if (unlikely(!nhc || !nhc->compress)) {
78 ret = -EINVAL;
79 goto out;
80 }
81
82 /* In the case of RAW sockets the transport header is not set by
83 * the ip6 stack so we must set it ourselves
84 */
85 if (skb->transport_header == skb->network_header)
86 skb_set_transport_header(skb, sizeof(struct ipv6hdr));
87
88 ret = nhc->compress(skb, hc_ptr);
89 if (ret < 0)
90 goto out;
91
92 /* skip the transport header */
93 skb_pull(skb, nhc->nexthdrlen);
94
95 out:
96 spin_unlock_bh(&lowpan_nhc_lock);
97
98 return ret;
99 }
100
101 int lowpan_nhc_do_uncompression(struct sk_buff *skb,
102 const struct net_device *dev,
103 struct ipv6hdr *hdr)
104 {
105 const struct lowpan_nhc *nhc;
106 int ret;
107
108 spin_lock_bh(&lowpan_nhc_lock);
109
110 nhc = lowpan_nhc_by_nhcid(skb);
111 if (nhc) {
112 if (nhc->uncompress) {
113 ret = nhc->uncompress(skb, sizeof(struct ipv6hdr) +
114 nhc->nexthdrlen);
115 if (ret < 0) {
116 spin_unlock_bh(&lowpan_nhc_lock);
117 return ret;
118 }
119 } else {
120 spin_unlock_bh(&lowpan_nhc_lock);
121 netdev_warn(dev, "received nhc id for %s which is not implemented.\n",
122 nhc->name);
123 return -ENOTSUPP;
124 }
125 } else {
126 spin_unlock_bh(&lowpan_nhc_lock);
127 netdev_warn(dev, "received unknown nhc id which was not found.\n");
128 return -ENOENT;
129 }
130
131 hdr->nexthdr = nhc->nexthdr;
132 skb_reset_transport_header(skb);
133 raw_dump_table(__func__, "raw transport header dump",
134 skb_transport_header(skb), nhc->nexthdrlen);
135
136 spin_unlock_bh(&lowpan_nhc_lock);
137
138 return 0;
139 }
140
141 int lowpan_nhc_add(const struct lowpan_nhc *nhc)
142 {
143 int ret = 0;
144
145 spin_lock_bh(&lowpan_nhc_lock);
146
147 if (lowpan_nexthdr_nhcs[nhc->nexthdr]) {
148 ret = -EEXIST;
149 goto out;
150 }
151
152 lowpan_nexthdr_nhcs[nhc->nexthdr] = nhc;
153 out:
154 spin_unlock_bh(&lowpan_nhc_lock);
155 return ret;
156 }
157 EXPORT_SYMBOL(lowpan_nhc_add);
158
159 void lowpan_nhc_del(const struct lowpan_nhc *nhc)
160 {
161 spin_lock_bh(&lowpan_nhc_lock);
162
163 lowpan_nexthdr_nhcs[nhc->nexthdr] = NULL;
164
165 spin_unlock_bh(&lowpan_nhc_lock);
166
167 synchronize_net();
168 }
169 EXPORT_SYMBOL(lowpan_nhc_del);
170
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