1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3 * 6LoWPAN IPv6 UDP compression according to RFC6282
4 *
5 * Authors:
6 * Alexander Aring <aar@pengutronix.de>
7 *
8 * Original written by:
9 * Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
10 * Jon Smirl <jonsmirl@gmail.com>
11 */
12
13 #include "nhc.h"
14
15 #define LOWPAN_NHC_UDP_MASK 0xF8
16 #define LOWPAN_NHC_UDP_ID 0xF0
17
18 #define LOWPAN_NHC_UDP_4BIT_PORT 0xF0B0
19 #define LOWPAN_NHC_UDP_4BIT_MASK 0xFFF0
20 #define LOWPAN_NHC_UDP_8BIT_PORT 0xF000
21 #define LOWPAN_NHC_UDP_8BIT_MASK 0xFF00
22
23 /* values for port compression, _with checksum_ ie bit 5 set to 0 */
24
25 /* all inline */
26 #define LOWPAN_NHC_UDP_CS_P_00 0xF0
27 /* source 16bit inline, dest = 0xF0 + 8 bit inline */
28 #define LOWPAN_NHC_UDP_CS_P_01 0xF1
29 /* source = 0xF0 + 8bit inline, dest = 16 bit inline */
30 #define LOWPAN_NHC_UDP_CS_P_10 0xF2
31 /* source & dest = 0xF0B + 4bit inline */
32 #define LOWPAN_NHC_UDP_CS_P_11 0xF3
33 /* checksum elided */
34 #define LOWPAN_NHC_UDP_CS_C 0x04
35
36 static int udp_uncompress(struct sk_buff *skb, size_t needed)
37 {
38 u8 tmp = 0, val = 0;
39 struct udphdr uh;
40 bool fail;
41 int err;
42
43 fail = lowpan_fetch_skb(skb, &tmp, sizeof(tmp));
44
45 pr_debug("UDP header uncompression\n");
46 switch (tmp & LOWPAN_NHC_UDP_CS_P_11) {
47 case LOWPAN_NHC_UDP_CS_P_00:
48 fail |= lowpan_fetch_skb(skb, &uh.source, sizeof(uh.source));
49 fail |= lowpan_fetch_skb(skb, &uh.dest, sizeof(uh.dest));
50 break;
51 case LOWPAN_NHC_UDP_CS_P_01:
52 fail |= lowpan_fetch_skb(skb, &uh.source, sizeof(uh.source));
53 fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
54 uh.dest = htons(val + LOWPAN_NHC_UDP_8BIT_PORT);
55 break;
56 case LOWPAN_NHC_UDP_CS_P_10:
57 fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
58 uh.source = htons(val + LOWPAN_NHC_UDP_8BIT_PORT);
59 fail |= lowpan_fetch_skb(skb, &uh.dest, sizeof(uh.dest));
60 break;
61 case LOWPAN_NHC_UDP_CS_P_11:
62 fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
63 uh.source = htons(LOWPAN_NHC_UDP_4BIT_PORT + (val >> 4));
64 uh.dest = htons(LOWPAN_NHC_UDP_4BIT_PORT + (val & 0x0f));
65 break;
66 default:
67 BUG();
68 }
69
70 pr_debug("uncompressed UDP ports: src = %d, dst = %d\n",
71 ntohs(uh.source), ntohs(uh.dest));
72
73 /* checksum */
74 if (tmp & LOWPAN_NHC_UDP_CS_C) {
75 pr_debug_ratelimited("checksum elided currently not supported\n");
76 fail = true;
77 } else {
78 fail |= lowpan_fetch_skb(skb, &uh.check, sizeof(uh.check));
79 }
80
81 if (fail)
82 return -EINVAL;
83
84 /* UDP length needs to be inferred from the lower layers
85 * here, we obtain the hint from the remaining size of the
86 * frame
87 */
88 switch (lowpan_dev(skb->dev)->lltype) {
89 case LOWPAN_LLTYPE_IEEE802154:
90 if (lowpan_802154_cb(skb)->d_size)
91 uh.len = htons(lowpan_802154_cb(skb)->d_size -
92 sizeof(struct ipv6hdr));
93 else
94 uh.len = htons(skb->len + sizeof(struct udphdr));
95 break;
96 default:
97 uh.len = htons(skb->len + sizeof(struct udphdr));
98 break;
99 }
100 pr_debug("uncompressed UDP length: src = %d", ntohs(uh.len));
101
102 /* replace the compressed UDP head by the uncompressed UDP
103 * header
104 */
105 err = skb_cow(skb, needed);
106 if (unlikely(err))
107 return err;
108
109 skb_push(skb, sizeof(struct udphdr));
110 skb_copy_to_linear_data(skb, &uh, sizeof(struct udphdr));
111
112 return 0;
113 }
114
115 static int udp_compress(struct sk_buff *skb, u8 **hc_ptr)
116 {
117 const struct udphdr *uh = udp_hdr(skb);
118 u8 tmp;
119
120 if (((ntohs(uh->source) & LOWPAN_NHC_UDP_4BIT_MASK) ==
121 LOWPAN_NHC_UDP_4BIT_PORT) &&
122 ((ntohs(uh->dest) & LOWPAN_NHC_UDP_4BIT_MASK) ==
123 LOWPAN_NHC_UDP_4BIT_PORT)) {
124 pr_debug("UDP header: both ports compression to 4 bits\n");
125 /* compression value */
126 tmp = LOWPAN_NHC_UDP_CS_P_11;
127 lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
128 /* source and destination port */
129 tmp = ntohs(uh->dest) - LOWPAN_NHC_UDP_4BIT_PORT +
130 ((ntohs(uh->source) - LOWPAN_NHC_UDP_4BIT_PORT) << 4);
131 lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
132 } else if ((ntohs(uh->dest) & LOWPAN_NHC_UDP_8BIT_MASK) ==
133 LOWPAN_NHC_UDP_8BIT_PORT) {
134 pr_debug("UDP header: remove 8 bits of dest\n");
135 /* compression value */
136 tmp = LOWPAN_NHC_UDP_CS_P_01;
137 lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
138 /* source port */
139 lowpan_push_hc_data(hc_ptr, &uh->source, sizeof(uh->source));
140 /* destination port */
141 tmp = ntohs(uh->dest) - LOWPAN_NHC_UDP_8BIT_PORT;
142 lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
143 } else if ((ntohs(uh->source) & LOWPAN_NHC_UDP_8BIT_MASK) ==
144 LOWPAN_NHC_UDP_8BIT_PORT) {
145 pr_debug("UDP header: remove 8 bits of source\n");
146 /* compression value */
147 tmp = LOWPAN_NHC_UDP_CS_P_10;
148 lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
149 /* source port */
150 tmp = ntohs(uh->source) - LOWPAN_NHC_UDP_8BIT_PORT;
151 lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
152 /* destination port */
153 lowpan_push_hc_data(hc_ptr, &uh->dest, sizeof(uh->dest));
154 } else {
155 pr_debug("UDP header: can't compress\n");
156 /* compression value */
157 tmp = LOWPAN_NHC_UDP_CS_P_00;
158 lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
159 /* source port */
160 lowpan_push_hc_data(hc_ptr, &uh->source, sizeof(uh->source));
161 /* destination port */
162 lowpan_push_hc_data(hc_ptr, &uh->dest, sizeof(uh->dest));
163 }
164
165 /* checksum is always inline */
166 lowpan_push_hc_data(hc_ptr, &uh->check, sizeof(uh->check));
167
168 return 0;
169 }
170
171 LOWPAN_NHC(nhc_udp, "RFC6282 UDP", NEXTHDR_UDP, sizeof(struct udphdr),
172 LOWPAN_NHC_UDP_ID, LOWPAN_NHC_UDP_MASK, udp_uncompress, udp_compress);
173
174 module_lowpan_nhc(nhc_udp);
175 MODULE_DESCRIPTION("6LoWPAN next header RFC6282 UDP compression");
176 MODULE_LICENSE("GPL");
177
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