summaryrefslogtreecommitdiffstats
path: root/net/6lowpan/nhc_udp.c
blob: 0a506c77283dded62c7b316ef0430313f596b0a8 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *	6LoWPAN IPv6 UDP compression according to RFC6282
 *
 *	Authors:
 *	Alexander Aring	<aar@pengutronix.de>
 *
 *	Original written by:
 *	Alexander Smirnov <alex.bluesman.smirnov@gmail.com>
 *	Jon Smirl <jonsmirl@gmail.com>
 */

#include "nhc.h"

#define LOWPAN_NHC_UDP_MASK		0xF8
#define LOWPAN_NHC_UDP_ID		0xF0

#define LOWPAN_NHC_UDP_4BIT_PORT	0xF0B0
#define LOWPAN_NHC_UDP_4BIT_MASK	0xFFF0
#define LOWPAN_NHC_UDP_8BIT_PORT	0xF000
#define LOWPAN_NHC_UDP_8BIT_MASK	0xFF00

/* values for port compression, _with checksum_ ie bit 5 set to 0 */

/* all inline */
#define LOWPAN_NHC_UDP_CS_P_00	0xF0
/* source 16bit inline, dest = 0xF0 + 8 bit inline */
#define LOWPAN_NHC_UDP_CS_P_01	0xF1
/* source = 0xF0 + 8bit inline, dest = 16 bit inline */
#define LOWPAN_NHC_UDP_CS_P_10	0xF2
/* source & dest = 0xF0B + 4bit inline */
#define LOWPAN_NHC_UDP_CS_P_11	0xF3
/* checksum elided */
#define LOWPAN_NHC_UDP_CS_C	0x04

static int udp_uncompress(struct sk_buff *skb, size_t needed)
{
	u8 tmp = 0, val = 0;
	struct udphdr uh;
	bool fail;
	int err;

	fail = lowpan_fetch_skb(skb, &tmp, sizeof(tmp));

	pr_debug("UDP header uncompression\n");
	switch (tmp & LOWPAN_NHC_UDP_CS_P_11) {
	case LOWPAN_NHC_UDP_CS_P_00:
		fail |= lowpan_fetch_skb(skb, &uh.source, sizeof(uh.source));
		fail |= lowpan_fetch_skb(skb, &uh.dest, sizeof(uh.dest));
		break;
	case LOWPAN_NHC_UDP_CS_P_01:
		fail |= lowpan_fetch_skb(skb, &uh.source, sizeof(uh.source));
		fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
		uh.dest = htons(val + LOWPAN_NHC_UDP_8BIT_PORT);
		break;
	case LOWPAN_NHC_UDP_CS_P_10:
		fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
		uh.source = htons(val + LOWPAN_NHC_UDP_8BIT_PORT);
		fail |= lowpan_fetch_skb(skb, &uh.dest, sizeof(uh.dest));
		break;
	case LOWPAN_NHC_UDP_CS_P_11:
		fail |= lowpan_fetch_skb(skb, &val, sizeof(val));
		uh.source = htons(LOWPAN_NHC_UDP_4BIT_PORT + (val >> 4));
		uh.dest = htons(LOWPAN_NHC_UDP_4BIT_PORT + (val & 0x0f));
		break;
	default:
		BUG();
	}

	pr_debug("uncompressed UDP ports: src = %d, dst = %d\n",
		 ntohs(uh.source), ntohs(uh.dest));

	/* checksum */
	if (tmp & LOWPAN_NHC_UDP_CS_C) {
		pr_debug_ratelimited("checksum elided currently not supported\n");
		fail = true;
	} else {
		fail |= lowpan_fetch_skb(skb, &uh.check, sizeof(uh.check));
	}

	if (fail)
		return -EINVAL;

	/* UDP length needs to be inferred from the lower layers
	 * here, we obtain the hint from the remaining size of the
	 * frame
	 */
	switch (lowpan_dev(skb->dev)->lltype) {
	case LOWPAN_LLTYPE_IEEE802154:
		if (lowpan_802154_cb(skb)->d_size)
			uh.len = htons(lowpan_802154_cb(skb)->d_size -
				       sizeof(struct ipv6hdr));
		else
			uh.len = htons(skb->len + sizeof(struct udphdr));
		break;
	default:
		uh.len = htons(skb->len + sizeof(struct udphdr));
		break;
	}
	pr_debug("uncompressed UDP length: src = %d", ntohs(uh.len));

	/* replace the compressed UDP head by the uncompressed UDP
	 * header
	 */
	err = skb_cow(skb, needed);
	if (unlikely(err))
		return err;

	skb_push(skb, sizeof(struct udphdr));
	skb_copy_to_linear_data(skb, &uh, sizeof(struct udphdr));

	return 0;
}

static int udp_compress(struct sk_buff *skb, u8 **hc_ptr)
{
	const struct udphdr *uh = udp_hdr(skb);
	u8 tmp;

	if (((ntohs(uh->source) & LOWPAN_NHC_UDP_4BIT_MASK) ==
	     LOWPAN_NHC_UDP_4BIT_PORT) &&
	    ((ntohs(uh->dest) & LOWPAN_NHC_UDP_4BIT_MASK) ==
	     LOWPAN_NHC_UDP_4BIT_PORT)) {
		pr_debug("UDP header: both ports compression to 4 bits\n");
		/* compression value */
		tmp = LOWPAN_NHC_UDP_CS_P_11;
		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
		/* source and destination port */
		tmp = ntohs(uh->dest) - LOWPAN_NHC_UDP_4BIT_PORT +
		      ((ntohs(uh->source) - LOWPAN_NHC_UDP_4BIT_PORT) << 4);
		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
	} else if ((ntohs(uh->dest) & LOWPAN_NHC_UDP_8BIT_MASK) ==
			LOWPAN_NHC_UDP_8BIT_PORT) {
		pr_debug("UDP header: remove 8 bits of dest\n");
		/* compression value */
		tmp = LOWPAN_NHC_UDP_CS_P_01;
		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
		/* source port */
		lowpan_push_hc_data(hc_ptr, &uh->source, sizeof(uh->source));
		/* destination port */
		tmp = ntohs(uh->dest) - LOWPAN_NHC_UDP_8BIT_PORT;
		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
	} else if ((ntohs(uh->source) & LOWPAN_NHC_UDP_8BIT_MASK) ==
			LOWPAN_NHC_UDP_8BIT_PORT) {
		pr_debug("UDP header: remove 8 bits of source\n");
		/* compression value */
		tmp = LOWPAN_NHC_UDP_CS_P_10;
		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
		/* source port */
		tmp = ntohs(uh->source) - LOWPAN_NHC_UDP_8BIT_PORT;
		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
		/* destination port */
		lowpan_push_hc_data(hc_ptr, &uh->dest, sizeof(uh->dest));
	} else {
		pr_debug("UDP header: can't compress\n");
		/* compression value */
		tmp = LOWPAN_NHC_UDP_CS_P_00;
		lowpan_push_hc_data(hc_ptr, &tmp, sizeof(tmp));
		/* source port */
		lowpan_push_hc_data(hc_ptr, &uh->source, sizeof(uh->source));
		/* destination port */
		lowpan_push_hc_data(hc_ptr, &uh->dest, sizeof(uh->dest));
	}

	/* checksum is always inline */
	lowpan_push_hc_data(hc_ptr, &uh->check, sizeof(uh->check));

	return 0;
}

LOWPAN_NHC(nhc_udp, "RFC6282 UDP", NEXTHDR_UDP, sizeof(struct udphdr),
	   LOWPAN_NHC_UDP_ID, LOWPAN_NHC_UDP_MASK, udp_uncompress, udp_compress);

module_lowpan_nhc(nhc_udp);
MODULE_DESCRIPTION("6LoWPAN next header RFC6282 UDP compression");
MODULE_LICENSE("GPL");