1// SPDX-License-Identifier: GPL-2.0-only
2/*
3 * Authors:
4 * (C) 2020 Alexander Aring <alex.aring@gmail.com>
5 */
6
7#include <net/ipv6.h>
8#include <net/rpl.h>
9
10#define IPV6_PFXTAIL_LEN(x) (sizeof(struct in6_addr) - (x))
11#define IPV6_RPL_BEST_ADDR_COMPRESSION 15
12
13static void ipv6_rpl_addr_decompress(struct in6_addr *dst,
14				     const struct in6_addr *daddr,
15				     const void *post, unsigned char pfx)
16{
17	memcpy(dst, daddr, pfx);
18	memcpy(&dst->s6_addr[pfx], post, IPV6_PFXTAIL_LEN(pfx));
19}
20
21static void ipv6_rpl_addr_compress(void *dst, const struct in6_addr *addr,
22				   unsigned char pfx)
23{
24	memcpy(dst, &addr->s6_addr[pfx], IPV6_PFXTAIL_LEN(pfx));
25}
26
27static void *ipv6_rpl_segdata_pos(const struct ipv6_rpl_sr_hdr *hdr, int i)
28{
29	return (void *)&hdr->rpl_segdata[i * IPV6_PFXTAIL_LEN(hdr->cmpri)];
30}
31
32void ipv6_rpl_srh_decompress(struct ipv6_rpl_sr_hdr *outhdr,
33			     const struct ipv6_rpl_sr_hdr *inhdr,
34			     const struct in6_addr *daddr, unsigned char n)
35{
36	int i;
37
38	outhdr->nexthdr = inhdr->nexthdr;
39	outhdr->hdrlen = (((n + 1) * sizeof(struct in6_addr)) >> 3);
40	outhdr->pad = 0;
41	outhdr->type = inhdr->type;
42	outhdr->segments_left = inhdr->segments_left;
43	outhdr->cmpri = 0;
44	outhdr->cmpre = 0;
45
46	for (i = 0; i < n; i++)
47		ipv6_rpl_addr_decompress(&outhdr->rpl_segaddr[i], daddr,
48					 ipv6_rpl_segdata_pos(inhdr, i),
49					 inhdr->cmpri);
50
51	ipv6_rpl_addr_decompress(&outhdr->rpl_segaddr[n], daddr,
52				 ipv6_rpl_segdata_pos(inhdr, n),
53				 inhdr->cmpre);
54}
55
56static unsigned char ipv6_rpl_srh_calc_cmpri(const struct ipv6_rpl_sr_hdr *inhdr,
57					     const struct in6_addr *daddr,
58					     unsigned char n)
59{
60	unsigned char plen;
61	int i;
62
63	for (plen = 0; plen < sizeof(*daddr); plen++) {
64		for (i = 0; i < n; i++) {
65			if (daddr->s6_addr[plen] !=
66			    inhdr->rpl_segaddr[i].s6_addr[plen])
67				return plen;
68		}
69	}
70
71	return IPV6_RPL_BEST_ADDR_COMPRESSION;
72}
73
74static unsigned char ipv6_rpl_srh_calc_cmpre(const struct in6_addr *daddr,
75					     const struct in6_addr *last_segment)
76{
77	unsigned int plen;
78
79	for (plen = 0; plen < sizeof(*daddr); plen++) {
80		if (daddr->s6_addr[plen] != last_segment->s6_addr[plen])
81			return plen;
82	}
83
84	return IPV6_RPL_BEST_ADDR_COMPRESSION;
85}
86
87void ipv6_rpl_srh_compress(struct ipv6_rpl_sr_hdr *outhdr,
88			   const struct ipv6_rpl_sr_hdr *inhdr,
89			   const struct in6_addr *daddr, unsigned char n)
90{
91	unsigned char cmpri, cmpre;
92	size_t seglen;
93	int i;
94
95	cmpri = ipv6_rpl_srh_calc_cmpri(inhdr, daddr, n);
96	cmpre = ipv6_rpl_srh_calc_cmpre(daddr, &inhdr->rpl_segaddr[n]);
97
98	outhdr->nexthdr = inhdr->nexthdr;
99	seglen = (n * IPV6_PFXTAIL_LEN(cmpri)) + IPV6_PFXTAIL_LEN(cmpre);
100	outhdr->hdrlen = seglen >> 3;
101	if (seglen & 0x7) {
102		outhdr->hdrlen++;
103		outhdr->pad = 8 - (seglen & 0x7);
104	} else {
105		outhdr->pad = 0;
106	}
107	outhdr->type = inhdr->type;
108	outhdr->segments_left = inhdr->segments_left;
109	outhdr->cmpri = cmpri;
110	outhdr->cmpre = cmpre;
111
112	for (i = 0; i < n; i++)
113		ipv6_rpl_addr_compress(ipv6_rpl_segdata_pos(outhdr, i),
114				       &inhdr->rpl_segaddr[i], cmpri);
115
116	ipv6_rpl_addr_compress(ipv6_rpl_segdata_pos(outhdr, n),
117			       &inhdr->rpl_segaddr[n], cmpre);
118}
119