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 
ipv6_rpl_addr_decompress(struct in6_addr * dst,const struct in6_addr * daddr,const void * post,unsigned char pfx)13 static 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 
ipv6_rpl_addr_compress(void * dst,const struct in6_addr * addr,unsigned char pfx)21 static 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 
ipv6_rpl_segdata_pos(const struct ipv6_rpl_sr_hdr * hdr,int i)27 static 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 
ipv6_rpl_srh_size(unsigned char n,unsigned char cmpri,unsigned char cmpre)32 size_t ipv6_rpl_srh_size(unsigned char n, unsigned char cmpri,
33 			 unsigned char cmpre)
34 {
35 	return (n * IPV6_PFXTAIL_LEN(cmpri)) + IPV6_PFXTAIL_LEN(cmpre);
36 }
37 
ipv6_rpl_srh_decompress(struct ipv6_rpl_sr_hdr * outhdr,const struct ipv6_rpl_sr_hdr * inhdr,const struct in6_addr * daddr,unsigned char n)38 void ipv6_rpl_srh_decompress(struct ipv6_rpl_sr_hdr *outhdr,
39 			     const struct ipv6_rpl_sr_hdr *inhdr,
40 			     const struct in6_addr *daddr, unsigned char n)
41 {
42 	int i;
43 
44 	outhdr->nexthdr = inhdr->nexthdr;
45 	outhdr->hdrlen = (((n + 1) * sizeof(struct in6_addr)) >> 3);
46 	outhdr->pad = 0;
47 	outhdr->type = inhdr->type;
48 	outhdr->segments_left = inhdr->segments_left;
49 	outhdr->cmpri = 0;
50 	outhdr->cmpre = 0;
51 
52 	for (i = 0; i < n; i++)
53 		ipv6_rpl_addr_decompress(&outhdr->rpl_segaddr[i], daddr,
54 					 ipv6_rpl_segdata_pos(inhdr, i),
55 					 inhdr->cmpri);
56 
57 	ipv6_rpl_addr_decompress(&outhdr->rpl_segaddr[n], daddr,
58 				 ipv6_rpl_segdata_pos(inhdr, n),
59 				 inhdr->cmpre);
60 }
61 
ipv6_rpl_srh_calc_cmpri(const struct ipv6_rpl_sr_hdr * inhdr,const struct in6_addr * daddr,unsigned char n)62 static unsigned char ipv6_rpl_srh_calc_cmpri(const struct ipv6_rpl_sr_hdr *inhdr,
63 					     const struct in6_addr *daddr,
64 					     unsigned char n)
65 {
66 	unsigned char plen;
67 	int i;
68 
69 	for (plen = 0; plen < sizeof(*daddr); plen++) {
70 		for (i = 0; i < n; i++) {
71 			if (daddr->s6_addr[plen] !=
72 			    inhdr->rpl_segaddr[i].s6_addr[plen])
73 				return plen;
74 		}
75 	}
76 
77 	return IPV6_RPL_BEST_ADDR_COMPRESSION;
78 }
79 
ipv6_rpl_srh_calc_cmpre(const struct in6_addr * daddr,const struct in6_addr * last_segment)80 static unsigned char ipv6_rpl_srh_calc_cmpre(const struct in6_addr *daddr,
81 					     const struct in6_addr *last_segment)
82 {
83 	unsigned int plen;
84 
85 	for (plen = 0; plen < sizeof(*daddr); plen++) {
86 		if (daddr->s6_addr[plen] != last_segment->s6_addr[plen])
87 			return plen;
88 	}
89 
90 	return IPV6_RPL_BEST_ADDR_COMPRESSION;
91 }
92 
ipv6_rpl_srh_compress(struct ipv6_rpl_sr_hdr * outhdr,const struct ipv6_rpl_sr_hdr * inhdr,const struct in6_addr * daddr,unsigned char n)93 void ipv6_rpl_srh_compress(struct ipv6_rpl_sr_hdr *outhdr,
94 			   const struct ipv6_rpl_sr_hdr *inhdr,
95 			   const struct in6_addr *daddr, unsigned char n)
96 {
97 	unsigned char cmpri, cmpre;
98 	size_t seglen;
99 	int i;
100 
101 	cmpri = ipv6_rpl_srh_calc_cmpri(inhdr, daddr, n);
102 	cmpre = ipv6_rpl_srh_calc_cmpre(daddr, &inhdr->rpl_segaddr[n]);
103 
104 	outhdr->nexthdr = inhdr->nexthdr;
105 	seglen = (n * IPV6_PFXTAIL_LEN(cmpri)) + IPV6_PFXTAIL_LEN(cmpre);
106 	outhdr->hdrlen = seglen >> 3;
107 	if (seglen & 0x7) {
108 		outhdr->hdrlen++;
109 		outhdr->pad = 8 - (seglen & 0x7);
110 	} else {
111 		outhdr->pad = 0;
112 	}
113 	outhdr->type = inhdr->type;
114 	outhdr->segments_left = inhdr->segments_left;
115 	outhdr->cmpri = cmpri;
116 	outhdr->cmpre = cmpre;
117 
118 	for (i = 0; i < n; i++)
119 		ipv6_rpl_addr_compress(ipv6_rpl_segdata_pos(outhdr, i),
120 				       &inhdr->rpl_segaddr[i], cmpri);
121 
122 	ipv6_rpl_addr_compress(ipv6_rpl_segdata_pos(outhdr, n),
123 			       &inhdr->rpl_segaddr[n], cmpre);
124 }
125