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
 32size_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
 38void 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
 62static 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
 80static 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
 93void 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}