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}