net/ipv6/rpl.c

   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
  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
  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
  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
  32 void 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
  56 static 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
  74 static 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
  87 void 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 }