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