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 (n * IPV6_PFXTAIL_LEN(cmpri)) + IPV6_PFXTAIL_LEN(cmpre);
  36 }
  37
  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
  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
  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
  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 }