net/ipv6/rpl.c

0001 // SPDX-License-Identifier: GPL-2.0-only
0002 /*
0003  * Authors:
0004  * (C) 2020 Alexander Aring <alex.aring@gmail.com>
0005  */
0006
0007 #include <net/ipv6.h>
0008 #include <net/rpl.h>
0009
0010 #define IPV6_PFXTAIL_LEN(x) (sizeof(struct in6_addr) - (x))
0011 #define IPV6_RPL_BEST_ADDR_COMPRESSION 15
0012
0013 static void ipv6_rpl_addr_decompress(struct in6_addr *dst,
0014                      const struct in6_addr *daddr,
0015                      const void *post, unsigned char pfx)
0016 {
0017     memcpy(dst, daddr, pfx);
0018     memcpy(&dst->s6_addr[pfx], post, IPV6_PFXTAIL_LEN(pfx));
0019 }
0020
0021 static void ipv6_rpl_addr_compress(void *dst, const struct in6_addr *addr,
0022                    unsigned char pfx)
0023 {
0024     memcpy(dst, &addr->s6_addr[pfx], IPV6_PFXTAIL_LEN(pfx));
0025 }
0026
0027 static void *ipv6_rpl_segdata_pos(const struct ipv6_rpl_sr_hdr *hdr, int i)
0028 {
0029     return (void *)&hdr->rpl_segdata[i * IPV6_PFXTAIL_LEN(hdr->cmpri)];
0030 }
0031
0032 size_t ipv6_rpl_srh_size(unsigned char n, unsigned char cmpri,
0033              unsigned char cmpre)
0034 {
0035     return (n * IPV6_PFXTAIL_LEN(cmpri)) + IPV6_PFXTAIL_LEN(cmpre);
0036 }
0037
0038 void ipv6_rpl_srh_decompress(struct ipv6_rpl_sr_hdr *outhdr,
0039                  const struct ipv6_rpl_sr_hdr *inhdr,
0040                  const struct in6_addr *daddr, unsigned char n)
0041 {
0042     int i;
0043
0044     outhdr->nexthdr = inhdr->nexthdr;
0045     outhdr->hdrlen = (((n + 1) * sizeof(struct in6_addr)) >> 3);
0046     outhdr->pad = 0;
0047     outhdr->type = inhdr->type;
0048     outhdr->segments_left = inhdr->segments_left;
0049     outhdr->cmpri = 0;
0050     outhdr->cmpre = 0;
0051
0052     for (i = 0; i < n; i++)
0053         ipv6_rpl_addr_decompress(&outhdr->rpl_segaddr[i], daddr,
0054                      ipv6_rpl_segdata_pos(inhdr, i),
0055                      inhdr->cmpri);
0056
0057     ipv6_rpl_addr_decompress(&outhdr->rpl_segaddr[n], daddr,
0058                  ipv6_rpl_segdata_pos(inhdr, n),
0059                  inhdr->cmpre);
0060 }
0061
0062 static unsigned char ipv6_rpl_srh_calc_cmpri(const struct ipv6_rpl_sr_hdr *inhdr,
0063                          const struct in6_addr *daddr,
0064                          unsigned char n)
0065 {
0066     unsigned char plen;
0067     int i;
0068
0069     for (plen = 0; plen < sizeof(*daddr); plen++) {
0070         for (i = 0; i < n; i++) {
0071             if (daddr->s6_addr[plen] !=
0072                 inhdr->rpl_segaddr[i].s6_addr[plen])
0073                 return plen;
0074         }
0075     }
0076
0077     return IPV6_RPL_BEST_ADDR_COMPRESSION;
0078 }
0079
0080 static unsigned char ipv6_rpl_srh_calc_cmpre(const struct in6_addr *daddr,
0081                          const struct in6_addr *last_segment)
0082 {
0083     unsigned int plen;
0084
0085     for (plen = 0; plen < sizeof(*daddr); plen++) {
0086         if (daddr->s6_addr[plen] != last_segment->s6_addr[plen])
0087             return plen;
0088     }
0089
0090     return IPV6_RPL_BEST_ADDR_COMPRESSION;
0091 }
0092
0093 void ipv6_rpl_srh_compress(struct ipv6_rpl_sr_hdr *outhdr,
0094                const struct ipv6_rpl_sr_hdr *inhdr,
0095                const struct in6_addr *daddr, unsigned char n)
0096 {
0097     unsigned char cmpri, cmpre;
0098     size_t seglen;
0099     int i;
0100
0101     cmpri = ipv6_rpl_srh_calc_cmpri(inhdr, daddr, n);
0102     cmpre = ipv6_rpl_srh_calc_cmpre(daddr, &inhdr->rpl_segaddr[n]);
0103
0104     outhdr->nexthdr = inhdr->nexthdr;
0105     seglen = (n * IPV6_PFXTAIL_LEN(cmpri)) + IPV6_PFXTAIL_LEN(cmpre);
0106     outhdr->hdrlen = seglen >> 3;
0107     if (seglen & 0x7) {
0108         outhdr->hdrlen++;
0109         outhdr->pad = 8 - (seglen & 0x7);
0110     } else {
0111         outhdr->pad = 0;
0112     }
0113     outhdr->type = inhdr->type;
0114     outhdr->segments_left = inhdr->segments_left;
0115     outhdr->cmpri = cmpri;
0116     outhdr->cmpre = cmpre;
0117
0118     for (i = 0; i < n; i++)
0119         ipv6_rpl_addr_compress(ipv6_rpl_segdata_pos(outhdr, i),
0120                        &inhdr->rpl_segaddr[i], cmpri);
0121
0122     ipv6_rpl_addr_compress(ipv6_rpl_segdata_pos(outhdr, n),
0123                    &inhdr->rpl_segaddr[n], cmpre);
0124 }