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Linux/net/ipv6/rpl.c

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  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 }
125 

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