icmp.c

   1 // L2TPNS: icmp
   2
   3 #include <arpa/inet.h>
   4 #include <linux/ip.h>
   5 #include <linux/icmp.h>
   6 #include <netinet/icmp6.h>
   7 #include <unistd.h>
   8 #include <netinet/ip6.h>
   9
  10 #include "dhcp6.h"
  11 #include "l2tpns.h"
  12 #include "ipv6_u.h"
  13
  14 static uint16_t _checksum(uint8_t *addr, int count);
  15
  16 void host_unreachable(in_addr_t destination, uint16_t id, in_addr_t source, uint8_t *packet, int packet_len)
  17 {
  18         char buf[128] = {0};
  19         struct iphdr *iph;
  20         struct icmphdr *icmp;
  21         int len = 0, on = 1, icmp_socket;
  22         struct sockaddr_in whereto = {0};
  23
  24         if ((icmp_socket = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0)
  25                 return;
  26
  27         setsockopt(icmp_socket, IPPROTO_IP, IP_HDRINCL, (char *)&on, sizeof(on));
  28
  29         whereto.sin_addr.s_addr = destination;
  30         whereto.sin_family = AF_INET;
  31
  32         iph = (struct iphdr *)(buf);
  33         len = sizeof(struct iphdr);
  34         icmp = (struct icmphdr *)(buf + len);
  35         len += sizeof(struct icmphdr);
  36
  37         /* ip header + first 8 bytes of payload */
  38         if (packet_len > (sizeof(struct iphdr) + 8))
  39                 packet_len = sizeof(struct iphdr) + 8;
  40
  41         memcpy(buf + len, packet, packet_len);
  42         len += packet_len;
  43
  44         iph->tos = 0;
  45         iph->id = id;
  46         iph->frag_off = 0;
  47         iph->ttl = 30;
  48         iph->check = 0;
  49         iph->version = 4;
  50         iph->ihl = 5;
  51         iph->protocol = 1;
  52         iph->check = 0;
  53         iph->daddr = destination;
  54         iph->saddr = source;
  55
  56         iph->tot_len = ntohs(len);
  57
  58         icmp->type = ICMP_DEST_UNREACH;
  59         icmp->code = ICMP_HOST_UNREACH;
  60         icmp->checksum = _checksum((uint8_t *) icmp, sizeof(struct icmphdr) + packet_len);
  61
  62         iph->check = _checksum((uint8_t *) iph, sizeof(struct iphdr));
  63
  64         sendto(icmp_socket, buf, len, 0, (struct sockaddr *)&whereto, sizeof(struct sockaddr));
  65         close(icmp_socket);
  66 }
  67
  68 static uint16_t _checksum(uint8_t *addr, int count)
  69 {
  70         register long sum = 0;
  71
  72         for (; count > 1; count -= 2)
  73         {
  74                 sum += ntohs(*(uint16_t *) addr);
  75                 addr += 2;
  76         }
  77
  78         if (count > 0) sum += *(unsigned char *)addr;
  79
  80         // take only 16 bits out of the 32 bit sum and add up the carries
  81         while (sum >> 16)
  82                 sum = (sum & 0xFFFF) + (sum >> 16);
  83
  84         // one's complement the result
  85         sum = ~sum;
  86
  87         return htons((uint16_t) sum);
  88 }
  89
  90 void send_ipv6_ra(sessionidt s, tunnelidt t, struct in6_addr *ip)
  91 {
  92         struct nd_opt_prefix_info *pinfo;
  93         struct ip6_hdr *p_ip6_hdr;
  94         struct nd_router_advert *p_nra;
  95         uint8_t b[MAXETHER + 20];
  96         struct ipv6_pseudo_hdr pseudo_hdr;
  97         int l;
  98
  99         LOG(3, s, t, "Sending IPv6 RA\n");
 100
 101         memset(b, 0, sizeof(b));
 102         p_ip6_hdr = (struct ip6_hdr *) makeppp(b, sizeof(b), 0, 0, s, t, PPPIPV6, 0, 0, 0);
 103
 104         if (!p_ip6_hdr)
 105         {
 106                 LOG(3, s, t, "failed to send IPv6 RA\n");
 107                 return;
 108         }
 109
 110         p_ip6_hdr->ip6_vfc = 0x60;                      // IPv6
 111         p_ip6_hdr->ip6_plen = 0;                        // Length of payload (not header) (calculation below)
 112         p_ip6_hdr->ip6_nxt = IPPROTO_ICMPV6;                    // icmp6 is next
 113         p_ip6_hdr->ip6_hlim = 255;                      // Hop limit
 114         // IPv6 0xFE80::1
 115         inet_pton(AF_INET6, "FE80::1", &p_ip6_hdr->ip6_src.s6_addr);
 116
 117         if (ip != NULL)
 118         {
 119                 memcpy(p_ip6_hdr->ip6_dst.s6_addr, ip, 16);     // dest = ip
 120         }
 121         else
 122         {
 123                 // FF02::1 - all hosts
 124                 inet_pton(AF_INET6, "FF02::1", &p_ip6_hdr->ip6_dst.s6_addr);
 125         }
 126
 127         // RA message after Ipv6 header
 128         p_nra = (struct nd_router_advert *) &p_ip6_hdr[1];
 129         p_nra->nd_ra_type = ND_ROUTER_ADVERT; // RA message (134)
 130         p_nra->nd_ra_code = 0;          // Code
 131         p_nra->nd_ra_cksum = 0;         // Checksum
 132         p_nra->nd_ra_curhoplimit = 64;          // Hop count
 133         p_nra->nd_ra_flags_reserved = (ND_RA_FLAG_MANAGED|ND_RA_FLAG_OTHER); // Flags
 134         p_nra->nd_ra_router_lifetime = 0xFFFF;  // Lifetime
 135         p_nra->nd_ra_reachable = 0;     // Reachable time
 136         p_nra->nd_ra_retransmit = 0;    // Retrans timer
 137         // Option PI after RA message (rfc4861)
 138         pinfo = (struct nd_opt_prefix_info *) &p_nra[1];
 139         pinfo->nd_opt_pi_type           = ND_OPT_PREFIX_INFORMATION;
 140         pinfo->nd_opt_pi_len            = 4;
 141         pinfo->nd_opt_pi_flags_reserved = ND_OPT_PI_FLAG_ONLINK | ND_OPT_PI_FLAG_AUTO;
 142         pinfo->nd_opt_pi_valid_time     = htonl(2592000);
 143         pinfo->nd_opt_pi_preferred_time = htonl(604800);
 144         pinfo->nd_opt_pi_reserved2      = 0;
 145         pinfo->nd_opt_pi_prefix_len     = 64; // prefix length
 146         if (session[s].ipv6address.s6_addr[0])
 147         {
 148                 // MSB 64bits of assigned IPv6 address to user (see radius attribut Framed-IPv6-Address)
 149                 memcpy(&pinfo->nd_opt_pi_prefix, &session[s].ipv6address.s6_addr[0], 8);
 150         }
 151         else
 152                 pinfo->nd_opt_pi_prefix     = config->ipv6_prefix;
 153
 154         // // Length of payload (not header)
 155         p_ip6_hdr->ip6_plen = htons(sizeof(*pinfo) + sizeof(*p_nra));
 156
 157         l = sizeof(*pinfo) + sizeof(*p_nra) + sizeof(*p_ip6_hdr);
 158
 159         /* Use pseudo hearder for checksum calculation */
 160         memset(&pseudo_hdr, 0, sizeof(pseudo_hdr));
 161         memcpy(&pseudo_hdr.src, &p_ip6_hdr->ip6_src, 16);
 162         memcpy(&pseudo_hdr.dest, &p_ip6_hdr->ip6_dst, 16);
 163         pseudo_hdr.ulp_length = htonl(sizeof(*pinfo) + sizeof(*p_nra)); // Lenght whitout Ipv6 header
 164         pseudo_hdr.nexthdr = IPPROTO_ICMPV6;
 165         // Checksum is over the icmp6 payload plus the pseudo header
 166         p_nra->nd_ra_cksum = ipv6_checksum(&pseudo_hdr, (uint8_t *) p_nra, (sizeof(*pinfo) + sizeof(*p_nra)));
 167
 168         tunnelsend(b, l + (((uint8_t *) p_ip6_hdr)-b), t); // send it...
 169         return;
 170 }