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 <linux/rtnetlink.h>
   9 #include <netinet/ip6.h>
  10
  11 #include "dhcp6.h"
  12 #include "l2tpns.h"
  13 #include "ipv6_u.h"
  14
  15 static uint16_t _checksum(uint8_t *addr, int count);
  16
  17 void host_unreachable(in_addr_t destination, uint16_t id, in_addr_t source, uint8_t *packet, int packet_len)
  18 {
  19         char buf[128] = {0};
  20         struct iphdr *iph;
  21         struct icmphdr *icmp;
  22         int len = 0, on = 1, icmp_socket;
  23         struct sockaddr_in whereto = {0};
  24
  25         if ((icmp_socket = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0)
  26                 return;
  27
  28         setsockopt(icmp_socket, IPPROTO_IP, IP_HDRINCL, (char *)&on, sizeof(on));
  29
  30         whereto.sin_addr.s_addr = destination;
  31         whereto.sin_family = AF_INET;
  32
  33         iph = (struct iphdr *)(buf);
  34         len = sizeof(struct iphdr);
  35         icmp = (struct icmphdr *)(buf + len);
  36         len += sizeof(struct icmphdr);
  37
  38         /* ip header + first 8 bytes of payload */
  39         if (packet_len > (sizeof(struct iphdr) + 8))
  40                 packet_len = sizeof(struct iphdr) + 8;
  41
  42         memcpy(buf + len, packet, packet_len);
  43         len += packet_len;
  44
  45         iph->tos = 0;
  46         iph->id = id;
  47         iph->frag_off = 0;
  48         iph->ttl = 30;
  49         iph->check = 0;
  50         iph->version = 4;
  51         iph->ihl = 5;
  52         iph->protocol = 1;
  53         iph->check = 0;
  54         iph->daddr = destination;
  55         iph->saddr = source;
  56
  57         iph->tot_len = ntohs(len);
  58
  59         icmp->type = ICMP_DEST_UNREACH;
  60         icmp->code = ICMP_HOST_UNREACH;
  61         icmp->checksum = _checksum((uint8_t *) icmp, sizeof(struct icmphdr) + packet_len);
  62
  63         iph->check = _checksum((uint8_t *) iph, sizeof(struct iphdr));
  64
  65         sendto(icmp_socket, buf, len, 0, (struct sockaddr *)&whereto, sizeof(struct sockaddr));
  66         close(icmp_socket);
  67 }
  68
  69 static uint16_t _checksum(uint8_t *addr, int count)
  70 {
  71         register long sum = 0;
  72
  73         for (; count > 1; count -= 2)
  74         {
  75                 sum += ntohs(*(uint16_t *) addr);
  76                 addr += 2;
  77         }
  78
  79         if (count > 0) sum += *(unsigned char *)addr;
  80
  81         // take only 16 bits out of the 32 bit sum and add up the carries
  82         while (sum >> 16)
  83                 sum = (sum & 0xFFFF) + (sum >> 16);
  84
  85         // one's complement the result
  86         sum = ~sum;
  87
  88         return htons((uint16_t) sum);
  89 }
  90
  91 void send_ipv6_ra(sessionidt s, tunnelidt t, struct in6_addr *ip)
  92 {
  93         struct nd_opt_prefix_info *pinfo;
  94         struct ip6_hdr *p_ip6_hdr;
  95         struct nd_router_advert *p_nra;
  96         uint8_t b[MAXETHER + 20];
  97         struct ipv6_pseudo_hdr pseudo_hdr;
  98         int l;
  99
 100         LOG(3, s, t, "Sending IPv6 RA\n");
 101
 102         memset(b, 0, sizeof(b));
 103         p_ip6_hdr = (struct ip6_hdr *) makeppp(b, sizeof(b), 0, 0, s, t, PPPIPV6, 0, 0, 0);
 104
 105         if (!p_ip6_hdr)
 106         {
 107                 LOG(3, s, t, "failed to send IPv6 RA\n");
 108                 return;
 109         }
 110
 111         p_ip6_hdr->ip6_vfc = 0x60;                      // IPv6
 112         p_ip6_hdr->ip6_plen = 0;                        // Length of payload (not header) (calculation below)
 113         p_ip6_hdr->ip6_nxt = IPPROTO_ICMPV6;                    // icmp6 is next
 114         p_ip6_hdr->ip6_hlim = 255;                      // Hop limit
 115         // IPv6 0xFE80::1
 116         inet_pton(AF_INET6, "FE80::1", &p_ip6_hdr->ip6_src.s6_addr);
 117
 118         if (ip != NULL)
 119         {
 120                 memcpy(p_ip6_hdr->ip6_dst.s6_addr, ip, 16);     // dest = ip
 121         }
 122         else
 123         {
 124                 // FF02::1 - all hosts
 125                 inet_pton(AF_INET6, "FF02::1", &p_ip6_hdr->ip6_dst.s6_addr);
 126         }
 127
 128         // RA message after Ipv6 header
 129         p_nra = (struct nd_router_advert *) &p_ip6_hdr[1];
 130         p_nra->nd_ra_type = ND_ROUTER_ADVERT; // RA message (134)
 131         p_nra->nd_ra_code = 0;          // Code
 132         p_nra->nd_ra_cksum = 0;         // Checksum
 133         p_nra->nd_ra_curhoplimit = 64;          // Hop count
 134         p_nra->nd_ra_flags_reserved = (ND_RA_FLAG_MANAGED|ND_RA_FLAG_OTHER); // Flags
 135         p_nra->nd_ra_router_lifetime = 0xFFFF;  // Lifetime
 136         p_nra->nd_ra_reachable = 0;     // Reachable time
 137         p_nra->nd_ra_retransmit = 0;    // Retrans timer
 138         // Option PI after RA message (rfc4861)
 139         pinfo = (struct nd_opt_prefix_info *) &p_nra[1];
 140         pinfo->nd_opt_pi_type           = ND_OPT_PREFIX_INFORMATION;
 141         pinfo->nd_opt_pi_len            = 4;
 142         pinfo->nd_opt_pi_flags_reserved = ND_OPT_PI_FLAG_ONLINK | ND_OPT_PI_FLAG_AUTO;
 143         pinfo->nd_opt_pi_valid_time     = htonl(2592000);
 144         pinfo->nd_opt_pi_preferred_time = htonl(604800);
 145         pinfo->nd_opt_pi_reserved2      = 0;
 146         pinfo->nd_opt_pi_prefix_len     = 64; // prefix length
 147         if (session[s].ipv6address.s6_addr[0])
 148         {
 149                 // MSB 64bits of assigned IPv6 address to user (see radius attribut Framed-IPv6-Address)
 150                 memcpy(&pinfo->nd_opt_pi_prefix, &session[s].ipv6address.s6_addr[0], 8);
 151         }
 152         else
 153                 pinfo->nd_opt_pi_prefix     = config->ipv6_prefix;
 154
 155         // // Length of payload (not header)
 156         p_ip6_hdr->ip6_plen = htons(sizeof(*pinfo) + sizeof(*p_nra));
 157
 158         l = sizeof(*pinfo) + sizeof(*p_nra) + sizeof(*p_ip6_hdr);
 159
 160         /* Use pseudo hearder for checksum calculation */
 161         memset(&pseudo_hdr, 0, sizeof(pseudo_hdr));
 162         memcpy(&pseudo_hdr.src, &p_ip6_hdr->ip6_src, 16);
 163         memcpy(&pseudo_hdr.dest, &p_ip6_hdr->ip6_dst, 16);
 164         pseudo_hdr.ulp_length = htonl(sizeof(*pinfo) + sizeof(*p_nra)); // Lenght whitout Ipv6 header
 165         pseudo_hdr.nexthdr = IPPROTO_ICMPV6;
 166         // Checksum is over the icmp6 payload plus the pseudo header
 167         p_nra->nd_ra_cksum = ipv6_checksum(&pseudo_hdr, (uint8_t *) p_nra, (sizeof(*pinfo) + sizeof(*p_nra)));
 168
 169         tunnelsend(b, l + (((uint8_t *) p_ip6_hdr)-b), t); // send it...
 170         return;
 171 }