icmp.c

   1 // L2TPNS: icmp
   2
   3 #include <arpa/inet.h>
   4 #include <netdb.h>
   5 #include <netinet/in.h>
   6 #include <asm/types.h>
   7 #include <linux/ip.h>
   8 #include <linux/icmp.h>
   9 #include <netinet/icmp6.h>
  10 #include <stdio.h>
  11 #include <sys/socket.h>
  12 #include <unistd.h>
  13 #include <sys/types.h>
  14 #include <sys/wait.h>
  15 #include <memory.h>
  16
  17 #include "l2tpns.h"
  18
  19 static uint16_t _checksum(uint8_t *addr, int count);
  20
  21 struct ipv6_pseudo_hdr {
  22         struct in6_addr src;
  23         struct in6_addr dest;
  24         uint32_t ulp_length;
  25         uint32_t zero    : 24;
  26         uint32_t nexthdr :  8;
  27 };
  28
  29 void host_unreachable(in_addr_t destination, uint16_t id, in_addr_t source, uint8_t *packet, int packet_len)
  30 {
  31         char buf[128] = {0};
  32         struct iphdr *iph;
  33         struct icmphdr *icmp;
  34         int len = 0, on = 1, icmp_socket;
  35         struct sockaddr_in whereto = {0};
  36
  37         if ((icmp_socket = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0)
  38                 return;
  39
  40         setsockopt(icmp_socket, IPPROTO_IP, IP_HDRINCL, (char *)&on, sizeof(on));
  41
  42         whereto.sin_addr.s_addr = destination;
  43         whereto.sin_family = AF_INET;
  44
  45         iph = (struct iphdr *)(buf);
  46         len = sizeof(struct iphdr);
  47         icmp = (struct icmphdr *)(buf + len);
  48         len += sizeof(struct icmphdr);
  49
  50         /* ip header + first 8 bytes of payload */
  51         if (packet_len > (sizeof(struct iphdr) + 8))
  52                 packet_len = sizeof(struct iphdr) + 8;
  53
  54         memcpy(buf + len, packet, packet_len);
  55         len += packet_len;
  56
  57         iph->tos = 0;
  58         iph->id = id;
  59         iph->frag_off = 0;
  60         iph->ttl = 30;
  61         iph->check = 0;
  62         iph->version = 4;
  63         iph->ihl = 5;
  64         iph->protocol = 1;
  65         iph->check = 0;
  66         iph->daddr = destination;
  67         iph->saddr = source;
  68
  69         iph->tot_len = ntohs(len);
  70
  71         icmp->type = ICMP_DEST_UNREACH;
  72         icmp->code = ICMP_HOST_UNREACH;
  73         icmp->checksum = _checksum((uint8_t *) icmp, sizeof(struct icmphdr) + packet_len);
  74
  75         iph->check = _checksum((uint8_t *) iph, sizeof(struct iphdr));
  76
  77         sendto(icmp_socket, buf, len, 0, (struct sockaddr *)&whereto, sizeof(struct sockaddr));
  78         close(icmp_socket);
  79 }
  80
  81 static uint16_t _checksum(uint8_t *addr, int count)
  82 {
  83         register long sum = 0;
  84
  85         for (; count > 1; count -= 2)
  86         {
  87                 sum += ntohs(*(uint32_t *) addr);
  88                 addr += 2;
  89         }
  90
  91         if (count > 1) sum += *(unsigned char *)addr;
  92
  93         // take only 16 bits out of the 32 bit sum and add up the carries
  94         while (sum >> 16)
  95                 sum = (sum & 0xFFFF) + (sum >> 16);
  96
  97         // one's complement the result
  98         sum = ~sum;
  99
 100         return htons((uint16_t) sum);
 101 }
 102
 103 void send_ipv6_ra(sessionidt s, tunnelidt t, struct in6_addr *ip)
 104 {
 105         struct nd_opt_prefix_info *pinfo;
 106         struct ipv6_pseudo_hdr *phdr;
 107         uint8_t b[MAXETHER + 20];
 108         uint8_t c[MAXETHER + 20];
 109         int l;
 110         uint8_t *o;
 111
 112         LOG(3, s, t, "Sending IPv6 RA\n");
 113
 114         memset(b, 0, sizeof(b));
 115         o = makeppp(b, sizeof(b), 0, 0, s, t, PPPIPV6, 0, 0, 0);
 116
 117         if (!o)
 118         {
 119                 LOG(3, s, t, "failed to send IPv6 RA\n");
 120                 return;
 121         }
 122
 123         *o = 0x60;                      // IPv6
 124         *(o+1) = 0;
 125         *(o+5) = 48;                    // Length of payload (not header)
 126         *(o+6) = 58;                    // icmp6 is next
 127         *(o+7) = 255;                   // Hop limit
 128         memset(o+8, 0, 16);             // source = FE80::1
 129         *(o+8) = 0xFE;
 130         *(o+9) = 0x80;
 131         *(o+23) = 1;
 132         if (ip != NULL)
 133                 memcpy(o+24, ip, 16);   // dest = ip
 134         else
 135         {
 136                 // FF02::1 - all hosts
 137                 *(o+24) = 0xFF;
 138                 *(o+25) = 2;
 139                 *(o+39) = 1;
 140         }
 141         *(o+40) = 134;                  // RA message
 142         *(o+41) = 0;                    // Code
 143         *(o+42) = *(o+43) = 0;          // Checksum
 144         *(o+44) = 64;                   // Hop count
 145         *(o+45) = 0;                    // Flags
 146         *(o+46) = *(o+47) = 255;        // Lifetime
 147         *(uint32_t *)(o+48) = 0;        // Reachable time
 148         *(uint32_t *)(o+52) = 0;        // Retrans timer
 149         pinfo = (struct nd_opt_prefix_info *)(o+56);
 150         pinfo->nd_opt_pi_type           = ND_OPT_PREFIX_INFORMATION;
 151         pinfo->nd_opt_pi_len            = 4;
 152         pinfo->nd_opt_pi_prefix_len     = 64; // prefix length
 153         pinfo->nd_opt_pi_flags_reserved = ND_OPT_PI_FLAG_ONLINK;
 154         pinfo->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_AUTO;
 155         pinfo->nd_opt_pi_valid_time     = htonl(2592000);
 156         pinfo->nd_opt_pi_preferred_time = htonl(604800);
 157         pinfo->nd_opt_pi_reserved2      = 0;
 158         pinfo->nd_opt_pi_prefix         = config->ipv6_prefix;
 159         l = sizeof(*pinfo) + 56;
 160
 161         memset(c, 0, sizeof(c));
 162         phdr = (struct ipv6_pseudo_hdr *) c;
 163         memcpy(&phdr->src, o+8, 16);
 164         memcpy(&phdr->dest, o+24, 16);
 165         phdr->ulp_length = htonl(l - 40);
 166         phdr->nexthdr = IPPROTO_ICMPV6;
 167
 168         memcpy(c + sizeof(*phdr), o + 40, l - 40);
 169
 170         // Checksum is over the icmp6 payload plus the pseudo header
 171         *(uint16_t *)(o+42) = _checksum(c, l - 40 + sizeof(*phdr));
 172
 173         tunnelsend(b, l + (o-b), t); // send it...
 174         return;
 175 }