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 #include "pppoe.h"
  19
  20 static uint16_t _checksum(uint8_t *addr, int count);
  21
  22 struct ipv6_pseudo_hdr {
  23         struct in6_addr src;
  24         struct in6_addr dest;
  25         uint32_t ulp_length;
  26         uint32_t zero    : 24;
  27         uint32_t nexthdr :  8;
  28 };
  29
  30 void host_unreachable(in_addr_t destination, uint16_t id, in_addr_t source, uint8_t *packet, int packet_len)
  31 {
  32         char buf[128] = {0};
  33         struct iphdr *iph;
  34         struct icmphdr *icmp;
  35         int len = 0, on = 1, icmp_socket;
  36         struct sockaddr_in whereto = {0};
  37
  38         if ((icmp_socket = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0)
  39                 return;
  40
  41         setsockopt(icmp_socket, IPPROTO_IP, IP_HDRINCL, (char *)&on, sizeof(on));
  42
  43         whereto.sin_addr.s_addr = destination;
  44         whereto.sin_family = AF_INET;
  45
  46         iph = (struct iphdr *)(buf);
  47         len = sizeof(struct iphdr);
  48         icmp = (struct icmphdr *)(buf + len);
  49         len += sizeof(struct icmphdr);
  50
  51         /* ip header + first 8 bytes of payload */
  52         if (packet_len > (sizeof(struct iphdr) + 8))
  53                 packet_len = sizeof(struct iphdr) + 8;
  54
  55         memcpy(buf + len, packet, packet_len);
  56         len += packet_len;
  57
  58         iph->tos = 0;
  59         iph->id = id;
  60         iph->frag_off = 0;
  61         iph->ttl = 30;
  62         iph->check = 0;
  63         iph->version = 4;
  64         iph->ihl = 5;
  65         iph->protocol = 1;
  66         iph->check = 0;
  67         iph->daddr = destination;
  68         iph->saddr = source;
  69
  70         iph->tot_len = ntohs(len);
  71
  72         icmp->type = ICMP_DEST_UNREACH;
  73         icmp->code = ICMP_HOST_UNREACH;
  74         icmp->checksum = _checksum((uint8_t *) icmp, sizeof(struct icmphdr) + packet_len);
  75
  76         iph->check = _checksum((uint8_t *) iph, sizeof(struct iphdr));
  77
  78         sendto(icmp_socket, buf, len, 0, (struct sockaddr *)&whereto, sizeof(struct sockaddr));
  79         close(icmp_socket);
  80 }
  81
  82 static uint16_t _checksum(uint8_t *addr, int count)
  83 {
  84         register long sum = 0;
  85
  86         for (; count > 1; count -= 2)
  87         {
  88                 sum += ntohs(*(uint32_t *) addr);
  89                 addr += 2;
  90         }
  91
  92         if (count > 1) sum += *(unsigned char *)addr;
  93
  94         // take only 16 bits out of the 32 bit sum and add up the carries
  95         while (sum >> 16)
  96                 sum = (sum & 0xFFFF) + (sum >> 16);
  97
  98         // one's complement the result
  99         sum = ~sum;
 100
 101         return htons((uint16_t) sum);
 102 }
 103
 104 void send_ipv6_ra(sessionidt s, tunnelidt t, struct in6_addr *ip)
 105 {
 106         struct nd_opt_prefix_info *pinfo;
 107         struct ipv6_pseudo_hdr *phdr;
 108         uint8_t b[MAXETHER + 20];
 109         uint8_t c[MAXETHER + 20];
 110         int l;
 111         uint8_t *o;
 112
 113         LOG(3, s, t, "Sending IPv6 RA\n");
 114
 115         memset(b, 0, sizeof(b));
 116         o = makeppp(b, sizeof(b), 0, 0, s, t, PPPIPV6, 0, 0, 0);
 117
 118         if (!o)
 119         {
 120                 LOG(3, s, t, "failed to send IPv6 RA\n");
 121                 return;
 122         }
 123
 124         *o = 0x60;                      // IPv6
 125         *(o+1) = 0;
 126         *(o+5) = 48;                    // Length of payload (not header)
 127         *(o+6) = 58;                    // icmp6 is next
 128         *(o+7) = 255;                   // Hop limit
 129         memset(o+8, 0, 16);             // source = FE80::1
 130         *(o+8) = 0xFE;
 131         *(o+9) = 0x80;
 132         *(o+23) = 1;
 133         if (ip != NULL)
 134         {
 135                 memcpy(o+24, ip, 16);   // dest = ip
 136         }
 137         else
 138         {
 139                 // FF02::1 - all hosts
 140                 *(o+24) = 0xFF;
 141                 *(o+25) = 2;
 142                 *(o+39) = 1;
 143         }
 144         *(o+40) = 134;                  // RA message
 145         *(o+41) = 0;                    // Code
 146         *(o+42) = *(o+43) = 0;          // Checksum
 147         *(o+44) = 64;                   // Hop count
 148         *(o+45) = 0;                    // Flags
 149         *(o+46) = *(o+47) = 255;        // Lifetime
 150         *(uint32_t *)(o+48) = 0;        // Reachable time
 151         *(uint32_t *)(o+52) = 0;        // Retrans timer
 152         pinfo = (struct nd_opt_prefix_info *)(o+56);
 153         pinfo->nd_opt_pi_type           = ND_OPT_PREFIX_INFORMATION;
 154         pinfo->nd_opt_pi_len            = 4;
 155         pinfo->nd_opt_pi_prefix_len     = 64; // prefix length
 156         pinfo->nd_opt_pi_flags_reserved = ND_OPT_PI_FLAG_ONLINK;
 157         pinfo->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_AUTO;
 158         pinfo->nd_opt_pi_valid_time     = htonl(2592000);
 159         pinfo->nd_opt_pi_preferred_time = htonl(604800);
 160         pinfo->nd_opt_pi_reserved2      = 0;
 161         pinfo->nd_opt_pi_prefix         = config->ipv6_prefix;
 162         l = sizeof(*pinfo) + 56;
 163
 164         memset(c, 0, sizeof(c));
 165         phdr = (struct ipv6_pseudo_hdr *) c;
 166         memcpy(&phdr->src, o+8, 16);
 167         memcpy(&phdr->dest, o+24, 16);
 168         phdr->ulp_length = htonl(l - 40);
 169         phdr->nexthdr = IPPROTO_ICMPV6;
 170
 171         memcpy(c + sizeof(*phdr), o + 40, l - 40);
 172
 173         // Checksum is over the icmp6 payload plus the pseudo header
 174         *(uint16_t *)(o+42) = _checksum(c, l - 40 + sizeof(*phdr));
 175
 176         tunnelsend(b, l + (o-b), t); // send it...
 177         return;
 178 }