icmp.c

   1 // L2TPNS: icmp
   2
   3 char const *cvs_id_icmp = "$Id: icmp.c,v 1.7 2005/01/25 04:19:05 bodea Exp $";
   4
   5 #include <arpa/inet.h>
   6 #include <netdb.h>
   7 #include <netinet/in.h>
   8 #include <asm/types.h>
   9 #include <linux/ip.h>
  10 #include <linux/icmp.h>
  11 #include <netinet/icmp6.h>
  12 #include <stdio.h>
  13 #include <sys/socket.h>
  14 #include <unistd.h>
  15 #include <sys/types.h>
  16 #include <sys/wait.h>
  17 #include <memory.h>
  18
  19 #include "l2tpns.h"
  20
  21 static uint16_t _checksum(unsigned char *addr, int count);
  22
  23 struct ipv6_pseudo_hdr {
  24         struct in6_addr src;
  25         struct in6_addr dest;
  26         uint32_t ulp_length;
  27         uint32_t zero    : 24;
  28         uint32_t nexthdr :  8;
  29 };
  30
  31 void host_unreachable(in_addr_t destination, uint16_t id, in_addr_t source, char *packet, int packet_len)
  32 {
  33         char buf[128] = {0};
  34         struct iphdr *iph;
  35         struct icmphdr *icmp;
  36         char *data;
  37         int len = 0, on = 1, icmp_socket;
  38         struct sockaddr_in whereto = {0};
  39
  40         if ((icmp_socket = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0)
  41                 return;
  42
  43         setsockopt(icmp_socket, IPPROTO_IP, IP_HDRINCL, (char *)&on, sizeof(on));
  44
  45         whereto.sin_addr.s_addr = destination;
  46         whereto.sin_family = AF_INET;
  47
  48         iph = (struct iphdr *)(buf);
  49         len = sizeof(struct iphdr);
  50         icmp = (struct icmphdr *)(buf + len);
  51         len += sizeof(struct icmphdr);
  52         data = (char *)(buf + len);
  53         len += (packet_len < 64) ? packet_len : 64;
  54         memcpy(data, packet, (packet_len < 64) ? packet_len : 64);
  55
  56         iph->tos = 0;
  57         iph->id = id;
  58         iph->frag_off = 0;
  59         iph->ttl = 30;
  60         iph->check = 0;
  61         iph->version = 4;
  62         iph->ihl = 5;
  63         iph->protocol = 1;
  64         iph->check = 0;
  65         iph->daddr = destination;
  66         iph->saddr = source;
  67
  68         iph->tot_len = ntohs(len);
  69
  70         icmp->type = ICMP_DEST_UNREACH;
  71         icmp->code = ICMP_HOST_UNREACH;
  72         icmp->checksum = _checksum((char *) icmp, sizeof(struct icmphdr) + ((packet_len < 64) ? packet_len : 64));
  73
  74         iph->check = _checksum((char *) iph, sizeof(struct iphdr));
  75
  76         sendto(icmp_socket, (char *)buf, len, 0, (struct sockaddr *)&whereto, sizeof(struct sockaddr));
  77         close(icmp_socket);
  78 }
  79
  80 static uint16_t _checksum(unsigned char *addr, int count)
  81 {
  82         register long sum = 0;
  83
  84         for (; count > 1; count -= 2)
  85         {
  86                 sum += ntohs(*(uint32_t *) addr);
  87                 addr += 2;
  88         }
  89
  90         if (count > 1) sum += *(unsigned char *)addr;
  91
  92         // take only 16 bits out of the 32 bit sum and add up the carries
  93         while (sum >> 16)
  94                 sum = (sum & 0xFFFF) + (sum >> 16);
  95
  96         // one's complement the result
  97         sum = ~sum;
  98
  99         return htons((uint16_t) sum);
 100 }
 101
 102 void send_ipv6_ra(tunnelidt t, sessionidt s, struct in6_addr *ip)
 103 {
 104         struct nd_opt_prefix_info *pinfo;
 105         struct ipv6_pseudo_hdr *phdr;
 106         uint8_t b[MAXETHER + 20];
 107         uint8_t c[MAXETHER + 20];
 108         int l;
 109         uint8_t *o;
 110
 111         LOG(3, s, t, "Sending IPv6 RA\n");
 112
 113         memset(b, 0, sizeof(b));
 114         o = makeppp(b, sizeof(b), 0, 0, t, s, PPPIPV6);
 115
 116         if (!o)
 117         {
 118                 LOG(3, s, t, "failed to send IPv6 RA\n");
 119                 return;
 120         }
 121
 122         *o = 0x60;                      // IPv6
 123         *(o+1) = 0;
 124         *(o+5) = 48;                    // Length of payload (not header)
 125         *(o+6) = 58;                    // icmp6 is next
 126         *(o+7) = 255;                   // Hop limit
 127         memset(o+8, 0, 16);             // source = FE80::1
 128         *(o+8) = 0xFE;
 129         *(o+9) = 0x80;
 130         *(o+23) = 1;
 131         if (ip != NULL)
 132                 memcpy(o+24, ip, 16);   // dest = ip
 133         else
 134         {
 135                 // FF02::1 - all hosts
 136                 *(o+24) = 0xFF;
 137                 *(o+25) = 2;
 138                 *(o+39) = 1;
 139         }
 140         *(o+40) = 134;                  // RA message
 141         *(o+41) = 0;                    // Code
 142         *(o+42) = *(o+43) = 0;          // Checksum
 143         *(o+44) = 64;                   // Hop count
 144         *(o+45) = 0;                    // Flags
 145         *(o+46) = *(o+47) = 255;        // Lifetime
 146         *(uint32_t *)(o+48) = 0;        // Reachable time
 147         *(uint32_t *)(o+52) = 0;        // Retrans timer
 148         pinfo = (struct nd_opt_prefix_info *)(o+56);
 149         pinfo->nd_opt_pi_type           = ND_OPT_PREFIX_INFORMATION;
 150         pinfo->nd_opt_pi_len            = 4;
 151         pinfo->nd_opt_pi_prefix_len     = 64; // prefix length
 152         pinfo->nd_opt_pi_flags_reserved = ND_OPT_PI_FLAG_ONLINK;
 153         pinfo->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_AUTO;
 154         pinfo->nd_opt_pi_valid_time     = htonl(2592000);
 155         pinfo->nd_opt_pi_preferred_time = htonl(604800);
 156         pinfo->nd_opt_pi_reserved2      = 0;
 157         pinfo->nd_opt_pi_prefix         = config->ipv6_prefix;
 158         l = sizeof(*pinfo) + 56;
 159
 160         memset(c, 0, sizeof(c));
 161         phdr = (struct ipv6_pseudo_hdr *) c;
 162         memcpy(&phdr->src, o+8, 16);
 163         memcpy(&phdr->dest, o+24, 16);
 164         phdr->ulp_length = htonl(l - 40);
 165         phdr->nexthdr = IPPROTO_ICMPV6;
 166
 167         memcpy(c + sizeof(*phdr), o + 40, l - 40);
 168
 169         // Checksum is over the icmp6 payload plus the pseudo header
 170         *(uint16_t *)(o+42) = _checksum(c, l - 40 + sizeof(*phdr));
 171
 172         tunnelsend(b, l + (o-b), t); // send it...
 173         return;
 174 }