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icmp.c

// L2TPNS: icmp

char const *cvs_id_icmp = "$Id: icmp.c,v 1.10 2005/08/10 11:25:56 bodea Exp $";

#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in.h>
#include <asm/types.h>
#include <linux/ip.h>
#include <linux/icmp.h>
#include <netinet/icmp6.h>
#include <stdio.h>
#include <sys/socket.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <memory.h>

#include "l2tpns.h"

static uint16_t _checksum(uint8_t *addr, int count);

struct ipv6_pseudo_hdr {
      struct in6_addr src;
      struct in6_addr dest;
      uint32_t ulp_length;
      uint32_t zero    : 24;
      uint32_t nexthdr :  8;
};

void host_unreachable(in_addr_t destination, uint16_t id, in_addr_t source, uint8_t *packet, int packet_len)
{
      char buf[128] = {0};
      struct iphdr *iph;
      struct icmphdr *icmp;
      int len = 0, on = 1, icmp_socket;
      struct sockaddr_in whereto = {0};

      if ((icmp_socket = socket(AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0)
            return;

      setsockopt(icmp_socket, IPPROTO_IP, IP_HDRINCL, (char *)&on, sizeof(on));

      whereto.sin_addr.s_addr = destination;
      whereto.sin_family = AF_INET;

      iph = (struct iphdr *)(buf);
      len = sizeof(struct iphdr);
      icmp = (struct icmphdr *)(buf + len);
      len += sizeof(struct icmphdr);

      /* ip header + first 8 bytes of payload */
      if (packet_len > (sizeof(struct iphdr) + 8))
            packet_len = sizeof(struct iphdr) + 8;

      memcpy(buf + len, packet, packet_len);
      len += packet_len;

      iph->tos = 0;
      iph->id = id;
      iph->frag_off = 0;
      iph->ttl = 30;
      iph->check = 0;
      iph->version = 4;
      iph->ihl = 5;
      iph->protocol = 1;
      iph->check = 0;
      iph->daddr = destination;
      iph->saddr = source;

      iph->tot_len = ntohs(len);

      icmp->type = ICMP_DEST_UNREACH;
      icmp->code = ICMP_HOST_UNREACH;
      icmp->checksum = _checksum((uint8_t *) icmp, sizeof(struct icmphdr) + packet_len);

      iph->check = _checksum((uint8_t *) iph, sizeof(struct iphdr));

      sendto(icmp_socket, buf, len, 0, (struct sockaddr *)&whereto, sizeof(struct sockaddr));
      close(icmp_socket);
}

static uint16_t _checksum(uint8_t *addr, int count)
{
      register long sum = 0;

      for (; count > 1; count -= 2)
      {
            sum += ntohs(*(uint32_t *) addr);
            addr += 2;
      }

      if (count > 1) sum += *(unsigned char *)addr;

      // take only 16 bits out of the 32 bit sum and add up the carries
      while (sum >> 16)
            sum = (sum & 0xFFFF) + (sum >> 16);

      // one's complement the result
      sum = ~sum;

      return htons((uint16_t) sum);
}

void send_ipv6_ra(sessionidt s, tunnelidt t, struct in6_addr *ip)
{
      struct nd_opt_prefix_info *pinfo;
      struct ipv6_pseudo_hdr *phdr;
      uint8_t b[MAXETHER + 20];
      uint8_t c[MAXETHER + 20];
      int l;
      uint8_t *o;

      LOG(3, s, t, "Sending IPv6 RA\n");
            
      memset(b, 0, sizeof(b));
      o = makeppp(b, sizeof(b), 0, 0, s, t, PPPIPV6);

      if (!o)
      {
            LOG(3, s, t, "failed to send IPv6 RA\n");
            return;
      }

      *o = 0x60;              // IPv6
      *(o+1) = 0;
      *(o+5) = 48;                  // Length of payload (not header)
      *(o+6) = 58;                  // icmp6 is next
      *(o+7) = 255;                 // Hop limit
      memset(o+8, 0, 16);           // source = FE80::1
      *(o+8) = 0xFE;
      *(o+9) = 0x80;
      *(o+23) = 1;
      if (ip != NULL)
            memcpy(o+24, ip, 16);   // dest = ip
      else
      {
            // FF02::1 - all hosts
            *(o+24) = 0xFF;
            *(o+25) = 2;
            *(o+39) = 1;
      }
      *(o+40) = 134;                // RA message
      *(o+41) = 0;                  // Code
      *(o+42) = *(o+43) = 0;        // Checksum
      *(o+44) = 64;                 // Hop count
      *(o+45) = 0;                  // Flags
      *(o+46) = *(o+47) = 255;      // Lifetime
      *(uint32_t *)(o+48) = 0;      // Reachable time
      *(uint32_t *)(o+52) = 0;      // Retrans timer
      pinfo = (struct nd_opt_prefix_info *)(o+56);
      pinfo->nd_opt_pi_type           = ND_OPT_PREFIX_INFORMATION;
      pinfo->nd_opt_pi_len            = 4;
      pinfo->nd_opt_pi_prefix_len     = 64; // prefix length
      pinfo->nd_opt_pi_flags_reserved = ND_OPT_PI_FLAG_ONLINK;
      pinfo->nd_opt_pi_flags_reserved |= ND_OPT_PI_FLAG_AUTO;
      pinfo->nd_opt_pi_valid_time     = htonl(2592000);
      pinfo->nd_opt_pi_preferred_time = htonl(604800);
      pinfo->nd_opt_pi_reserved2      = 0;
      pinfo->nd_opt_pi_prefix         = config->ipv6_prefix;
      l = sizeof(*pinfo) + 56;

      memset(c, 0, sizeof(c));
      phdr = (struct ipv6_pseudo_hdr *) c;
      memcpy(&phdr->src, o+8, 16);
      memcpy(&phdr->dest, o+24, 16);
      phdr->ulp_length = htonl(l - 40);
      phdr->nexthdr = IPPROTO_ICMPV6;

      memcpy(c + sizeof(*phdr), o + 40, l - 40);

      // Checksum is over the icmp6 payload plus the pseudo header
      *(uint16_t *)(o+42) = _checksum(c, l - 40 + sizeof(*phdr));

      tunnelsend(b, l + (o-b), t); // send it...
      return;
}

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