src/tests/kits/net/sock/sourceroute.c

   1 /* -*- c-basic-offset: 8; -*-
   2  *
   3  * Copyright (c) 1993 W. Richard Stevens.  All rights reserved.
   4  * Permission to use or modify this software and its documentation only for
   5  * educational purposes and without fee is hereby granted, provided that
   6  * the above copyright notice appear in all copies.  The author makes no
   7  * representations about the suitability of this software for any purpose.
   8  * It is provided "as is" without express or implied warranty.
   9  */
  10
  11 #include <stdio.h>
  12 #include "sock.h"
  13 #include <netinet/ip.h>
  14 #include <netdb.h>
  15 #include <netinet/in.h>
  16 #include <arpa/inet.h>
  17
  18 /*
  19  * There is a fundamental limit of 9 IP addresses in a source route.
  20  * But we allocate sroute_opt[44] with room for 10 IP addresses (and
  21  * the 3-byte source route type/len/offset) because with the BSD
  22  * IP_OPTIONS socket option we can specify up to 9 addresses, followed
  23  * by the destination address.  The in_pcbopts() function in the kernel
  24  * then takes the final address in the list (the destination) and moves
  25  * it to the front, as shown in Figure 9.33 of "TCP/IP Illustrated,
  26  * Volume 2".  Also note that this destination address that we pass as
  27  * the final IP address in our array overrides the destination address
  28  * of the sendto() (Figure 9.28 of Volume 2).
  29  */
  30
  31 u_char  sroute_opt[44];         /* some implementations require this to be
  32                                                            on a 4-byte boundary */
  33 u_char  *optr;                          /* pointer into options being formed */
  34
  35 /*
  36  * Process either the -g (loose) or -G (strict) command-line option,
  37  * specifying one hop in a source route.
  38  * Either option can be specified up to 9 times.
  39  * With IPv4 the entire source route is either loose or strict, but we
  40  * set the source route type field based on the first option encountered,
  41  * either -g or -G.
  42  */
  43
  44 void
  45 sroute_doopt(int strict, char *argptr)
  46 {
  47         struct in_addr  inaddr;
  48         struct hostent  *hp;
  49
  50         if (sroute_cnt >= 9)
  51                 err_quit("too many source routes with: %s", argptr);
  52
  53         if (sroute_cnt == 0) {  /* first one */
  54                 bzero(sroute_opt, sizeof(sroute_opt));
  55                 optr = sroute_opt;
  56                 *optr++ = strict ? IPOPT_SSRR : IPOPT_LSRR;
  57                 optr++;                 /* we fill in the total length later */
  58                 *optr++ = 4;    /* ptr to first source-route address */
  59         }
  60
  61         if (inet_aton(argptr, &inaddr) == 1) {
  62                 bcopy(&inaddr, optr, sizeof(u_long));   /* dotted decimal */
  63                 if (verbose)
  64                         fprintf(stderr, "source route to %s\n", inet_ntoa(inaddr));
  65         } else if ( (hp = gethostbyname(argptr)) != NULL) {
  66                 bcopy(hp->h_addr, optr, sizeof(u_long));/* hostname */
  67                 if (verbose)
  68                         fprintf(stderr, "source route to %s\n",
  69                                                         inet_ntoa(*((struct in_addr *) hp->h_addr)));
  70         } else
  71                 err_quit("unknown host: %s\n", argptr);
  72
  73         optr += sizeof(u_long);         /* for next IP addr in list */
  74         sroute_cnt++;
  75 }
  76
  77 /*
  78  * Set the actual source route with the IP_OPTIONS socket option.
  79  * This function is called if srouce_cnt is nonzero.
  80  * The final destination goes at the end of the list of IP addresses.
  81  */
  82
  83 void
  84 sroute_set(int sockfd)
  85 {
  86         sroute_cnt++;                         /* account for destination */
  87         sroute_opt[1] = 3 + (sroute_cnt * 4); /* total length, incl. destination */
  88
  89         /* destination must be stored as final entry */
  90         bcopy(&servaddr.sin_addr, optr, sizeof(u_long));
  91         optr += sizeof(u_long);
  92         if (verbose) {
  93                 fprintf(stderr, "source route to %s\n", inet_ntoa(servaddr.sin_addr));
  94                 fprintf(stderr, "source route size %d bytes\n", sroute_opt[1]);
  95         }
  96
  97         /*
  98          * The number of bytes that we pass to setsockopt() must be a multiple
  99          * of 4.  Since the buffer was initialized to 0, this leaves an EOL
 100          * following the final IP address.
 101          * For optimization we could put a NOP before the 3-byte type/len/offset
 102          * field, which would then align all the IP addresses on 4-byte boundaries,
 103          * but the source routing code is not exactly in the fast path of most
 104          * routers.
 105          */
 106         while ((optr - sroute_opt) & 3)
 107                 optr++;
 108
 109         if (setsockopt(sockfd, IPPROTO_IP, IP_OPTIONS,
 110                        sroute_opt, optr - sroute_opt) < 0)
 111                 err_sys("setsockopt error for IP_OPTIONS");
 112
 113         sroute_cnt = 0;         /* don't call this function again */
 114 }