On Wed, 5 Feb 1997, Nigel Metheringham wrote:
> To save me having to extract a copy of sendmail (after just going to the
> trouble of preventing it being installed when I upgraded a Linux system
> yesterday), could you split out the code fragment that sendmail uses to do
> this, please.
Okay, here follows the code from daemon.c sendmail-8.8.3 which display the
source routes , I will annotate the bug in it:
#if IP_SRCROUTE
/*
** Extract IP source routing information.
**
** Format of output for a connection from site a through b
** through c to d:
** loose: @site-c@site-b:site-a
** strict: !@site-c@site-b:site-a
**
** o - pointer within ipopt_list structure.
** q - pointer within ls/ss rr route data
** p - pointer to hbuf
*/
if (RealHostAddr.sa.sa_family == AF_INET)
{
int ipoptlen, j;
u_char *q;
u_char *o;
int l;
struct in_addr addr;
struct ipoption ipopt;
ipoptlen = sizeof ipopt;
if (getsockopt(fd, IPPROTO_IP, IP_OPTIONS,
(char *) &ipopt, &ipoptlen) < 0)
goto noipsr;
if (ipoptlen == 0)
goto noipsr;
o = (u_char *) ipopt.ipopt_list;
while (o != NULL && o < (u_char *) &ipopt + ipoptlen)
{
switch (*o)
{
case IPOPT_EOL:
o = NULL;
break;
case IPOPT_NOP:
o++;
break;
case IPOPT_SSRR:
case IPOPT_LSRR:
p = &hbuf[strlen(hbuf)];
l = sizeof hbuf - (hbuf - p) - 6;
snprintf(p, SPACELEFT(hbuf, p), " [%s@%.*s",
*o == IPOPT_SSRR ? "!" : "",
l > 240 ? 120 : l / 2,
inet_ntoa(ipopt.ipopt_dst));
i = strlen(p);
p += i;
l -= strlen(p);
/* o[1] is option length */
j = *++o / sizeof(struct in_addr) - 1;
/* q skips length and router pointer to data */
q = o + 2;
for ( ; j >= 0; j--)
{
memcpy(&addr, q, sizeof(addr));
snprintf(p, SPACELEFT(hbuf, p),
"%c%.*s",
j != 0 ? '@' : ':',
l > 240 ? 120 :
j == 0 ? l : l / 2,
inet_ntoa(addr));
i = strlen(p);
p += i;
l -= i + 1;
q += sizeof(struct in_addr);
}
o += *o;
[ According to rfc791 the option length gives the length of option type
plus option length plus all data bytes, so the code should read:
o += *o -1;
or something to the same end. ]
break;
default:
/* Skip over option */
o += o[1];
break;
}
}
snprintf(p, SPACELEFT(hbuf, p), "]");
goto postipsr;
}
#endif
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Niels Provos
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