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Return the last host before skipping an octet in an IPv4 range exclude

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group. Not doing this was the cause of off-by-one errors that led to
assertion failures and, potentially, excluded hosts being scanned. Here
is the comment I added:

  /* The decision to skip a range was based on the address that came immediately
     before what our current array contains now. For example, if we have just
     handed out 0.0.0.0 from the the range 0-5.0.0.0, and we're asked to skip
     the first octet, we want to advance to 1.0.0.0. But 1.0.0.0 is what is in
     the current array right now, because TargetGroup::get_next_host advances
     the array after returning an address. If we didn't step back we would
     erroneously skip ahead to 2.0.0.0. */
This commit is contained in:
david
2009-11-18 01:17:59 +00:00
parent 714dd18f7f
commit a4fc71afb6
2 changed files with 19 additions and 3 deletions
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13
TargetGroup.cc
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@@ -351,6 +351,15 @@ int TargetGroup::skip_range(_octet_nums octet) {
if (targets_type != IPV4_RANGES)
return -1;
/* The decision to skip a range was based on the address that came immediately
before what our current array contains now. For example, if we have just
handed out 0.0.0.0 from the the range 0-5.0.0.0, and we're asked to skip
the first octet, we want to advance to 1.0.0.0. But 1.0.0.0 is what is in
the current array right now, because TargetGroup::get_next_host advances
the array after returning an address. If we didn't step back we would
erroneously skip ahead to 2.0.0.0. */
return_last_host();
switch (octet) {
case FIRST_OCTET:
oct = 0;
@@ -386,9 +395,7 @@ int TargetGroup::skip_range(_octet_nums octet) {
current[i] = 0;
}
/* we actually don't skip the current, it was accounted for
* by get_next_host */
ipsleft -= hosts_skipped - 1;
ipsleft -= hosts_skipped;
return hosts_skipped;
}