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Fix global congestion control in OS scan.

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Like ultra_scan, OS scan has global and host-based congestion control
mechanisms like those in TCP. Part of global congestion control is
keeping track of how many probes are outstanding in the network; OS scan
keeps the number in a member variable called num_probes_active.

num_probes_active is meant to be the sum of the sizes of each host's
list of outstanding probes. It was correctly being decremented whenever
a probe was removed from an active list, but it was never incremented.
num_probes_active was always zero or negative, and therefore never
exceeded the global congestion window. This almost completely disabled
global congestion control.

With this fix OS scan will send a maximum of ten probes immediately at
the beginning of the scan. Previously it was limited only by the number
of hosts being scanned (20 or 30).
This commit is contained in:
david
2008-12-18 04:49:49 +00:00
parent 9a37ef907f
commit eb7fda541e
1 changed files with 6 additions and 1 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
osscan2.cc
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@@ -991,6 +991,7 @@ void HostOsScan::updateActiveSeqProbes(HostOsScanStats *hss) {
/* Is the probe timedout? */
if (TIMEVAL_SUBTRACT(now, probe->sent) > (long) timeProbeTimeout(hss)) {
hss->removeActiveProbe(probeI);
assert(stats->num_probes_active > 0);
stats->num_probes_active--;
}
}
@@ -1074,11 +1075,13 @@ void HostOsScan::updateActiveTUIProbes(HostOsScanStats *hss) {
if(probe->tryno >= 3) {
/* The probe is expired. */
hss->removeActiveProbe(probeI);
assert(stats->num_probes_active > 0);
stats->num_probes_active--;
}
else {
/* It is timedout, move it to the sendlist */
hss->moveProbeToUnSendList(probeI);
assert(stats->num_probes_active > 0);
stats->num_probes_active--;
}
}
@@ -1276,6 +1279,7 @@ void HostOsScan::sendNextProbe(HostOsScanStats *hss) {
stats->num_probes_sent++;
hss->moveProbeToActiveList(probeI);
stats->num_probes_active++;
if (o.debugging > 1) {
log_write(LOG_PLAIN, "Send probe (type: %s, subid: %d) to %s\n",
@@ -1521,7 +1525,8 @@ bool HostOsScan::processResp(HostOsScanStats *hss, struct ip *ip, unsigned int l
/* delete the probe. */
hss->removeActiveProbe(probeI);
this->stats->num_probes_active--;
assert(stats->num_probes_active > 0);
stats->num_probes_active--;
return true;
}