can be used in /etc/resolv.conf or with the --dns-servers option. The
parallel reverse DNS resolver still only support IPv4 addresses, but
it can look them up over IPv6. [Ankur Nandwani]
and --script-trace. It was set at 5, now it's 2. That's enough to see
all the Nsock events and the contents of reads and writes. At 3 you
start to get messages like
PCAP do_actual_pcap_read READ (IOD #%li) (EID #%li) size=%i
The message "wait_for_events" isn't printed until level 4. Getting rid
of that is the main reason for this change.
functions. Previously system DNS resolution was encapulated inside the parallel
DNS function, inside a big if block. Now the if is on the outside and decides
which of the two functions to call.
o Nsock now supports binding to a local address and setting IPv4 options
with nsi_set_localaddr() and nsi_set_ipoptions(), respectively. [Kris]
o Nmap's Nsock-utilizing subsystems (DNS, NSE, version detection) have been
updated to support the -S and --ip-options flags. [Kris]
might negitivly effect how efficiently nmap stores cache values in a hash
table. Now ntohl is called to correctly reorder the values on little endian
platforms before the hash calculation is preformed.
This changes the DNS engine to use addto_etchosts to add entries from
/etc/hosts into the DNS cache, rather than just inserting them using
push_front.
The reason for this is that there is a static unsigned variable in
addto_etchosts that keeps track of how many entries there are in the
cache. Using push_front bypassed this variable, allowing the entries in
/etc/hosts to sneak in under the radar. Thus is was possible for the
cache to contain, say, 266 entries when it thought it only had 256.
When the cache size is greater than or equal to 256, addto_etchosts runs
a deletion pass aiming to reduce the number of entries to 126. But the
peculiar loop logic of that function means that more than 256 entries
can be deleted. (How many more depends in part on how many entries there
are in /etc/hosts. There must be at least one for the hang to occur.)
When this happens, the signed counter underflows and becomes large
positive, ~65000. The code empties the cache trying to get the counter
under 127, but it can never happen.
To reproduce the hang, make an /etc/hosts file like this:
1.0.0.1 host-1-1
1.0.0.2 host-1-2
1.0.0.3 host-1-3
1.0.0.4 host-1-4
1.0.0.5 host-1-5
1.0.0.6 host-1-6
1.0.0.7 host-1-7
1.0.0.8 host-1-8
1.0.0.9 host-1-9
1.0.0.10 host-1-10
2.0.0.1 host-2
3.0.0.1 host-3
...
254.0.0.1 host-254
255.0.0.1 host-255
The hang can occur with even one entry in /etc/hosts, but saturating the
cache like this makes the hang less dependent on network conditions.
Then list-scan a netblock that is greater in size than 256 and is dense
in DNS entries (at least 256 entries per 4096 IP addresses). For
example,
nmap -sL scanme.nmap.org/22
works for me currently.
