The problem: how to fix this warning: [ Expert Info (Warning/Sequence): No response seen to ICMP request]
The story: I'm playing with scapy. I have two tools: A is the sender ( which sends a echo-request ) and B is the recipient ( which sends a echo-reply AFTER it sniffs a echo-request ). The code of A:
....
pinger = IP(dst=x.x.x.x)/ICMP(id=0x7ccb, seq=1)/text
....
The code of B:
.....
sniff(filter=f"src host x.x.x.x and dst host x.x.x.x and icmp",
iface="XX", count=1)
send(IP(dst=x.x.x.x)/ICMP(type="echo-reply", id=0x7ccb, seq=1)/textback)
....
The result:
enter image description here
It appears that if the payloads ( text of A and textback of B ) are the same, this warning does not get displayed. However, for my goal, the text shall be different. So, how do I get rid of this warning while keeping both payloads not the same?
The data received in the echo message must be returned in the echo reply message.
Related
I am trying to develop a Traps receiver for SNMPv1 and SNMPv2c with OpenVPN. I have used the PURESNMP and PYSNMP libraries with Python. PYSNMP can receive SNMPv1 and SNMPv2c Traps, while PURESNMP only works with SNMPv2c. My project works as follows: the OpenVPN file is loaded into a Router so that it can connect, and several devices are connected behind the Router to be monitored by SNMP.
OpenVPN Router IP: 10.8.0.18,
LAN Router IP: 192.168.2.1
Team A IP: 192.168.2.3
OpenVPN Server IP: 10.8.0.1
Client2 IP: 10.8.0.10
I manage to receive the Traps, but I cannot distinguish where the information comes from, if in the LAN behind the Router how is it possible to identify from which the alarm came. This is the Team's SNMPv1 Trap response:
Agent is listening SNMP Trap on 10.8.0.10 , Port : 162
-------------------------------------------------- ------------------------
SourceIP: ('10.8.0.18', 49181)
----------------------Received new Trap message------------------------ ---
1.3.6.1.2.1.1.3.0 = 910296
1.3.6.1.6.3.1.1.4.1.0 = 1.3.6.1.4.1.1918.2.13.0.700
1.3.6.1.6.3.18.1.3.0 = 10.168.2.3
1.3.6.1.6.3.18.1.4.0 = public
1.3.6.1.6.3.1.1.4.3.0 = 1.3.6.1.4.1.1918.2.13
1.3.6.1.4.1.1918.2.13.10.111.12.0 = 1
1.3.6.1.4.1.1918.2.13.10.111.10.0 = 3
1.3.6.1.4.1.1918.2.13.10.111.11.0 = Digital Input 1
1.3.6.1.4.1.1918.2.13.10.111.14.0 = 4
1.3.6.1.4.1.1918.2.13.10.10.40.0 = System Location
1.3.6.1.4.1.1918.2.13.10.10.50.0 = SiteName
1.3.6.1.4.1.1918.2.13.10.10.60.0 = SiteAddress
1.3.6.1.4.1.1918.2.13.10.111.13.0 = Input D01 Disconnected.
In “IP Source”, a function is used to obtain the source IP, but it shows me the IP of the Router and not of the device that is alarmed. If you look at the third line of the traps, it indicates a source IP that the SNMPV1 protocol itself has incorporated:
1.3.6.1.6.3.18.1.3.0 = 10.168.2.3
But it is not from the device or from the Router, it is as if the Router's network segment had been mixed with the device's hots segment. This is the response when receiving SNMPv2c Traps:
Agent is listening SNMP Trap on 10.8.0.10 , Port : 162
-------------------------------------------------- --------------------------
SourceIP: ('10.8.0.18', 49180)
----------------------Received new Trap message------------------------ -----
1.3.6.1.2.1.1.3.0 = 896022
1.3.6.1.6.3.1.1.4.1.0 = 1.3.6.1.4.1.1918.2.13.20.700
1.3.6.1.4.1.1918.2.13.10.111.12.0 = 1
1.3.6.1.4.1.1918.2.13.10.111.10.0 = 3
1.3.6.1.4.1.1918.2.13.10.111.11.0 = Digital Input 1
1.3.6.1.4.1.1918.2.13.10.111.14.0 = 5
1.3.6.1.4.1.1918.2.13.10.10.40.0 = System Location
1.3.6.1.4.1.1918.2.13.10.10.50.0 = SiteName
1.3.6.1.4.1.1918.2.13.10.10.60.0 = SiteAddress
1.3.6.1.4.1.1918.2.13.10.111.13.0 = Input D01 Disconnected.
In Trap SNMPv2c, you can only get the source IP but it shows the IP of the Router, but it does not work for me since there are several devices behind the Router, and there is no way to identify which one the alarm came from. I am doing the tests from an OpenVPN client, and not yet from the server, it will be uploaded to the server once it works well.
Could you help me because that can happen. Since I thought it was a problem with the libraries and I used another trap receiving software and the answer was the same.
This is the Server configuration:
port 1194
proto udp
dev tun
ca ca.crt
cert server.crt
key server.key
dh none
server 10.8.0.0 255.255.0.0
ifconfig-pool-persist /var/log/openvpn/ipp.txt
client-config-dir ccd
route 192.168.0.0 255.255.0.0
keepalive 10 120
tls-crypt ta.key
cipher AES-256-GCM
auth SHA256
user nobody
group nogroup
persist-key
persist-tun
status /var/log/openvpn/openvpn-status.log
verb 3
explicit-exit-notify 1
This is the client configuration:
client
dev tun
proto udp
remote x.x.x.x 1194
resolv-retry infinite
nobind
user nobody
group nogroup
persist-key
persist-tun
remote-cert-tls server
cipher AES-256-GCM
auth SHA256
key-direction 1
verb 3
<ca>
</ca>
<cert>
</cert>
<key>
</key>
<tls-crypt>
#
#
</tls-crypt>
Firewall configuration on the server:
# START OPENVPN RULES
# NAT table rules
*nat
:POSTROUTING ACCEPT [0:0]
# Allow traffic from OpenVPN client to eth0 (change to the interface you discovered!)
-A POSTROUTING -s 10.8.0.0/8 -o eth0 -j MASQUERADE
COMMIT
# END OPENVPN RULES
This is the code to Receive SNMPv1 and SNMPv2c Traps:
from pysnmp.carrier.asynsock.dispatch import AsynsockDispatcher
#python snmp trap receiver
from pysnmp.entity import engine, config
from pysnmp.carrier.asyncore.dgram import udp
from pysnmp.entity.rfc3413 import ntfrcv
from pysnmp.proto import api
datosnmp = []
snmpEngine = engine.SnmpEngine()
TrapAgentAddress='10.8.0.10' #Trap listerner address
Port=162 #trap listerner port
print("Agent is listening SNMP Trap on "+TrapAgentAddress+" , Port : " +str(Port))
print('--------------------------------------------------------------------------')
config.addTransport(snmpEngine, udp.domainName + (1,), udp.UdpTransport().openServerMode((TrapAgentAddress, Port)))
#Configure community here
config.addV1System(snmpEngine, 'my-area', 'public')
def cbFun(snmpEngine, stateReference, contextEngineId, contextName,varBinds, cbCtx):
global datosnmp
#while wholeMsg:
execContext = snmpEngine.observer.getExecutionContext('rfc3412.receiveMessage:request')
print("IP Source: ", execContext['transportAddress']) #IP Origen del Trap
#print('snmpEngine : {0}'.format(snmpEngine))
#print('stateReference : {0}'.format(stateReference))
#print('contextEngineId : {0}'.format(contextEngineId))
#print('contextName : {0}'.format(contextName))
#print('cbCtx : {0}'.format(cbCtx))
print('{0}Received new Trap message{0}\n'.format('-' * 40))
for oid, val in varBinds:
datosnmp.append(val.prettyPrint())
print('%s = %s' % (oid.prettyPrint(), val.prettyPrint())) #name = OID, val = contenido de la OID
#print(datosnmp)
ntfrcv.NotificationReceiver(snmpEngine, cbFun)
snmpEngine.transportDispatcher.jobStarted(1)
try:
snmpEngine.transportDispatcher.runDispatcher()
except:
snmpEngine.transportDispatcher.closeDispatcher()
raise
Could you please help me if it could be a configuration error of the OpenVPN server, or maybe something else needs to be added. Have you seen a similar lake?
Any comment is appreciated.
I'm playing with scapy. I'm trying to forge JUST PSH/ACK and ACK packets in sequence
I coded two tools: A which sends PSH/ACK packets and then sniffs the resulting ACK, writing the sequence in a file to use it later
.....
bitack = random.randrange(1,656787969)
bitseq = random.randrange(1,4294967295)
if os.path.exists('test.txt'):
with open('test.txt','r') as f:
bitseq = int(f.read())
else:
with open('test.txt','w') as f:
f.write(str(bitseq))
.....
text = "Ok"
TSval = int(time.time())
TSecr = TSval
acker = IP(src="127.0.0.1",dst=destinazione"127.0.0.1")/TCP(sport=88,dport=8888,
flags="PA", seq=bitseq, ack=bitack, options=[('Timestamp', (TSval, TSecr))])/text
send(acker)
.....
rx = sniff(filter="host 127.0.0.1 and src port 8888", iface="lo", count=1)
seqcc = rx[0].getlayer(TCP).seq
ackcc = rx[0].getlayer(TCP).ack
with open('test.txt','w') as f:
f.write(str(ackcc))
print("SEQFINALE=", ackcc)
B: which sends ACK packets AFTER it sniffs a PSH/ACK packet from A. I know the ack packets contain text ( in this example the same of A), but this is what I want
....
rx = sniff(filter="host 127.0.0.1 and dst port 8888", iface="lo", count=1)
seqcc = rx[0].getlayer(TCP).seq
print("seq:", seqcc)
ackcc = rx[0].getlayer(TCP).ack
print("ack:", ackcc)
var = rx[0][Raw].load.decode(encoding='utf-8', errors='ignore')
acker = IP(src="127.0.0.1",dst="127.0.0.1")/TCP(sport=8888,dport=88, flags="A",
seq=ackcc, ack=seqcc + int(len(var)), options=[('Timestamp', (TSval, TSecr))])/var
send(acker)
.....
Everything works fine expect that wireshark gives some warning and I don't understand why:
"Expert Info (Note/Sequence): This frame is a (suspected) retransmission"
The first two packets are perfect:
Is there any issue in how I handle the sequence number/ ack number?
This makes me crazy
It is a retransmission. Your capture shows a frame from 8888 to 88 at seq=1 with 52 bytes of data (len=52). If you ever send another frame from 8888 to 88 at seq=1, it's a retransmission. TCP streams are in a single direction: A sends to B, B ACK's what A sent. (in this case, there should be an ACK=53 in a frame from 88 to 8888, either alone or piggybacking data.)
Short description:
when I try to send a SMS I receive the error: "Failed to get SMSC number from phone."
so I try to set the SMSC number and I receive the error: "Entry is empty."
Commnads are:
root#mail:/home/victor# echo "Dragon Ball super is Awsome!" | gammu --sendsms TEXT +40740863629
Failed to get SMSC number from phone.
root#mail:/home/victor# gammu setsmsc 1 "+40748438759"
Entry is empty.
Result of command gammu identify is:
root#mail:/home/victor# gammu identify
Device : /dev/ttyUSB0
Manufacturer : Qualcomm
Model : unknown (HSDPA Modem)
Firmware : 01.02.04 1 [Nov 27 2015 14:33:39]
SIM IMSI : +CIMI:226102317883481
Maybe my device is not supported by gammu?
This is my configuration file ... I tried different configuration:
[gammu]
port = /dev/ttyUSB0
model =
connection = at19200
synchronizetime = no
logfile = /var/log/gammu.log
logformat = textall
use_locking =
gammuloc =
I used my Ubuntu gammu version 1.37.
I just read the manual of the device, the solution is to load the right driver:
modprobe usbserial vendor=0x5c6 product=0x6000
After this the SMS can be send, no need to set SMSC manualy
The situation i have is Linux client is using UDP Socket. Client is sending message and in case no response within 10 seconds , Client will retry again in 10 seconds intervals.
The case is when connection is down , many trials are sent from client at the same time nothing was received on server side . Once the connection is up i found all previous messages are received at the same moment on server which means it was buffered and it causes a lot of problems because of duplicated messages received on the same moment on server side .
TCPDUMP ON client Side:
21:01:14.691903 IP 172.123.13211 > 172.34.13211: length 88 "1st at second 14"
21:01:24.692791 IP 172.123.13211 > 172.34.13211: length 88 "2nd at second 24"
21:01:34.694930 IP 172.123.13211 > 172.34.13211: length 88 "3rd at second 34"
21:01:44.696020 IP 172.123.13211 > 172.34.13211: length 88 "4th ate second 44"
Server TCPDUMP once the connection is up :
12:02:01.509518 IP 172.123.13211 > 13211: length 88 "Received 1st at second 1"
12:02:01.517841 IP 172.123.13211 > 13211: length 88 "Received 2nd at second 1"
12:02:01.543759 IP 172.123.13211 > 13211 length 88 "Received 3rd at second 1"
12:02:01.550741 IP 13211 > 172.123.13211: length 36
12:02:01.567948 IP 172.123.13211 > .13211: length 88
I need to understand in case of UDP socket is used and Connection is down .
how to avoid buffering packets during shortage
Client Code is in C++
Thank you
you might be looking for this :
How to flush Input Buffer of an UDP Socket in C?
Also the language you have used in the question is wrong. Please be more clean and precise and use relevant terminology
If I generate an Ethernet frame without any upper layers payload and send it at layer two with sendp(), then I receive the "Mac address to reach destination not found. Using broadcast." warning and frame put to wire indeed uses ff:ff:ff:ff:ff:ff as a destination MAC address. Why is this so? Shouldn't the Scapy send exactly the frame I constructed?
My crafted package can be seen below:
>>> ls(x)
dst : DestMACField = '01:00:0c:cc:cc:cc' (None)
src : SourceMACField = '00:11:22:33:44:55' (None)
type : XShortEnumField = 0 (0)
>>> sendp(x, iface="eth0")
WARNING: Mac address to reach destination not found. Using broadcast.
.
Sent 1 packets.
>>>
Most people encountering this issue are incorrectly using send() (or sr(), sr1(), srloop()) instead of sendp() (or srp(), srp1(), srploop()). For the record, the "without-p" functions like send() are for sending layer 3 packets (send(IP())) while the "with-p" variants are for sending layer 2 packets (sendp(Ether() / IP())).
If you define x like I do below and use sendp() (and not send()) and you still have this issue, you should probably try with the latest version from the project's git repository (see https://github.com/secdev/scapy).
I've tried:
>>> x = Ether(src='01:00:0c:cc:cc:cc', dst='00:11:22:33:44:55')
>>> ls(x)
dst : DestMACField = '00:11:22:33:44:55' (None)
src : SourceMACField = '01:00:0c:cc:cc:cc' (None)
type : XShortEnumField = 0 (0)
>>> sendp(x, iface='eth0')
.
Sent 1 packets.
At the same time I was running tcpdump:
# tcpdump -eni eth0 ether host 00:11:22:33:44:55
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on eth0, link-type EN10MB (Ethernet), capture size 65535 bytes
12:33:47.774570 01:00:0c:cc:cc:cc > 00:11:22:33:44:55, 802.3, length 14: [|llc]