Develop Reference

python/scapy - packets sent but unable to receive them

I'm trying to do an ARP scan and print MAC addresses of reachable IP addresses.
Here's the part of my code where I use ARP ping method :
ans, unans = srp(Ether(dst="ff:ff:ff:ff:ff:ff")/ARP(pdst="192.168.1.0/24"),timeout=2)
ans.summary(lambda s,r: r.sprintf("%Ether.src% %ARP.psrc%"))
I put a random IP address for the example.
Here's my response, I really don't understand why my packets are not received :
Begin emission:
Finished sending 1 packets.
Received 0 packets, got 0 answers, remaining 1 packets

ARP packets with scapy are unanswered

I'm building a network scanner with Python using Scapy. I've been trying to send ARP packets but for some reason they don't get responded to.
#!/usr/bin/env python3
from scapy.all import *
def scan(ip):
arp_request = ARP(pdst=ip)
broadcast = Ether(dst="ff:ff:ff:ff:ff:ff")
arp_request_broadcast = arp_request/broadcast
answered_list = srp(arp_request_broadcast, timeout=2)[0]
for element in answered_list:
print(element[1].show())
scan("192.168.1.0/24")
Running it results in the following:
[void#Void Network Scanner]$ sudo python3 tutorial_netscanner.py
[sudo] password for void:
Begin emission:
Finished sending 256 packets.
............................................................
Received 60 packets, got 0 answers, remaining 256 packets
The strange part is that if I run this from the scapy interactive shell it works and the arp packets do get answered.
arping("192.168.1.0/24")
Super confused as to why this isn't working, the code seems perfectly fine to me, if anyone could help me out that would be great. Thank you.

arp_request/broadcast is incorrect. The outer-most protocols go on the left. If you use Wireshark to see what's going on (the first thing you should do when something like this happens), you can see that it's not what you'd expect it to be:
It's essentially a malformed packet. You need broadcast / arp_request; although specifying the Ether layer is optional. You can use simply ARP (and sr).
Use Wireshark. It's an invaluable tool. You should only run it on networks that you have control over/permission to snoop, but it really is indispensable.

Scapy - Function 'sr1()' doesn't Return Response-Packet

Hello guys I have a problem with Scapy in Python 3 on Windows 10. I tried to send a Ping (ICMP) request to my default-gateway. This is the packet command:
p = IP(dst='10.0.0.138')/ICMP(type='echo-request')/Raw('Hello')
But after I write r = sr1(ping) the program is stuck on this output:
Begin emission:
Finished sending 1 packets.
I used Wireshark to check the packets and I saw the both packets: Request and response. What do I do wrong? This has been working for me for whole life until now.
Edit: I am using the Scapy-Shell right now.

the problem is solved, I just needed to give networks privileges to the Python Interpreter. Thanks for all your help.

Python Raw Socket cannot recieve ICMP messages; show up in Wireshark

I am trying to implement a python traceroute that sends UDP messages and receives the ICMP responses via raw sockets. I've run into an issue where the ICMP packets seem to avoid capture at all cost. The ICMP responses show up in wireshark as exactly what I'd expect, but the socket never receives any data to read. Another complication is that I am running the code on VirtualBox running Ubuntu, as the sendto() would not get the packets on the wire in Windows 7. (I'm running wireshark in windows to capture the packets). The strange thing is that wireshark will capture the ICMP messages when I run the python script from the virtual machine. However, when I try to run the script on windows, the ICMP messages don't show up in wireshark. (The UDP packets have magically started working on windows)
I've played around with all sorts of different versions of setting up the socket from online examples, and played around with using bind() and not using it, but no configuration seems to produce a socket that reads. It will just time out waiting to read the ICMP message.
It should also be noted that if I try to read my udp sending socket, it successfully reads the udp packets. As soon as I set IPPROTO_ICMP the read times out.
receive_response method:
def receive_response(rec_socket, packetid, tsend, timeout):
remain = timeout
print packetid
while remain > 0:
ready = select.select([rec_socket], [], [], remain)
if ready[0] == []:
return
print 'got something'
setting up the socket:
rec_socket = socket.socket(socket.AF_INET, socket.SOCK_RAW, ICMP_CODE)
rec_socket.setsockopt(socket.SOL_IP, socket.IP_HDRINCL, 1)
rec_socket.bind(("",0)) #played with using this statement and skipping it
call to receive is simply:
reached = receive_response(rec_socket, packetid, time.time(), timeout)

It looks like the problem is VirtualBox will default to using NAT to connect to the network. This means that the virtual machine won't receive the ICMP messages by virtue of them being ICMP messages. It seems like the solution to this is to configure VirtualBox networking to use "Bridged networking" mode. Unfortunately I cannot confirm this as I can't set up the virtual machine on my university's network within bridged mode. As for the reason they didn't work in windows, it must be related to windows' lack of support for raw sockets.

Scapy waiting for multiple packets

In order to perform a HTTP GET, I need to send a packet (the GET / HTTP/1.0\n\n) and wait for 3 packets:
The ACK of my GET
The GET answer: HTTP/1.0 200 OK
and the FIN ACK of the transmission
I found 2 ways:
=> use sr() with multi option
=> use sniff just after sending my GET request
For sr() function, the problem is to stop the sniffing, the only option is to set a timeout, but my script will test many different sites, so many different of time's answer, it could be hard to choose a static timeout value where I'm sure that no site exceed it anytime.
For sniff, there is no the same problem because I can set "count" argument to take only the 3 packets. But it's hard to make a filter good enough to be sure the 3 packets recorded are the 3 that I want (and no ARP, DNS or anything else).
But the main problem is sometimes the fist answer packet come before "sniff" is launched (between send(GET_PACKET) and answers=sniff(...)). In this case, I lost some information and all my post-treatment is corrupted.
The perfect way would be to use sr() function with "count=3" option to only get 3 packets, but that option doesn't exist with sr().
Anynone have an idea?
Thanks a lot
Sorry for my language, I'm French

Use Sniff and set the filter to TCP port 80
and for delay problem you can use a thread, first start your sniffer in thread then send the packets :
def sniffer():
packets=sniff(filter="tcp port 80" , count=5)
wrcap("test.cap" , packets) #save packets in .cap file
t = threading.Thread(target=sniffer)
t.start()
But you can use a better way that explained HERE. send your packets manually.

This is more of a hint than an answer, but the problem might be that you want to inspect transport layer packets for a application layer request. You could split up your HTTP GET down to transport layer by sending SYN, waiting for and answer and then send ACK, GET. Here is a link describing what you might want.