Re: pkg/55446 (scapy function send() does not work)

["David H. Gutteridge" <david%gutteridge.ca@localhost>]

The following reply was made to PR pkg/55446; it has been noted by GNATS.

From: "David H. Gutteridge" <david%gutteridge.ca@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: 
Subject: Re: pkg/55446 (scapy function send() does not work)
Date: Tue, 14 Jul 2020 22:22:45 -0400

 On Fri, 2020-07-10 at 23:43 +0300, tmp%bh0.amt.ru@localhost wrote:
 > On 07/10/20 23:35, tmp%bh0.amt.ru@localhost wrote:
 > >  On 07/06/20 01:25, David H. Gutteridge wrote:
 > >  >  I hadn't had occasion to try interacting with a loopback device with
 > >  >  Scapy before, but I borrowed that example from the Scapy test suite
 > >  >  (where it recorded a pass for me on NetBSD 8.1 when I ran it while
 > >  >  doing the last package update), but, the difference is, their test
 > >  >  example targets the IP address "8.8.8.8".
 > >  
 > >  I tried "8.8.8.8", the result was:
 [...]                                
 > >  >>> sendp(IP(dst="8.8.8.8")/ICMP()/"test"
 > >  ... help
 > >    File "<console>", line 2
 > >      help
 > >         ^
 > >  SyntaxError: invalid syntax
 > >  >>> 
 > 
 > I'm sorry for the mistake, the right output is:
 > 
 > > > > send(IP(dst="8.8.8.8")/ICMP()/"test"
 > ... help
 >   File "<console>", line 2
 >     help
 >        ^
 > SyntaxError: invalid syntax
 > >  I realized that something went wrong.
 
 I think you're missing a closing bracket in those examples?
 
 Taking Scapy's ICMP test cases "Sending an ICMP message at layer 2 and
 layer 3" from their test/regression.uts (lines 1337-1344) and running
 them manually (without any prior explicit configration of any kind) on
 8.2_STABLE/amd64, I get something different:
 
 >>> send(IP(dst="8.8.8.8")/ICMP(), return_packets=True, realtime=True)
 WARNING: Mac address to reach destination not found. Using broadcast.
 .
 Sent 1 packets.
 <PacketList: TCP:0 UDP:0 ICMP:1 Other:0>
 >>> sendp(Ether()/IP(dst="8.8.8.8")/ICMP(), return_packets=True,
 realtime=True)
 WARNING: Mac address to reach destination not found. Using broadcast.
 .
 Sent 1 packets.
 <PacketList: TCP:0 UDP:0 ICMP:1 Other:0>
 >>> 
 
 (In my case, I have a wired wm0 active.)
 
 > >  > Anyway, you'll want to have a
 > >  >  look at the following link in the Scapy documentation:
 > >  >  
 > > https://scapy.readthedocs.io/en/latest/troubleshooting.html#i-can-t-ping-127-0-0-1-scapy-does-not-work-with-127-0-0-1-or-on-the-loopback-interface
 > >  
 > >  I tried the above, the result was:
 > >  
 > >  # scapy
 > >  INFO: Can't import matplotlib. Won't be able to plot.
 > >  INFO: Can't import PyX. Won't be able to use psdump() or pdfdump().
 > >  INFO: No IPv6 support in kernel
 > >  WARNING: No route found for IPv6 destination :: (no default route?)
 > >  INFO: Can't import python-cryptography v1.7+. Disabled WEP
 > > decryption/encryption. (Dot11)
 > >  INFO: Can't import python-cryptography v1.7+. Disabled IPsec
 > > encryption/authentication.
 > >  WARNING: IPython not available. Using standard Python shell
 > > instead.
 > >  AutoCompletion, History are disabled.
 > >                                        
 > >                       aSPY//YASa       
 > >               apyyyyCY//////////YCa       |
 > >              sY//////YSpcs  scpCY//Pp     | Welcome to Scapy
 > >   ayp ayyyyyyySCP//Pp           syY//C    | Version git-
 > > archive.dev304758016
 > >   AYAsAYYYYYYYY///Ps              cY//S   |
 > >           pCCCCY//p          cSSps y//Y   | 
 > > https://github.com/secdev/scapy
 > >           SPPPP///a          pP///AC//Y   |
 > >                A//A            cyP////C   | Have fun!
 > >                p///Ac            sC///a   |
 > >                P////YCpc           A//A   | Wanna support scapy?
 > > Rate it on
 > >         scccccp///pSP///p          p//Y   | sectools!
 > >        sY/////////y  caa           S//P   | 
 > > http://sectools.org/tool/scapy/
 > >         cayCyayP//Ya              pY/Ya   |             -- Satoshi
 > > Nakamoto
 > >          sY/PsY////YCc          aC//Yp    |
 > >           sc  sccaCY//PCypaapyCP//YSs  
 > >                    spCPY//////YPSps    
 > >                         ccaacs         
 > >                                        
 > >  >>> conf.L3socket
 > >  <L3bpfSocket: read/write packets using BPF>
 > >  >>> conf.L3socket=L3RawSocket
 > >  >>> conf.L3socket
 > >  <L3RawSocket: Layer 3 using Raw sockets (PF_INET/SOCK_RAW)>
 > >  >>> p=IP(dst="127.0.0.1")/ICMP()/"test"
 > >  >>> p.show2()
 > >  ###[ IP ]### 
 > >    version= 4
 > >    ihl= 5
 > >    tos= 0x0
 > >    len= 32
 > >    id= 1
 > >    flags= 
 > >    frag= 0
 > >    ttl= 64
 > >    proto= icmp
 > >    chksum= 0x7cda
 > >    src= 127.0.0.1
 > >    dst= 127.0.0.1
 > >    \options\
 > >  ###[ ICMP ]### 
 > >       type= echo-request
 > >       code= 0
 > >       chksum= 0x1026
 > >       id= 0x0
 > >       seq= 0x0
 > >  ###[ Raw ]### 
 > >          load= 'test'
 > >  
 > >  >>> send(p)
 > >  Traceback (most recent call last):
 > >    File "<console>", line 1, in <module>
 > >    File "/usr/pkg/lib/python3.7/site-packages/scapy/sendrecv.py",
 > > line 316, in send
 > >      socket = socket or conf.L3socket(*args, **kargs)
 > >    File "/usr/pkg/lib/python3.7/site-packages/scapy/supersocket.py", 
 > > line 150, in __init__
 > >      self.ins = socket.socket(socket.AF_PACKET, socket.SOCK_RAW,
 > > socket.htons(type))  # noqa: E501
 > >  AttributeError: module 'socket' has no attribute 'AF_PACKET'
 > >  
 > >  >  Separately...
 > >  >  
 > >  >  >I'd like to clarify the environment of the bug:
 > >  >  >(1) I have no active Ethernet or SLIP interfaces;
 > >  >  >(2) I have active Wi-Fi and tun interfaces.
 > >  >  >
 > >  >  >According to the "man 4 bpf": "A packet can be sent out on the network
 > >  >  >by writing to a bpf file descriptor. The writes are unbuffered, meaning
 > >  >  >only one packet can be processed per write. Currently, only writes to
 > >  >  >Ethernets and SLIP links are supported."
 > >  >  
 > >  >  I think there may be a documentation issue or two there. That last
 > >  >  statement is perhaps outdated (I haven't checked in detail), and refers
 > >  >  to writes to a link layer which Wi-Fi devices also use. (Note your
 > >  >  tcpdump output states your iwi0 device's "link-type" is "Ethernet".)
 > >  >  
 > >  >  From looking at Scapy commits, it seems NetBSD 8 was the release they
 > >  >  developed against. So generally we should expect at minimum it's more
 > >  >  likely to work on 8.x than newer releases.
 > >  >  
 > >  >  I don't use Scapy much; I was using bits of it before for specific
 > >  >  purposes, but not most of its functionality, so issues with it haven't
 > >  >  been a priority for me to chase. I think in this case some of this
 > >  >  issue is better directed to the Scapy project. (I will look into the
 > >  >  bpf documentation aspect.)
 > >  >  
 > >  >  Dave
 > >  
 > >  OK. I'll write to the Scapy project.
 
 Once submitted, please add the Scapy issue number to this PR. We'll keep
 this open, as it may require something from our end. (Separate from any
 NetBSD documentation that needs to be adjusted still.)
 
 Dave