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: Sun, 05 Jul 2020 18:24:07 -0400

 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". 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
 
 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 statement is perhaps outdated (I haven't checked in detail), and refers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