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Jeroen W. Pluimers on .NET, C#, Delphi, databases, and personal interests

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Archive for the ‘*nix’ Category

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Listing information on all active interfaces on MacOS part 1: getting the active interface names

Posted by jpluimers on 2021/07/29

Listing Listing information on all active interfaces on MacOS is a process involving multiple pieces, which then can be combined together.

Listing all active interfaces try 1

This involves both the -l (list with optional criteria) and -u parameter (the up criterion) as per excerpts from the [Archive.is] ifconfig(8) [osx man page] / [WayBack] ifconfig Man Page – macOS – SS64.com:

NAME
     ifconfig -- configure network interface parameters

SYNOPSIS
     ...
     ifconfig -l [-d] [-u] [address_family]
     ...

DESCRIPTION
     The ifconfig utility is used to assign an address to a network interface and/or configure network interface parameters.

     The following options are available:

     ...

     address_family
             Specify the address family which affects interpretation of the remaining parameters.  Since an interface can receive transmissions
             in differing protocols with different naming schemes, specifying the address family is recommended.  The address or protocol fami-
             lies currently supported are ``inet'', ``inet6'', and ``link''.  The default is ``inet''.  ``ether'' and ``lladdr'' are synonyms
             for ``link''.

     ...

     The -l flag may be used to list all available interfaces on the system, with no other additional information.  Use of this flag is mutually
     exclusive with all other flags and commands, except for -d (only list interfaces that are down) and -u (only list interfaces that are up).

Example:

ifconfig -l -u

Each interface on one line:

ifconfig -l -u | xargs -n1 echo

The problem is that on my system, it also lists bridges as active, whereas they are not:

# ifconfig -l -u | xargs -n1 echo
lo0
en1
en2
en0
p2p0
awdl0
bridge0
utun0
en10

# ifconfig bridge0
bridge0: flags=8863<UP,BROADCAST,SMART,RUNNING,SIMPLEX,MULTICAST> mtu 1500
    options=63<RXCSUM,TXCSUM,TSO4,TSO6>
    ether 6a:00:02:9a:23:f0 
    Configuration:
        id 0:0:0:0:0:0 priority 0 hellotime 0 fwddelay 0
        maxage 0 holdcnt 0 proto stp maxaddr 100 timeout 1200
        root id 0:0:0:0:0:0 priority 0 ifcost 0 port 0
        ipfilter disabled flags 0x2
    member: en1 flags=3<LEARNING,DISCOVER>
            ifmaxaddr 0 port 5 priority 0 path cost 0
    member: en2 flags=3<LEARNING,DISCOVER>
            ifmaxaddr 0 port 6 priority 0 path cost 0
    Address cache:
    nd6 options=201<PERFORMNUD,DAD>
    media: 
    status: inactive

So this is where the MacOS and BSD documentation is inaccurate.

Interface types

The above interfaces are many more than just ethernet or WiFi interfaces; there is a list at [WayBack] macos – What are en0, en1, p2p, and so on, that are displayed after executing ifconfig? – Stack Overflow by [WayBack] mcint:

In arbitrary order of my familarity / widespread relevance:

lo0 is loopback.

en0 at one point “ethernet”, now is WiFi (and I have no idea what extra en1 or en2 are used for).

fw0 is the FireWire network interface.

stf0 is an IPv6 to IPv4 tunnel interface to support the transition from IPv4 to the IPv6 standard.

gif0 is a more generic tunneling interface [46]-to-[46].

awdl0 is Apple Wireless Direct Link

p2p0 is related to AWDL features. Either as an old version, or virtual interface with different semantics than awdl.

…

many VPNs will add additional devices, often “utun#” or “utap#” following TUN/TAP (L3/L2)virtual networking devices.

More on AWDL at [WayBack] ios – What is AWDL (Apple Wireless Direct Link) and how does it work? – Stack Overflow.

Listing all active interfaces try 2

Read the rest of this entry »

Posted in *nix, *nix-tools, Apple, bash, Development, ifconfig, Mac OS X / OS X / MacOS, Power User, Scripting, Software Development | Leave a Comment »

-r argument to pipe (no argument for MacOS)- If no input is given to xargs, don’t let xargs run the utility – Unix & Linux Stack Exchange

Posted by jpluimers on 2021/07/28

TL;DR

There is a non-standard -r option to xargs that allows it to skip executing when there are no arguments at all.

On some operating systems, the -r is default.

MacOS has no -r, but does not execute xargs if there are no arguments given.

Read the rest of this entry »

Posted in *nix, *nix-tools, bash, bash, Development, Power User, Scripting, Software Development, xargs | Leave a Comment »

Listing information on all active interfaces on MacOS part 2: adding DHCP/BOOTP and routing details

Posted by jpluimers on 2021/07/27

This is a continuation of yesterdays

Listing information on all active interfaces on MacOS part 1: getting the active interface names.

It is based on ideas in these StackExchange posts:

I threw most of the implementation details in the ideas away, as they were way to much based on empirical trial and error, than proper research.

So I tried doing the research and came up with the things below.

Getting the IPv4 address and DHCP/BOOTP information of a NIC

By using the ipconfig command, you can get specific details for a NIC like an IPv4 (with the getifaddr) or DHCP (with the getpacket option to get the latest DHCP packet):

for i in $(ifconfig -l -u); do if ifconfig $i | grep -q "status: active" ; then echo $i; fi; done | xargs -n1 -I_nic_ sh -c 'echo "_nic_: $(ipconfig getifaddr _nic_)"'

or DHCP/BOOTP:

for i in $(ifconfig -l -u); do if ifconfig $i | grep -q "status: active" ; then echo $i; fi; done | xargs -n1 -I_nic_ sh -c 'echo "_nic_: $(ipconfig getpacket _nic_)"'

The latter returns a very long list, which I wanted to shorten into a more readable format.

ipconfig syntax

You can find more information in the [Archive.is] ipconfig(8) [osx man page] / [WayBack] ipconfig Man Page – macOS – SS64.com excerpt:

Read the rest of this entry »

Posted in *nix, *nix-tools, Apple, bash, Development, ifconfig, Mac OS X / OS X / MacOS, Power User, Scripting, Software Development | Leave a Comment »

Ken Thompson’s 1980 Unix password got cracked only a while ago: he used much entropy in his password

Posted by jpluimers on 2021/07/22

A few years back, Ken Thompson’s 1980 Unix password got cracked.

It took that long because his password p/q2-q4! had enough entropy by using uncommon characters so the crypt(3) based hash ZghOT0eRm4U9s was hard to crack.

The password was an opening chess move noted in the variety of the descriptive notation. A shorter notation would have been P-Q4, which would require months to crack in that era.

In modern chess notation, it would be 1. d4, moving the Queen’s Pawn from d2 to d4.

References (many interesting messages in the TUHS thread below):

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Posted in *nix, B, C, Development, Power User, Security, Software Development | Leave a Comment »

Filezilla: figuring out the cause of “Connection timed out after 20 seconds of inactivity”

Posted by jpluimers on 2021/07/21

On one of my Raspberry Pi boxes, somehow I could not access files over SFTP (SSH File Transfer Protocol) via FileZilla.

I would consistently get this error:

"Connection timed out after 20 seconds of inactivity"

Figuring the exact cause took a while.

TL;DR: SFTP uses an interactive non-login shell, then interprets the output from that shell. For that kind of shell, ensure few or none scripts run that output text.

These links finally got me to the cause

These helped me solve the cause

This solved my problem

This is what my /etc/bash.bashrc.local looked like:

# /etc/bash.bashrc.local for SUSE Linux
#
# PLEASE DO NOT CHANGE /etc/bash.bashrc There are chances that your changes
# will be lost during system upgrades.  Instead use /etc/bash.bashrc.local
# for bash or /etc/ksh.kshrc.local for ksh or /etc/zsh.zshrc.local for the
# zsh or /etc/ash.ashrc.local for the plain ash bourne shell  for your local
# settings, favourite global aliases, VISUAL and EDITOR variables, etc ...

. /etc/bash.aliases/_load-aliases.sh

#
# End of /etc/bash.bashrc.local
#

This is what it looks like now:

# /etc/bash.bashrc.local for SUSE Linux
#
# PLEASE DO NOT CHANGE /etc/bash.bashrc There are chances that your changes
# will be lost during system upgrades.  Instead use /etc/bash.bashrc.local
# for bash or /etc/ksh.kshrc.local for ksh or /etc/zsh.zshrc.local for the
# zsh or /etc/ash.ashrc.local for the plain ash bourne shell  for your local
# settings, favourite global aliases, VISUAL and EDITOR variables, etc ...

if [ "$SSH_TTY" ]
then
   source /etc/bash.aliases/_load-aliases.sh
fi

#
# End of /etc/bash.bashrc.local
#

–jeroen

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Posted in *nix, Communications Development, Conference Topics, Conferences, Development, Event, Internet protocol suite, Power User, SFTP, Software Development, SSH, TCP | Leave a Comment »

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