Suppose you've configured IPv6 proxy NDP on one of your Linux systems like so:
ip -6 neighbor add proxy 2001:db8:1234::5 dev eth1
How do you verify that the configuration took? ip -6 neighbor show doesn't appear to show proxy entries and ip -6 neighbor show proxy isn't a supported command.
What are some of the most common and wrong ways to configure a firewall? I'll start the list with the following:
Blindly blocking ICMP. This was common practice in 1998 when smurf attacks were all the rage. Today you run the risk of creating a PMTU black hole and making it hard to diagnose problems. If you must block ICMP, at least allow fragmentation needed and echo request/replies through.
Stale Rules. It's too bad we can't set an expiration date on rules. When I migrate a service I often forget to remove the rules for the old service.
We would like to save the output of a program run on a Linux console which spans many lines. Unfortunately it wasn't logged or run under screen, or any other way that lets us easily capture the output. The best method we've been able to come up with so far is:
Log into the machine via a separate SSH session
In the console session, page to the top of the buffer
Repeat:
In the SSH session, run "cat /dev/vcs >> screendump.txt"
In the console session, page down one screen
Dump the final screen in the SSH session
Is there a better way? It seems like if the VC memory were contiguous and you knew where it was you could use dd to pull the console text directly out of kernel memory and into a file.
I would like to add an "X-Slogan" header to Apache's responses set to a value chosen at random from a list of strings. The best solution I've been able to come up with so far is to rotate through the strings based on TIME_SEC, e.g.
UnsetEnv HEAD_X_SLOGAN_1
UnsetEnv HEAD_X_SLOGAN_2
UnsetEnv HEAD_X_SLOGAN_3
UnsetEnv HEAD_X_SLOGAN_4
RewriteCond %{TIME_SEC} <15
RewriteRule . - [env=HEAD_X_SLOGAN_1:%{TIME_SEC},last]
RewriteCond %{TIME_SEC} >14
RewriteCond %{TIME_SEC} <30
RewriteRule . - [env=HEAD_X_SLOGAN_2:%{TIME_SEC},last]
RewriteCond %{TIME_SEC} >29
RewriteCond %{TIME_SEC} <45
RewriteRule . - [env=HEAD_X_SLOGAN_3:%{TIME_SEC},last]
RewriteCond %{TIME_SEC} >44
RewriteRule . - [env=HEAD_X_SLOGAN_4:%{TIME_SEC},last]
Header set X-Slogan "Palm trees" env=HEAD_X_SLOGAN_1
Header set X-Slogan "Oranges" env=HEAD_X_SLOGAN_2
Header set X-Slogan "Shoes" env=HEAD_X_SLOGAN_3
Header set X-Slogan "Velociraptors" env=HEAD_X_SLOGAN_4
However, this isn't really random. Is there a better way to do this?