rp_filter

[Mike A. Harris]

If one enables rp_filter with:

echo 1 > /proc/sys/net/ipv4/conf/all/rp_filter

... does it enable SAV on ALL interfaces past, present and
future, or just the ones that are up?

What document describes the conf/ dirs/files in detail?  I've
looked at various files in Documentation which do help, however
I'm still left puzzled.

In several scripts people have sent me there is code like the
following:

    if [ -e $PROCNET/conf/all/rp_filter ]; then
        echo -n "Enabling kernel level source address verification "
        echo -n "IP spoofing protection: "
        for f in $PROCNET/conf/*/rp_filter
        do
            echo 1 > $f
        done
        echo "done."
    else
        echo "WARNING: SAV IP spoofing could not be enabled."
        echo "Manual rule based IP spoofing not implemented yet."
    fi

When I read the above, the for loop seems redundant to me.  Why
echo 1 to every dir's rp_filter?  Is that not what the "all"
directory is for?

Are the following two equivalent?

1)	for f in /proc/sys/net/ipv4/conf/*/rp_filter
	do
		echo 1 > $f
	done

2)	echo 1 > /proc/sys/net/ipv4/conf/all/rp_filter

What is the "default" one for?

Please feel free to point me to the exact document that
accurately and unambiguously describes all of this.

I really appreciate it, thanks.
TTYL

--
Mike A. Harris                                     Linux advocate     
Computer Consultant                                  GNU advocate  
Capslock Consulting                          Open Source advocate

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