portforwarding.md

Port Forwarding in Yosemite

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####1. anchor file Create an anchor file under /etc/pf.anchors/<anchor file> with your redirection rule like:

rdr pass on lo0 inet proto tcp from any to 127.0.0.2 port 80 -> 127.0.0.1 port 40070

####2. Test the anchor file Parse and test your anchor file to make sure there are no errors:

sudo pfctl -vnf <anchor file>

####3. Reference the anchor in pf.conf /etc/pf.conf is the main configuration file that pf loads at boot. We'll need to load the anchor file we previously created:

rdr-anchor "forwarding"
load anchor "forwarding" from "/etc/pf.anchors/<anchor file>"

Make sure to add these entries to the appropriate spot.

scrub-anchor "com.apple/*"
nat-anchor "com.apple/*"
rdr-anchor "com.apple/*"
rdr-anchor "forwarding"
dummynet-anchor "com.apple/*"
anchor "com.apple/*"
load anchor "com.apple" from "/etc/pf.anchors/com.apple"
load anchor "forwarding" from "/etc/pf.anchors/<anchor file>"

####4. Load and enabling pf pf is not enabled by default in Mavericks, few ways to enable this:

• Manually load and enable from a pf.conf file via sudo pfctl -ef /etc/pf.conf

• Auto enable by creating a launch daemon via this doc to run pfctl -ef /etc/pf.conf on boot.

• Auto enable by adding an -e(enable) to the pfctl ProgramArgument in /System/Library/LaunchDaemons/com.apple.pfctl.plist like this:

<key>ProgramArguments</key>
<array>
<string>pfctl</string>
<string>-e</string>
<string>-f</string>
<string>/etc/pf.conf</string>
</array>

To manually disable:

• sudo pfctl -df /etc/pf.conf

####5. Forwarding across interfaces By default, pf does not forward between interfaces. Here's a snippet from man for pfctl with help from 2sidedfigure:

The packet filter does not itself forward packets between interfaces.  Forwarding can be enabled by setting the sysctl(8) variables net.inet.ip.forwarding and/or net.inet6.ip6.forwarding to 1.  Set them permanently in sysctl.conf(5).

We'll need to enable this by adding to /etc/sysctl.conf:

net.inet.ip.forwarding=1
net.inet6.ip6.forwarding=1

Caution

There is the possibility that pf.conf will be overriden with updates to the OS. It might be best to create your own pf config file and load them in additon to the main pf.conf to prevent this.