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Port forwarding in Mavericks

Port Forwarding in Mavericks


Since Mavericks stopped using the deprecated ipfw (as of Mountain Lion), we'll be using pf to allow port forwarding.

####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.

####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 <pf.conf file>

  • Auto enable by creating a launch daemon via this doc to run pfctl -ef <pf.conf file> 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>

####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.

@sergeyzwezdin
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sergeyzwezdin commented May 1, 2019

@ctgreybeard @dandriana @snimavat the same problem for me - worked with local IP, but unable to route to external IP. Have you managed to solve the problem guys?

@jbis9051
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jbis9051 commented Jun 24, 2019

@sergeyzwezdin any progress?

@sergeyzwezdin
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sergeyzwezdin commented Jun 25, 2019

@jbis9051
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jbis9051 commented Jun 25, 2019

@sergeyzwezdin Ok. Thanks. I will use that as a last resort, still going to look for a pf solution.

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