Port forwarding in Mavericks

portforwarding.md

Port Forwarding in Mavericks

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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.

Regarding SIP: Do not disable SIP. Instead, do the following for editing the com.apple.pfctl service:

1. sudo launchctl unload -w /System/Library/LaunchDaemon/com.apple.pfctl.plist
2. sudo cp /System/Library/LaunchDaemon/com.apple.pfctl.plist /Library/LaunchDaemon/com.apple.pfctl-override.plist
   (You must give the service a different name due to the directory search order)
3. # Edit /Library/LaunchDaemon/com.apple.pfctl-override.plist to your heart's content
4. # Don't forget to edit the <Label> to match the filename
5. sudo launchctl load -w /Library/LaunchDaemon/com.apple.pfctl-override.plist
6. Profit $$$

I cannot stress this enough: never, ever, ever, ever disable SIP. If you find yourself faced with a situation where you think disabling SIP is the solution: STOP! SIP is there for a very good reason. There is always a better solution. :)

Not working at all, exact same situation with @helderco . My rule is:
rdr pass on {lo0,en0} inet proto tcp from any to 103.211.228.142 port {http,https} -> 127.0.0.1 port 32794

running pfctl -s info gives the result:

State Table                          Total             Rate
  current entries                        0
  searches                             707           23.6/s
  inserts                                0            0.0/s
  removals                               0            0.0/s
Counters
  match                                581           19.4/s
  bad-offset                             0            0.0/s
  fragment                               0            0.0/s
  short                                  0            0.0/s
  normalize                              0            0.0/s
  memory                                 0            0.0/s
  bad-timestamp                          0            0.0/s
  congestion                             0            0.0/s
  ip-option                              0            0.0/s
  proto-cksum                            0            0.0/s
  state-mismatch                         0            0.0/s
  state-insert                           0            0.0/s
  state-limit                            0            0.0/s
  src-limit                              0            0.0/s
  synproxy                               0            0.0/s
  dummynet                               0            0.0/s

only the match counter and searches are increasing. but I receive nothing at localhost port 32794.

Also, I tested what @dandriana said, and it is true, it works only when port forwarding is set to the same machine.

This was the only blog or entry anywhere on the web that worked for me. I'm running Sierra, developing a website that must get to a backend with CORS rules that make testing difficult. (I don't own the CORS filter. I have to somehow conform to it.) I develop in Eclipse, and deploy to Tomcat locally (from within Eclipse). Eclipse fails to start Tomcat on port 80, so I have to start it on 8080, but that won't allow me to get past the CORS filter. So, I had to set up a redirect from 10.0.0.1 port 80 to 127.0.0.1 port 8080, then set up a host in hosts file naming 10.0.0.1 in such a way that my requests pass the filter.

Would be nice to show how to do this temporarily as well. something like:

echo "
rdr pass on lo0 inet proto tcp from any to 127.0.0.2 port 80 -> 127.0.0.1 port 40070
" | sudo pfctl -ef -

not exactly sure what the code would be like. But something like that. it won't persist a restart, but i don't want mine to.

@inoicouldalwaysturn2u - what you have is close to what works for me (on macOS 10.13.4):

echo "rdr pass inet proto tcp from any to any port 80 -> 127.0.0.1 port 8000" | sudo pfctl -ef -

@dlo thank you, this is the best answer on the internet. Works on Sierra.

@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?

@sergeyzwezdin any progress?

@ctgreybeard, @dandriana, @snimavat, and @sergeyzwezdin https://apple.stackexchange.com/questions/363099/how-to-forward-traffic-from-one-machine-to-another-with-pfctl

@jbis9051 I use SSH for this. See my answer on stackexchange - https://apple.stackexchange.com/questions/359102/routing-localhost-traffic-to-external-ip-address

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