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    pfSense Rewrites Source IP for ICMP Errors Breaking Traceroute

    Scheduled Pinned Locked Moved General pfSense Questions
    icmptraceroutenat
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    • M
      miki725
      last edited by

      @johnpoz said in pfSense Rewrites Source IP for ICMP Errors Breaking Traceroute:

      What is your outbound nat..

      Im using Automatic outbound NAT rule generation. (IPsec passthrough included):

      900ab6d4-871f-4031-81dd-8d580d053cae-image.png

      Here are my nat rules I see in /tmp/rules.debug:

      # Outbound NAT rules (automatic)
      
      # Subnets to NAT
      table <tonatsubnets> { 192.168.1.10/32 127.0.0.0/8 ::1/128 10.10.10.0/24 10.10.5.0/24 10.10.20.0/24 10.10.30.0/24 10.10.40.0/24 10.10.50.0/24 10.10.60.0/24 10.10.70.0/24 10.10.80.0/24 10.10.90.0/24 10.10.100.0/24 10.10.255.1/24 }
      nat on $WAN inet from <tonatsubnets> to any port 500 -> x.x.x.x/32  static-port
      nat on $WAN inet6 from <tonatsubnets> to any port 500 -> (lagg0.4090)  static-port
      nat on $WAN inet from <tonatsubnets> to any -> x.x.x.x/32 port 1024:65535
      nat on $WAN inet6 from <tonatsubnets> to any -> (lagg0.4090) port 1024:65535
      

      500 port rule I think is coming from IPSec:

      17a74f2f-e0fc-45f2-aa4e-4947532b7f2b-image.png

      Sorry Im new to NAT in general (thats among the reasons I got pfSense since I want to learn networking better). If my understanding is correct NAT should rewrite the source IP on outbound connections, add entry of the flow table, and finally for inbound connections, change the destination IP address so the packet can be redirected to an IP inside LAN. If so I dont fully understand why source IP is rewritten on the inbound connection.

      Also keep in mind that responses from the hops would be ICMP but if you using linux for example the actual data sent doing the trace would be UDP packets.. Or sure you could even send TCP... But default to udp on linux, and windows would be icmp sent, etc..

      Thanks! Looks like in this case traceroute is using UDP with ICMP error responses.

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      • johnpozJ
        johnpoz LAYER 8 Global Moderator
        last edited by

        So yes the nat would send the traffic back into your sender of the traceroute.. So I am just thinking you are confused to how nat works in general... But seeing missing spots in your trace that do not answer is quite normal these days of everyone blocking shit ;)

        Are you doing anything odd on your lan side interface for rules or policy routing?

        I sure an the hell can not duplicate your issue, and can traceroute from any machine on my network just fine using either icmp, udp or even tcp...

        $ tcptraceroute -n www.google.com 443
        Selected device ens3, address 192.168.2.12, port 50519 for outgoing packets
        Tracing the path to www.google.com (172.217.8.196) on TCP port 443 (https), 30 hops max
         1  192.168.2.253  0.493 ms  0.332 ms  0.324 ms
         2  50.4.135.1  11.620 ms  12.213 ms  11.700 ms
         3  76.73.191.106  10.921 ms  12.476 ms  11.911 ms
         4  76.73.164.142  9.586 ms  18.234 ms  12.953 ms
         5  76.73.164.154  20.807 ms  20.399 ms  20.238 ms
         6  76.73.191.242  14.286 ms  11.709 ms  14.869 ms
         7  143.59.95.224  28.425 ms  12.980 ms  13.262 ms
         8  75.76.35.8  11.605 ms  22.702 ms  10.050 ms
         9  72.14.211.145  11.355 ms  31.802 ms  18.859 ms
        10  108.170.243.225  23.928 ms  13.804 ms  14.214 ms
        11  72.14.232.187  12.821 ms  12.967 ms  13.243 ms
        12  172.217.8.196 [open]  21.723 ms  31.557 ms  17.055 ms
        

        An intelligent man is sometimes forced to be drunk to spend time with his fools
        If you get confused: Listen to the Music Play
        Please don't Chat/PM me for help, unless mod related
        SG-4860 24.11 | Lab VMs 2.8, 24.11

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        • M
          miki725
          last edited by

          Didnt do anything crazy as far as I know:

          fd42625e-ec02-4575-b93d-e0c225c71fee-image.png

          Ill keep digging on my end. Thanks for your help.

          A 1 Reply Last reply Reply Quote 0
          • A
            Alex Atkin UK @miki725
            last edited by

            @miki725 Is it the same problem documented here? https://redmine.pfsense.org/issues/9263

            M 1 Reply Last reply Reply Quote 1
            • GertjanG
              Gertjan
              last edited by

              You're using traffic (ICMP) shaping ?

              No "help me" PM's please. Use the forum, the community will thank you.
              Edit : and where are the logs ??

              1 Reply Last reply Reply Quote 0
              • johnpozJ
                johnpoz LAYER 8 Global Moderator
                last edited by

                Sure looks like that is his problem... @Alex-Atkin-UK

                An intelligent man is sometimes forced to be drunk to spend time with his fools
                If you get confused: Listen to the Music Play
                Please don't Chat/PM me for help, unless mod related
                SG-4860 24.11 | Lab VMs 2.8, 24.11

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                • M
                  miki725 @Alex Atkin UK
                  last edited by

                  @Alex-Atkin-UK

                  ooooh. I forgot about the limiter:

                  d8918570-58cb-43e5-a943-7dfd6d5a99ca-image.png

                  can confirm that when I disabled floating rule with the queue, traceroute works as expected inside LAN.

                  Thank a lot for linking to that. Now would be curious why a limiter would have that affect.

                  1 Reply Last reply Reply Quote 0
                  • johnpozJ
                    johnpoz LAYER 8 Global Moderator
                    last edited by johnpoz

                    @miki725 said in pfSense Rewrites Source IP for ICMP Errors Breaking Traceroute:

                    Now would be curious why a limiter would have that affect.

                    It shouldn't - therefore the bug report ;)

                    You should of brought up the limiter, when asked doing anything odd on lan side rules (floating would be considered lan side) hehehe.. I will make sure to always mention floating rules going forward..

                    An intelligent man is sometimes forced to be drunk to spend time with his fools
                    If you get confused: Listen to the Music Play
                    Please don't Chat/PM me for help, unless mod related
                    SG-4860 24.11 | Lab VMs 2.8, 24.11

                    M 1 Reply Last reply Reply Quote 0
                    • M
                      miki725 @johnpoz
                      last edited by

                      @johnpoz said in pfSense Rewrites Source IP for ICMP Errors Breaking Traceroute:

                      You should of brought up the limiter, when asked doing anything odd on lan side rules (floating would be considered lan side) hehehe.. I will make sure to always mention floating rules going forward..

                      My apologies. Forgot about them. Makes perfect sense that they are as legitimate LAN side rule as any other.

                      Thanks everyone for helping even with limited provided information. Really appreciate everyones time and effort. Stay safe!

                      A 1 Reply Last reply Reply Quote 0
                      • A
                        Alex Atkin UK @miki725
                        last edited by Alex Atkin UK

                        @miki725 I remembered it as I had the same problem.

                        As I recall you have to add a Pass floating rule for the WAN interface at the top of the list for echo reply/requests with Quick ticked, so it bypasses the limiter rule.

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                        • GertjanG
                          Gertjan
                          last edited by Gertjan

                          @Alex-Atkin-UK : Thanks.

                          That were those for :

                          1b20b041-6cb8-43d4-8451-16f015d4f5a0-image.png

                          ( bottom two rules )

                          No "help me" PM's please. Use the forum, the community will thank you.
                          Edit : and where are the logs ??

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                          • M
                            miki725
                            last edited by

                            Thanks for the suggestion. Didnt even think of bypassing it.

                            Where is a standard place to add limiter rules? Mine is currently is a floating rule. Even with the ICMP bypass rule with Quick above it, traceroute is still impacted:

                            e1a36188-e928-4cd2-8906-4b18b6976bc2-image.png

                            I tried removing the Quick from the limiter rule but that does not seem to help. Only thing which helps is disabling the limiter altogether. Im probably not doing something correctly if this works for you.

                            1 Reply Last reply Reply Quote 1
                            • GertjanG
                              Gertjan
                              last edited by

                              Like me, you added floating rules to do something about buffer bloat.

                              These are all my floating rules :

                              bf4bc721-c6d5-485e-9c04-57ccd1ca8c31-image.png

                              You're missing one IPv4 rule : the "direction : IN" rule.
                              You have the "Out" rule, the one with the gateway (WAN_DHCP).

                              I also use IPv6 - so that adds 3 more rules.

                              No "help me" PM's please. Use the forum, the community will thank you.
                              Edit : and where are the logs ??

                              1 Reply Last reply Reply Quote 0
                              • B
                                bobbenheim
                                last edited by

                                In your ICMP rule setting direction: out, interface: WAN and change default to your actual gateway in advanced > Gateway
                                should do the job.

                                1 Reply Last reply Reply Quote 0
                                • J
                                  jamesonp
                                  last edited by

                                  This got me today. I can confirm the floating rule for ICMP solves the issue.

                                  1 Reply Last reply Reply Quote 0
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