FreeBSD as multicast router

[Victor Gamov]

On 06/11/2019 05:41, Mike Karels wrote:
>> On 05/11/2019 09:09, Mike Karels wrote:
>>>> On 03/11/2019 08:22, Mike Karels wrote:
>>>>>>>>> Hi All
>>>>>>>>>
>>>>>>>>> I have (noob) questions about multicast routing under FreeBSD.
>>>>>>>>>
>>>>>>>>> I have FreeBSD box with two (or more) multicast enabled interfaces (e.x.
>>>>>>>>> vlan750 and vlan299).  vlan750 connected to multicast source.
>>>>>>>>>
>>>>>>>>> Then pimd installed and only this two interfaces enabled in pimd config.
>>>>>>>>> Multicast routes successfully installed by pimd and listed by `netstat
>>>>>>>>> -g -f inet`
>>>>>>>>>
>>>>>>>>> Then client on vlan299 send IGMP-Join (this Join received by FreeBSD on
>>>>>>>>> vlan299)
>>>>>>>>>
>>>>>>>>> The question is:  who will forward muilticast from one interface
>>>>>>>>> (vlan750) to another (vlan299)?  Is it kernel specific job or I need
>>>>>>>>> additional software?
>>>>>>>
>>>>>>>> Please read the manpage multicast(4) "man 4 multicast",
>>>>>>>> you should need to build a custom kernel with the "options MROUTING"
>>>>>>>> to enable the multicast forwarding in the kernel.
>>>>>>>
>>>>>>> If "netstat -g" shows routes, the kernel must have been built with "options
>>>>>>> MROUTING".
>>>>>
>>>>>> Indeed.
>>>>>
>>>>>>>
>>>>>>> The kernel does the forwarding, according to those routing tables installed
>>>>>>> by pimd or another multicast routing program.  Is it not working?  It sounds
>>>>>>> like you are very close.
>>>>>
>>>>>> Could it be sysctl net.inet.ip.forwarding?  Does that still apply to mroutes?
>>>>>
>>>>> No, they are separate.  The test is just whether MROUTING is enabled, and
>>>>> whether a multicast router like pimd is active.
>>>>>
>>>>> One other thing to check would be "netstat -gs" (multicast stats).
>>>
>>>> Oops!
>>>
>>>> =====
>>>> # netstat -f inet -gs
>>>> No IPv4 MROUTING kernel support.
>>>> =====
>>>
>>> This looks like a bug in netstat; it is doing a test that is wrong for
>>> the loadable module.
> 
> I don't know how much the stats might help, but if you let me know what
> version you are running, I can build a fixed netstat.  Or I can send
> a source patch.
> 
>>>> But I have ip_mroute.ko loaded and netstat -g shows something like
>>>
>>>> =====
>>>> # netstat -f inet -g
>>>
>>>> IPv4 Virtual Interface Table
>>>>     Vif   Thresh   Local-Address   Remote-Address    Pkts-In   Pkts-Out
>>>>      0         1   A.A.A.A                           0          0
>>>>      1         1   B.B.B.19                          0          0
>>>>      2        10   10.199.199.102                          0          0
>>>>      3        15   10.200.200.6                        77440          0
>>>>      4         1   A.A.A.A                           0      77440
>>>
>>>> IPv4 Multicast Forwarding Table
>>>>     Origin          Group             Packets In-Vif  Out-Vifs:Ttls
>>>>     10.200.200.5    232.232.8.33        1844    3    4:1
>>>>     10.200.200.5    232.232.8.171        1843    3    4:1
>>>>     10.200.200.5    232.232.8.58         4609    3    4:1
>>>>     10.200.200.5    232.232.8.154        1844    3    4:1
>>>>     10.200.200.5    232.232.8.170        1844    3    4:1
> 
> I missed this before.  Looks like the last column should include 2:1 in
> each case if pimd saw the join.  The multicasts are only being sent to
> Vif 4, the register-vif (see below); the Pkts-Out for it is the same
> as the input on 3.  I'm not familiar enough with pimd to guess what is
> wrong.


I still have misunderstood here.  Pimd installs multicast routes and 
this routes displayed by `netstat -g`.  So, the system knows interface 
where multicast received.  When Join received  via interface 2 (vlan299) 
who must resend multicast from input interface 3 (vlan750) to output 
interface 2 (vlan299)?  I guess it kernel-specific task  and kernel must 
resend multicast without any other helpers.  Is it wrong?


P.S. I rebuild kernel with MROUTING option but
=====
# netstat -gs -f inet
No IPv4 MROUTING kernel support
=====

still here

-- 
CU,
Victor Gamov