Packet forwarder, filtering incoming packages on netid

dlfr · June 15, 2022, 10:28am

Hi, I have been running a TTN package forwarder for several years now and notice most of the traffic received is intended for another network. However, it still gets forwarded to the TTN routers which I think is a waste of the project’s resources.

Is there a way to filter and only forward traffic bound for the TTN netid 000013?
And would this be acceptable practice?

My node runs Basicstation. I notice there is a variable that suggests support for a netid filter in the source code, but the docs don’t descrive how to configure that setting through parameters or config file.

github.com

lorabasics/basicstation/blob/master/src/lora.c#L83

      
        
            // | mhdr| devaddr |fctrl|  fcnt | fopts | port | payload | MIC |
            // +-----+---------+-----+-------+-------+------+---------+-----+
            #define OFF_devaddr     1
            #define OFF_fctrl       5
            #define OFF_fcnt        6
            #define OFF_fopts       8
            #define OFF_df_minlen  12
            
            

            
uL_t* s2e_joineuiFilter;
            u4_t  s2e_netidFilter[4] = { 0xffFFffFF, 0xffFFffFF, 0xffFFffFF, 0xffFFffFF };
            
            

            
int s2e_parse_lora_frame (ujbuf_t* buf, const u1_t* frame , int len, dbuf_t* lbuf) {
                if( len == 0 ) {
                badframe:
                    LOG(MOD_S2E|DEBUG, "Not a LoRaWAN frame: %16.4H", len, frame);
                    return 0;
                }
                int ftype = frame[OFF_mhdr] & MHDR_FTYPE;
                if( (len < OFF_df_minlen && ftype != FRMTYPE_PROP) ||

Jeff-UK · June 15, 2022, 10:33am

Sorry but you have no way of knowing that - you dont know if the other network has a roaming agreement in place nor will you know if packets are perhaps then handed off to PacketBroker for onward processing or for use on a private instance of TTS under alternate NetID. Even if no arrangements in place today you cant know how might change tomorrow or next week or next year… filter and you break things.

Bottom line is do not attempt to filter at the GW (essentially per TTN Manifesto and useage policy), and per guidance previously issued on TTN Forum discussions (search)…

dlfr · June 15, 2022, 12:28pm

Thank you for the extensive answer. Didn’t consider roaming agreements.
In that case I won’t mess around with a custom build of BasicStation.

My apologies for asking a previously asked and answered question. I did do a forum search, but it did not return related results. My search must have been too focused on BasicStation.

system · June 16, 2022, 12:28pm

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