CC2652P: Source Routing will effect to MTU

Hello,

If source routing is used, then you won't be able to fit a max payload size of 82-bytes, due to intermediate addresses added to the overall packet.
And generally, if the payload is too large for a single APS packet, then Fragmentation should resolve it.

Note that the zstack_afDataReq_t has a way to specify no source routing, which will maximize the application data payload size in a single packet.
See zstack_afDataReq_t --> n_relayList (/** Number of entries in relayList (use 0 for non-source routing) */)

Thanks,
Toby

How to calculate if the source routing would happen when "AF_DataRequestExt" sending message?

I have fixed “afDataReqMTU” like this, but it will trigger Fragment though there is no Source-Routing triggered.

uint8_t afDataReqMTU( afDataReqMTU_t* fields )
{
  uint8_t len;
  uint8_t hdr;

  if ( fields->kvp == TRUE )
  {
    hdr = AF_HDR_KVP_MAX_LEN;
  }
  else
  {
    hdr = AF_HDR_V1_1_MAX_LEN;
  }

  len = (uint8_t)(APSDE_DataReqMTU(&fields->aps) - hdr);

  //match rtg table to recalculate MTU, fixed by luoyiming 2025-01-04
  if(afRtgDstAddress != 0xFFFE)
  {
    rtgSrcEntry_t* rtgSrcEntry = afGetRtgSrcEntry(afRtgDstAddress);
    if(rtgSrcEntry)
    {
      if(rtgSrcEntry->relayCount)
      {
        len -= (2 + rtgSrcEntry->relayCount * sizeof(uint16_t));
      }
    }
    afRtgDstAddress = 0xFFFE;
  }

  return len;
}

I have found that when Source Routing is needed in AF-sending,  the Fragment-sending will be not working.