[v6ops] DHCPv6 PD client on cellular on some IoT platform

[Alexandre Petrescu <[e-mail]>]

Hello,

We discussed extensively about the potential use of DHCPv6 Prefix 
Delegation on cellular links.

The chicken issue is the lack of DHCPv6 PD software on typical User 
Equipment.  For example, there is no DHCPv6-PD app on Android.  The egg 
issue is the lack of operator support of DHCPv6-PD towards the User 
Terminal.  For example, there is no cellular operator answering to 
DHCPv6-PD requests issued by the User Terminal.

To address the chicken issue, we started with an ISC DHCP open software 
client, which does implement Prefix Delegation.  It can be 
(cross)compiled on various platforms; then type "./dhclient -6 -P"; this 
sends an DHCPv6 Solicit Identity Associtaion for Prefix Delegation 
message on the interface.

However, whereas this software runs ok on interfaces such as Ethernet, 
USBnet and WiFi interfaces, it breaks if run on the cellular interface 
of some IoT cellular platform.  The error can be corrected by the 
quick-and-dirty solution below.

Alex

------------------------------------------------------------------------
The error says "//UNSUPPORTED DEVICE TYPE 503 FOR RMNET0."
dhcp-4.3.5
./common/lpf.c
line number: 551

//default:
//      log_fatal("Unsupported device type %ld for \"%s\"",
//                (long int)sa->sa_family, name);
   default:
         hw->hlen = 7;
         hw->hbuf[0] = HTYPE_ETHER;
         memcpy(&hw->hbuf[1], sa->sa_data, 6);
   break;

(two programmers worked this out).

Alex