Understanding TCP/IP Model Internals and Interfaces

1508 Understanding TCP/IP Model Internals and Interfaces
Coding Changes
Make the Necessary Coding Changes to Handle a Packet from IP
1. Open the function block (Code Blocks / Function Block or button) of the simple_mac
process model.
2. Scroll down to the simple_mac_packet_from_ip_handle function (line 105).
3. Edit the function as follows. (Lines to be added are in bold).
FIN (simple_mac_packet_from_ip_handle (ip_pkptr));
/* Get the ici associated with the interrupt. The */
/* destination address of the packet will be specified */
/* in the ici. */
arp_ici_ptr = op_intrpt_ici ();
/* Get the destination address from the ici. */
op_ici_attr_get_int32 (arp_ici_ptr, "dest_addr", &dest_addr);
/* Print a trace Message */
if (SMC_LTRACE_ACTIVE)
{
sprintf (msg, "Destination Address: %d", dest_addr);
op_prg_odb_print_major ("Received a Packet from IP",
msg, OPC_NIL);
}
/* Create the MAC Packet. */
mac_pkptr = op_pk_create_fmt ("simple_mac");
/* Set the source and dest addresses in the packet */
op_pk_nfd_set_int32 (mac_pkptr, "source address", my_address);
op_pk_nfd_set_int32 (mac_pkptr, "dest address", dest_addr);
/* Encapsulate the IP Datagram in the MAC Packet */
op_pk_nfd_set_pkt (mac_pkptr, "data", ip_pkptr);
/* Send the packet out to the transmitter. */
op_pk_send (mac_pkptr, SMC_OUT_STRM_INDEX_TO_XMT);
FOUT;
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