前面已经描述了ethcoax_station_adv节点模型的基本结构，其中burstry_gen模块产生无格式包，发送给eth_mac_intf模块处理，本文分析其处理过程。
首先注意该模块上的包流：
stream : eth_mac_intf [0] -> sink [1]
stream : eth_mac_intf [1] -> mac [1]
stream : bursty_gen [0] -> eth_mac_intf [1]
stream : mac [1] -> eth_mac_intf [0]
该模块的进程模型为ethernet_mac_interface，状态机如下：
该模块没有local/global statistic，但是有两个attribute，分别为high dest address和low dest address，表示dest address的最大值和最小值。状态机中只有两个强制状态，其它为非强制状态。
一，init状态的入口代码：
/* This function initializes its state variables and registers itself in the process registry */
eth_mac_higher_layer_intf_init (); //调用该函数初始化，包括初始化状态变量 和注册进程
/* Set up an interface control information (ICI) structure to */
/* communicate parameters to the MAC layer process. We will */
/* leave this ICI installed for the entire simulation. */
intf_mac_req_iciptr = op_ici_create ("mac_request"); //创建一个ICI结构体，以便与MAC层通信，注意返回值类型为Ici*，而"mac_request"是预定义好的结构体（在哪里定义？？？）（syntax:op_ici_create(fmt_name);）
op_ici_install (intf_mac_req_iciptr); //绑定？？？？，这个ICI被自动绑定到被唤醒进程向外发送的中断，注意ICI指针可以由op_ici_create()和op_intrpt_ici()返回，其中前者返回一个新创建的ICI（在ICI发送进程），后者返回一个与即将到来的中断关联的ICI（在ICI接收进程）。
/* Schedules a self interrrupt */
op_intrpt_schedule_self (op_sim_time (), 0); //自中断，时间为当前时间
二，分析该模块的初始化函数eth_mac_higher_layer_intf_init ()：
static void eth_mac_higher_layer_intf_init ()
{
/** Initializes the state variables for this process model and registers itself in the model-wide reigtry */
FIN (eth_mac_higher_layer_intf_init ());
/* Gets its own id */
my_id = op_id_self (); //获得自己模块的objid。
/* Gets the object id of the node to which this module belongs */
own_node_objid = op_topo_parent (my_id); //获得自己模块所在节点的objid。
/* Gets the objid of its subnet */
subnet_objid = op_topo_parent (own_node_objid); //获得自己模块所在节点的子网的objid。
/* Gets a handle to its process */
own_prohandle = op_pro_self (); //获得当前运行进程的句柄，有何用处？？？（可以获取进程模型的各种属性）
/* Gets the name of its process model */
op_ima_obj_attr_get (my_id, "process model", proc_model_name); //通过objid获得当前进程模型的process model属性，送到proc_model_name，注意proc_model_name是char[20]。
/* Gets a process record handle to record its process in the registry */
//在model registry(进程登记库)中注册进程，并返回handle，注意model registry是进程注册的一个表，通过返回的handle操作，可以注册、查询、设置等。
//model registry的目的是在各层协议模块间共享数据，具体见《大解密》P286，
//进程登记库的目的是：（1）为仿真中所有进程提供全局的信息注册机制，（2）允许进程在节点内共享信息，进程可以设置多种类型的属性（3）进程注册后，可以用多种查询参数找到并访问其公开信息。相关文件为oms_pr.h和oms_pr.ex.c
own_process_record_handle = (OmsT_Pr_Handle) oms_pr_process_register (own_node_objid, my_id,
own_prohandle, proc_model_name); //注意返回值类型是OmsT_Pr_Handle
/* Sets the required attributes in the process registry */
//利用返回的handle，设置进程在process registry的属性
oms_pr_attr_set (own_process_record_handle, "location", OMSC_PR_STRING, "mac_if",
"subnet", OMSC_PR_OBJID, subnet_objid, OPC_NIL); //syntax：oms_pr_attr_set(pr_handle,attr0_name,attr0_type,attr0_value,……,OPC_NIL);，最后一个常量表示结束。登记了两个属性，分别为location 和subnet
/* Stream numbers to the mac layer and from the mac layer which */
/* which will be set in the exit execs of the wait state */
//进出的stream index，这两个量会在wait状态的出口代码中被赋值，这里被设置为无效值。
outstrm_to_mac = OPC_INT_UNDEF;
instrm_from_mac = OPC_INT_UNDEF;
FOUT;
}
三，init2状态的入口代码：
/* Schedule a self interrupt to wait for lower layer Ethernet MAC process*/
/* to initialize and register itself in the model-wide process registry. */
op_intrpt_schedule_self (op_sim_time (), 0); //自中断，时间为当前时间，目的是等待底层的MAC进程初始化并注册，目的是用于一些系统的初始化配置，比如你的网络开始运行之前，你需要为每一个节点分配适当的地址，并且你必须保证每一个节点配置了初始节点网络才能够开始运行。这就是用两个unforced init模块模块的原因。
四，wait状态的入口代码：同上。
出口代码：（要从节点内的进程登记库中提取MAC的流信息，所以必须等待所有底层的进程完成初始化才开始）
/* Obtain the MAC layer information for the local MAC process from the model-wide registry. */
proc_record_handle_list_ptr = op_prg_list_create (); //功能是分配一个新的空表
oms_pr_process_discover (my_id, proc_record_handle_list_ptr, "node objid", OMSC_PR_OBJID, own_node_objid,
"protocol", OMSC_PR_STRING, "mac",OPC_NIL); //在进程登记库中发现符合条件的进程，这里是本节点内部的协议为“mac”的进程，（syntax：oms_pr_process_discover(neighber_objid,pr_handle_lptr, attr0_name, attr0_type, attr0_value,...., OPC_NIL)）
/* If the MAC process registered itself, then there must be a valid match*/
record_handle_list_size = op_prg_list_size (proc_record_handle_list_ptr); //判断是否是正好一个match的进程
if (record_handle_list_size != 1)
{
/* An error should be created if there are more than one Ethernet-MAC process in the local node, or if no match is found. */
op_sim_end ("Error: either zero or several Ethernet MAC processes found in the interface", "", "", ""); //多于一个，出错了
}
else
{
/* Obtain a handle on the process record. */ //正确，只有一个，通过在进程登记库中的位置，获得MAC进程的handle，并送到process_record_handle
process_record_handle = (OmsT_Pr_Handle) op_prg_list_access (proc_record_handle_list_ptr, OPC_LISTPOS_HEAD);
/* Obtain the module objid for the Ethernet MAC module. */ //获得MAC模块的objid并记录到变量mac_module_objid中，注意mac模块应登记了objid
oms_pr_attr_get (process_record_handle, "module objid", OMSC_PR_OBJID, &mac_module_objid);
//pr就是process record
/* Obtain the address handle maintained by the MAC process. */ //获得MAC模块的属性，包括mac地址和auto address handle？？？
oms_pr_attr_get (process_record_handle, "address", OMSC_PR_INT64, &ne_address);
oms_pr_attr_get (process_record_handle, "auto address handle", OMSC_PR_POINTER, &oms_aa_handle);
/* Set the variable to indicate the MAC address of the associated MAC layer process.*/
mac_address = ne_address; //得到mac地址
/* Obtain the stream numbers connected to and from the Ethernet MAC layer process. */
//获得MAC模块连接的stream index，并送到instrm_from_mac和outstrm_to_mac。
oms_tan_neighbor_streams_find (my_id, mac_module_objid, &instrm_from_mac, &outstrm_to_mac);
}
//---------------------------------------------------------------------------下面是获取目的地址，可以是设定或随机选择的
if (oms_aa_handle == OPC_NIL)
{
/* This is a unconnected node. Do nothing */
}
else
{
/* Determine address range for destination assignment. */
if ((op_ima_obj_attr_get (my_id, "low dest address", &low_dest_addr) == OPC_COMPCODE_FAILURE) || //从属性中获取地址范围
(op_ima_obj_attr_get (my_id, "high dest address", &high_dest_addr) == OPC_COMPCODE_FAILURE))
{
eth_mac_higher_layer_intf_error ("Unable to read destination address range.", OPC_NIL, OPC_NIL);
}
/* If any single address is specified as broadcast, indicate this as an error */
/* Both the low and high destination addresses together can be specified as broadcast */ //注意-1是广播地址？？？
if (((low_dest_addr == -1) && (high_dest_addr != -1)) ||
((high_dest_addr == -1) && (low_dest_addr != -1)))
{
eth_mac_higher_layer_intf_error ("Both the Lowest and Highest Destination addresses must be specified as Broadcast", "Any one attribute cannot be Broadcast", OPC_NIL);
}
/* Check whether highest destination address is not lower than the lowest destination */
/* address (also check it is not a broadcast address or MAX_DEST_ADDR). */
if ((high_dest_addr < low_dest_addr) && (high_dest_addr >= 0))
{
eth_mac_higher_layer_intf_warn ("Specified lowest destination address is greater than specified highest destination address.",
"Setting the lowest destination address to Minimum Dest Address, and the highest to Maximum Dest Address.", OPC_NIL);
/* If so, then set the lowest destination address to the minimum destination address */
/* and the highest destination address to the highest destination address. */
low_dest_addr = MIN_DEST_ADDR;
high_dest_addr = MAX_DEST_ADDR;
}
/* Determine our destination or destination range. Start by initializing the range indices, which are used if a range is specified. */
//确定目的地址的range
low_dest_index = OMSC_AA_UNINIT_ADDR;
high_dest_index = OMSC_AA_UNINIT_ADDR;
if ((low_dest_addr == MIN_DEST_ADDR) && (high_dest_addr == MAX_DEST_ADDR)) //前面判断地址范围有问题时
{
/* We randomly pick our destination from universal address set. */
destination_address = OMSC_AA_AUTO_ASSIGN;
}
else if (low_dest_addr == high_dest_addr)
{
/* We have a unique destination address specified. Check its validity. */
if (low_dest_addr == -1)
destination_address = OMSC_AA_BROADCAST;
else if (oms_aa_dest_addr_check (oms_aa_handle, low_dest_addr) == OPC_TRUE)
destination_address = low_dest_addr; //正确的唯一地址
else
{
sprintf (err_msg, "%d", low_dest_addr);
eth_mac_higher_layer_intf_error ("Invalid destination MAC address.", "No MAC was found with the address:",err_msg);
}
}
else
{
/* We randomly pick our destination addresses from a subset of the */
/* universal address set. Determine the lower and upper indices of this */
/* subset in the global address array. */
if (low_dest_addr == MIN_DEST_ADDR)
low_dest_index = 0;
else
{
low_dest_index = oms_aa_address_find (oms_aa_handle, low_dest_addr);
/* Check validity of the lower bound. */
if (low_dest_index < 0)
{
sprintf (err_msg, "%d", low_dest_addr);
eth_mac_higher_layer_intf_error ("Invalid destination MAC address.", "No MAC was found with the address:", err_msg);
}
else if (oms_aa_dest_addr_check (oms_aa_handle, low_dest_addr) == OPC_FALSE)
{
sprintf (err_msg, "MAC address specified as the lowest destination address (%d)", low_dest_addr);
eth_mac_higher_layer_intf_error (err_msg, "is not configured as a valid destination address.",
"Most probably that MAC belongs to a switch or bridge node.");
}
}
/* Now determine the upper bound. */
if (high_dest_addr == MAX_DEST_ADDR)
high_dest_index = oms_aa_max_addr_index_get (oms_aa_handle);
else
{
high_dest_index = oms_aa_address_find (oms_aa_handle, high_dest_addr);
/* Check validity of the upper bound. */
if (high_dest_index < 0)
{
sprintf (err_msg, "%d", high_dest_addr);
eth_mac_higher_layer_intf_error ("Invalid destination MAC address.", "No MAC was found with the address:", err_msg);
}
else if (oms_aa_dest_addr_check (oms_aa_handle, high_dest_addr) == OPC_FALSE)
{
sprintf (err_msg, "MAC address specified as the highest destination address (%d)", high_dest_addr);
eth_mac_higher_layer_intf_error (err_msg, "is not configured as a valid destination address.",
"Most probably that MAC belongs to a switch or bridge node.");
}
}
}
}
//-----------------------------------------------------地址完成
五，idle状态的入口代码为空，当收到中断时，根据条件执行出口代码：
注意在header block中定义的条件：当stream index是从mac来时为MAC中断，其它为应用层中断。
/* Definition for the transition conditions */
#define MAC_LAYER_PKT_ARRVL (intrpt_type == OPC_INTRPT_STRM && intrpt_strm == instrm_from_mac)
#define APPL_LAYER_PKT_ARRVL (intrpt_type == OPC_INTRPT_STRM && intrpt_strm != instrm_from_mac)
首先执行出口代码：
/* The only interrupt expected in this state is a stream interrupt. It can be either from the MAC*/
/* layer for a packet destined for this node or from the application layer for a packet destined for some other node.*/
intrpt_type = op_intrpt_type (); //首先得到中断类型和stream index
intrpt_strm = op_intrpt_strm ();
/*Get the packet from the appropriate stream */
pkptr = op_pk_get (intrpt_strm); //得到包指针，注意由于包需要在不同的状态处理，所以pkpt是state variable，始终有效
五，appl layer arrival状态，由于该状态是强制状态，执行入口代码后马上跳回idle：这里只是分配了mac地址和ICI信息。
/* A packet has arrived from the application layer. Pick a random */
/* destination, unless an explicit destination is specified. Don't try infinite times.*/
num_tries = 0;
do
{
/* Increment the try counter. This will prevent an infinite loop. */ //不能无穷的尝试发送
num_tries++;
/* Pick a random destination address unless the destination address is already set to a specific value. */
if (low_dest_index + high_dest_index > 0) //地址没有设定，可能的最高加最低地址大于零，即非广播地址，
{
oms_aa_dest_addr_from_range_get (oms_aa_handle, &integer_mac_address, low_dest_index, high_dest_index); //用该函数随机获取地址范围内的一个地址，并送到integer_mac_address。
curr_dest_addr = integer_mac_address;
}
else
{
integer_mac_address = destination_address; //地址已经确定
oms_aa_dest_addr_get (oms_aa_handle, &integer_mac_address); //获取一个随机地址从address list
curr_dest_addr = integer_mac_address;
}
} while ((curr_dest_addr == mac_address) && (num_tries < TRY_THRESH)); //目的地址不能是自己，也不能无限循环
if (curr_dest_addr == mac_address)
eth_mac_higher_layer_intf_error ("Unable to choose remote address.", OPC_NIL, OPC_NIL);
if (curr_dest_addr == OMSC_AA_UNINIT_ADDR)
{
op_pk_destroy (pkptr);
}
else
{
/* Set this information in the interface control information to be sent to the MAC layer. */
op_ici_attr_set_int64 (intf_mac_req_iciptr, "dest_addr", curr_dest_addr); //向MAC层提交ICI信息，内容是mac地址
/* Send the packet to the lower layer */
op_pk_send (pkptr, outstrm_to_mac); //发送包，注意op_pk_send()函数会默认销毁包
}
六，mac layer arr状态，对于mac层的包，直接发送给应用层，由于本模型应用层是sink模块，所以直接发送即可。
/* A packet arrived from the MAC layer. Since the MAC layer would have forwarded this only if it were */
/* destined for this node, forward this packet to the application layer. */
op_pk_send (pkptr, 0); //默认的stream index为0的是连接到sink模块
总结：eth_mac_intf模块是在应用层与mac层之间的接口，功能是（1）从上层传递的包，随机（或指定）一个mac地址，然后发送给mac层，其中地址作为ICI信息发送。（2）mac层传过来的包直接发给上层，因为上层是sink模块，直接把包销毁，所以不需要做其它的工作了。
注意的：（1）自中断等待其它进程完成初始化。（2）进程登记库及相关函数（pr），用于得到本节点内其它模块的属性，共享信息。（3）用ICI在层间传递信息，这里是传递mac地址到mac层。（4）自动分配地址，oms_aa_dest_addr_from_range_get（）系列函数。