protocol源码阅读分析.txt

PROTOCOL
struct inet_protocol
{
    int (*handler)(struct sk_buff*skb,struct device*dev,
	              struct options*opt,unsigned long daddr,unsigned short len,
				  unsigned long saddr,int redo,struct inet_protocol*protocol);
	int (*frag_handler)(struct sk_buff*skb,struct device*dev,
	              struct options*opt,unsigned long daddr,unsigned short len,
				  unsigned long saddr,int redo,struct inet_protocol*protocol);			  
    int (*err_handler)(int err,unsigned char*buff,unsigned long daddr,unsigned long saddr,
	                   struct inet_protocol*protocol)
	struct inet_protocol*next;
    unsigned char  protocol;
    unsigned cahr  copy:1;
    void           *data;	
	char           *name;
}


struct  inet_protocol*inet_protocol_base;管理所有网络层之上的数据
指向 inet_protos[MAX_INET_PROTOS]
void inet_add_protocol(struct inet_protocol*prot)
{
    hash=prot->protocol&(MAX_INET_PROTOS-1);
	prot->next=inet_protos[hash];
	inet_prots[hash]=prot;//插入链表
	prot->copy=0;
	p2=(struct inet_protocol*)prot->next;
	while(p2!=NULL)
	{
	    if(p2->protocol==prot->protocol)
		{
		    prot->copy=1;//找到相同的协议设置copy=1
			break;
		}
		p2=(struct inet_protocol*)p2->next;
		 
	}
}



void inet_del_protocol(struct inet_protocol*prot)
{
    hash=prot->protocol&([MAX_INET_PROTOS-1);
	if(prot==inet_protos[hash])
	{
	    inet_prots[hash]=(struct inet_protocol*)prot->next;找到相同的协议删除
		return 0;
	}
	p=(struct inet_protocol*)inet_prots[hash];
	while(p!=NULL)
	{
	    if(p!=NULL&&p==prot)
		{
		    if(p->copy==0&&lp!=NULL)//若prot后面没有协议了则prot->copy被设置成0
			   lp->copy=0;//找到相同的协议存在多个删除一个更新其他协议的copy字段
			p->next=prot->next;
			return 0;
		}
		if(p->next！=NULL&&p->next->protocol==prot->protocol)
		    lp=p;
		p=(struct inet_protocol*)p->next;	//判断若删除的prot是最后个元素则设置前面一个元素copy为1
	}
	return -1;
}

struct inet_protocol*inet_get_protocol(unsigned char prot)//prot是协议号
{
    hash=prot&(MAX_INET_PROTOS-1);
	for(p=inet_prots[hash];p!=NULL;p=p->next)
	    if(p->protocol==prot) 
		   return ((struct inet_protocol*)p); 
	
    return NULL;	
}