radix.c

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		p->rn_left = t;
	else
		p->rn_right = t;
	x->rn_parent = t;/*填入父节点*/
	t->rn_parent = p; /* frees x, p as temp vars below */
	if ((cp[t->rn_offset] & t->rn_bmask) == 0) {
		t->rn_right = x;
	} else {
		t->rn_right = tt;
		t->rn_left = x;
	}
#ifdef RN_DEBUG/*调试时打印一些信息*/
	if (rn_debug)
		log(LOG_DEBUG, "rn_insert: Coming Out:\n"), traverse(p);
#endif
    }
	return (tt);
}
/*在掩码radix树中加入一节点*/
struct radix_node *
rn_addmask(n_arg, search, skip)/*n_arg是掩码的sockaddr_in结构指针*/
	int search, skip;
	void *n_arg;
{
	caddr_t netmask = (caddr_t)n_arg;/*如果是IP协议,就强制转换成sockaddr_in结构的指针.*/
	register struct radix_node *x;
	register caddr_t cp, cplim;
	register int b = 0, mlen, j;
	int maskduplicated, m0, isnormal;
	struct radix_node *saved_x;
	static int last_zeroed = 0;

	if ((mlen = *(u_char *)netmask) > max_keylen)/*C语言要熟悉哦,*(u_char *)netmask代表取指针netmask指向的第一个字节,*/
												/*因为任何sockaddr结构(如sockaddr_in,sockaddr_dl等)第一个字节代表该协议地址的长度*/
		mlen = max_keylen;/*意思是不能超过初始化时定义的最大协议地址长度*/
	if (skip == 0)
		skip = 1;
	if (mlen <= skip)
		return (mask_rnhead->rnh_nodes);
	if (skip > 1)
		Bcopy(rn_ones + 1, addmask_key + 1, skip - 1);
	if ((m0 = mlen) > skip)
		Bcopy(netmask + skip, addmask_key + skip, mlen - skip);
	/*
	 * 修整尾部的0.
	 */
	for (cp = addmask_key + mlen; (cp > addmask_key) && cp[-1] == 0;)
		cp--;
	mlen = cp - addmask_key;
	if (mlen <= skip) {
		if (m0 >= last_zeroed)
			last_zeroed = mlen;
		return (mask_rnhead->rnh_nodes);
	}
	if (m0 < last_zeroed)
		Bzero(addmask_key + m0, last_zeroed - m0);
	*addmask_key = last_zeroed = mlen;
	x = rn_search(addmask_key, rn_masktop);
	if (Bcmp(addmask_key, x->rn_key, mlen) != 0)
		x = 0;
	if (x || search)
		return (x);
	R_Malloc(x, struct radix_node *, max_keylen + 2 * sizeof (*x));
	if ((saved_x = x) == 0)
		return (0);
	Bzero(x, max_keylen + 2 * sizeof (*x));
	netmask = cp = (caddr_t)(x + 2);
	Bcopy(addmask_key, cp, mlen);
	x = rn_insert(cp, mask_rnhead, &maskduplicated, x);
	if (maskduplicated) {
		log(LOG_ERR, "rn_addmask: mask impossibly already in tree");
		Free(saved_x);
		return (x);
	}
	/*
	 * Calculate index of mask, and check for normalcy.
	 */
	cplim = netmask + mlen; isnormal = 1;
	for (cp = netmask + skip; (cp < cplim) && *(u_char *)cp == 0xff;)
		cp++;
	if (cp != cplim) {
		for (j = 0x80; (j & *cp) != 0; j >>= 1)
			b++;
		if (*cp != normal_chars[b] || cp != (cplim - 1))
			isnormal = 0;
	}
	b += (cp - netmask) << 3;
	x->rn_bit = -1 - b;
	if (isnormal)
		x->rn_flags |= RNF_NORMAL;
	return (x);
}

static int	/* XXX: arbitrary ordering for non-contiguous masks */
rn_lexobetter(m_arg, n_arg)
	void *m_arg, *n_arg;
{
	register u_char *mp = m_arg, *np = n_arg, *lim;

	if (*mp > *np)
		return 1;  /* not really, but need to check longer one first */
	if (*mp == *np)
		for (lim = mp + *mp; mp < lim;)
			if (*mp++ > *np++)
				return 1;
	return 0;
}
/*共享键(既重复键)中加一新的掩码*/
static struct radix_mask *
rn_new_radix_mask(tt, next)
	register struct radix_node *tt;/*共享的节点或叶子*/
	register struct radix_mask *next;/*新的掩码*/
{
	register struct radix_mask *m;

	MKGet(m);/*申请一长度为radix_mask结构长的块,m是指向该块的指针*/
	if (m == 0) {
		log(LOG_ERR, "Mask for route not entered\n");
		return (0);
	}
	Bzero(m, sizeof *m);/*内容先初始化为0*/
	m->rm_bit = tt->rn_bit;/*拷贝*/
	m->rm_flags = tt->rn_flags;
	if (tt->rn_flags & RNF_NORMAL)/*tt是一个叶子*/
		m->rm_leaf = tt;
	else
		m->rm_mask = tt->rn_mask;/*tt是一个掩码*/
	m->rm_mklist = next;/*链表操作*/
	tt->rn_mklist = m;
	return m;
}
/*该函数在NET/3中由以下两个调用(在文件in_rmx.c中的函数in_addroute)*/
/*in_rmx.c(112):	ret = rn_addroute(v_arg, n_arg, head, treenodes);*/
/*in_rmx.c(131):    ret = rn_addroute(v_arg, n_arg, head,treenodes);*/
struct radix_node *
rn_addroute(v_arg, n_arg, head, treenodes)
	void *v_arg, *n_arg;/*sockaddr_in结构指针,v_arg在IP协议中是IP的sockaddr_in地址结构指针,n_arg是掩码指针*/
	struct radix_node_head *head;/*在IP协议中是radix树的顶部*/
	struct radix_node treenodes[2];/*是即将加入的节点和叶子,一个路由表一定是要加一个节点和一个叶子.*/
{
	caddr_t v = (caddr_t)v_arg, netmask = (caddr_t)n_arg;/*在IP协议中将强制转换成sockaddr_in结构的指针*/
	register struct radix_node *t, *x = 0, *tt;/**/
	struct radix_node *saved_tt, *top = head->rnh_treetop;/*top指向该协议的radix树的顶部的中间的radix节点*/
	short b = 0, b_leaf = 0;
	int keyduplicated;
	caddr_t mmask;
	struct radix_mask *m, **mp;

	/*
	 * In dealing with non-contiguous masks, there may be
	 * many different routes which have the same mask.
	 * We will find it useful to have a unique pointer to
	 * the mask to speed avoiding duplicate references at
	 * nodes and possibly save time in calculating indices.
	 */
	if (netmask)  {/*如果有掩码*/
		if ((x = rn_addmask(netmask, 0, top->rn_offset)) == 0)/*加入掩码,函数在上面*/
			return (0);
		b_leaf = x->rn_bit;
		b = -1 - x->rn_bit;
		netmask = x->rn_key;
	}
	/*
	 * Deal with duplicated keys: attach node to previous instance
	 */
	saved_tt = tt = rn_insert(v, head, &keyduplicated, treenodes);
	if (keyduplicated) {
		for (t = tt; tt; t = tt, tt = tt->rn_dupedkey) {
			if (tt->rn_mask == netmask)
				return (0);
			if (netmask == 0 ||
			    (tt->rn_mask &&
			     ((b_leaf < tt->rn_bit) /* index(netmask) > node */
			      || rn_refines(netmask, tt->rn_mask)
			      || rn_lexobetter(netmask, tt->rn_mask))))
				break;
		}
		/*
		 * If the mask is not duplicated, we wouldn't
		 * find it among possible duplicate key entries
		 * anyway, so the above test doesn't hurt.
		 *
		 * We sort the masks for a duplicated key the same way as
		 * in a masklist -- most specific to least specific.
		 * This may require the unfortunate nuisance of relocating
		 * the head of the list.
		 *
		 * We also reverse, or doubly link the list through the
		 * parent pointer.
		 */
		if (tt == saved_tt) {
			struct	radix_node *xx = x;
			/* link in at head of list */
			(tt = treenodes)->rn_dupedkey = t;
			tt->rn_flags = t->rn_flags;
			tt->rn_parent = x = t->rn_parent;
			t->rn_parent = tt;	 		/* parent */
			if (x->rn_left == t)
				x->rn_left = tt;
			else
				x->rn_right = tt;
			saved_tt = tt; x = xx;
		} else {
			(tt = treenodes)->rn_dupedkey = t->rn_dupedkey;
			t->rn_dupedkey = tt;
			tt->rn_parent = t;			/* parent */
			if (tt->rn_dupedkey)			/* parent */
				tt->rn_dupedkey->rn_parent = tt; /* parent */
		}
#ifdef RN_DEBUG
		t=tt+1; tt->rn_info = rn_nodenum++; t->rn_info = rn_nodenum++;
		tt->rn_twin = t; tt->rn_ybro = rn_clist; rn_clist = tt;
#endif
		tt->rn_key = (caddr_t) v;
		tt->rn_bit = -1;
		tt->rn_flags = RNF_ACTIVE;
	}
	/*
	 * Put mask in tree.
	 */
	if (netmask) {
		tt->rn_mask = netmask;
		tt->rn_bit = x->rn_bit;
		tt->rn_flags |= x->rn_flags & RNF_NORMAL;
	}
	t = saved_tt->rn_parent;
	if (keyduplicated)
		goto on2;
	b_leaf = -1 - t->rn_bit;
	if (t->rn_right == saved_tt)
		x = t->rn_left;
	else
		x = t->rn_right;
	/* Promote general routes from below */
	if (x->rn_bit < 0) {
	    for (mp = &t->rn_mklist; x; x = x->rn_dupedkey)
		if (x->rn_mask && (x->rn_bit >= b_leaf) && x->rn_mklist == 0) {
			*mp = m = rn_new_radix_mask(x, 0);
			if (m)
				mp = &m->rm_mklist;
		}
	} else if (x->rn_mklist) {
		/*
		 * Skip over masks whose index is > that of new node
		 */
		for (mp = &x->rn_mklist; (m = *mp); mp = &m->rm_mklist)
			if (m->rm_bit >= b_leaf)
				break;
		t->rn_mklist = m; *mp = 0;
	}
on2:
	/* Add new route to highest possible ancestor's list */
	if ((netmask == 0) || (b > t->rn_bit ))
		return tt; /* can't lift at all */
	b_leaf = tt->rn_bit;
	do {
		x = t;
		t = t->rn_parent;
	} while (b <= t->rn_bit && x != top);
	/*
	 * Search through routes associated with node to
	 * insert new route according to index.
	 * Need same criteria as when sorting dupedkeys to avoid
	 * double loop on deletion.
	 */
	for (mp = &x->rn_mklist; (m = *mp); mp = &m->rm_mklist) {
		if (m->rm_bit < b_leaf)
			continue;
		if (m->rm_bit > b_leaf)
			break;
		if (m->rm_flags & RNF_NORMAL) {
			mmask = m->rm_leaf->rn_mask;
			if (tt->rn_flags & RNF_NORMAL) {
			    log(LOG_ERR,"Non-unique normal route, mask not entered\n");
				return tt;
			}
		} else
			mmask = m->rm_mask;
		if (mmask == netmask) {
			m->rm_refs++;
			tt->rn_mklist = m;
			return tt;
		}
		if (rn_refines(netmask, mmask)
		    || rn_lexobetter(netmask, mmask))
			break;
	}
	*mp = rn_new_radix_mask(tt, *mp);
	return tt;
}
/*该函数用来删除一叶子*/
struct radix_node *
rn_delete(v_arg, netmask_arg, head)
	void *v_arg, *netmask_arg;
	struct radix_node_head *head;
{
	register struct radix_node *t, *p, *x, *tt;
	struct radix_mask *m, *saved_m, **mp;
	struct radix_node *dupedkey, *saved_tt, *top;
	caddr_t v, netmask;
	int b, head_off, vlen;

	v = v_arg;
	netmask = netmask_arg;
	x = head->rnh_treetop;
	tt = rn_search(v, x);
	head_off = x->rn_offset;
	vlen =  *(u_char *)v;
	saved_tt = tt;
	top = x;
	if (tt == 0 ||
	    Bcmp(v + head_off, tt->rn_key + head_off, vlen - head_off))
		return (0);
	/*
	 * Delete our route from mask lists.
	 */
	if (netmask) {
		if ((x = rn_addmask(netmask, 1, head_off)) == 0)
			return (0);
		netmask = x->rn_key;
		while (tt->rn_mask != netmask)
			if ((tt = tt->rn_dupedkey) == 0)
				return (0);
	}
	if (tt->rn_mask == 0 || (saved_m = m = tt->rn_mklist) == 0)
		goto on1;
	if (tt->rn_flags & RNF_NORMAL) {
		if (m->rm_leaf != tt || m->rm_refs > 0) {
			log(LOG_ERR, "rn_delete: inconsistent annotation\n");
			return 0;  /* dangling ref could cause disaster */
		}
	} else {
		if (m->rm_mask != tt->rn_mask) {
			log(LOG_ERR, "rn_delete: inconsistent annotation\n");
			goto on1;
		}
		if (--m->rm_refs >= 0)