fib_semantics.c

ARM 嵌入式 系统 设计与实例开发 实验教材 二源码

/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		IPv4 Forwarding Information Base: semantics.
 *
 * Version:	$Id: fib_semantics.c,v 1.18.2.2 2002/01/12 07:54:15 davem Exp $
 *
 * Authors:	Alexey Kuznetsov, <[e-mail]>
 *
 *		This program is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 */

#include <linux/config.h>
#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/bitops.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/socket.h>
#include <linux/sockios.h>
#include <linux/errno.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/netdevice.h>
#include <linux/if_arp.h>
#include <linux/proc_fs.h>
#include <linux/skbuff.h>
#include <linux/netlink.h>
#include <linux/init.h>

#include <net/ip.h>
#include <net/protocol.h>
#include <net/route.h>
#include <net/tcp.h>
#include <net/sock.h>
#include <net/ip_fib.h>

#define FSprintk(a...)

static struct fib_info 	*fib_info_list;
static rwlock_t fib_info_lock = RW_LOCK_UNLOCKED;
int fib_info_cnt;

#define for_fib_info() { struct fib_info *fi; \
	for (fi = fib_info_list; fi; fi = fi->fib_next)

#define endfor_fib_info() }

#ifdef CONFIG_IP_ROUTE_MULTIPATH

#define for_nexthops(fi) { int nhsel; const struct fib_nh * nh; \
for (nhsel=0, nh = (fi)->fib_nh; nhsel < (fi)->fib_nhs; nh++, nhsel++)

#define change_nexthops(fi) { int nhsel; struct fib_nh * nh; \
for (nhsel=0, nh = (struct fib_nh*)((fi)->fib_nh); nhsel < (fi)->fib_nhs; nh++, nhsel++)

#else /* CONFIG_IP_ROUTE_MULTIPATH */

/* Hope, that gcc will optimize it to get rid of dummy loop */

#define for_nexthops(fi) { int nhsel=0; const struct fib_nh * nh = (fi)->fib_nh; \
for (nhsel=0; nhsel < 1; nhsel++)

#define change_nexthops(fi) { int nhsel=0; struct fib_nh * nh = (struct fib_nh*)((fi)->fib_nh); \
for (nhsel=0; nhsel < 1; nhsel++)

#endif /* CONFIG_IP_ROUTE_MULTIPATH */

#define endfor_nexthops(fi) }


static struct 
{
	int	error;
	u8	scope;
} fib_props[RTA_MAX+1] = {
        { 0, RT_SCOPE_NOWHERE},		/* RTN_UNSPEC */
	{ 0, RT_SCOPE_UNIVERSE},	/* RTN_UNICAST */
	{ 0, RT_SCOPE_HOST},		/* RTN_LOCAL */
	{ 0, RT_SCOPE_LINK},		/* RTN_BROADCAST */
	{ 0, RT_SCOPE_LINK},		/* RTN_ANYCAST */
	{ 0, RT_SCOPE_UNIVERSE},	/* RTN_MULTICAST */
	{ -EINVAL, RT_SCOPE_UNIVERSE},	/* RTN_BLACKHOLE */
	{ -EHOSTUNREACH, RT_SCOPE_UNIVERSE},/* RTN_UNREACHABLE */
	{ -EACCES, RT_SCOPE_UNIVERSE},	/* RTN_PROHIBIT */
	{ -EAGAIN, RT_SCOPE_UNIVERSE},	/* RTN_THROW */
#ifdef CONFIG_IP_ROUTE_NAT
	{ 0, RT_SCOPE_HOST},		/* RTN_NAT */
#else
	{ -EINVAL, RT_SCOPE_NOWHERE},	/* RTN_NAT */
#endif
	{ -EINVAL, RT_SCOPE_NOWHERE}	/* RTN_XRESOLVE */
};


/* Release a nexthop info record */

void free_fib_info(struct fib_info *fi)
{
	if (fi->fib_dead == 0) {
		printk("Freeing alive fib_info %p\n", fi);
		return;
	}
	change_nexthops(fi) {
		if (nh->nh_dev)
			dev_put(nh->nh_dev);
		nh->nh_dev = NULL;
	} endfor_nexthops(fi);
	fib_info_cnt--;
	kfree(fi);
}

void fib_release_info(struct fib_info *fi)
{
	write_lock(&fib_info_lock);
	if (fi && --fi->fib_treeref == 0) {
		if (fi->fib_next)
			fi->fib_next->fib_prev = fi->fib_prev;
		if (fi->fib_prev)
			fi->fib_prev->fib_next = fi->fib_next;
		if (fi == fib_info_list)
			fib_info_list = fi->fib_next;
		fi->fib_dead = 1;
		fib_info_put(fi);
	}
	write_unlock(&fib_info_lock);
}

static __inline__ int nh_comp(const struct fib_info *fi, const struct fib_info *ofi)
{
	const struct fib_nh *onh = ofi->fib_nh;

	for_nexthops(fi) {
		if (nh->nh_oif != onh->nh_oif ||
		    nh->nh_gw  != onh->nh_gw ||
		    nh->nh_scope != onh->nh_scope ||
#ifdef CONFIG_IP_ROUTE_MULTIPATH
		    nh->nh_weight != onh->nh_weight ||
#endif
#ifdef CONFIG_NET_CLS_ROUTE
		    nh->nh_tclassid != onh->nh_tclassid ||
#endif
		    ((nh->nh_flags^onh->nh_flags)&~RTNH_F_DEAD))
			return -1;
		onh++;
	} endfor_nexthops(fi);
	return 0;
}

static __inline__ struct fib_info * fib_find_info(const struct fib_info *nfi)
{
	for_fib_info() {
		if (fi->fib_nhs != nfi->fib_nhs)
			continue;
		if (nfi->fib_protocol == fi->fib_protocol &&
		    nfi->fib_prefsrc == fi->fib_prefsrc &&
		    nfi->fib_priority == fi->fib_priority &&
		    memcmp(nfi->fib_metrics, fi->fib_metrics, sizeof(fi->fib_metrics)) == 0 &&
		    ((nfi->fib_flags^fi->fib_flags)&~RTNH_F_DEAD) == 0 &&
		    (nfi->fib_nhs == 0 || nh_comp(fi, nfi) == 0))
			return fi;
	} endfor_fib_info();
	return NULL;
}

/* Check, that the gateway is already configured.
   Used only by redirect accept routine.
 */

int ip_fib_check_default(u32 gw, struct net_device *dev)
{
	read_lock(&fib_info_lock);
	for_fib_info() {
		if (fi->fib_flags & RTNH_F_DEAD)
			continue;
		for_nexthops(fi) {
			if (nh->nh_dev == dev && nh->nh_gw == gw &&
			    !(nh->nh_flags&RTNH_F_DEAD)) {
				read_unlock(&fib_info_lock);
				return 0;
			}
		} endfor_nexthops(fi);
	} endfor_fib_info();
	read_unlock(&fib_info_lock);
	return -1;
}

#ifdef CONFIG_IP_ROUTE_MULTIPATH

static u32 fib_get_attr32(struct rtattr *attr, int attrlen, int type)
{
	while (RTA_OK(attr,attrlen)) {
		if (attr->rta_type == type)
			return *(u32*)RTA_DATA(attr);
		attr = RTA_NEXT(attr, attrlen);
	}
	return 0;
}

static int
fib_count_nexthops(struct rtattr *rta)
{
	int nhs = 0;
	struct rtnexthop *nhp = RTA_DATA(rta);
	int nhlen = RTA_PAYLOAD(rta);

	while (nhlen >= (int)sizeof(struct rtnexthop)) {
		if ((nhlen -= nhp->rtnh_len) < 0)
			return 0;
		nhs++;
		nhp = RTNH_NEXT(nhp);
	};
	return nhs;
}

static int
fib_get_nhs(struct fib_info *fi, const struct rtattr *rta, const struct rtmsg *r)
{
	struct rtnexthop *nhp = RTA_DATA(rta);
	int nhlen = RTA_PAYLOAD(rta);

	change_nexthops(fi) {
		int attrlen = nhlen - sizeof(struct rtnexthop);
		if (attrlen < 0 || (nhlen -= nhp->rtnh_len) < 0)
			return -EINVAL;
		nh->nh_flags = (r->rtm_flags&~0xFF) | nhp->rtnh_flags;
		nh->nh_oif = nhp->rtnh_ifindex;
		nh->nh_weight = nhp->rtnh_hops + 1;
		if (attrlen) {
			nh->nh_gw = fib_get_attr32(RTNH_DATA(nhp), attrlen, RTA_GATEWAY);
#ifdef CONFIG_NET_CLS_ROUTE
			nh->nh_tclassid = fib_get_attr32(RTNH_DATA(nhp), attrlen, RTA_FLOW);
#endif
		}
		nhp = RTNH_NEXT(nhp);
	} endfor_nexthops(fi);
	return 0;
}

#endif

int fib_nh_match(struct rtmsg *r, struct nlmsghdr *nlh, struct kern_rta *rta,
		 struct fib_info *fi)
{
#ifdef CONFIG_IP_ROUTE_MULTIPATH
	struct rtnexthop *nhp;
	int nhlen;
#endif

	if (rta->rta_priority &&
	    *rta->rta_priority != fi->fib_priority)
		return 1;

	if (rta->rta_oif || rta->rta_gw) {
		if ((!rta->rta_oif || *rta->rta_oif == fi->fib_nh->nh_oif) &&
		    (!rta->rta_gw  || memcmp(rta->rta_gw, &fi->fib_nh->nh_gw, 4) == 0))
			return 0;
		return 1;
	}

#ifdef CONFIG_IP_ROUTE_MULTIPATH
	if (rta->rta_mp == NULL)
		return 0;
	nhp = RTA_DATA(rta->rta_mp);
	nhlen = RTA_PAYLOAD(rta->rta_mp);
	
	for_nexthops(fi) {
		int attrlen = nhlen - sizeof(struct rtnexthop);
		u32 gw;

		if (attrlen < 0 || (nhlen -= nhp->rtnh_len) < 0)
			return -EINVAL;
		if (nhp->rtnh_ifindex && nhp->rtnh_ifindex != nh->nh_oif)
			return 1;
		if (attrlen) {
			gw = fib_get_attr32(RTNH_DATA(nhp), attrlen, RTA_GATEWAY);
			if (gw && gw != nh->nh_gw)
				return 1;
#ifdef CONFIG_NET_CLS_ROUTE
			gw = fib_get_attr32(RTNH_DATA(nhp), attrlen, RTA_FLOW);
			if (gw && gw != nh->nh_tclassid)
				return 1;
#endif
		}
		nhp = RTNH_NEXT(nhp);
	} endfor_nexthops(fi);
#endif
	return 0;
}


/*
   Picture
   -------

   Semantics of nexthop is very messy by historical reasons.
   We have to take into account, that:
   a) gateway can be actually local interface address,
      so that gatewayed route is direct.
   b) gateway must be on-link address, possibly
      described not by an ifaddr, but also by a direct route.
   c) If both gateway and interface are specified, they should not
      contradict.
   d) If we use tunnel routes, gateway could be not on-link.

   Attempt to reconcile all of these (alas, self-contradictory) conditions
   results in pretty ugly and hairy code with obscure logic.

   I choosed to generalized it instead, so that the size
   of code does not increase practically, but it becomes
   much more general.
   Every prefix is assigned a "scope" value: "host" is local address,
   "link" is direct route,
   [ ... "site" ... "interior" ... ]
   and "universe" is true gateway route with global meaning.

   Every prefix refers to a set of "nexthop"s (gw, oif),
   where gw must have narrower scope. This recursion stops
   when gw has LOCAL scope or if "nexthop" is declared ONLINK,
   which means that gw is forced to be on link.

   Code is still hairy, but now it is apparently logically
   consistent and very flexible. F.e. as by-product it allows
   to co-exists in peace independent exterior and interior
   routing processes.

   Normally it looks as following.

   {universe prefix}  -> (gw, oif) [scope link]
                          |
			  |-> {link prefix} -> (gw, oif) [scope local]
			                        |
						|-> {local prefix} (terminal node)
 */

static int fib_check_nh(const struct rtmsg *r, struct fib_info *fi, struct fib_nh *nh)
{
	int err;

	if (nh->nh_gw) {
		struct rt_key key;
		struct fib_result res;

#ifdef CONFIG_IP_ROUTE_PERVASIVE
		if (nh->nh_flags&RTNH_F_PERVASIVE)
			return 0;
#endif
		if (nh->nh_flags&RTNH_F_ONLINK) {
			struct net_device *dev;

			if (r->rtm_scope >= RT_SCOPE_LINK)
				return -EINVAL;
			if (inet_addr_type(nh->nh_gw) != RTN_UNICAST)
				return -EINVAL;
			if ((dev = __dev_get_by_index(nh->nh_oif)) == NULL)
				return -ENODEV;
			if (!(dev->flags&IFF_UP))
				return -ENETDOWN;
			nh->nh_dev = dev;
			atomic_inc(&dev->refcnt);
			nh->nh_scope = RT_SCOPE_LINK;
			return 0;
		}
		memset(&key, 0, sizeof(key));
		key.dst = nh->nh_gw;
		key.oif = nh->nh_oif;
		key.scope = r->rtm_scope + 1;

		/* It is not necessary, but requires a bit of thinking */
		if (key.scope < RT_SCOPE_LINK)
			key.scope = RT_SCOPE_LINK;

		if ((err = fib_lookup(&key, &res)) != 0)
			return err;
		nh->nh_scope = res.scope;
		nh->nh_oif = FIB_RES_OIF(res);
		nh->nh_dev = FIB_RES_DEV(res);
		if (nh->nh_dev)
			atomic_inc(&nh->nh_dev->refcnt);
		fib_res_put(&res);
	} else {
		struct in_device *in_dev;

		if (nh->nh_flags&(RTNH_F_PERVASIVE|RTNH_F_ONLINK))
			return -EINVAL;

		in_dev = inetdev_by_index(nh->nh_oif);
		if (in_dev == NULL)
			return -ENODEV;
		if (!(in_dev->dev->flags&IFF_UP)) {
			in_dev_put(in_dev);
			return -ENETDOWN;
		}
		nh->nh_dev = in_dev->dev;
		atomic_inc(&nh->nh_dev->refcnt);
		nh->nh_scope = RT_SCOPE_HOST;
		in_dev_put(in_dev);
	}
	return 0;
}

struct fib_info *
fib_create_info(const struct rtmsg *r, struct kern_rta *rta,
		const struct nlmsghdr *nlh, int *errp)
{
	int err;
	struct fib_info *fi = NULL;
	struct fib_info *ofi;
#ifdef CONFIG_IP_ROUTE_MULTIPATH
	int nhs = 1;
#else
	const int nhs = 1;
#endif

	/* Fast check to catch the most weird cases */
	if (fib_props[r->rtm_type].scope > r->rtm_scope)
		goto err_inval;

#ifdef CONFIG_IP_ROUTE_MULTIPATH
	if (rta->rta_mp) {
		nhs = fib_count_nexthops(rta->rta_mp);
		if (nhs == 0)
			goto err_inval;
	}
#endif

	fi = kmalloc(sizeof(*fi)+nhs*sizeof(struct fib_nh), GFP_KERNEL);
	err = -ENOBUFS;
	if (fi == NULL)
		goto failure;
	fib_info_cnt++;
	memset(fi, 0, sizeof(*fi)+nhs*sizeof(struct fib_nh));

	fi->fib_protocol = r->rtm_protocol;
	fi->fib_nhs = nhs;
	fi->fib_flags = r->rtm_flags;
	if (rta->rta_priority)
		fi->fib_priority = *rta->rta_priority;
	if (rta->rta_mx) {
		int attrlen = RTA_PAYLOAD(rta->rta_mx);
		struct rtattr *attr = RTA_DATA(rta->rta_mx);

		while (RTA_OK(attr, attrlen)) {
			unsigned flavor = attr->rta_type;
			if (flavor) {
				if (flavor > RTAX_MAX)
					goto err_inval;
				fi->fib_metrics[flavor-1] = *(unsigned*)RTA_DATA(attr);
			}
			attr = RTA_NEXT(attr, attrlen);
		}
	}
	if (rta->rta_prefsrc)
		memcpy(&fi->fib_prefsrc, rta->rta_prefsrc, 4);

	if (rta->rta_mp) {
#ifdef CONFIG_IP_ROUTE_MULTIPATH
		if ((err = fib_get_nhs(fi, rta->rta_mp, r)) != 0)
			goto failure;
		if (rta->rta_oif && fi->fib_nh->nh_oif != *rta->rta_oif)
			goto err_inval;
		if (rta->rta_gw && memcmp(&fi->fib_nh->nh_gw, rta->rta_gw, 4))
			goto err_inval;
#ifdef CONFIG_NET_CLS_ROUTE
		if (rta->rta_flow && memcmp(&fi->fib_nh->nh_tclassid, rta->rta_flow, 4))
			goto err_inval;
#endif
#else
		goto err_inval;
#endif
	} else {
		struct fib_nh *nh = fi->fib_nh;
		if (rta->rta_oif)
			nh->nh_oif = *rta->rta_oif;
		if (rta->rta_gw)
			memcpy(&nh->nh_gw, rta->rta_gw, 4);
#ifdef CONFIG_NET_CLS_ROUTE
		if (rta->rta_flow)
			memcpy(&nh->nh_tclassid, rta->rta_flow, 4);
#endif
		nh->nh_flags = r->rtm_flags;
#ifdef CONFIG_IP_ROUTE_MULTIPATH
		nh->nh_weight = 1;
#endif
	}

#ifdef CONFIG_IP_ROUTE_NAT
	if (r->rtm_type == RTN_NAT) {
		if (rta->rta_gw == NULL || nhs != 1 || rta->rta_oif)
			goto err_inval;
		memcpy(&fi->fib_nh->nh_gw, rta->rta_gw, 4);
		goto link_it;
	}
#endif

	if (fib_props[r->rtm_type].error) {
		if (rta->rta_gw || rta->rta_oif || rta->rta_mp)
			goto err_inval;
		goto link_it;
	}