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Commit afc154e9 authored by Hannes Frederic Sowa's avatar Hannes Frederic Sowa Committed by David S. Miller
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ipv6: fix route selection if kernel is not compiled with CONFIG_IPV6_ROUTER_PREF 



This is a follow-up patch to 3630d400
("ipv6: rt6_check_neigh should successfully verify neigh if no NUD
information are available").

Since the removal of rt->n in rt6_info we can end up with a dst ==
NULL in rt6_check_neigh. In case the kernel is not compiled with
CONFIG_IPV6_ROUTER_PREF we should also select a route with unkown
NUD state but we must not avoid doing round robin selection on routes
with the same target. So introduce and pass down a boolean ``do_rr'' to
indicate when we should update rt->rr_ptr. As soon as no route is valid
we do backtracking and do a lookup on a higher level in the fib trie.

v2:
a) Improved rt6_check_neigh logic (no need to create neighbour there)
   and documented return values.

v3:
a) Introduce enum rt6_nud_state to get rid of the magic numbers
   (thanks to David Miller).
b) Update and shorten commit message a bit to actualy reflect
   the source.

Reported-by: default avatarPierre Emeriaud <petrus.lt@gmail.com>
Cc: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: default avatarHannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1b4fc0e2

net/ipv6/route.c

+40 −23
Original line number Diff line number Diff line
@@ -65,6 +65,12 @@ 
#include <linux/sysctl.h>

#endif



enum rt6_nud_state {

	RT6_NUD_FAIL_HARD = -2,

	RT6_NUD_FAIL_SOFT = -1,

	RT6_NUD_SUCCEED = 1

};



static struct rt6_info *ip6_rt_copy(struct rt6_info *ort,

				    const struct in6_addr *dest);

static struct dst_entry	*ip6_dst_check(struct dst_entry *dst, u32 cookie);
@@ -531,28 +537,29 @@ static inline int rt6_check_dev(struct rt6_info *rt, int oif) 
	return 0;

}



static inline bool rt6_check_neigh(struct rt6_info *rt)

static inline enum rt6_nud_state rt6_check_neigh(struct rt6_info *rt)

{

	struct neighbour *neigh;

	bool ret = false;

	enum rt6_nud_state ret = RT6_NUD_FAIL_HARD;



	if (rt->rt6i_flags & RTF_NONEXTHOP ||

	    !(rt->rt6i_flags & RTF_GATEWAY))

		return true;

		return RT6_NUD_SUCCEED;



	rcu_read_lock_bh();

	neigh = __ipv6_neigh_lookup_noref(rt->dst.dev, &rt->rt6i_gateway);

	if (neigh) {

		read_lock(&neigh->lock);

		if (neigh->nud_state & NUD_VALID)

			ret = true;

			ret = RT6_NUD_SUCCEED;

#ifdef CONFIG_IPV6_ROUTER_PREF

		else if (!(neigh->nud_state & NUD_FAILED))

			ret = true;

			ret = RT6_NUD_SUCCEED;

#endif

		read_unlock(&neigh->lock);

	} else if (IS_ENABLED(CONFIG_IPV6_ROUTER_PREF)) {

		ret = true;

	} else {

		ret = IS_ENABLED(CONFIG_IPV6_ROUTER_PREF) ?

		      RT6_NUD_SUCCEED : RT6_NUD_FAIL_SOFT;

	}

	rcu_read_unlock_bh();
@@ -566,43 +573,52 @@ static int rt6_score_route(struct rt6_info *rt, int oif, 


	m = rt6_check_dev(rt, oif);

	if (!m && (strict & RT6_LOOKUP_F_IFACE))

		return -1;

		return RT6_NUD_FAIL_HARD;

#ifdef CONFIG_IPV6_ROUTER_PREF

	m |= IPV6_DECODE_PREF(IPV6_EXTRACT_PREF(rt->rt6i_flags)) << 2;

#endif

	if (!rt6_check_neigh(rt) && (strict & RT6_LOOKUP_F_REACHABLE))

		return -1;

	if (strict & RT6_LOOKUP_F_REACHABLE) {

		int n = rt6_check_neigh(rt);

		if (n < 0)

			return n;

	}

	return m;

}



static struct rt6_info *find_match(struct rt6_info *rt, int oif, int strict,

				   int *mpri, struct rt6_info *match)

				   int *mpri, struct rt6_info *match,

				   bool *do_rr)

{

	int m;

	bool match_do_rr = false;



	if (rt6_check_expired(rt))

		goto out;



	m = rt6_score_route(rt, oif, strict);

	if (m < 0)

	if (m == RT6_NUD_FAIL_SOFT && !IS_ENABLED(CONFIG_IPV6_ROUTER_PREF)) {

		match_do_rr = true;

		m = 0; /* lowest valid score */

	} else if (m < 0) {

		goto out;

	}



	if (m > *mpri) {

	if (strict & RT6_LOOKUP_F_REACHABLE)

			rt6_probe(match);

		rt6_probe(rt);



	if (m > *mpri) {

		*do_rr = match_do_rr;

		*mpri = m;

		match = rt;

	} else if (strict & RT6_LOOKUP_F_REACHABLE) {

		rt6_probe(rt);

	}



out:

	return match;

}



static struct rt6_info *find_rr_leaf(struct fib6_node *fn,

				     struct rt6_info *rr_head,

				     u32 metric, int oif, int strict)

				     u32 metric, int oif, int strict,

				     bool *do_rr)

{

	struct rt6_info *rt, *match;

	int mpri = -1;
@@ -610,10 +626,10 @@ static struct rt6_info *find_rr_leaf(struct fib6_node *fn, 
	match = NULL;

	for (rt = rr_head; rt && rt->rt6i_metric == metric;

	     rt = rt->dst.rt6_next)

		match = find_match(rt, oif, strict, &mpri, match);

		match = find_match(rt, oif, strict, &mpri, match, do_rr);

	for (rt = fn->leaf; rt && rt != rr_head && rt->rt6i_metric == metric;

	     rt = rt->dst.rt6_next)

		match = find_match(rt, oif, strict, &mpri, match);

		match = find_match(rt, oif, strict, &mpri, match, do_rr);



	return match;

}
@@ -622,15 +638,16 @@ static struct rt6_info *rt6_select(struct fib6_node *fn, int oif, int strict) 
{

	struct rt6_info *match, *rt0;

	struct net *net;

	bool do_rr = false;



	rt0 = fn->rr_ptr;

	if (!rt0)

		fn->rr_ptr = rt0 = fn->leaf;



	match = find_rr_leaf(fn, rt0, rt0->rt6i_metric, oif, strict);

	match = find_rr_leaf(fn, rt0, rt0->rt6i_metric, oif, strict,

			     &do_rr);



	if (!match &&

	    (strict & RT6_LOOKUP_F_REACHABLE)) {

	if (do_rr) {

		struct rt6_info *next = rt0->dst.rt6_next;



		/* no entries matched; do round-robin */