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Date: Wed, 10 Jul 2013 23:00:12 +0200
From: Hannes Frederic Sowa <hannes@...essinduktion.org>
To: netdev@...r.kernel.org
Cc: petrus.lt@...il.com, yoshfuji@...ux-ipv6.org
Subject: [PATCH net RESEND v2] ipv6: fix route selection if kernel is not compiled with CONFIG_IPV6_ROUTER_PREF
This is a follow-up patch to 3630d40067a21d4dfbadc6002bb469ce26ac5d52
("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.
To hold correct state on the NUD selection we need to create a neighbour
entry as soon as we tried to validate a nexthop.
I changed the return value of rt6_check_neigh to:
1 in case of the dst entry validated
-1 in case of we had no dst_entry and we need to do rr now
-2 in case a we had a dst_entry and it did not validate
In case of CONFIG_IPV6_ROUTER_PREF, rt6_probe does not allocate an
neighbour entry (!CONFIG_IPV6_ROUTER_PREF: rt6_probe is a nop). Because
of this, we have to create a neighbour entry on nexthop validation to
track earlier validation errors. We recheck NUD state here to shortcurcuit
NUD_NOARP neighbours.
This seems to be the least complex fix for stable and net. I'll introduce
a new route lookup flag 'idempotent' as soon as next opens to not let
ip route get trigger active NUD validation if CONFIG_IPV6_ROUTER_PREF
is enabled. Currently we trigger active NUD validation if compiled with
CONFIG_IPV6_ROUTER_PREF.
It also seems advantageous to make CONFIG_IPV6_ROUTER_PREF a runtime
switch and just select the default operation on compile-time.
v2:
a) improved rt6_check_neigh logic and documented return values
Reported-by: Pierre Emeriaud <petrus.lt@...il.com>
Cc: YOSHIFUJI Hideaki <yoshfuji@...ux-ipv6.org>
Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
---
net/ipv6/route.c | 62 +++++++++++++++++++++++++++++++++++---------------------
1 file changed, 39 insertions(+), 23 deletions(-)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index bd5fd70..c5d9e68 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -531,28 +531,34 @@ static inline int rt6_check_dev(struct rt6_info *rt, int oif)
return 0;
}
-static inline bool rt6_check_neigh(struct rt6_info *rt)
+/* This function checks if a neighbour is reachable for routing
+ * purposes. It returns -2 in case the neighbour should not get
+ * selected as a viable router, -1 in case it should get selected with
+ * lowest score and afterwards trying roundrobin. 1 indicates a
+ * successfull verification.
+ */
+static inline int rt6_check_neigh(struct rt6_info *rt)
{
struct neighbour *neigh;
- bool ret = false;
+ int ret = -2;
if (rt->rt6i_flags & RTF_NONEXTHOP ||
!(rt->rt6i_flags & RTF_GATEWAY))
- return true;
+ return 1;
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 = 1;
#ifdef CONFIG_IPV6_ROUTER_PREF
else if (!(neigh->nud_state & NUD_FAILED))
- ret = true;
+ ret = 1;
#endif
read_unlock(&neigh->lock);
- } else if (IS_ENABLED(CONFIG_IPV6_ROUTER_PREF)) {
- ret = true;
+ } else {
+ ret = IS_ENABLED(CONFIG_IPV6_ROUTER_PREF) ? 1 : -1;
}
rcu_read_unlock_bh();
@@ -566,43 +572,52 @@ 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 -2;
#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 == -1 && !IS_ENABLED(CONFIG_IPV6_ROUTER_PREF)) {
+ match_do_rr = true;
+ m = 0; /* lowest valid score */
+ } else if (m < 0) {
goto out;
+ }
+
+ if (strict & RT6_LOOKUP_F_REACHABLE)
+ rt6_probe(rt);
if (m > *mpri) {
- if (strict & RT6_LOOKUP_F_REACHABLE)
- rt6_probe(match);
+ *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 +625,10 @@ 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 +637,16 @@ 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 */
--
1.8.1.4
--
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