Hello!
Linux changes default router even while it is probably reachable.
Once it becomes "non-REACHABLE," Linux trys to select one in round-robin
fashion, but once it reached end of list, it would be stuck there.
Here's the patch against 2.4.19.
Thank you in advance.
-------------------------------------------------------------------
Patch-Name: Default Router Selection Round-robin
Patch-Id: FIX_2_4_19_DEFRTR_SELECT-20020919
Patch-Author: YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org>
Credit: YOSHIFUJI Hideaki / USAGI Project <yoshfuji@linux-ipv6.org>
Reference: RFC2461
-------------------------------------------------------------------
Index: net/ipv6/route.c
===================================================================
RCS file: /cvsroot/usagi/usagi-backport/linux24/net/ipv6/route.c,v
retrieving revision 1.1.1.1
retrieving revision 1.1.1.1.14.1
diff -u -r1.1.1.1 -r1.1.1.1.14.1
--- net/ipv6/route.c 2002/08/20 09:47:02 1.1.1.1
+++ net/ipv6/route.c 2002/09/19 16:28:03 1.1.1.1.14.1
@@ -13,6 +13,17 @@
* 2 of the License, or (at your option) any later version.
*/
+/* Changes:
+ *
+ * YOSHIFUJI Hideaki @USAGI
+ * reworked default router selection.
+ * - respect outgoing interface
+ * - select from (probably) reachable routers (i.e.
+ * routers in REACHABLE, STALE, DELAY or PROBE states).
+ * - always select the same router if it is (probably)
+ * reachable. otherwise, round-robin the list.
+ */
+
#include <linux/config.h>
#include <linux/errno.h>
#include <linux/types.h>
@@ -168,6 +179,7 @@
static struct rt6_info *rt6_dflt_pointer = NULL;
static spinlock_t rt6_dflt_lock = SPIN_LOCK_UNLOCKED;
+/* Default Router Selection (RFC 2461 6.3.6) */
static struct rt6_info *rt6_best_dflt(struct rt6_info *rt, int oif)
{
struct rt6_info *match = NULL;
@@ -176,63 +188,117 @@
for (sprt = rt; sprt; sprt = sprt->u.next) {
struct neighbour *neigh;
+ int m = 0;
- if ((neigh = sprt->rt6i_nexthop) != NULL) {
- int m = -1;
+ if (!oif ||
+ (sprt->rt6i_dev &&
+ sprt->rt6i_dev->ifindex == oif))
+ m += 8;
+ if (sprt == rt6_dflt_pointer)
+ m += 4;
+
+ if ((neigh = sprt->rt6i_nexthop) != NULL) {
+ read_lock_bh(&neigh->lock);
switch (neigh->nud_state) {
case NUD_REACHABLE:
- if (sprt != rt6_dflt_pointer) {
- rt = sprt;
- goto out;
- }
- m = 2;
+ m += 3;
break;
+ case NUD_STALE:
case NUD_DELAY:
- m = 1;
+ case NUD_PROBE:
+ m += 2;
break;
- case NUD_STALE:
- m = 1;
+ case NUD_NOARP:
+ case NUD_PERMANENT:
+ m += 1;
break;
- };
- if (oif && sprt->rt6i_dev->ifindex == oif) {
- m += 2;
+ case NUD_INCOMPLETE:
+ default:
+ read_unlock_bh(&neigh->lock);
+ continue;
}
+ read_unlock_bh(&neigh->lock);
+ } else {
+ continue;
+ }
- if (m >= mpri) {
- mpri = m;
- match = sprt;
+ if (m > mpri || m >= 12) {
+ match = sprt;
+ mpri = m;
+ if (m >= 12) {
+ /* we choose the lastest default router if it
+ * is in (probably) reachable state.
+ * If route changed, we should do pmtu
+ * discovery. --yoshfuji
+ */
+ break;
}
}
}
- if (match) {
- rt = match;
- } else {
+ spin_lock(&rt6_dflt_lock);
+ if (!match) {
/*
* No default routers are known to be reachable.
* SHOULD round robin
*/
- spin_lock(&rt6_dflt_lock);
if (rt6_dflt_pointer) {
- struct rt6_info *next;
-
- if ((next = rt6_dflt_pointer->u.next) != NULL &&
- next->u.dst.obsolete <= 0 &&
- next->u.dst.error == 0)
- rt = next;
+ for (sprt = rt6_dflt_pointer->u.next;
+ sprt; sprt = sprt->u.next) {
+ if (sprt->u.dst.obsolete <= 0 &&
+ sprt->u.dst.error == 0) {
+ match = sprt;
+ break;
+ }
+ }
+ for (sprt = rt;
+ !match && sprt && sprt != rt6_dflt_pointer;
+ sprt = sprt->u.next) {
+ if (sprt->u.dst.obsolete <= 0 &&
+ sprt->u.dst.error == 0) {
+ match = sprt;
+ break;
+ }
+ }
}
- spin_unlock(&rt6_dflt_lock);
}
-out:
- spin_lock(&rt6_dflt_lock);
- rt6_dflt_pointer = rt;
+ if (match) {
+ if (rt6_dflt_pointer != match)
+ RT6_TRACE1(KERN_INFO
+ "changed default router: %p->%p\n",
+ rt6_dflt_pointer, match);
+ rt6_dflt_pointer = match;
+ }
spin_unlock(&rt6_dflt_lock);
- return rt;
+
+ if (!match) {
+ /*
+ * Last Resort: if no default routers found,
+ * use addrconf default route.
+ * We don't record this route.
+ */
+ for (sprt = ip6_routing_table.leaf;
+ sprt; sprt = sprt->u.next) {
+ if ((sprt->rt6i_flags & RTF_DEFAULT) &&
+ (!oif ||
+ (sprt->rt6i_dev &&
+ sprt->rt6i_dev->ifindex == oif))) {
+ match = sprt;
+ break;
+ }
+ }
+ if (!match) {
+ /* no default route. give up. */
+ match = &ip6_null_entry;
+ }
+ }
+
+ return match;
}
struct rt6_info *rt6_lookup(struct in6_addr *daddr, struct in6_addr *saddr,
-- Hideaki YOSHIFUJI @ USAGI Project <yoshfuji@linux-ipv6.org> GPG FP: 9022 65EB 1ECF 3AD1 0BDF 80D8 4807 F894 E062 0EEA - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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