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Date: Tue, 2 Jun 2015 23:07:19 -0400
From: Andy Gospodarek <gospo@...ulusnetworks.com>
To: netdev@...r.kernel.org, davem@...emloft.net
Cc: ddutt@...ulusnetworks.com,
Andy Gospodarek <gospo@...ulusnetworks.com>
Subject: [PATCH net-next] net: change fib behavior based on interface link status
This patch adds the ability to have the Linux kernel track whether or
not a particular route should be used based on the link-status of the
interface associated with the next-hop.
Before this patch any link-failure on an interface that was serving as a
gateway for some systems could result in those systems being isolated
from the rest of the network as the stack would continue to attempt to
send frames out of an interface that is actually linked-down. When the
kernel is responsible for all forwarding, it should also be responsible
for taking action when the traffic can no longer be forwarded -- there
is no real need to outsource link-monitoring to userspace anymore.
This feature is only enabled with the new sysctl set (default is off):
net.core.kill_routes_on_linkdown = 1
When this is set, the following behavior can be observed (interface p8p1
is link-down):
# ip route show
default via 10.0.5.2 dev p9p1
10.0.5.0/24 dev p9p1 proto kernel scope link src 10.0.5.15
70.0.0.0/24 dev p7p1 proto kernel scope link src 70.0.0.1
80.0.0.0/24 dev p8p1 proto kernel scope link src 80.0.0.1 dead
90.0.0.0/24 via 80.0.0.2 dev p8p1 metric 1 dead
90.0.0.0/24 via 70.0.0.2 dev p7p1 metric 2
# ip route get 90.0.0.1
90.0.0.1 via 70.0.0.2 dev p7p1 src 70.0.0.1
cache
# ip route get 80.0.0.1
local 80.0.0.1 dev lo src 80.0.0.1
cache <local>
# ip route get 80.0.0.2
80.0.0.2 via 10.0.5.2 dev p9p1 src 10.0.5.15
cache
While the route does remain in the table (so it can be modified if
needed rather than being wiped away as it would be if IFF_UP was
cleared), the proper next-hop is chosen automatically when the link is
down. Now interface p8p1 is linked-up:
# ip route show
default via 10.0.5.2 dev p9p1
10.0.5.0/24 dev p9p1 proto kernel scope link src 10.0.5.15
70.0.0.0/24 dev p7p1 proto kernel scope link src 70.0.0.1
80.0.0.0/24 dev p8p1 proto kernel scope link src 80.0.0.1
90.0.0.0/24 via 80.0.0.2 dev p8p1 metric 1
90.0.0.0/24 via 70.0.0.2 dev p7p1 metric 2
192.168.56.0/24 dev p2p1 proto kernel scope link src 192.168.56.2
# ip route get 90.0.0.1
90.0.0.1 via 80.0.0.2 dev p8p1 src 80.0.0.1
cache
# ip route get 80.0.0.1
local 80.0.0.1 dev lo src 80.0.0.1
cache <local>
# ip route get 80.0.0.2
80.0.0.2 dev p8p1 src 80.0.0.1
cache
and the output changes to what one would expect.
Signed-off-by: Andy Gospodarek <gospo@...ulusnetworks.com>
Suggested-by: Dinesh Dutt <ddutt@...ulusnetworks.com>
---
Though there were some that preferred not to have a configuration option
and to make this behavior the default when it was discussed in Ottawa
earlier this year since "it was time to do this." I wanted to propose
the config option to preserve the current behavior for those that desire
it. I'll happily remove it if Dave and Linus approve.
An IPv6 implementation is also needed (DECnet too!), but I wanted to
start with the IPv4 implementation to get people comfortable with the
idea before moving forward. If this is accepted the IPv6 implementation
can be posted shortly.
FWIW, we have been running this patch with the sysctl setting above and
our customers have been happily using a backported version for IPv4 and
IPv6 for >6 months.
include/linux/netdevice.h | 1 +
include/net/fib_rules.h | 1 +
include/net/ip_fib.h | 1 +
include/uapi/linux/rtnetlink.h | 1 +
include/uapi/linux/sysctl.h | 1 +
kernel/sysctl_binary.c | 1 +
net/core/dev.c | 2 ++
net/core/sysctl_net_core.c | 7 +++++++
net/ipv4/fib_frontend.c | 12 +++++++++--
net/ipv4/fib_rules.c | 7 ++++++-
net/ipv4/fib_semantics.c | 46 ++++++++++++++++++++++++++++++++++++------
net/ipv4/fib_trie.c | 19 +++++++++++++----
12 files changed, 86 insertions(+), 13 deletions(-)
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 6f5f71f..5bd953c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2986,6 +2986,7 @@ int dev_forward_skb(struct net_device *dev, struct sk_buff *skb);
bool is_skb_forwardable(struct net_device *dev, struct sk_buff *skb);
extern int netdev_budget;
+extern int kill_routes_on_linkdown;
/* Called by rtnetlink.c:rtnl_unlock() */
void netdev_run_todo(void);
diff --git a/include/net/fib_rules.h b/include/net/fib_rules.h
index 6d67383..4fbfda5 100644
--- a/include/net/fib_rules.h
+++ b/include/net/fib_rules.h
@@ -37,6 +37,7 @@ struct fib_lookup_arg {
struct fib_rule *rule;
int flags;
#define FIB_LOOKUP_NOREF 1
+#define FIB_LOOKUP_ALLOWDEAD 2
};
struct fib_rules_ops {
diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index 54271ed..efb195b 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h
@@ -250,6 +250,7 @@ struct fib_table *fib_new_table(struct net *net, u32 id);
struct fib_table *fib_get_table(struct net *net, u32 id);
int __fib_lookup(struct net *net, struct flowi4 *flp, struct fib_result *res);
+int fib_lookup_flags(struct net *n, struct flowi4 *flp, struct fib_result *res, int flags);
static inline int fib_lookup(struct net *net, struct flowi4 *flp,
struct fib_result *res)
diff --git a/include/uapi/linux/rtnetlink.h b/include/uapi/linux/rtnetlink.h
index 17fb02f..bc264d4 100644
--- a/include/uapi/linux/rtnetlink.h
+++ b/include/uapi/linux/rtnetlink.h
@@ -338,6 +338,7 @@ struct rtnexthop {
#define RTNH_F_PERVASIVE 2 /* Do recursive gateway lookup */
#define RTNH_F_ONLINK 4 /* Gateway is forced on link */
#define RTNH_F_OFFLOAD 8 /* offloaded route */
+#define RTNH_F_DEAD_LINKDOWN 16 /* Route dead due to carrier down */
/* Macros to handle hexthops */
diff --git a/include/uapi/linux/sysctl.h b/include/uapi/linux/sysctl.h
index 0956373..b6632dc 100644
--- a/include/uapi/linux/sysctl.h
+++ b/include/uapi/linux/sysctl.h
@@ -276,6 +276,7 @@ enum
NET_CORE_AEVENT_ETIME=20,
NET_CORE_AEVENT_RSEQTH=21,
NET_CORE_WARNINGS=22,
+ NET_CORE_KILL_ROUTES_ON_LINKDOWN=23,
};
/* /proc/sys/net/ethernet */
diff --git a/kernel/sysctl_binary.c b/kernel/sysctl_binary.c
index 7e7746a..f319116 100644
--- a/kernel/sysctl_binary.c
+++ b/kernel/sysctl_binary.c
@@ -196,6 +196,7 @@ static const struct bin_table bin_net_core_table[] = {
{ CTL_INT, NET_CORE_AEVENT_ETIME, "xfrm_aevent_etime" },
{ CTL_INT, NET_CORE_AEVENT_RSEQTH, "xfrm_aevent_rseqth" },
{ CTL_INT, NET_CORE_WARNINGS, "warnings" },
+ { CTL_INT, NET_CORE_KILL_ROUTES_ON_LINKDOWN, "kill_routes_on_linkdown" },
{},
};
diff --git a/net/core/dev.c b/net/core/dev.c
index 0602e91..50dc19c 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3167,6 +3167,8 @@ EXPORT_SYMBOL(netdev_max_backlog);
int netdev_tstamp_prequeue __read_mostly = 1;
int netdev_budget __read_mostly = 300;
int weight_p __read_mostly = 64; /* old backlog weight */
+int kill_routes_on_linkdown = 0;
+EXPORT_SYMBOL(kill_routes_on_linkdown);
/* Called with irq disabled */
static inline void ____napi_schedule(struct softnet_data *sd,
diff --git a/net/core/sysctl_net_core.c b/net/core/sysctl_net_core.c
index 95b6139..fef1804 100644
--- a/net/core/sysctl_net_core.c
+++ b/net/core/sysctl_net_core.c
@@ -392,6 +392,13 @@ static struct ctl_table net_core_table[] = {
.mode = 0644,
.proc_handler = proc_dointvec
},
+ {
+ .procname = "kill_routes_on_linkdown",
+ .data = &kill_routes_on_linkdown,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec
+ },
{ }
};
diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index 872494e..94348c7 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c
@@ -1107,6 +1107,7 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
struct net_device *dev = netdev_notifier_info_to_dev(ptr);
struct in_device *in_dev;
struct net *net = dev_net(dev);
+ unsigned flags;
if (event == NETDEV_UNREGISTER) {
fib_disable_ip(dev, 2);
@@ -1130,10 +1131,17 @@ static int fib_netdev_event(struct notifier_block *this, unsigned long event, vo
rt_cache_flush(net);
break;
case NETDEV_DOWN:
- fib_disable_ip(dev, 0);
+ fib_disable_ip(dev, 1);
break;
- case NETDEV_CHANGEMTU:
case NETDEV_CHANGE:
+ if (kill_routes_on_linkdown) {
+ flags = dev_get_flags(dev);
+ if (flags & (IFF_RUNNING|IFF_LOWER_UP))
+ fib_sync_up(dev);
+ else
+ fib_sync_down_dev(dev, 0);
+ }
+ case NETDEV_CHANGEMTU:
rt_cache_flush(net);
break;
}
diff --git a/net/ipv4/fib_rules.c b/net/ipv4/fib_rules.c
index 5615198..d135ec9 100644
--- a/net/ipv4/fib_rules.c
+++ b/net/ipv4/fib_rules.c
@@ -49,9 +49,14 @@ struct fib4_rule {
int __fib_lookup(struct net *net, struct flowi4 *flp, struct fib_result *res)
{
+ return fib_lookup_flags(net, flp, res, 0);
+}
+
+int fib_lookup_flags(struct net *net, struct flowi4 *flp, struct fib_result *res, int flags)
+{
struct fib_lookup_arg arg = {
.result = res,
- .flags = FIB_LOOKUP_NOREF,
+ .flags = FIB_LOOKUP_NOREF | flags,
};
int err;
diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 28ec3c1..c0874ee 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -266,7 +266,7 @@ static inline int nh_comp(const struct fib_info *fi, const struct fib_info *ofi)
#ifdef CONFIG_IP_ROUTE_CLASSID
nh->nh_tclassid != onh->nh_tclassid ||
#endif
- ((nh->nh_flags ^ onh->nh_flags) & ~RTNH_F_DEAD))
+ ((nh->nh_flags ^ onh->nh_flags) & ~(RTNH_F_DEAD|RTNH_F_DEAD_LINKDOWN)))
return -1;
onh++;
} endfor_nexthops(fi);
@@ -318,7 +318,7 @@ static struct fib_info *fib_find_info(const struct fib_info *nfi)
nfi->fib_type == fi->fib_type &&
memcmp(nfi->fib_metrics, fi->fib_metrics,
sizeof(u32) * RTAX_MAX) == 0 &&
- ((nfi->fib_flags ^ fi->fib_flags) & ~RTNH_F_DEAD) == 0 &&
+ ((nfi->fib_flags ^ fi->fib_flags) & ~(RTNH_F_DEAD|RTNH_F_DEAD_LINKDOWN)) == 0 &&
(nfi->fib_nhs == 0 || nh_comp(fi, nfi) == 0))
return fi;
}
@@ -604,6 +604,8 @@ static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
return -ENODEV;
if (!(dev->flags & IFF_UP))
return -ENETDOWN;
+ if (!netif_carrier_ok(dev) && kill_routes_on_linkdown)
+ nh->nh_flags |= RTNH_F_DEAD;
nh->nh_dev = dev;
dev_hold(dev);
nh->nh_scope = RT_SCOPE_LINK;
@@ -621,7 +623,7 @@ static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
/* It is not necessary, but requires a bit of thinking */
if (fl4.flowi4_scope < RT_SCOPE_LINK)
fl4.flowi4_scope = RT_SCOPE_LINK;
- err = fib_lookup(net, &fl4, &res);
+ err = fib_lookup_flags(net, &fl4, &res, FIB_LOOKUP_ALLOWDEAD);
if (err) {
rcu_read_unlock();
return err;
@@ -636,6 +638,8 @@ static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
if (!dev)
goto out;
dev_hold(dev);
+ if (!netif_carrier_ok(dev) && kill_routes_on_linkdown)
+ nh->nh_flags |= RTNH_F_DEAD;
err = (dev->flags & IFF_UP) ? 0 : -ENETDOWN;
} else {
struct in_device *in_dev;
@@ -654,6 +658,8 @@ static int fib_check_nh(struct fib_config *cfg, struct fib_info *fi,
nh->nh_dev = in_dev->dev;
dev_hold(nh->nh_dev);
nh->nh_scope = RT_SCOPE_HOST;
+ if (!netif_carrier_ok(nh->nh_dev) && kill_routes_on_linkdown)
+ nh->nh_flags |= RTNH_F_DEAD;
err = 0;
}
out:
@@ -760,6 +766,7 @@ struct fib_info *fib_create_info(struct fib_config *cfg)
struct fib_info *ofi;
int nhs = 1;
struct net *net = cfg->fc_nlinfo.nl_net;
+ int dead;
if (cfg->fc_type > RTN_MAX)
goto err_inval;
@@ -920,11 +927,18 @@ struct fib_info *fib_create_info(struct fib_config *cfg)
if (!nh->nh_dev)
goto failure;
} else {
+ dead = 0;
change_nexthops(fi) {
err = fib_check_nh(cfg, fi, nexthop_nh);
if (err != 0)
goto failure;
+ if (nexthop_nh->nh_flags & RTNH_F_DEAD)
+ dead++;
} endfor_nexthops(fi)
+ if ((dead == fi->fib_nhs)) {
+ fi->fib_flags |= RTNH_F_DEAD;
+ fi->fib_flags |= RTNH_F_DEAD_LINKDOWN;
+ }
}
if (fi->fib_prefsrc) {
@@ -1097,6 +1111,8 @@ int fib_sync_down_addr(struct net *net, __be32 local)
continue;
if (fi->fib_prefsrc == local) {
fi->fib_flags |= RTNH_F_DEAD;
+ /* Addr is gone, more serious than a linkdown */
+ fi->fib_flags &= ~RTNH_F_DEAD_LINKDOWN;
ret++;
}
}
@@ -1112,7 +1128,7 @@ int fib_sync_down_dev(struct net_device *dev, int force)
struct hlist_head *head = &fib_info_devhash[hash];
struct fib_nh *nh;
- if (force)
+ if (force > 1)
scope = -1;
hlist_for_each_entry(nh, head, nh_hash) {
@@ -1147,6 +1163,11 @@ int fib_sync_down_dev(struct net_device *dev, int force)
} endfor_nexthops(fi)
if (dead == fi->fib_nhs) {
fi->fib_flags |= RTNH_F_DEAD;
+ /* force marks route down due to admin down and device removal. */
+ if (!force)
+ fi->fib_flags |= RTNH_F_DEAD_LINKDOWN;
+ else
+ fi->fib_flags &= ~RTNH_F_DEAD_LINKDOWN;
ret++;
}
}
@@ -1223,10 +1244,12 @@ int fib_sync_up(struct net_device *dev)
struct hlist_head *head;
struct fib_nh *nh;
int ret;
+ int link_up;
if (!(dev->flags & IFF_UP))
return 0;
+ link_up = netif_carrier_ok(dev);
prev_fi = NULL;
hash = fib_devindex_hashfn(dev->ifindex);
head = &fib_info_devhash[hash];
@@ -1253,16 +1276,27 @@ int fib_sync_up(struct net_device *dev)
if (nexthop_nh->nh_dev != dev ||
!__in_dev_get_rtnl(dev))
continue;
- alive++;
+ if (link_up) {
+ /* Link is up, so mark NH as alive */
+ nexthop_nh->nh_flags &= ~RTNH_F_DEAD;
+ alive++;
+ } else
+ nexthop_nh->nh_flags |= RTNH_F_DEAD;
+
spin_lock_bh(&fib_multipath_lock);
nexthop_nh->nh_power = 0;
- nexthop_nh->nh_flags &= ~RTNH_F_DEAD;
spin_unlock_bh(&fib_multipath_lock);
} endfor_nexthops(fi)
if (alive > 0) {
+ /* Some NHs are alive, unmark the route as dead */
+ fi->fib_flags &= ~RTNH_F_DEAD_LINKDOWN;
fi->fib_flags &= ~RTNH_F_DEAD;
ret++;
+ } else {
+ /* No NHs are alive, mark the route as dead */
+ fi->fib_flags |= RTNH_F_DEAD_LINKDOWN;
+ fi->fib_flags |= RTNH_F_DEAD;
}
}
diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 01bce15..eedf287 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -1401,12 +1401,18 @@ found:
#endif
return err;
}
- if (fi->fib_flags & RTNH_F_DEAD)
- continue;
+ if (!(fib_flags & FIB_LOOKUP_ALLOWDEAD)) {
+ /* if route is dead and link is down, keep looking */
+ if ((fi->fib_flags & RTNH_F_DEAD) &&
+ (fi->fib_flags & RTNH_F_DEAD_LINKDOWN))
+ continue;
+ }
for (nhsel = 0; nhsel < fi->fib_nhs; nhsel++) {
const struct fib_nh *nh = &fi->fib_nh[nhsel];
- if (nh->nh_flags & RTNH_F_DEAD)
+ /* allow next-hop to be added if link is down */
+ if ((nh->nh_flags & RTNH_F_DEAD) &&
+ !(fi->fib_flags & RTNH_F_DEAD_LINKDOWN))
continue;
if (flp->flowi4_oif && flp->flowi4_oif != nh->nh_oif)
continue;
@@ -1829,7 +1835,12 @@ int fib_table_flush(struct fib_table *tb)
hlist_for_each_entry_safe(fa, tmp, &n->leaf, fa_list) {
struct fib_info *fi = fa->fa_info;
- if (!fi || !(fi->fib_flags & RTNH_F_DEAD)) {
+ /* DEAD and DEAD_LINKDOWN will not both be set
+ * with IFF_UP is cleared, so do not flush
+ * entries with only DEAD set
+ */
+ if (!fi || !((fi->fib_flags & RTNH_F_DEAD) &&
+ !(fi->fib_flags & RTNH_F_DEAD_LINKDOWN))) {
slen = fa->fa_slen;
continue;
}
--
1.9.3
--
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