Subject: [PATCH net-next v5 1/5] net/ipv6: set expires in rt6_add_dflt_router().

From: [email-masked]
Date: Wed, 7 Feb 2024 11:29:29 -0800

From: Kui-Feng Lee <[email-masked]>

Pass the duration of a lifetime (in seconds) to the function
rt6_add_dflt_router() so that it can properly set the expiration time.

The function ndisc_router_discovery() is the only one that calls
rt6_add_dflt_router(), and it will later set the expiration time for the
route created by rt6_add_dflt_router(). However, there is a gap of time
between calling rt6_add_dflt_router() and setting the expiration time in
ndisc_router_discovery(). During this period, there is a possibility that a
new route may be removed from the routing table. By setting the correct
expiration time in rt6_add_dflt_router(), we can prevent this from
happening. The reason for setting RTF_EXPIRES in rt6_add_dflt_router() is
to start the Garbage Collection (GC) timer, as it only activates when a
route with RTF_EXPIRES is added to a table.

Suggested-by: David Ahern <[email-masked]>
Reviewed-by: Hangbin Liu <[email-masked]>
Reviewed-by: David Ahern <[email-masked]>
Signed-off-by: Kui-Feng Lee <[email-masked]>
---
 include/net/ip6_route.h | 3 ++-
 net/ipv6/ndisc.c        | 3 ++-
 net/ipv6/route.c        | 4 +++-
 3 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 28b065790261..52a51c69aa9d 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -170,7 +170,8 @@ struct fib6_info *rt6_get_dflt_router(struct net *net,
 struct fib6_info *rt6_add_dflt_router(struct net *net,
 				     const struct in6_addr *gwaddr,
 				     struct net_device *dev, unsigned int pref,
-				     u32 defrtr_usr_metric);
+				     u32 defrtr_usr_metric,
+				     int lifetime);
 
 void rt6_purge_dflt_routers(struct net *net);
 
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index a19999b30bc0..a68462668158 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1382,7 +1382,8 @@ static enum skb_drop_reason ndisc_router_discovery(struct sk_buff *skb)
 			neigh_release(neigh);
 
 		rt = rt6_add_dflt_router(net, &ipv6_hdr(skb)->saddr,
-					 skb->dev, pref, defrtr_usr_metric);
+					 skb->dev, pref, defrtr_usr_metric,
+					 lifetime);
 		if (!rt) {
 			ND_PRINTK(0, err,
 				  "RA: %s failed to add default route\n",
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 63b4c6056582..98abba8f15cd 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -4355,7 +4355,8 @@ struct fib6_info *rt6_add_dflt_router(struct net *net,
 				     const struct in6_addr *gwaddr,
 				     struct net_device *dev,
 				     unsigned int pref,
-				     u32 defrtr_usr_metric)
+				     u32 defrtr_usr_metric,
+				     int lifetime)
 {
 	struct fib6_config cfg = {
 		.fc_table	= l3mdev_fib_table(dev) ? : RT6_TABLE_DFLT,
@@ -4368,6 +4369,7 @@ struct fib6_info *rt6_add_dflt_router(struct net *net,
 		.fc_nlinfo.portid = 0,
 		.fc_nlinfo.nlh = NULL,
 		.fc_nlinfo.nl_net = net,
+		.fc_expires = jiffies_to_clock_t(lifetime * HZ),
 	};
 
 	cfg.fc_gateway = *gwaddr;
-- 
2.34.1