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authorPraveen Chaudhary <praveen5582@gmail.com>2021-01-26 00:44:30 +0300
committerJakub Kicinski <kuba@kernel.org>2021-01-27 05:39:45 +0300
commit6b2e04bc240fe9be9e690059f710e9f95346d34d (patch)
tree65afe8c4d881489a8fd8be3db2b84291b57ca6f1 /net/ipv6/ndisc.c
parent6626a0266566c5aea16178c5e6cd7fc4db3f2f56 (diff)
downloadlinux-6b2e04bc240fe9be9e690059f710e9f95346d34d.tar.xz
net: allow user to set metric on default route learned via Router Advertisement
For IPv4, default route is learned via DHCPv4 and user is allowed to change metric using config etc/network/interfaces. But for IPv6, default route can be learned via RA, for which, currently a fixed metric value 1024 is used. Ideally, user should be able to configure metric on default route for IPv6 similar to IPv4. This patch adds sysctl for the same. Logs: For IPv4: Config in etc/network/interfaces: auto eth0 iface eth0 inet dhcp metric 4261413864 IPv4 Kernel Route Table: $ ip route list default via 172.21.47.1 dev eth0 metric 4261413864 FRR Table, if a static route is configured: [In real scenario, it is useful to prefer BGP learned default route over DHCPv4 default route.] Codes: K - kernel route, C - connected, S - static, R - RIP, O - OSPF, I - IS-IS, B - BGP, P - PIM, E - EIGRP, N - NHRP, T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP, > - selected route, * - FIB route S>* 0.0.0.0/0 [20/0] is directly connected, eth0, 00:00:03 K 0.0.0.0/0 [254/1000] via 172.21.47.1, eth0, 6d08h51m i.e. User can prefer Default Router learned via Routing Protocol in IPv4. Similar behavior is not possible for IPv6, without this fix. After fix [for IPv6]: sudo sysctl -w net.ipv6.conf.eth0.net.ipv6.conf.eth0.ra_defrtr_metric=1996489705 IP monitor: [When IPv6 RA is received] default via fe80::xx16:xxxx:feb3:ce8e dev eth0 proto ra metric 1996489705 pref high Kernel IPv6 routing table $ ip -6 route list default via fe80::be16:65ff:feb3:ce8e dev eth0 proto ra metric 1996489705 expires 21sec hoplimit 64 pref high FRR Table, if a static route is configured: [In real scenario, it is useful to prefer BGP learned default route over IPv6 RA default route.] Codes: K - kernel route, C - connected, S - static, R - RIPng, O - OSPFv3, I - IS-IS, B - BGP, N - NHRP, T - Table, v - VNC, V - VNC-Direct, A - Babel, D - SHARP, > - selected route, * - FIB route S>* ::/0 [20/0] is directly connected, eth0, 00:00:06 K ::/0 [119/1001] via fe80::xx16:xxxx:feb3:ce8e, eth0, 6d07h43m If the metric is changed later, the effect will be seen only when next IPv6 RA is received, because the default route must be fully controlled by RA msg. Below metric is changed from 1996489705 to 1996489704. $ sudo sysctl -w net.ipv6.conf.eth0.ra_defrtr_metric=1996489704 net.ipv6.conf.eth0.ra_defrtr_metric = 1996489704 IP monitor: [On next IPv6 RA msg, Kernel deletes prev route and installs new route with updated metric] Deleted default via fe80::xx16:xxxx:feb3:ce8e dev eth0 proto ra metric 1996489705 expires 3sec hoplimit 64 pref high default via fe80::xx16:xxxx:feb3:ce8e dev eth0 proto ra metric 1996489704 pref high Signed-off-by: Praveen Chaudhary <pchaudhary@linkedin.com> Signed-off-by: Zhenggen Xu <zxu@linkedin.com> Reviewed-by: David Ahern <dsahern@kernel.org> Link: https://lore.kernel.org/r/20210125214430.24079-1-pchaudhary@linkedin.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net/ipv6/ndisc.c')
-rw-r--r--net/ipv6/ndisc.c12
1 files changed, 8 insertions, 4 deletions
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 76717478f173..c467c6419893 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1173,6 +1173,7 @@ static void ndisc_router_discovery(struct sk_buff *skb)
struct neighbour *neigh = NULL;
struct inet6_dev *in6_dev;
struct fib6_info *rt = NULL;
+ u32 defrtr_usr_metric;
struct net *net;
int lifetime;
struct ndisc_options ndopts;
@@ -1303,18 +1304,21 @@ static void ndisc_router_discovery(struct sk_buff *skb)
return;
}
}
- if (rt && lifetime == 0) {
+ /* Set default route metric as specified by user */
+ defrtr_usr_metric = in6_dev->cnf.ra_defrtr_metric;
+ /* delete the route if lifetime is 0 or if metric needs change */
+ if (rt && (lifetime == 0 || rt->fib6_metric != defrtr_usr_metric)) {
ip6_del_rt(net, rt, false);
rt = NULL;
}
- ND_PRINTK(3, info, "RA: rt: %p lifetime: %d, for dev: %s\n",
- rt, lifetime, skb->dev->name);
+ ND_PRINTK(3, info, "RA: rt: %p lifetime: %d, metric: %d, for dev: %s\n",
+ rt, lifetime, defrtr_usr_metric, skb->dev->name);
if (!rt && lifetime) {
ND_PRINTK(3, info, "RA: adding default router\n");
rt = rt6_add_dflt_router(net, &ipv6_hdr(skb)->saddr,
- skb->dev, pref);
+ skb->dev, pref, defrtr_usr_metric);
if (!rt) {
ND_PRINTK(0, err,
"RA: %s failed to add default route\n",