From 76c03bf8e2624076b88d93542d78e22d5345c88e Mon Sep 17 00:00:00 2001 From: Ido Schimmel Date: Thu, 4 Mar 2021 10:57:53 +0200 Subject: nexthop: Do not flush blackhole nexthops when loopback goes down As far as user space is concerned, blackhole nexthops do not have a nexthop device and therefore should not be affected by the administrative or carrier state of any netdev. However, when the loopback netdev goes down all the blackhole nexthops are flushed. This happens because internally the kernel associates blackhole nexthops with the loopback netdev. This behavior is both confusing to those not familiar with kernel internals and also diverges from the legacy API where blackhole IPv4 routes are not flushed when the loopback netdev goes down: # ip route add blackhole 198.51.100.0/24 # ip link set dev lo down # ip route show 198.51.100.0/24 blackhole 198.51.100.0/24 Blackhole IPv6 routes are flushed, but at least user space knows that they are associated with the loopback netdev: # ip -6 route show 2001:db8:1::/64 blackhole 2001:db8:1::/64 dev lo metric 1024 pref medium Fix this by only flushing blackhole nexthops when the loopback netdev is unregistered. Fixes: ab84be7e54fc ("net: Initial nexthop code") Signed-off-by: Ido Schimmel Reported-by: Donald Sharp Reviewed-by: David Ahern Signed-off-by: David S. Miller --- net/ipv4/nexthop.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c index f1c6cbdb9e43..743777bce179 100644 --- a/net/ipv4/nexthop.c +++ b/net/ipv4/nexthop.c @@ -1399,7 +1399,7 @@ out: /* rtnl */ /* remove all nexthops tied to a device being deleted */ -static void nexthop_flush_dev(struct net_device *dev) +static void nexthop_flush_dev(struct net_device *dev, unsigned long event) { unsigned int hash = nh_dev_hashfn(dev->ifindex); struct net *net = dev_net(dev); @@ -1411,6 +1411,10 @@ static void nexthop_flush_dev(struct net_device *dev) if (nhi->fib_nhc.nhc_dev != dev) continue; + if (nhi->reject_nh && + (event == NETDEV_DOWN || event == NETDEV_CHANGE)) + continue; + remove_nexthop(net, nhi->nh_parent, NULL); } } @@ -2189,11 +2193,11 @@ static int nh_netdev_event(struct notifier_block *this, switch (event) { case NETDEV_DOWN: case NETDEV_UNREGISTER: - nexthop_flush_dev(dev); + nexthop_flush_dev(dev, event); break; case NETDEV_CHANGE: if (!(dev_get_flags(dev) & (IFF_RUNNING | IFF_LOWER_UP))) - nexthop_flush_dev(dev); + nexthop_flush_dev(dev, event); break; case NETDEV_CHANGEMTU: info_ext = ptr; -- cgit v1.2.3 From 3a1099d3147f391fa11320a759bbcb1bb857fca1 Mon Sep 17 00:00:00 2001 From: Ido Schimmel Date: Thu, 4 Mar 2021 10:57:54 +0200 Subject: selftests: fib_nexthops: Test blackhole nexthops when loopback goes down Test that blackhole nexthops are not flushed when the loopback device goes down. Output without previous patch: # ./fib_nexthops.sh -t basic Basic functional tests ---------------------- TEST: List with nothing defined [ OK ] TEST: Nexthop get on non-existent id [ OK ] TEST: Nexthop with no device or gateway [ OK ] TEST: Nexthop with down device [ OK ] TEST: Nexthop with device that is linkdown [ OK ] TEST: Nexthop with device only [ OK ] TEST: Nexthop with duplicate id [ OK ] TEST: Blackhole nexthop [ OK ] TEST: Blackhole nexthop with other attributes [ OK ] TEST: Blackhole nexthop with loopback device down [FAIL] TEST: Create group [ OK ] TEST: Create group with blackhole nexthop [FAIL] TEST: Create multipath group where 1 path is a blackhole [ OK ] TEST: Multipath group can not have a member replaced by blackhole [ OK ] TEST: Create group with non-existent nexthop [ OK ] TEST: Create group with same nexthop multiple times [ OK ] TEST: Replace nexthop with nexthop group [ OK ] TEST: Replace nexthop group with nexthop [ OK ] TEST: Nexthop group and device [ OK ] TEST: Test proto flush [ OK ] TEST: Nexthop group and blackhole [ OK ] Tests passed: 19 Tests failed: 2 Output with previous patch: # ./fib_nexthops.sh -t basic Basic functional tests ---------------------- TEST: List with nothing defined [ OK ] TEST: Nexthop get on non-existent id [ OK ] TEST: Nexthop with no device or gateway [ OK ] TEST: Nexthop with down device [ OK ] TEST: Nexthop with device that is linkdown [ OK ] TEST: Nexthop with device only [ OK ] TEST: Nexthop with duplicate id [ OK ] TEST: Blackhole nexthop [ OK ] TEST: Blackhole nexthop with other attributes [ OK ] TEST: Blackhole nexthop with loopback device down [ OK ] TEST: Create group [ OK ] TEST: Create group with blackhole nexthop [ OK ] TEST: Create multipath group where 1 path is a blackhole [ OK ] TEST: Multipath group can not have a member replaced by blackhole [ OK ] TEST: Create group with non-existent nexthop [ OK ] TEST: Create group with same nexthop multiple times [ OK ] TEST: Replace nexthop with nexthop group [ OK ] TEST: Replace nexthop group with nexthop [ OK ] TEST: Nexthop group and device [ OK ] TEST: Test proto flush [ OK ] TEST: Nexthop group and blackhole [ OK ] Tests passed: 21 Tests failed: 0 Signed-off-by: Ido Schimmel Reviewed-by: David Ahern Signed-off-by: David S. Miller --- tools/testing/selftests/net/fib_nexthops.sh | 8 ++++++++ 1 file changed, 8 insertions(+) diff --git a/tools/testing/selftests/net/fib_nexthops.sh b/tools/testing/selftests/net/fib_nexthops.sh index 4c7d33618437..d98fb85e201c 100755 --- a/tools/testing/selftests/net/fib_nexthops.sh +++ b/tools/testing/selftests/net/fib_nexthops.sh @@ -1524,6 +1524,14 @@ basic() run_cmd "$IP nexthop replace id 2 blackhole dev veth1" log_test $? 2 "Blackhole nexthop with other attributes" + # blackhole nexthop should not be affected by the state of the loopback + # device + run_cmd "$IP link set dev lo down" + check_nexthop "id 2" "id 2 blackhole" + log_test $? 0 "Blackhole nexthop with loopback device down" + + run_cmd "$IP link set dev lo up" + # # groups # -- cgit v1.2.3