[PATCH 1/2 net-next v5] ipv6: addrconf: fix temp address generation after prefix deprecation

[PATCH 1/2 net-next v5] ipv6: addrconf: fix temp address generation after prefix deprecation

[Fernando Fernandez Mancera]

When a router temporarily deprecates an IPv6 prefix (either by sending a
Router Advertisement with Preferred Lifetime = 0 or by letting the
lifetime expire) and later restores it, the kernel permanently loses its
ability to generate temporary privacy addresses (RFC 8981) for that
prefix.

This happens because the address worker attempts to generate a
replacement temporary address when the current one nears expiration. As
the base prefix is deprecated already, the generation fails after
marking the temporary address as already having spawned a replacement
(ifp->regen_count++).

When the router eventually restores the prefix, the temporary address
becomes active again. However, once it naturally expires, the address
worker sees this temporary address already tried to generate one and
skips the regeneration.

Fix the issue by resetting the regen_count check of the latest temp
address generated for the prefix updated by the incoming RA.

Reported-by: Łukasz Stelmach <steelman@post.pl>
Closes: https://lore.kernel.org/netdev/87340td30q.fsf%25steelman@post.pl/
Suggested-by: Ido Schimmel <idosch@nvidia.com>
Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
---
v2: adjusted commit message, adjusted the implementation to cover all
race conditions
v3: regen now if ipv6_create_tempaddr failed due to timer to avoid an
infinite loop as we restart the loop and we need to check now against
prefered_lft again.
v4: change the proposed fix completely, now we address the problem when
doing manage_tempaddrs().
v5: reset regen_count for the most recent temp address when a non
0-lft RA arrives.
---
 net/ipv6/addrconf.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index da0f07e21e3f..d7b03196725f 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -1174,6 +1174,7 @@ ipv6_add_addr(struct inet6_dev *idev, struct ifa6_config *cfg,
 	ipv6_link_dev_addr(idev, ifa);
 
 	if (ifa->flags&IFA_F_TEMPORARY) {
+		/* manage_tempaddrs() relies on addresses being added to the head */
 		list_add(&ifa->tmp_list, &idev->tempaddr_list);
 		in6_ifa_hold(ifa);
 	}
@@ -2602,8 +2603,10 @@ static void manage_tempaddrs(struct inet6_dev *idev,
 			     __u32 valid_lft, __u32 prefered_lft,
 			     bool create, unsigned long now)
 {
-	u32 flags;
+	u32 orig_prefered_lft = prefered_lft;
 	struct inet6_ifaddr *ift;
+	bool reset_done = false;
+	u32 flags;
 
 	read_lock_bh(&idev->lock);
 	/* update all temporary addresses in the list */
@@ -2638,6 +2641,11 @@ static void manage_tempaddrs(struct inet6_dev *idev,
 			prefered_lft = max_prefered;
 
 		spin_lock(&ift->lock);
+		/* the first match is the most recent temp address */
+		if (!reset_done && orig_prefered_lft > 0) {
+			ift->regen_count = 0;
+			reset_done = true;
+		}
 		flags = ift->flags;
 		ift->valid_lft = valid_lft;
 		ift->prefered_lft = prefered_lft;
-- 
2.53.0

[PATCH 2/2 net-next v5] selftests: fib_tests: add temporary IPv6 address renewal test

[Fernando Fernandez Mancera]

Add a test to check that temporary IPv6 address is regenerated properly
after the base prefix is deprecated and restored.

Fib6 temporary address renewal test
    TEST: IPv6 temporary address cleanly deprecated and regenerated     [ OK ]

Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
---
v2: adjusted the sleep so there is enough time for the issue to trigger,
added cleanup at the end
v3: no changes
v4: no changes
v5: no changes
---
 tools/testing/selftests/net/fib_tests.sh | 59 +++++++++++++++++++++++-
 1 file changed, 58 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/net/fib_tests.sh b/tools/testing/selftests/net/fib_tests.sh
index af64f93bb2e1..8f10de0eb985 100755
--- a/tools/testing/selftests/net/fib_tests.sh
+++ b/tools/testing/selftests/net/fib_tests.sh
@@ -12,7 +12,7 @@ TESTS="unregister down carrier nexthop suppress ipv6_notify ipv4_notify \
        ipv4_route_metrics ipv4_route_v6_gw rp_filter ipv4_del_addr \
        ipv6_del_addr ipv4_mangle ipv6_mangle ipv4_bcast_neigh fib6_gc_test \
        ipv4_mpath_list ipv6_mpath_list ipv4_mpath_balance ipv6_mpath_balance \
-       ipv4_mpath_balance_preferred fib6_ra_to_static"
+       ipv4_mpath_balance_preferred fib6_ra_to_static fib6_temp_addr_renewal"
 
 VERBOSE=0
 PAUSE_ON_FAIL=no
@@ -1611,6 +1611,62 @@ fib6_ra_to_static()
 	cleanup &> /dev/null
 }
 
+fib6_temp_addr_renewal() {
+	setup
+
+	echo
+	echo "Fib6 temporary address renewal test"
+	set -e
+
+	# ra6 is required for the test. (ipv6toolkit)
+	if [ ! -x "$(command -v ra6)" ]; then
+	    echo "SKIP: ra6 not found."
+	    set +e
+	    cleanup &> /dev/null
+	    return
+	fi
+
+	# Create a pair of veth devices to send a RA message from one
+	# device to another.
+	$IP link add veth1 type veth peer name veth2
+	$IP link set dev veth1 up
+	$IP link set dev veth2 up
+
+	# Make veth1 ready to receive RA messages.
+	$NS_EXEC sysctl -wq net.ipv6.conf.veth1.accept_ra=2
+	$NS_EXEC sysctl -wq net.ipv6.conf.veth1.use_tempaddr=2
+	$NS_EXEC sysctl -wq net.ipv6.conf.veth1.temp_prefered_lft=15
+	$NS_EXEC sysctl -wq net.ipv6.conf.veth1.max_desync_factor=0
+
+	# Send a RA message with a prefix from veth2.
+	$NS_EXEC ra6 -i veth2 -s fe80::1 -d ff02::1 -P 2001:12::/64\#LA\#3600\#3600 -e
+	sleep 3
+
+	# Deprecate it
+	$NS_EXEC ra6 -i veth2 -s fe80::1 -d ff02::1 -P 2001:12::/64\#LA\#3600\#0 -e
+	sleep 3
+
+	# Restore it
+	$NS_EXEC ra6 -i veth2 -s fe80::1 -d ff02::1 -P 2001:12::/64\#LA\#3600\#3600 -e
+
+	ret=1
+	for i in $(seq 1 25); do
+		sleep 1
+		num_dep="$($IP -6 addr | grep -c "temporary deprecated" || true)"
+		num_tot="$($IP -6 addr | grep -c "temporary" || true)"
+
+		if [ "$num_dep" -eq 1 ] && [ "$num_tot" -ge 2 ]; then
+			ret=0
+			break
+		fi
+	done
+	log_test "$ret" 0 "IPv6 temporary address cleanly deprecated and regenerated"
+
+	set +e
+
+	cleanup &> /dev/null
+}
+
 # add route for a prefix, flushing any existing routes first
 # expected to be the first step of a test
 add_route()
@@ -3002,6 +3058,7 @@ do
 	ipv6_mpath_balance)		ipv6_mpath_balance_test;;
 	ipv4_mpath_balance_preferred)	ipv4_mpath_balance_preferred_test;;
 	fib6_ra_to_static)		fib6_ra_to_static;;
+	fib6_temp_addr_renewal)		fib6_temp_addr_renewal;;
 
 	help) echo "Test names: $TESTS"; exit 0;;
 	esac
-- 
2.53.0