[PATCH 1/1] Address regression in inet6_validate_link_af

[Jonas Bonn]

Patch 7dc2bccab0ee37ac28096b8fcdc390a679a15841 introduces a regression
with systemd 241.  In that revision, systemd-networkd fails to pass the
required flags early enough.  This appears to be addressed in later
versions of systemd, but for users of version 241 where systemd-networkd
nonetheless worked with earlier kernels, the strict check introduced by
the patch causes a regression in behaviour.

This patch converts the failure to supply the required flags from an
error into a warning.  With this, systemd-networkd version 241 once
again is able to bring up the link, albeit not quite as intended and
thereby with a warning in the kernel log.

CC: Maxim Mikityanskiy <maximmi@xxxxxxxxxxxx>
CC: David S. Miller <davem@xxxxxxxxxxxxx>
CC: Alexey Kuznetsov <kuznet@xxxxxxxxxxxxx>
CC: Hideaki YOSHIFUJI <yoshfuji@xxxxxxxxxxxxxx>
Signed-off-by: Jonas Bonn <jonas@xxxxxxxxxxx>
---
 net/ipv6/addrconf.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 081bb517e40d..e2477bf92e12 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -5696,7 +5696,8 @@ static int inet6_validate_link_af(const struct net_device *dev,
 		return err;
 
 	if (!tb[IFLA_INET6_TOKEN] && !tb[IFLA_INET6_ADDR_GEN_MODE])
-		return -EINVAL;
+		net_warn_ratelimited(
+			"required link flag omitted: TOKEN/ADDR_GEN_MODE\n");
 
 	if (tb[IFLA_INET6_ADDR_GEN_MODE]) {
 		u8 mode = nla_get_u8(tb[IFLA_INET6_ADDR_GEN_MODE]);
-- 
2.20.1