[PATCH AUTOSEL 4.19 03/65] xfrm: Make set-mark default behavior backward compatible

From: Sasha Levin
Date: Sat Feb 23 2019 - 16:28:06 EST

From: Benedict Wong <benedictwong@xxxxxxxxxx>

[ Upstream commit e2612cd496e7b465711d219ea6118893d7253f52 ]

Fixes 9b42c1f179a6, which changed the default route lookup behavior for
tunnel mode SAs in the outbound direction to use the skb mark, whereas
previously mark=0 was used if the output mark was unspecified. In
mark-based routing schemes such as Androidâs, this change in default
behavior causes routing loops or lookup failures.

This patch restores the default behavior of using a 0 mark while still
incorporating the skb mark if the SET_MARK (and SET_MARK_MASK) is

Tested with additions to Android's kernel unit test suite:

Fixes: 9b42c1f179a6 ("xfrm: Extend the output_mark to support input direction and masking")
Signed-off-by: Benedict Wong <benedictwong@xxxxxxxxxx>
Signed-off-by: Steffen Klassert <steffen.klassert@xxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
net/xfrm/xfrm_policy.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/net/xfrm/xfrm_policy.c b/net/xfrm/xfrm_policy.c
index 119a427d9b2b2..6ea8036fcdbeb 100644
--- a/net/xfrm/xfrm_policy.c
+++ b/net/xfrm/xfrm_policy.c
@@ -1628,7 +1628,10 @@ static struct dst_entry *xfrm_bundle_create(struct xfrm_policy *policy,
dst_copy_metrics(dst1, dst);

if (xfrm[i]->props.mode != XFRM_MODE_TRANSPORT) {
- __u32 mark = xfrm_smark_get(fl->flowi_mark, xfrm[i]);
+ __u32 mark = 0;
+ if (xfrm[i]->props.smark.v || xfrm[i]->props.smark.m)
+ mark = xfrm_smark_get(fl->flowi_mark, xfrm[i]);

family = xfrm[i]->props.family;
dst = xfrm_dst_lookup(xfrm[i], tos, fl->flowi_oif,