[PATCH ipsec-next] xfrm: Allow Output Mark to be Updated Using UPDSA

[Nathan Harold <nharold@google.com>]

Allow UPDSA to change output_mark to permit
policy separation of packet routing decisions from
SA keying in systems that use mark-based routing.

In the output_mark, used as a routing and firewall
mark for outbound packets, is made update-able which
allows routing decisions to be handled independently
of keying/SA creation. To maintain consistency with
other optional attributes, the output mark is only
updated if sent with a non-zero value. Once set, the
output mark may not be reset to zero, which ensures
that updating the SA does not require the mark to
be re-sent to avoid the value being clobbered.

The per-SA lock and the xfrm_state_lock are taken in
that order to avoid a deadlock with
xfrm_timer_handler(), which also takes the locks in
that order.

Signed-off-by: Nathan Harold <nharold@google.com>
Change-Id: Ia05c6733a94c1901cd1e54eb7c7e237704678d71
---
 net/xfrm/xfrm_state.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/net/xfrm/xfrm_state.c b/net/xfrm/xfrm_state.c
index f595797a20ce..5d6085e81030 100644
--- a/net/xfrm/xfrm_state.c
+++ b/net/xfrm/xfrm_state.c
@@ -1554,6 +1554,13 @@ int xfrm_state_update(struct xfrm_state *x)
 		if (x1->curlft.use_time)
 			xfrm_state_check_expire(x1);
 
+		spin_lock_bh(&net->xfrm.xfrm_state_lock);
+		if (x->props.output_mark) {
+			x1->props.output_mark = x->props.output_mark;
+			__xfrm_state_bump_genids(x1);
+		}
+		spin_unlock_bh(&net->xfrm.xfrm_state_lock);
+
 		err = 0;
 		x->km.state = XFRM_STATE_DEAD;
 		__xfrm_state_put(x);
-- 
2.17.0.441.gb46fe60e1d-goog