[ipsec,1/2] xfrm: make user policy API complete

Commit Message

Nicolas Dichtel Sept. 7, 2021, 7:35 p.m. UTC

>From a userland POV, this API was based on some magic values:
 - dirmask and action were bitfields but meaning of bits
   (XFRM_POL_DEFAULT_*) are not exported;
 - action is confusing, if a bit is set, does it mean drop or accept?

Let's try to simplify this uapi by using explicit field and macros.

Fixes: 2d151d39073a ("xfrm: Add possibility to set the default to block if we have no policy")
Signed-off-by: Nicolas Dichtel <[e-mail]>
---
 include/uapi/linux/xfrm.h |  9 ++++++---
 net/xfrm/xfrm_user.c      | 27 ++++++++++++++++++---------
 2 files changed, 24 insertions(+), 12 deletions(-)

Patch

diff --git a/include/uapi/linux/xfrm.h b/include/uapi/linux/xfrm.h
index b96c1ea7166d..3e605b09eb6f 100644
--- a/include/uapi/linux/xfrm.h
+++ b/include/uapi/linux/xfrm.h
@@ -514,9 +514,12 @@  struct xfrm_user_offload {
 #define XFRM_OFFLOAD_INBOUND	2
 
 struct xfrm_userpolicy_default {
-#define XFRM_USERPOLICY_DIRMASK_MAX	(sizeof(__u8) * 8)
-	__u8				dirmask;
-	__u8				action;
+#define XFRM_USERPOLICY_UNSPEC	0
+#define XFRM_USERPOLICY_BLOCK	1
+#define XFRM_USERPOLICY_ACCEPT	2
+	__u8				in;
+	__u8				fwd;
+	__u8				out;
 };
 
 #ifndef __KERNEL__
diff --git a/net/xfrm/xfrm_user.c b/net/xfrm/xfrm_user.c
index 03b66d154b2b..4e1c4dd53fe2 100644
--- a/net/xfrm/xfrm_user.c
+++ b/net/xfrm/xfrm_user.c
@@ -1966,16 +1966,21 @@  static int xfrm_set_default(struct sk_buff *skb, struct nlmsghdr *nlh,
 {
 	struct net *net = sock_net(skb->sk);
 	struct xfrm_userpolicy_default *up = nlmsg_data(nlh);
-	u8 dirmask;
-	u8 old_default = net->xfrm.policy_default;
 
-	if (up->dirmask >= XFRM_USERPOLICY_DIRMASK_MAX)
-		return -EINVAL;
+	if (up->in == XFRM_USERPOLICY_BLOCK)
+		net->xfrm.policy_default |= XFRM_POL_DEFAULT_IN;
+	else if (up->in == XFRM_USERPOLICY_ACCEPT)
+		net->xfrm.policy_default &= ~XFRM_POL_DEFAULT_IN;
 
-	dirmask = (1 << up->dirmask) & XFRM_POL_DEFAULT_MASK;
+	if (up->fwd == XFRM_USERPOLICY_BLOCK)
+		net->xfrm.policy_default |= XFRM_POL_DEFAULT_FWD;
+	else if (up->fwd == XFRM_USERPOLICY_ACCEPT)
+		net->xfrm.policy_default &= ~XFRM_POL_DEFAULT_FWD;
 
-	net->xfrm.policy_default = (old_default & (0xff ^ dirmask))
-				    | (up->action << up->dirmask);
+	if (up->out == XFRM_USERPOLICY_BLOCK)
+		net->xfrm.policy_default |= XFRM_POL_DEFAULT_OUT;
+	else if (up->out == XFRM_USERPOLICY_ACCEPT)
+		net->xfrm.policy_default &= ~XFRM_POL_DEFAULT_OUT;
 
 	rt_genid_bump_all(net);
 
@@ -2007,8 +2012,12 @@  static int xfrm_get_default(struct sk_buff *skb, struct nlmsghdr *nlh,
 
 	r_up = nlmsg_data(r_nlh);
 
-	r_up->action = ((net->xfrm.policy_default & (1 << up->dirmask)) >> up->dirmask);
-	r_up->dirmask = up->dirmask;
+	r_up->in = net->xfrm.policy_default & XFRM_POL_DEFAULT_IN ?
+			XFRM_USERPOLICY_BLOCK : XFRM_USERPOLICY_ACCEPT;
+	r_up->fwd = net->xfrm.policy_default & XFRM_POL_DEFAULT_FWD ?
+			XFRM_USERPOLICY_BLOCK : XFRM_USERPOLICY_ACCEPT;
+	r_up->out = net->xfrm.policy_default & XFRM_POL_DEFAULT_OUT ?
+			XFRM_USERPOLICY_BLOCK : XFRM_USERPOLICY_ACCEPT;
 	nlmsg_end(r_skb, r_nlh);
 
 	return nlmsg_unicast(net->xfrm.nlsk, r_skb, portid);