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xfrm: make user policy API complete 

>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: 2d151d3907 ("xfrm: Add possibility to set the default to block if we have no policy")
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
This commit is contained in:
Nicolas Dichtel 2021-09-14 16:46:33 +02:00 committed by Steffen Klassert
parent 844f7eaaed
commit f8d858e607
2 changed files with 25 additions and 20 deletions
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9
include/uapi/linux/xfrm.h
View File

@ -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__

36
net/xfrm/xfrm_user.c
View File

@ -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);
@ -1988,13 +1993,11 @@ static int xfrm_get_default(struct sk_buff *skb, struct nlmsghdr *nlh,
struct sk_buff *r_skb;
struct nlmsghdr *r_nlh;
struct net *net = sock_net(skb->sk);
struct xfrm_userpolicy_default *r_up, *up;
struct xfrm_userpolicy_default *r_up;
int len = NLMSG_ALIGN(sizeof(struct xfrm_userpolicy_default));
u32 portid = NETLINK_CB(skb).portid;
u32 seq = nlh->nlmsg_seq;
up = nlmsg_data(nlh);
r_skb = nlmsg_new(len, GFP_ATOMIC);
if (!r_skb)
return -ENOMEM;
@ -2005,15 +2008,14 @@ static int xfrm_get_default(struct sk_buff *skb, struct nlmsghdr *nlh,
return -EMSGSIZE;
}
if (up->dirmask >= XFRM_USERPOLICY_DIRMASK_MAX) {
kfree_skb(r_skb);
return -EINVAL;
}
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);