xfrm: remove afinfo pointer from xfrm_mode

Adds an EXPORT_SYMBOL for afinfo_get_rcu, as it will now be called from
ipv6 in case of CONFIG_IPV6=m.

This change has virtually no effect on vmlinux size, but it reduces
afinfo size and allows followup patch to make xfrm modes const.

v2: mark if (afinfo) tests as likely (Sabrina)
    re-fetch afinfo according to inner_mode in xfrm_prepare_input().

Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>

include/net/xfrm.h

@@ -423,7 +423,6 @@ int xfrm_register_type_offload(const struct xfrm_type_offload *type, unsigned sh
 int xfrm_unregister_type_offload(const struct xfrm_type_offload *type, unsigned short family);
 
 struct xfrm_mode {
-	struct xfrm_state_afinfo *afinfo;
 	struct module *owner;
 	u8 encap;
 	u8 family;

net/ipv4/xfrm4_output.c

@@ -72,6 +72,8 @@ int xfrm4_output_finish(struct sock *sk, struct sk_buff *skb)
 static int __xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 	struct xfrm_state *x = skb_dst(skb)->xfrm;
+	const struct xfrm_state_afinfo *afinfo;
+	int ret = -EAFNOSUPPORT;
 
 #ifdef CONFIG_NETFILTER
 	if (!x) {
@@ -80,7 +82,15 @@ static int __xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 	}
 #endif
 
-	return x->outer_mode->afinfo->output_finish(sk, skb);
+	rcu_read_lock();
+	afinfo = xfrm_state_afinfo_get_rcu(x->outer_mode->family);
+	if (likely(afinfo))
+		ret = afinfo->output_finish(sk, skb);
+	else
+		kfree_skb(skb);
+	rcu_read_unlock();
+
+	return ret;
 }
 
 int xfrm4_output(struct net *net, struct sock *sk, struct sk_buff *skb)

net/ipv6/xfrm6_output.c

@@ -122,11 +122,28 @@ int xfrm6_output_finish(struct sock *sk, struct sk_buff *skb)
 	return xfrm_output(sk, skb);
 }
 
+static int __xfrm6_output_state_finish(struct xfrm_state *x, struct sock *sk,
+				       struct sk_buff *skb)
+{
+	const struct xfrm_state_afinfo *afinfo;
+	int ret = -EAFNOSUPPORT;
+
+	rcu_read_lock();
+	afinfo = xfrm_state_afinfo_get_rcu(x->outer_mode->family);
+	if (likely(afinfo))
+		ret = afinfo->output_finish(sk, skb);
+	else
+		kfree_skb(skb);
+	rcu_read_unlock();
+
+	return ret;
+}
+
 static int __xfrm6_output_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 	struct xfrm_state *x = skb_dst(skb)->xfrm;
 
-	return x->outer_mode->afinfo->output_finish(sk, skb);
+	return __xfrm6_output_state_finish(x, sk, skb);
 }
 
 static int __xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
@@ -168,7 +185,7 @@ static int __xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)
 				    __xfrm6_output_finish);
 
 skip_frag:
-	return x->outer_mode->afinfo->output_finish(sk, skb);
+	return __xfrm6_output_state_finish(x, sk, skb);
 }
 
 int xfrm6_output(struct net *net, struct sock *sk, struct sk_buff *skb)

net/xfrm/xfrm_input.c

@@ -352,19 +352,35 @@ xfrm_inner_mode_encap_remove(struct xfrm_state *x,
 static int xfrm_prepare_input(struct xfrm_state *x, struct sk_buff *skb)
 {
 	struct xfrm_mode *inner_mode = x->inner_mode;
-	int err;
+	const struct xfrm_state_afinfo *afinfo;
+	int err = -EAFNOSUPPORT;
 
-	err = x->outer_mode->afinfo->extract_input(x, skb);
-	if (err)
+	rcu_read_lock();
+	afinfo = xfrm_state_afinfo_get_rcu(x->outer_mode->family);
+	if (likely(afinfo))
+		err = afinfo->extract_input(x, skb);
+
+	if (err) {
+		rcu_read_unlock();
 		return err;
+	}
 
 	if (x->sel.family == AF_UNSPEC) {
 		inner_mode = xfrm_ip2inner_mode(x, XFRM_MODE_SKB_CB(skb)->protocol);
-		if (inner_mode == NULL)
+		if (!inner_mode) {
+			rcu_read_unlock();
 			return -EAFNOSUPPORT;
+		}
 	}
 
-	skb->protocol = inner_mode->afinfo->eth_proto;
+	afinfo = xfrm_state_afinfo_get_rcu(inner_mode->family);
+	if (unlikely(!afinfo)) {
+		rcu_read_unlock();
+		return -EAFNOSUPPORT;
+	}
+
+	skb->protocol = afinfo->eth_proto;
+	rcu_read_unlock();
 	return xfrm_inner_mode_encap_remove(x, inner_mode, skb);
 }
 
@@ -440,6 +456,7 @@ static int xfrm_inner_mode_input(struct xfrm_state *x,
 
 int xfrm_input(struct sk_buff *skb, int nexthdr, __be32 spi, int encap_type)
 {
+	const struct xfrm_state_afinfo *afinfo;
 	struct net *net = dev_net(skb->dev);
 	int err;
 	__be32 seq;
@@ -705,7 +722,12 @@ resume:
 		if (xo)
 			xfrm_gro = xo->flags & XFRM_GRO;
 
-		err = x->inner_mode->afinfo->transport_finish(skb, xfrm_gro || async);
+		err = -EAFNOSUPPORT;
+		rcu_read_lock();
+		afinfo = xfrm_state_afinfo_get_rcu(x->inner_mode->family);
+		if (likely(afinfo))
+			err = afinfo->transport_finish(skb, xfrm_gro || async);
+		rcu_read_unlock();
 		if (xfrm_gro) {
 			sp = skb_sec_path(skb);
 			if (sp)

net/xfrm/xfrm_output.c

@@ -623,7 +623,10 @@ EXPORT_SYMBOL_GPL(xfrm_output);
 
 static int xfrm_inner_extract_output(struct xfrm_state *x, struct sk_buff *skb)
 {
+	const struct xfrm_state_afinfo *afinfo;
 	struct xfrm_mode *inner_mode;
+	int err = -EAFNOSUPPORT;
+
 	if (x->sel.family == AF_UNSPEC)
 		inner_mode = xfrm_ip2inner_mode(x,
 				xfrm_af2proto(skb_dst(skb)->ops->family));
@@ -632,7 +635,14 @@ static int xfrm_inner_extract_output(struct xfrm_state *x, struct sk_buff *skb)
 
 	if (inner_mode == NULL)
 		return -EAFNOSUPPORT;
-	return inner_mode->afinfo->extract_output(x, skb);
+
+	rcu_read_lock();
+	afinfo = xfrm_state_afinfo_get_rcu(inner_mode->family);
+	if (likely(afinfo))
+		err = afinfo->extract_output(x, skb);
+	rcu_read_unlock();
+
+	return err;
 }
 
 void xfrm_local_error(struct sk_buff *skb, int mtu)

net/xfrm/xfrm_policy.c

@@ -2545,6 +2545,7 @@ static struct dst_entry *xfrm_bundle_create(struct xfrm_policy *policy,
 					    const struct flowi *fl,
 					    struct dst_entry *dst)
 {
+	const struct xfrm_state_afinfo *afinfo;
 	struct net *net = xp_net(policy);
 	unsigned long now = jiffies;
 	struct net_device *dev;
@@ -2622,7 +2623,14 @@ static struct dst_entry *xfrm_bundle_create(struct xfrm_policy *policy,
 		dst1->lastuse = now;
 
 		dst1->input = dst_discard;
-		dst1->output = inner_mode->afinfo->output;
+
+		rcu_read_lock();
+		afinfo = xfrm_state_afinfo_get_rcu(inner_mode->family);
+		if (likely(afinfo))
+			dst1->output = afinfo->output;
+		else
+			dst1->output = dst_discard_out;
+		rcu_read_unlock();
 
 		xdst_prev = xdst;
 

net/xfrm/xfrm_state.c

@@ -354,7 +354,6 @@ int xfrm_register_mode(struct xfrm_mode *mode)
 	if (!try_module_get(afinfo->owner))
 		goto out;
 
-	mode->afinfo = afinfo;
 	modemap[mode->encap] = mode;
 	err = 0;
 
@@ -378,7 +377,7 @@ void xfrm_unregister_mode(struct xfrm_mode *mode)
 	spin_lock_bh(&xfrm_mode_lock);
 	if (likely(modemap[mode->encap] == mode)) {
 		modemap[mode->encap] = NULL;
-		module_put(mode->afinfo->owner);
+		module_put(afinfo->owner);
 	}
 
 	spin_unlock_bh(&xfrm_mode_lock);
@@ -2188,6 +2187,7 @@ struct xfrm_state_afinfo *xfrm_state_afinfo_get_rcu(unsigned int family)
 
 	return rcu_dereference(xfrm_state_afinfo[family]);
 }
+EXPORT_SYMBOL_GPL(xfrm_state_afinfo_get_rcu);
 
 struct xfrm_state_afinfo *xfrm_state_get_afinfo(unsigned int family)
 {