xfrm: Remove xfrmi interface ID from flowi

In order to remove performance impact of having the extra u32 in every
single flowi, this change removes the flowi_xfrm struct, prefering to
take the if_id as a method parameter where needed.

In the inbound direction, if_id is only needed during the
__xfrm_check_policy() function, and the if_id can be determined at that
point based on the skb. As such, xfrmi_decode_session() is only called
with the skb in __xfrm_check_policy().

In the outbound direction, the only place where if_id is needed is the
xfrm_lookup() call in xfrmi_xmit2(). With this change, the if_id is
directly passed into the xfrm_lookup_with_ifid() call. All existing
callers can still call xfrm_lookup(), which uses a default if_id of 0.

This change does not change any behavior of XFRMIs except for improving
overall system performance via flowi size reduction.

This change has been tested against the Android Kernel Networking Tests:

https://android.googlesource.com/kernel/tests/+/master/net/test

Signed-off-by: Benedict Wong <[e-mail]>
Signed-off-by: Steffen Klassert <[e-mail]>

include/net/dst.h

···
 	return dst_orig;
 }
 
+static inline struct dst_entry *
+xfrm_lookup_with_ifid(struct net *net, struct dst_entry *dst_orig,
+		      const struct flowi *fl, const struct sock *sk,
+		      int flags, u32 if_id)
+{
+	return dst_orig;
+}
+
 static inline struct dst_entry *xfrm_lookup_route(struct net *net,
 						  struct dst_entry *dst_orig,
 						  const struct flowi *fl,
···
 struct dst_entry *xfrm_lookup(struct net *net, struct dst_entry *dst_orig,
 			      const struct flowi *fl, const struct sock *sk,
 			      int flags);
+
+struct dst_entry *xfrm_lookup_with_ifid(struct net *net,
+					struct dst_entry *dst_orig,
+					const struct flowi *fl,
+					const struct sock *sk, int flags,
+					u32 if_id);
 
 struct dst_entry *xfrm_lookup_route(struct net *net, struct dst_entry *dst_orig,
 				    const struct flowi *fl, const struct sock *sk,

include/net/flow.h

···
 	__be64			tun_id;
 };
 
-struct flowi_xfrm {
-	__u32			if_id;
-};
-
 struct flowi_common {
 	int	flowic_oif;
 	int	flowic_iif;
···
 #define FLOWI_FLAG_SKIP_NH_OIF		0x04
 	__u32	flowic_secid;
 	struct flowi_tunnel flowic_tun_key;
-	struct flowi_xfrm xfrm;
 	kuid_t  flowic_uid;
 };
 
···
 #define flowi4_secid		__fl_common.flowic_secid
 #define flowi4_tun_key		__fl_common.flowic_tun_key
 #define flowi4_uid		__fl_common.flowic_uid
-#define flowi4_xfrm		__fl_common.xfrm
 
 	/* (saddr,daddr) must be grouped, same order as in IP header */
 	__be32			saddr;
···
 	fl4->flowi4_flags = flags;
 	fl4->flowi4_secid = 0;
 	fl4->flowi4_tun_key.tun_id = 0;
-	fl4->flowi4_xfrm.if_id = 0;
 	fl4->flowi4_uid = uid;
 	fl4->daddr = daddr;
 	fl4->saddr = saddr;
···
 #define flowi6_secid		__fl_common.flowic_secid
 #define flowi6_tun_key		__fl_common.flowic_tun_key
 #define flowi6_uid		__fl_common.flowic_uid
-#define flowi6_xfrm		__fl_common.xfrm
 	struct in6_addr		daddr;
 	struct in6_addr		saddr;
 	/* Note: flowi6_tos is encoded in flowlabel, too. */
···
 #define flowi_secid	u.__fl_common.flowic_secid
 #define flowi_tun_key	u.__fl_common.flowic_tun_key
 #define flowi_uid	u.__fl_common.flowic_uid
-#define flowi_xfrm	u.__fl_common.xfrm
 } __attribute__((__aligned__(BITS_PER_LONG/8)));
 
 static inline struct flowi *flowi4_to_flowi(struct flowi4 *fl4)

include/net/xfrm.h

···
 				   const struct flowi *fl,
 				   struct xfrm_tmpl *tmpl,
 				   struct xfrm_policy *pol, int *err,
-				   unsigned short family);
+				   unsigned short family, u32 if_id);
 struct xfrm_state *xfrm_stateonly_find(struct net *net, u32 mark, u32 if_id,
 				       xfrm_address_t *daddr,
 				       xfrm_address_t *saddr,

net/xfrm/xfrm_interface.c

···
 	if (!dst)
 		goto tx_err_link_failure;
 
-	fl->flowi_xfrm.if_id = xi->p.if_id;
-
 	dst_hold(dst);
-	dst = xfrm_lookup(xi->net, dst, fl, NULL, 0);
+	dst = xfrm_lookup_with_ifid(xi->net, dst, fl, NULL, 0, xi->p.if_id);
 	if (IS_ERR(dst)) {
 		err = PTR_ERR(dst);
 		dst = NULL;

net/xfrm/xfrm_policy.c

···
  */
 static int xfrm_policy_match(const struct xfrm_policy *pol,
 			     const struct flowi *fl,
-			     u8 type, u16 family, int dir)
+			     u8 type, u16 family, int dir, u32 if_id)
 {
 	const struct xfrm_selector *sel = &pol->selector;
 	int ret = -ESRCH;
 	bool match;
 
 	if (pol->family != family ||
-	    pol->if_id != fl->flowi_xfrm.if_id ||
+	    pol->if_id != if_id ||
 	    (fl->flowi_mark & pol->mark.m) != pol->mark.v ||
 	    pol->type != type)
 		return ret;
···
 
 static struct xfrm_policy *xfrm_policy_lookup_bytype(struct net *net, u8 type,
 						     const struct flowi *fl,
-						     u16 family, u8 dir)
+						     u16 family, u8 dir,
+						     u32 if_id)
 {
 	int err;
 	struct xfrm_policy *pol, *ret;
···
 	priority = ~0U;
 	ret = NULL;
 	hlist_for_each_entry_rcu(pol, chain, bydst) {
-		err = xfrm_policy_match(pol, fl, type, family, dir);
+		err = xfrm_policy_match(pol, fl, type, family, dir, if_id);
 		if (err) {
 			if (err == -ESRCH)
 				continue;
···
 		if ((pol->priority >= priority) && ret)
 			break;
 
-		err = xfrm_policy_match(pol, fl, type, family, dir);
+		err = xfrm_policy_match(pol, fl, type, family, dir, if_id);
 		if (err) {
 			if (err == -ESRCH)
 				continue;
···
 	return ret;
 }
 
-static struct xfrm_policy *
-xfrm_policy_lookup(struct net *net, const struct flowi *fl, u16 family, u8 dir)
+static struct xfrm_policy *xfrm_policy_lookup(struct net *net,
+					      const struct flowi *fl,
+					      u16 family, u8 dir, u32 if_id)
 {
 #ifdef CONFIG_XFRM_SUB_POLICY
 	struct xfrm_policy *pol;
 
-	pol = xfrm_policy_lookup_bytype(net, XFRM_POLICY_TYPE_SUB, fl, family, dir);
+	pol = xfrm_policy_lookup_bytype(net, XFRM_POLICY_TYPE_SUB, fl, family,
+					dir, if_id);
 	if (pol != NULL)
 		return pol;
 #endif
-	return xfrm_policy_lookup_bytype(net, XFRM_POLICY_TYPE_MAIN, fl, family, dir);
+	return xfrm_policy_lookup_bytype(net, XFRM_POLICY_TYPE_MAIN, fl, family,
+					 dir, if_id);
 }
 
 static struct xfrm_policy *xfrm_sk_policy_lookup(const struct sock *sk, int dir,
-						 const struct flowi *fl, u16 family)
+						 const struct flowi *fl,
+						 u16 family, u32 if_id)
 {
 	struct xfrm_policy *pol;
 
···
 		match = xfrm_selector_match(&pol->selector, fl, family);
 		if (match) {
 			if ((sk->sk_mark & pol->mark.m) != pol->mark.v ||
-			    pol->if_id != fl->flowi_xfrm.if_id) {
+			    pol->if_id != if_id) {
 				pol = NULL;
 				goto out;
 			}
···
 			}
 		}
 
-		x = xfrm_state_find(remote, local, fl, tmpl, policy, &error, family);
+		x = xfrm_state_find(remote, local, fl, tmpl, policy, &error,
+				    family, policy->if_id);
 
 		if (x && x->km.state == XFRM_STATE_VALID) {
 			xfrm[nx++] = x;
···
 		pols[1] = xfrm_policy_lookup_bytype(xp_net(pols[0]),
 						    XFRM_POLICY_TYPE_MAIN,
 						    fl, family,
-						    XFRM_POLICY_OUT);
+						    XFRM_POLICY_OUT,
+						    pols[0]->if_id);
 		if (pols[1]) {
 			if (IS_ERR(pols[1])) {
 				xfrm_pols_put(pols, *num_pols);
···
 	goto out;
 }
 
-static struct xfrm_dst *
-xfrm_bundle_lookup(struct net *net, const struct flowi *fl, u16 family, u8 dir, struct xfrm_flo *xflo)
+static struct xfrm_dst *xfrm_bundle_lookup(struct net *net,
+					   const struct flowi *fl,
+					   u16 family, u8 dir,
+					   struct xfrm_flo *xflo, u32 if_id)
 {
 	struct xfrm_policy *pols[XFRM_POLICY_TYPE_MAX];
 	int num_pols = 0, num_xfrms = 0, err;
···
 	/* Resolve policies to use if we couldn't get them from
 	 * previous cache entry */
 	num_pols = 1;
-	pols[0] = xfrm_policy_lookup(net, fl, family, dir);
+	pols[0] = xfrm_policy_lookup(net, fl, family, dir, if_id);
 	err = xfrm_expand_policies(fl, family, pols,
 					   &num_pols, &num_xfrms);
 	if (err < 0)
···
 	return ret;
 }
 
-/* Main function: finds/creates a bundle for given flow.
+/* Finds/creates a bundle for given flow and if_id
  *
  * At the moment we eat a raw IP route. Mostly to speed up lookups
  * on interfaces with disabled IPsec.
+ *
+ * xfrm_lookup uses an if_id of 0 by default, and is provided for
+ * compatibility
  */
-struct dst_entry *xfrm_lookup(struct net *net, struct dst_entry *dst_orig,
-			      const struct flowi *fl,
-			      const struct sock *sk, int flags)
+struct dst_entry *xfrm_lookup_with_ifid(struct net *net,
+					struct dst_entry *dst_orig,
+					const struct flowi *fl,
+					const struct sock *sk,
+					int flags, u32 if_id)
 {
 	struct xfrm_policy *pols[XFRM_POLICY_TYPE_MAX];
 	struct xfrm_dst *xdst;
···
 	sk = sk_const_to_full_sk(sk);
 	if (sk && sk->sk_policy[XFRM_POLICY_OUT]) {
 		num_pols = 1;
-		pols[0] = xfrm_sk_policy_lookup(sk, XFRM_POLICY_OUT, fl, family);
+		pols[0] = xfrm_sk_policy_lookup(sk, XFRM_POLICY_OUT, fl, family,
+						if_id);
 		err = xfrm_expand_policies(fl, family, pols,
 					   &num_pols, &num_xfrms);
 		if (err < 0)
···
 		    !net->xfrm.policy_count[XFRM_POLICY_OUT])
 			goto nopol;
 
-		xdst = xfrm_bundle_lookup(net, fl, family, dir, &xflo);
+		xdst = xfrm_bundle_lookup(net, fl, family, dir, &xflo, if_id);
 		if (xdst == NULL)
 			goto nopol;
 		if (IS_ERR(xdst)) {
···
 		dst_release(dst_orig);
 	xfrm_pols_put(pols, drop_pols);
 	return ERR_PTR(err);
+}
+EXPORT_SYMBOL(xfrm_lookup_with_ifid);
+
+/* Main function: finds/creates a bundle for given flow.
+ *
+ * At the moment we eat a raw IP route. Mostly to speed up lookups
+ * on interfaces with disabled IPsec.
+ */
+struct dst_entry *xfrm_lookup(struct net *net, struct dst_entry *dst_orig,
+			      const struct flowi *fl, const struct sock *sk,
+			      int flags)
+{
+	return xfrm_lookup_with_ifid(net, dst_orig, fl, sk, flags, 0);
 }
 EXPORT_SYMBOL(xfrm_lookup);
 
···
 			  unsigned int family, int reverse)
 {
 	const struct xfrm_policy_afinfo *afinfo = xfrm_policy_get_afinfo(family);
-	const struct xfrm_if_cb *ifcb = xfrm_if_get_cb();
-	struct xfrm_if *xi;
 	int err;
 
 	if (unlikely(afinfo == NULL))
 		return -EAFNOSUPPORT;
 
 	afinfo->decode_session(skb, fl, reverse);
-	if (ifcb) {
-		xi = ifcb->decode_session(skb);
-		if (xi)
-			fl->flowi_xfrm.if_id = xi->p.if_id;
-	}
 
 	err = security_xfrm_decode_session(skb, &fl->flowi_secid);
 	rcu_read_unlock();
···
 	int reverse;
 	struct flowi fl;
 	int xerr_idx = -1;
+	const struct xfrm_if_cb *ifcb;
+	struct xfrm_if *xi;
+	u32 if_id = 0;
+
+	rcu_read_lock();
+	ifcb = xfrm_if_get_cb();
+
+	if (ifcb) {
+		xi = ifcb->decode_session(skb);
+		if (xi)
+			if_id = xi->p.if_id;
+	}
+	rcu_read_unlock();
 
 	reverse = dir & ~XFRM_POLICY_MASK;
 	dir &= XFRM_POLICY_MASK;
···
 	pol = NULL;
 	sk = sk_to_full_sk(sk);
 	if (sk && sk->sk_policy[dir]) {
-		pol = xfrm_sk_policy_lookup(sk, dir, &fl, family);
+		pol = xfrm_sk_policy_lookup(sk, dir, &fl, family, if_id);
 		if (IS_ERR(pol)) {
 			XFRM_INC_STATS(net, LINUX_MIB_XFRMINPOLERROR);
 			return 0;
···
 	}
 
 	if (!pol)
-		pol = xfrm_policy_lookup(net, &fl, family, dir);
+		pol = xfrm_policy_lookup(net, &fl, family, dir, if_id);
 
 	if (IS_ERR(pol)) {
 		XFRM_INC_STATS(net, LINUX_MIB_XFRMINPOLERROR);
···
 	if (pols[0]->type != XFRM_POLICY_TYPE_MAIN) {
 		pols[1] = xfrm_policy_lookup_bytype(net, XFRM_POLICY_TYPE_MAIN,
 						    &fl, family,
-						    XFRM_POLICY_IN);
+						    XFRM_POLICY_IN, if_id);
 		if (pols[1]) {
 			if (IS_ERR(pols[1])) {
 				XFRM_INC_STATS(net, LINUX_MIB_XFRMINPOLERROR);

net/xfrm/xfrm_state.c

···
 xfrm_state_find(const xfrm_address_t *daddr, const xfrm_address_t *saddr,
 		const struct flowi *fl, struct xfrm_tmpl *tmpl,
 		struct xfrm_policy *pol, int *err,
-		unsigned short family)
+		unsigned short family, u32 if_id)
 {
 	static xfrm_address_t saddr_wildcard = { };
 	struct net *net = xp_net(pol);
···
 	int error = 0;
 	struct xfrm_state *best = NULL;
 	u32 mark = pol->mark.v & pol->mark.m;
-	u32 if_id = fl->flowi_xfrm.if_id;
 	unsigned short encap_family = tmpl->encap_family;
 	unsigned int sequence;
 	struct km_event c;