Merge branch 'net-introduce-and-use-route-hint'

Paolo Abeni says:

====================
net: introduce and use route hint

This series leverages the listification infrastructure to avoid
unnecessary route lookup on ingress packets. In absence of custom rules,
packets with equal daddr will usually land on the same dst.

When processing packet bursts (lists) we can easily reference the previous
dst entry. When we hit the 'same destination' condition we can avoid the
route lookup, coping the already available dst.

Detailed performance numbers are available in the individual commit
messages.

v3 -> v4:
 - move helpers to their own patches (Eric D.)
 - enable hints for SUBTREE builds (David A.)
 - re-enable hints for ipv4 forward (David A.)

v2 -> v3:
 - use fib*_has_custom_rules() helpers (David A.)
 - add ip*_extract_route_hint() helper (Edward C.)
 - use prev skb as hint instead of copying data (Willem )

v1 -> v2:
 - fix build issue with !CONFIG_IP*_MULTIPLE_TABLES
 - fix potential race in ip6_list_rcv_finish()
====================

Acked-by: Edward Cree <ecree@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 31 insertions, 4 deletions

diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index 24a95126e698..aa438c6758a7 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -302,16 +302,31 @@ drop:
 	return true;
 }
 
+static bool ip_can_use_hint(const struct sk_buff *skb, const struct iphdr *iph,
+			    const struct sk_buff *hint)
+{
+	return hint && !skb_dst(skb) && ip_hdr(hint)->daddr == iph->daddr &&
+	       ip_hdr(hint)->tos == iph->tos;
+}
+
 INDIRECT_CALLABLE_DECLARE(int udp_v4_early_demux(struct sk_buff *));
 INDIRECT_CALLABLE_DECLARE(int tcp_v4_early_demux(struct sk_buff *));
 static int ip_rcv_finish_core(struct net *net, struct sock *sk,
-			      struct sk_buff *skb, struct net_device *dev)
+			      struct sk_buff *skb, struct net_device *dev,
+			      const struct sk_buff *hint)
 {
 	const struct iphdr *iph = ip_hdr(skb);
 	int (*edemux)(struct sk_buff *skb);
 	struct rtable *rt;
 	int err;
 
+	if (ip_can_use_hint(skb, iph, hint)) {
+		err = ip_route_use_hint(skb, iph->daddr, iph->saddr, iph->tos,
+					dev, hint);
+		if (unlikely(err))
+			goto drop_error;
+	}
+
 	if (net->ipv4.sysctl_ip_early_demux &&
 	    !skb_dst(skb) &&
 	    !skb->sk &&
@@ -408,7 +423,7 @@ static int ip_rcv_finish(struct net *net, struct sock *sk, struct sk_buff *skb)
 	if (!skb)
 		return NET_RX_SUCCESS;
 
-	ret = ip_rcv_finish_core(net, sk, skb, dev);
+	ret = ip_rcv_finish_core(net, sk, skb, dev, NULL);
 	if (ret != NET_RX_DROP)
 		ret = dst_input(skb);
 	return ret;
@@ -535,11 +550,20 @@ static void ip_sublist_rcv_finish(struct list_head *head)
 	}
 }
 
+static struct sk_buff *ip_extract_route_hint(const struct net *net,
+					     struct sk_buff *skb, int rt_type)
+{
+	if (fib4_has_custom_rules(net) || rt_type == RTN_BROADCAST)
+		return NULL;
+
+	return skb;
+}
+
 static void ip_list_rcv_finish(struct net *net, struct sock *sk,
 			       struct list_head *head)
 {
+	struct sk_buff *skb, *next, *hint = NULL;
 	struct dst_entry *curr_dst = NULL;
-	struct sk_buff *skb, *next;
 	struct list_head sublist;
 
 	INIT_LIST_HEAD(&sublist);
@@ -554,11 +578,14 @@ static void ip_list_rcv_finish(struct net *net, struct sock *sk,
 		skb = l3mdev_ip_rcv(skb);
 		if (!skb)
 			continue;
-		if (ip_rcv_finish_core(net, sk, skb, dev) == NET_RX_DROP)
+		if (ip_rcv_finish_core(net, sk, skb, dev, hint) == NET_RX_DROP)
 			continue;
 
 		dst = skb_dst(skb);
 		if (curr_dst != dst) {
+			hint = ip_extract_route_hint(net, skb,
+					       ((struct rtable *)dst)->rt_type);
+
 			/* dispatch old sublist */
 			if (!list_empty(&sublist))
 				ip_sublist_rcv_finish(&sublist);