Merge branch 'tcp-receive-path-optimizations'

Eric Dumazet says:

====================
tcp: receive path optimizations

This series aims to reduce cache line misses in RX path.

I am still working on better cache locality in tcp_sock but
this will wait few more weeks.
====================

Link: https://lore.kernel.org/r/20211025164825.259415-1-eric.dumazet@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/ipv6.h

@@ -282,7 +282,6 @@ struct ipv6_pinfo {
 	__be32			rcv_flowinfo;
 
 	__u32			dst_cookie;
-	__u32			rx_dst_cookie;
 
 	struct ipv6_mc_socklist	__rcu *ipv6_mc_list;
 	struct ipv6_ac_socklist	*ipv6_ac_list;

include/net/busy_poll.h

@@ -130,7 +130,8 @@ static inline void skb_mark_napi_id(struct sk_buff *skb,
 static inline void sk_mark_napi_id(struct sock *sk, const struct sk_buff *skb)
 {
 #ifdef CONFIG_NET_RX_BUSY_POLL
-	WRITE_ONCE(sk->sk_napi_id, skb->napi_id);
+	if (unlikely(READ_ONCE(sk->sk_napi_id) != skb->napi_id))
+		WRITE_ONCE(sk->sk_napi_id, skb->napi_id);
 #endif
 	sk_rx_queue_set(sk, skb);
 }

include/net/inet_sock.h

@@ -207,11 +207,10 @@ struct inet_sock {
 	__be32			inet_saddr;
 	__s16			uc_ttl;
 	__u16			cmsg_flags;
+	struct ip_options_rcu __rcu	*inet_opt;
 	__be16			inet_sport;
 	__u16			inet_id;
 
-	struct ip_options_rcu __rcu	*inet_opt;
-	int			rx_dst_ifindex;
 	__u8			tos;
 	__u8			min_ttl;
 	__u8			mc_ttl;

include/net/ip.h

@@ -24,6 +24,7 @@
 #include <linux/skbuff.h>
 #include <linux/jhash.h>
 #include <linux/sockptr.h>
+#include <linux/static_key.h>
 
 #include <net/inet_sock.h>
 #include <net/route.h>
@@ -750,6 +751,7 @@ void ip_cmsg_recv_offset(struct msghdr *msg, struct sock *sk,
 			 struct sk_buff *skb, int tlen, int offset);
 int ip_cmsg_send(struct sock *sk, struct msghdr *msg,
 		 struct ipcm_cookie *ipc, bool allow_ipv6);
+DECLARE_STATIC_KEY_FALSE(ip4_min_ttl);
 int ip_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval,
 		  unsigned int optlen);
 int ip_getsockopt(struct sock *sk, int level, int optname, char __user *optval,

include/net/ipv6.h

@@ -1092,6 +1092,7 @@ struct in6_addr *fl6_update_dst(struct flowi6 *fl6,
 /*
  *	socket options (ipv6_sockglue.c)
  */
+DECLARE_STATIC_KEY_FALSE(ip6_min_hopcount);
 
 int ipv6_setsockopt(struct sock *sk, int level, int optname, sockptr_t optval,
 		    unsigned int optlen);

include/net/sock.h

@@ -259,6 +259,8 @@ struct bpf_local_storage;
   *	@sk_rcvbuf: size of receive buffer in bytes
   *	@sk_wq: sock wait queue and async head
   *	@sk_rx_dst: receive input route used by early demux
+  *	@sk_rx_dst_ifindex: ifindex for @sk_rx_dst
+  *	@sk_rx_dst_cookie: cookie for @sk_rx_dst
   *	@sk_dst_cache: destination cache
   *	@sk_dst_pending_confirm: need to confirm neighbour
   *	@sk_policy: flow policy
@@ -430,6 +432,9 @@ struct sock {
 	struct xfrm_policy __rcu *sk_policy[2];
 #endif
 	struct dst_entry	*sk_rx_dst;
+	int			sk_rx_dst_ifindex;
+	u32			sk_rx_dst_cookie;
+
 	struct dst_entry __rcu	*sk_dst_cache;
 	atomic_t		sk_omem_alloc;
 	int			sk_sndbuf;
@@ -1911,10 +1916,8 @@ static inline void sk_rx_queue_set(struct sock *sk, const struct sk_buff *skb)
 	if (skb_rx_queue_recorded(skb)) {
 		u16 rx_queue = skb_get_rx_queue(skb);
 
-		if (WARN_ON_ONCE(rx_queue == NO_QUEUE_MAPPING))
-			return;
-
-		sk->sk_rx_queue_mapping = rx_queue;
+		if (unlikely(READ_ONCE(sk->sk_rx_queue_mapping) != rx_queue))
+			WRITE_ONCE(sk->sk_rx_queue_mapping, rx_queue);
 	}
 #endif
 }
@@ -1922,15 +1925,19 @@ static inline void sk_rx_queue_set(struct sock *sk, const struct sk_buff *skb)
 static inline void sk_rx_queue_clear(struct sock *sk)
 {
 #ifdef CONFIG_SOCK_RX_QUEUE_MAPPING
-	sk->sk_rx_queue_mapping = NO_QUEUE_MAPPING;
+	WRITE_ONCE(sk->sk_rx_queue_mapping, NO_QUEUE_MAPPING);
 #endif
 }
 
 static inline int sk_rx_queue_get(const struct sock *sk)
 {
 #ifdef CONFIG_SOCK_RX_QUEUE_MAPPING
-	if (sk && sk->sk_rx_queue_mapping != NO_QUEUE_MAPPING)
-		return sk->sk_rx_queue_mapping;
+	if (sk) {
+		int res = READ_ONCE(sk->sk_rx_queue_mapping);
+
+		if (res != NO_QUEUE_MAPPING)
+			return res;
+	}
 #endif
 
 	return -1;

net/ipv4/ip_sockglue.c

@@ -886,6 +886,8 @@ static int compat_ip_mcast_join_leave(struct sock *sk, int optname,
 	return ip_mc_leave_group(sk, &mreq);
 }
 
+DEFINE_STATIC_KEY_FALSE(ip4_min_ttl);
+
 static int do_ip_setsockopt(struct sock *sk, int level, int optname,
 		sockptr_t optval, unsigned int optlen)
 {
@@ -1352,7 +1354,14 @@ static int do_ip_setsockopt(struct sock *sk, int level, int optname,
 			goto e_inval;
 		if (val < 0 || val > 255)
 			goto e_inval;
-		inet->min_ttl = val;
+
+		if (val)
+			static_branch_enable(&ip4_min_ttl);
+
+		/* tcp_v4_err() and tcp_v4_rcv() might read min_ttl
+		 * while we are changint it.
+		 */
+		WRITE_ONCE(inet->min_ttl, val);
 		break;
 
 	default:

net/ipv4/tcp_ipv4.c

@@ -508,9 +508,12 @@ int tcp_v4_err(struct sk_buff *skb, u32 info)
 	if (sk->sk_state == TCP_CLOSE)
 		goto out;
 
-	if (unlikely(iph->ttl < inet_sk(sk)->min_ttl)) {
-		__NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP);
-		goto out;
+	if (static_branch_unlikely(&ip4_min_ttl)) {
+		/* min_ttl can be changed concurrently from do_ip_setsockopt() */
+		if (unlikely(iph->ttl < READ_ONCE(inet_sk(sk)->min_ttl))) {
+			__NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP);
+			goto out;
+		}
 	}
 
 	tp = tcp_sk(sk);
@@ -1703,7 +1706,7 @@ int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb)
 		sock_rps_save_rxhash(sk, skb);
 		sk_mark_napi_id(sk, skb);
 		if (dst) {
-			if (inet_sk(sk)->rx_dst_ifindex != skb->skb_iif ||
+			if (sk->sk_rx_dst_ifindex != skb->skb_iif ||
 			    !INDIRECT_CALL_1(dst->ops->check, ipv4_dst_check,
 					     dst, 0)) {
 				dst_release(dst);
@@ -1788,7 +1791,7 @@ int tcp_v4_early_demux(struct sk_buff *skb)
 			if (dst)
 				dst = dst_check(dst, 0);
 			if (dst &&
-			    inet_sk(sk)->rx_dst_ifindex == skb->skb_iif)
+			    sk->sk_rx_dst_ifindex == skb->skb_iif)
 				skb_dst_set_noref(skb, dst);
 		}
 	}
@@ -2068,9 +2071,13 @@ int tcp_v4_rcv(struct sk_buff *skb)
 			return 0;
 		}
 	}
-	if (unlikely(iph->ttl < inet_sk(sk)->min_ttl)) {
-		__NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP);
-		goto discard_and_relse;
+
+	if (static_branch_unlikely(&ip4_min_ttl)) {
+		/* min_ttl can be changed concurrently from do_ip_setsockopt() */
+		if (unlikely(iph->ttl < READ_ONCE(inet_sk(sk)->min_ttl))) {
+			__NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP);
+			goto discard_and_relse;
+		}
 	}
 
 	if (!xfrm4_policy_check(sk, XFRM_POLICY_IN, skb))
@@ -2195,7 +2202,7 @@ void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
 
 	if (dst && dst_hold_safe(dst)) {
 		sk->sk_rx_dst = dst;
-		inet_sk(sk)->rx_dst_ifindex = skb->skb_iif;
+		sk->sk_rx_dst_ifindex = skb->skb_iif;
 	}
 }
 EXPORT_SYMBOL(inet_sk_rx_dst_set);

net/ipv6/ipv6_sockglue.c

@@ -55,6 +55,8 @@
 struct ip6_ra_chain *ip6_ra_chain;
 DEFINE_RWLOCK(ip6_ra_lock);
 
+DEFINE_STATIC_KEY_FALSE(ip6_min_hopcount);
+
 int ip6_ra_control(struct sock *sk, int sel)
 {
 	struct ip6_ra_chain *ra, *new_ra, **rap;
@@ -950,7 +952,14 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 			goto e_inval;
 		if (val < 0 || val > 255)
 			goto e_inval;
-		np->min_hopcount = val;
+
+		if (val)
+			static_branch_enable(&ip6_min_hopcount);
+
+		/* tcp_v6_err() and tcp_v6_rcv() might read min_hopcount
+		 * while we are changing it.
+		 */
+		WRITE_ONCE(np->min_hopcount, val);
 		retv = 0;
 		break;
 	case IPV6_DONTFRAG:

net/ipv6/tcp_ipv6.c

@@ -108,8 +108,8 @@ static void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
 		const struct rt6_info *rt = (const struct rt6_info *)dst;
 
 		sk->sk_rx_dst = dst;
-		inet_sk(sk)->rx_dst_ifindex = skb->skb_iif;
-		tcp_inet6_sk(sk)->rx_dst_cookie = rt6_get_cookie(rt);
+		sk->sk_rx_dst_ifindex = skb->skb_iif;
+		sk->sk_rx_dst_cookie = rt6_get_cookie(rt);
 	}
 }
 
@@ -414,9 +414,12 @@ static int tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 	if (sk->sk_state == TCP_CLOSE)
 		goto out;
 
-	if (ipv6_hdr(skb)->hop_limit < tcp_inet6_sk(sk)->min_hopcount) {
-		__NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP);
-		goto out;
+	if (static_branch_unlikely(&ip6_min_hopcount)) {
+		/* min_hopcount can be changed concurrently from do_ipv6_setsockopt() */
+		if (ipv6_hdr(skb)->hop_limit < READ_ONCE(tcp_inet6_sk(sk)->min_hopcount)) {
+			__NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP);
+			goto out;
+		}
 	}
 
 	tp = tcp_sk(sk);
@@ -569,7 +572,7 @@ static int tcp_v6_send_synack(const struct sock *sk, struct dst_entry *dst,
 static void tcp_v6_reqsk_destructor(struct request_sock *req)
 {
 	kfree(inet_rsk(req)->ipv6_opt);
-	kfree_skb(inet_rsk(req)->pktopts);
+	consume_skb(inet_rsk(req)->pktopts);
 }
 
 #ifdef CONFIG_TCP_MD5SIG
@@ -1509,9 +1512,9 @@ static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
 		sock_rps_save_rxhash(sk, skb);
 		sk_mark_napi_id(sk, skb);
 		if (dst) {
-			if (inet_sk(sk)->rx_dst_ifindex != skb->skb_iif ||
+			if (sk->sk_rx_dst_ifindex != skb->skb_iif ||
 			    INDIRECT_CALL_1(dst->ops->check, ip6_dst_check,
-					    dst, np->rx_dst_cookie) == NULL) {
+					    dst, sk->sk_rx_dst_cookie) == NULL) {
 				dst_release(dst);
 				sk->sk_rx_dst = NULL;
 			}
@@ -1591,7 +1594,7 @@ static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
 		}
 	}
 
-	kfree_skb(opt_skb);
+	consume_skb(opt_skb);
 	return 0;
 }
 
@@ -1726,9 +1729,13 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
 			return 0;
 		}
 	}
-	if (hdr->hop_limit < tcp_inet6_sk(sk)->min_hopcount) {
-		__NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP);
-		goto discard_and_relse;
+
+	if (static_branch_unlikely(&ip6_min_hopcount)) {
+		/* min_hopcount can be changed concurrently from do_ipv6_setsockopt() */
+		if (hdr->hop_limit < READ_ONCE(tcp_inet6_sk(sk)->min_hopcount)) {
+			__NET_INC_STATS(net, LINUX_MIB_TCPMINTTLDROP);
+			goto discard_and_relse;
+		}
 	}
 
 	if (!xfrm6_policy_check(sk, XFRM_POLICY_IN, skb))
@@ -1872,9 +1879,9 @@ INDIRECT_CALLABLE_SCOPE void tcp_v6_early_demux(struct sk_buff *skb)
 			struct dst_entry *dst = READ_ONCE(sk->sk_rx_dst);
 
 			if (dst)
-				dst = dst_check(dst, tcp_inet6_sk(sk)->rx_dst_cookie);
+				dst = dst_check(dst, sk->sk_rx_dst_cookie);
 			if (dst &&
-			    inet_sk(sk)->rx_dst_ifindex == skb->skb_iif)
+			    sk->sk_rx_dst_ifindex == skb->skb_iif)
 				skb_dst_set_noref(skb, dst);
 		}
 	}

net/ipv6/udp.c

@@ -884,7 +884,7 @@ static void udp6_sk_rx_dst_set(struct sock *sk, struct dst_entry *dst)
 	if (udp_sk_rx_dst_set(sk, dst)) {
 		const struct rt6_info *rt = (const struct rt6_info *)dst;
 
-		inet6_sk(sk)->rx_dst_cookie = rt6_get_cookie(rt);
+		sk->sk_rx_dst_cookie = rt6_get_cookie(rt);
 	}
 }
 
@@ -1073,7 +1073,7 @@ INDIRECT_CALLABLE_SCOPE void udp_v6_early_demux(struct sk_buff *skb)
 	dst = READ_ONCE(sk->sk_rx_dst);
 
 	if (dst)
-		dst = dst_check(dst, inet6_sk(sk)->rx_dst_cookie);
+		dst = dst_check(dst, sk->sk_rx_dst_cookie);
 	if (dst) {
 		/* set noref for now.
 		 * any place which wants to hold dst has to call