[PATCH v2 net-next 00/10] tcp: receive path optimizations

[PATCH v2 net-next 00/10] tcp: receive path optimizations

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

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.

v2: Resent because v1 seems to have been lost.
    Added Soheil Acked-by, and added "net: annotate accesses to sk->sk_rx_queue_mapping"

Eric Dumazet (10):
  tcp: move inet->rx_dst_ifindex to sk->sk_rx_dst_ifindex
  ipv6: move inet6_sk(sk)->rx_dst_cookie to sk->sk_rx_dst_cookie
  net: avoid dirtying sk->sk_napi_id
  net: avoid dirtying sk->sk_rx_queue_mapping
  net: annotate accesses to sk->sk_rx_queue_mapping
  ipv6: annotate data races around np->min_hopcount
  ipv6: guard IPV6_MINHOPCOUNT with a static key
  ipv4: annotate data races arount inet->min_ttl
  ipv4: guard IP_MINTTL with a static key
  ipv6/tcp: small drop monitor changes

 include/linux/ipv6.h     |  1 -
 include/net/busy_poll.h  |  3 ++-
 include/net/inet_sock.h  |  3 +--
 include/net/ip.h         |  2 ++
 include/net/ipv6.h       |  1 +
 include/net/sock.h       | 21 ++++++++++++++-------
 net/ipv4/ip_sockglue.c   | 11 ++++++++++-
 net/ipv4/tcp_ipv4.c      | 25 ++++++++++++++++---------
 net/ipv6/ipv6_sockglue.c | 11 ++++++++++-
 net/ipv6/tcp_ipv6.c      | 35 +++++++++++++++++++++--------------
 net/ipv6/udp.c           |  4 ++--
 11 files changed, 79 insertions(+), 38 deletions(-)

-- 
2.33.0.1079.g6e70778dc9-goog

[PATCH v2 net-next 01/10] tcp: move inet->rx_dst_ifindex to sk->sk_rx_dst_ifindex

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

Increase cache locality by moving rx_dst_ifindex next to sk->sk_rx_dst

This is part of an effort to reduce cache line misses in TCP fast path.

This removes one cache line miss in early demux.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
---
 include/net/inet_sock.h | 3 +--
 include/net/sock.h      | 3 +++
 net/ipv4/tcp_ipv4.c     | 6 +++---
 net/ipv6/tcp_ipv6.c     | 6 +++---
 4 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/include/net/inet_sock.h b/include/net/inet_sock.h
index 89163ef8cf4be2aaf99d09806749911a121a56e0..9e1111f5915bd03b6ec5e2e4a74ea0079ede8263 100644
--- a/include/net/inet_sock.h
+++ b/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;
diff --git a/include/net/sock.h b/include/net/sock.h
index 596ba85611bc786affed2bf2b18e455b015f3774..0bfb3f138bdab01bd97498e1126d111743000c8c 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -259,6 +259,7 @@ 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_dst_cache: destination cache
   *	@sk_dst_pending_confirm: need to confirm neighbour
   *	@sk_policy: flow policy
@@ -430,6 +431,8 @@ struct sock {
 	struct xfrm_policy __rcu *sk_policy[2];
 #endif
 	struct dst_entry	*sk_rx_dst;
+	int			sk_rx_dst_ifindex;
+
 	struct dst_entry __rcu	*sk_dst_cache;
 	atomic_t		sk_omem_alloc;
 	int			sk_sndbuf;
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 5e6d8cb82ce5d8897ec33bf9113d94c42b55bb34..2bdc32c1afb65bb123a27444d9f6e4d01a188074 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1703,7 +1703,7 @@ 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 +1788,7 @@ 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);
 		}
 	}
@@ -2195,7 +2195,7 @@ 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);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 1ef27cd7dbff713a22835fc13b57e2eca529f87e..3e8669b6d636c2971f2afc0abf0f2ef51ca6e2d4 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -108,7 +108,7 @@ 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;
+		sk->sk_rx_dst_ifindex = skb->skb_iif;
 		tcp_inet6_sk(sk)->rx_dst_cookie = rt6_get_cookie(rt);
 	}
 }
@@ -1509,7 +1509,7 @@ 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_release(dst);
@@ -1874,7 +1874,7 @@ INDIRECT_CALLABLE_SCOPE void tcp_v6_early_demux(struct sk_buff *skb)
 			if (dst)
 				dst = dst_check(dst, tcp_inet6_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);
 		}
 	}
-- 
2.33.0.1079.g6e70778dc9-goog

[PATCH v2 net-next 02/10] ipv6: move inet6_sk(sk)->rx_dst_cookie to sk->sk_rx_dst_cookie

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

Increase cache locality by moving rx_dst_coookie next to sk->sk_rx_dst

This removes one or two cache line misses in IPv6 early demux (TCP/UDP)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
---
 include/linux/ipv6.h | 1 -
 include/net/sock.h   | 2 ++
 net/ipv6/tcp_ipv6.c  | 6 +++---
 net/ipv6/udp.c       | 4 ++--
 4 files changed, 7 insertions(+), 6 deletions(-)

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index ef4a69865737cee82a72c35f3421a535b607c7a6..c383630d3f0658908eac65c030daf97b0a0d0c7c 100644
--- a/include/linux/ipv6.h
+++ b/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;
diff --git a/include/net/sock.h b/include/net/sock.h
index 0bfb3f138bdab01bd97498e1126d111743000c8c..99c4194cb61add848e3a35db0f952c4193f5ea1f 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -260,6 +260,7 @@ struct bpf_local_storage;
   *	@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
@@ -432,6 +433,7 @@ struct sock {
 #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;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 3e8669b6d636c2971f2afc0abf0f2ef51ca6e2d4..50d9578e945bd2965247a46bc6d8b1adeb21d2f4 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -109,7 +109,7 @@ static void inet6_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb)
 
 		sk->sk_rx_dst = dst;
 		sk->sk_rx_dst_ifindex = skb->skb_iif;
-		tcp_inet6_sk(sk)->rx_dst_cookie = rt6_get_cookie(rt);
+		sk->sk_rx_dst_cookie = rt6_get_cookie(rt);
 	}
 }
 
@@ -1511,7 +1511,7 @@ static int tcp_v6_do_rcv(struct sock *sk, struct sk_buff *skb)
 		if (dst) {
 			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;
 			}
@@ -1872,7 +1872,7 @@ 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 &&
 			    sk->sk_rx_dst_ifindex == skb->skb_iif)
 				skb_dst_set_noref(skb, dst);
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 8d785232b4796b7cafe14a35dedcbb0aaa2c37c2..14a94cddcf0bcf63d8351c66b94a08770694a9c8 100644
--- a/net/ipv6/udp.c
+++ b/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
-- 
2.33.0.1079.g6e70778dc9-goog

[PATCH v2 net-next 03/10] net: avoid dirtying sk->sk_napi_id

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

sk_napi_id is located in a cache line that can be kept read mostly.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
---
 include/net/busy_poll.h | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h
index 40296ed976a9778ceb239b99ad783cb99b8b92ef..4202c609bb0b09345c0f1c5105adf409a3a89f74 100644
--- a/include/net/busy_poll.h
+++ b/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);
 }
-- 
2.33.0.1079.g6e70778dc9-goog

[PATCH v2 net-next 04/10] net: avoid dirtying sk->sk_rx_queue_mapping

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

sk_rx_queue_mapping is located in a cache line that should be kept read mostly.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
---
 include/net/sock.h | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index 99c4194cb61add848e3a35db0f952c4193f5ea1f..b4d3744b188ad869b4ec55f78e04236b710898de 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1916,10 +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
 }
-- 
2.33.0.1079.g6e70778dc9-goog

[PATCH v2 net-next 05/10] net: annotate accesses to sk->sk_rx_queue_mapping

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

sk->sk_rx_queue_mapping can be modified locklessly,
add a couple of READ_ONCE()/WRITE_ONCE() to document this fact.

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/sock.h | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index b4d3744b188ad869b4ec55f78e04236b710898de..b76be30674efc88434ed45d46b9c4600261b6271 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1925,15 +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;
-- 
2.33.0.1079.g6e70778dc9-goog

[PATCH v2 net-next 06/10] ipv6: annotate data races around np->min_hopcount

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

No report yet from KCSAN, yet worth documenting the races.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
---
 net/ipv6/ipv6_sockglue.c | 5 ++++-
 net/ipv6/tcp_ipv6.c      | 6 ++++--
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index e4bdb09c558670f342f1abad5dfd8252f497aa68..9c3d28764b5c3a47a73491ea5d656867ece4fed2 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -950,7 +950,10 @@ 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;
+		/* 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:
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 50d9578e945bd2965247a46bc6d8b1adeb21d2f4..c93b2d48bb89a845c880679572c75a8791589525 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -414,7 +414,8 @@ 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) {
+	/* 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;
 	}
@@ -1726,7 +1727,8 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
 			return 0;
 		}
 	}
-	if (hdr->hop_limit < tcp_inet6_sk(sk)->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;
 	}
-- 
2.33.0.1079.g6e70778dc9-goog

[PATCH v2 net-next 07/10] ipv6: guard IPV6_MINHOPCOUNT with a static key

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

RFC 5082 IPV6_MINHOPCOUNT is rarely used on hosts.

Add a static key to remove from TCP fast path useless code,
and potential cache line miss to fetch tcp_inet6_sk(sk)->min_hopcount

Note that once ip6_min_hopcount static key has been enabled,
it stays enabled until next boot.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
---
 include/net/ipv6.h       |  1 +
 net/ipv6/ipv6_sockglue.c |  6 ++++++
 net/ipv6/tcp_ipv6.c      | 21 +++++++++++++--------
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index f2d0ecc257bb28e6dd162d180c371e2b0487c8e3..c19bf51ded1d026e795a3f9ae0ff3be766fc174e 100644
--- a/include/net/ipv6.h
+++ b/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);
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 9c3d28764b5c3a47a73491ea5d656867ece4fed2..41efca817db4228f265235a471449a3790075ce7 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/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;
@@ -950,6 +952,10 @@ static int do_ipv6_setsockopt(struct sock *sk, int level, int optname,
 			goto e_inval;
 		if (val < 0 || val > 255)
 			goto e_inval;
+
+		if (val)
+			static_branch_enable(&ip6_min_hopcount);
+
 		/* tcp_v6_err() and tcp_v6_rcv() might read min_hopcount
 		 * while we are changing it.
 		 */
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index c93b2d48bb89a845c880679572c75a8791589525..6945583c0fa48256db5510866342e4aab672fd71 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -414,10 +414,12 @@ static int tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 	if (sk->sk_state == TCP_CLOSE)
 		goto out;
 
-	/* 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;
+	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);
@@ -1727,10 +1729,13 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
 			return 0;
 		}
 	}
-	/* 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 (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))
-- 
2.33.0.1079.g6e70778dc9-goog

[PATCH v2 net-next 08/10] ipv4: annotate data races arount inet->min_ttl

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

No report yet from KCSAN, yet worth documenting the races.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
---
 net/ipv4/ip_sockglue.c | 5 ++++-
 net/ipv4/tcp_ipv4.c    | 7 +++++--
 2 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index b297bb28556ec5cf383068f67ee910af38591cc3..d5487c8580674a01df8c7d8ce88f97c9add846b6 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/net/ipv4/ip_sockglue.c
@@ -1352,7 +1352,10 @@ 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;
+		/* tcp_v4_err() and tcp_v4_rcv() might read min_ttl
+		 * while we are changint it.
+		 */
+		WRITE_ONCE(inet->min_ttl, val);
 		break;
 
 	default:
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 2bdc32c1afb65bb123a27444d9f6e4d01a188074..a9cbc8e6b796207f4880b2b32ff9289321080068 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -508,7 +508,8 @@ 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)) {
+	/* 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;
 	}
@@ -2068,7 +2069,9 @@ int tcp_v4_rcv(struct sk_buff *skb)
 			return 0;
 		}
 	}
-	if (unlikely(iph->ttl < inet_sk(sk)->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;
 	}
-- 
2.33.0.1079.g6e70778dc9-goog

[PATCH v2 net-next 09/10] ipv4: guard IP_MINTTL with a static key

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

RFC 5082 IP_MINTTL option is rarely used on hosts.

Add a static key to remove from TCP fast path useless code,
and potential cache line miss to fetch inet_sk(sk)->min_ttl

Note that once ip4_min_ttl static key has been enabled,
it stays enabled until next boot.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
---
 include/net/ip.h       |  2 ++
 net/ipv4/ip_sockglue.c |  6 ++++++
 net/ipv4/tcp_ipv4.c    | 20 ++++++++++++--------
 3 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/include/net/ip.h b/include/net/ip.h
index cf229a53119428307da898af4b0dc23e1cecc053..b71e88507c4a0907011c41e1ed0148eb873b5186 100644
--- a/include/net/ip.h
+++ b/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,
diff --git a/net/ipv4/ip_sockglue.c b/net/ipv4/ip_sockglue.c
index d5487c8580674a01df8c7d8ce88f97c9add846b6..38d29b175ca6646c280e0626e8e935b348f00f08 100644
--- a/net/ipv4/ip_sockglue.c
+++ b/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)
 {
@@ -1352,6 +1354,10 @@ static int do_ip_setsockopt(struct sock *sk, int level, int optname,
 			goto e_inval;
 		if (val < 0 || val > 255)
 			goto e_inval;
+
+		if (val)
+			static_branch_enable(&ip4_min_ttl);
+
 		/* tcp_v4_err() and tcp_v4_rcv() might read min_ttl
 		 * while we are changint it.
 		 */
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index a9cbc8e6b796207f4880b2b32ff9289321080068..13d868c43284584ee0c58ddfd411bb52c8b0c830 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -508,10 +508,12 @@ int tcp_v4_err(struct sk_buff *skb, u32 info)
 	if (sk->sk_state == TCP_CLOSE)
 		goto out;
 
-	/* 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;
+	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);
@@ -2070,10 +2072,12 @@ int tcp_v4_rcv(struct sk_buff *skb)
 		}
 	}
 
-	/* 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 (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))
-- 
2.33.0.1079.g6e70778dc9-goog

[PATCH v2 net-next 10/10] ipv6/tcp: small drop monitor changes

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

Two kfree_skb() calls must be replaced by consume_skb()
for skbs that are not technically dropped.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
---
 net/ipv6/tcp_ipv6.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 6945583c0fa48256db5510866342e4aab672fd71..c678e778c1fb8f8cb7300c23cb876ef0d8e750c8 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -572,7 +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
@@ -1594,7 +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;
 }
 
-- 
2.33.0.1079.g6e70778dc9-goog

Re: [PATCH v2 net-next 00/10] tcp: receive path optimizations

[patchwork-bot+netdevbpf]

Hello:

This series was applied to netdev/net-next.git (master)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 25 Oct 2021 09:48:15 -0700 you wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> 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.
> 
> [...]

Here is the summary with links:
  - [v2,net-next,01/10] tcp: move inet->rx_dst_ifindex to sk->sk_rx_dst_ifindex
    https://git.kernel.org/netdev/net-next/c/0c0a5ef809f9
  - [v2,net-next,02/10] ipv6: move inet6_sk(sk)->rx_dst_cookie to sk->sk_rx_dst_cookie
    https://git.kernel.org/netdev/net-next/c/ef57c1610dd8
  - [v2,net-next,03/10] net: avoid dirtying sk->sk_napi_id
    https://git.kernel.org/netdev/net-next/c/2b13af8ade38
  - [v2,net-next,04/10] net: avoid dirtying sk->sk_rx_queue_mapping
    https://git.kernel.org/netdev/net-next/c/342159ee394d
  - [v2,net-next,05/10] net: annotate accesses to sk->sk_rx_queue_mapping
    https://git.kernel.org/netdev/net-next/c/09b898466792
  - [v2,net-next,06/10] ipv6: annotate data races around np->min_hopcount
    https://git.kernel.org/netdev/net-next/c/cc17c3c8e8b5
  - [v2,net-next,07/10] ipv6: guard IPV6_MINHOPCOUNT with a static key
    https://git.kernel.org/netdev/net-next/c/790eb67374d4
  - [v2,net-next,08/10] ipv4: annotate data races arount inet->min_ttl
    https://git.kernel.org/netdev/net-next/c/14834c4f4eb3
  - [v2,net-next,09/10] ipv4: guard IP_MINTTL with a static key
    https://git.kernel.org/netdev/net-next/c/020e71a3cf7f
  - [v2,net-next,10/10] ipv6/tcp: small drop monitor changes
    https://git.kernel.org/netdev/net-next/c/12c8691de307

You are awesome, thank you!
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