Merge branch 'soreuseport'

Tom Herbert says:

====================
This series implements so_reuseport (SO_REUSEPORT socket option) for
TCP and UDP.  For TCP, so_reuseport allows multiple listener sockets
to be bound to the same port.  In the case of UDP, so_reuseport allows
multiple sockets to bind to the same port.  To prevent port hijacking
all sockets bound to the same port using so_reuseport must have the
same uid.  Received packets are distributed to multiple sockets bound
to the same port using a 4-tuple hash.

The motivating case for so_resuseport in TCP would be something like
a web server binding to port 80 running with multiple threads, where
each thread might have it's own listener socket.  This could be done
as an alternative to other models: 1) have one listener thread which
dispatches completed connections to workers. 2) accept on a single
listener socket from multiple threads.  In case #1 the listener thread
can easily become the bottleneck with high connection turn-over rate.
In case #2, the proportion of connections accepted per thread tends
to be uneven under high connection load (assuming simple event loop:
while (1) { accept(); process() }, wakeup does not promote fairness
among the sockets.  We have seen the  disproportion to be as high
as 3:1 ratio between thread accepting most connections and the one
accepting the fewest.  With so_reusport the distribution is
uniform.

The TCP implementation has a problem in that the request sockets for a
listener are attached to a listener socket.  If a SYN is received, a
listener socket is chosen and request structure is created (SYN-RECV
state).  If the subsequent ack in 3WHS does not match the same port
by so_reusport, the connection state is not found (reset) and the
request structure is orphaned.  This scenario would occur when the
number of listener sockets bound to a port changes (new ones are
added, or old ones closed).  We are looking for a solution to this,
maybe allow multiple sockets to share the same request table...

The motivating case for so_reuseport in UDP would be something like a
DNS server.  An alternative would be to recv on the same socket from
multiple threads.  As in the case of TCP, the load across these threads
tends to be disproportionate and we also see a lot of contection on
the socket lock.  Note that SO_REUSEADDR already allows multiple UDP
sockets to bind to the same port, however there is no provision to
prevent hijacking and nothing to distribute packets across all the
sockets sharing the same bound port.  This patch does not change the
semantics of SO_REUSEADDR, but provides usable functionality of it
for unicast.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

arch/alpha/include/uapi/asm/socket.h

@@ -19,7 +19,7 @@
 #define SO_BROADCAST	0x0020
 #define SO_LINGER	0x0080
 #define SO_OOBINLINE	0x0100
-/* To add :#define SO_REUSEPORT 0x0200 */
+#define SO_REUSEPORT	0x0200
 
 #define SO_TYPE		0x1008
 #define SO_ERROR	0x1007

arch/avr32/include/uapi/asm/socket.h

@@ -22,7 +22,7 @@
 #define SO_PRIORITY	12
 #define SO_LINGER	13
 #define SO_BSDCOMPAT	14
-/* To add :#define SO_REUSEPORT 15 */
+#define SO_REUSEPORT	15
 #define SO_PASSCRED	16
 #define SO_PEERCRED	17
 #define SO_RCVLOWAT	18

arch/cris/include/uapi/asm/socket.h

@@ -24,7 +24,7 @@
 #define SO_PRIORITY	12
 #define SO_LINGER	13
 #define SO_BSDCOMPAT	14
-/* To add :#define SO_REUSEPORT 15 */
+#define SO_REUSEPORT	15
 #define SO_PASSCRED	16
 #define SO_PEERCRED	17
 #define SO_RCVLOWAT	18

arch/frv/include/uapi/asm/socket.h

@@ -22,7 +22,7 @@
 #define SO_PRIORITY	12
 #define SO_LINGER	13
 #define SO_BSDCOMPAT	14
-/* To add :#define SO_REUSEPORT 15 */
+#define SO_REUSEPORT	15
 #define SO_PASSCRED	16
 #define SO_PEERCRED	17
 #define SO_RCVLOWAT	18

arch/h8300/include/uapi/asm/socket.h

@@ -22,7 +22,7 @@
 #define SO_PRIORITY	12
 #define SO_LINGER	13
 #define SO_BSDCOMPAT	14
-/* To add :#define SO_REUSEPORT 15 */
+#define SO_REUSEPORT	15
 #define SO_PASSCRED	16
 #define SO_PEERCRED	17
 #define SO_RCVLOWAT	18

arch/ia64/include/uapi/asm/socket.h

@@ -31,7 +31,7 @@
 #define SO_PRIORITY	12
 #define SO_LINGER	13
 #define SO_BSDCOMPAT	14
-/* To add :#define SO_REUSEPORT 15 */
+#define SO_REUSEPORT	15
 #define SO_PASSCRED	16
 #define SO_PEERCRED	17
 #define SO_RCVLOWAT	18

arch/m32r/include/uapi/asm/socket.h

@@ -22,7 +22,7 @@
 #define SO_PRIORITY	12
 #define SO_LINGER	13
 #define SO_BSDCOMPAT	14
-/* To add :#define SO_REUSEPORT 15 */
+#define SO_REUSEPORT	15
 #define SO_PASSCRED	16
 #define SO_PEERCRED	17
 #define SO_RCVLOWAT	18

arch/mips/include/uapi/asm/socket.h

@@ -28,8 +28,7 @@
 #define SO_LINGER	0x0080	/* Block on close of a reliable
 				   socket to transmit pending data.  */
 #define SO_OOBINLINE 0x0100	/* Receive out-of-band data in-band.  */
-#if 0
-To add: #define SO_REUSEPORT 0x0200	/* Allow local address and port reuse.  */
+#define SO_REUSEPORT 0x0200	/* Allow local address and port reuse.  */
 #endif
 
 #define SO_TYPE		0x1008	/* Compatible name for SO_STYLE.  */

arch/mn10300/include/uapi/asm/socket.h

@@ -22,7 +22,7 @@
 #define SO_PRIORITY	12
 #define SO_LINGER	13
 #define SO_BSDCOMPAT	14
-/* To add :#define SO_REUSEPORT 15 */
+#define SO_REUSEPORT	15
 #define SO_PASSCRED	16
 #define SO_PEERCRED	17
 #define SO_RCVLOWAT	18

arch/parisc/include/uapi/asm/socket.h

@@ -13,7 +13,7 @@
 #define SO_BROADCAST	0x0020
 #define SO_LINGER	0x0080
 #define SO_OOBINLINE	0x0100
-/* To add :#define SO_REUSEPORT 0x0200 */
+#define SO_REUSEPORT	0x0200
 #define SO_SNDBUF	0x1001
 #define SO_RCVBUF	0x1002
 #define SO_SNDBUFFORCE	0x100a

arch/powerpc/include/uapi/asm/socket.h

@@ -29,7 +29,7 @@
 #define SO_PRIORITY	12
 #define SO_LINGER	13
 #define SO_BSDCOMPAT	14
-/* To add :#define SO_REUSEPORT 15 */
+#define SO_REUSEPORT	15
 #define SO_RCVLOWAT	16
 #define SO_SNDLOWAT	17
 #define SO_RCVTIMEO	18

arch/s390/include/uapi/asm/socket.h

@@ -28,7 +28,7 @@
 #define SO_PRIORITY	12
 #define SO_LINGER	13
 #define SO_BSDCOMPAT	14
-/* To add :#define SO_REUSEPORT 15 */
+#define SO_REUSEPORT	15
 #define SO_PASSCRED	16
 #define SO_PEERCRED	17
 #define SO_RCVLOWAT	18

arch/sparc/include/uapi/asm/socket.h

@@ -15,7 +15,7 @@
 #define SO_PEERCRED	0x0040
 #define SO_LINGER	0x0080
 #define SO_OOBINLINE	0x0100
-/* To add :#define SO_REUSEPORT 0x0200 */
+#define SO_REUSEPORT	0x0200
 #define SO_BSDCOMPAT    0x0400
 #define SO_RCVLOWAT     0x0800
 #define SO_SNDLOWAT     0x1000

arch/xtensa/include/uapi/asm/socket.h

@@ -32,7 +32,7 @@
 #define SO_PRIORITY	12
 #define SO_LINGER	13
 #define SO_BSDCOMPAT	14
-/* To add :#define SO_REUSEPORT 15 */
+#define SO_REUSEPORT	15
 #define SO_PASSCRED	16
 #define SO_PEERCRED	17
 #define SO_RCVLOWAT	18

include/linux/random.h

@@ -74,4 +74,10 @@ static inline int arch_get_random_int(unsigned int *v)
 }
 #endif
 
+/* Pseudo random number generator from numerical recipes. */
+static inline u32 next_pseudo_random32(u32 seed)
+{
+	return seed * 1664525 + 1013904223;
+}
+
 #endif /* _LINUX_RANDOM_H */

include/net/inet6_hashtables.h

@@ -71,6 +71,8 @@ extern struct sock *__inet6_lookup_established(struct net *net,
 
 extern struct sock *inet6_lookup_listener(struct net *net,
 					  struct inet_hashinfo *hashinfo,
+					  const struct in6_addr *saddr,
+					  const __be16 sport,
 					  const struct in6_addr *daddr,
 					  const unsigned short hnum,
 					  const int dif);
@@ -88,7 +90,8 @@ static inline struct sock *__inet6_lookup(struct net *net,
 	if (sk)
 		return sk;
 
-	return inet6_lookup_listener(net, hashinfo, daddr, hnum, dif);
+	return inet6_lookup_listener(net, hashinfo, saddr, sport,
+				     daddr, hnum, dif);
 }
 
 static inline struct sock *__inet6_lookup_skb(struct inet_hashinfo *hashinfo,

include/net/inet_hashtables.h

@@ -81,7 +81,9 @@ struct inet_bind_bucket {
 	struct net		*ib_net;
 #endif
 	unsigned short		port;
-	signed short		fastreuse;
+	signed char		fastreuse;
+	signed char		fastreuseport;
+	kuid_t			fastuid;
 	int			num_owners;
 	struct hlist_node	node;
 	struct hlist_head	owners;
@@ -257,15 +259,19 @@ extern void inet_unhash(struct sock *sk);
 
 extern struct sock *__inet_lookup_listener(struct net *net,
 					   struct inet_hashinfo *hashinfo,
+					   const __be32 saddr,
+					   const __be16 sport,
 					   const __be32 daddr,
 					   const unsigned short hnum,
 					   const int dif);
 
 static inline struct sock *inet_lookup_listener(struct net *net,
 		struct inet_hashinfo *hashinfo,
+		__be32 saddr, __be16 sport,
 		__be32 daddr, __be16 dport, int dif)
 {
-	return __inet_lookup_listener(net, hashinfo, daddr, ntohs(dport), dif);
+	return __inet_lookup_listener(net, hashinfo, saddr, sport,
+				      daddr, ntohs(dport), dif);
 }
 
 /* Socket demux engine toys. */
@@ -358,7 +364,8 @@ static inline struct sock *__inet_lookup(struct net *net,
 	struct sock *sk = __inet_lookup_established(net, hashinfo,
 				saddr, sport, daddr, hnum, dif);
 
-	return sk ? : __inet_lookup_listener(net, hashinfo, daddr, hnum, dif);
+	return sk ? : __inet_lookup_listener(net, hashinfo, saddr, sport,
+					     daddr, hnum, dif);
 }
 
 static inline struct sock *inet_lookup(struct net *net,

include/net/netfilter/nf_tproxy_core.h

@@ -82,6 +82,7 @@ nf_tproxy_get_sock_v4(struct net *net, const u8 protocol,
 			break;
 		case NFT_LOOKUP_LISTENER:
 			sk = inet_lookup_listener(net, &tcp_hashinfo,
+						    saddr, sport,
 						    daddr, dport,
 						    in->ifindex);
 
@@ -151,6 +152,7 @@ nf_tproxy_get_sock_v6(struct net *net, const u8 protocol,
 			break;
 		case NFT_LOOKUP_LISTENER:
 			sk = inet6_lookup_listener(net, &tcp_hashinfo,
+						   saddr, sport,
 						   daddr, ntohs(dport),
 						   in->ifindex);
 

include/net/sock.h

@@ -140,6 +140,7 @@ typedef __u64 __bitwise __addrpair;
  *	@skc_family: network address family
  *	@skc_state: Connection state
  *	@skc_reuse: %SO_REUSEADDR setting
+ *	@skc_reuseport: %SO_REUSEPORT setting
  *	@skc_bound_dev_if: bound device index if != 0
  *	@skc_bind_node: bind hash linkage for various protocol lookup tables
  *	@skc_portaddr_node: second hash linkage for UDP/UDP-Lite protocol
@@ -179,7 +180,8 @@ struct sock_common {
 
 	unsigned short		skc_family;
 	volatile unsigned char	skc_state;
-	unsigned char		skc_reuse;
+	unsigned char		skc_reuse:4;
+	unsigned char		skc_reuseport:4;
 	int			skc_bound_dev_if;
 	union {
 		struct hlist_node	skc_bind_node;
@@ -297,6 +299,7 @@ struct sock {
 #define sk_family		__sk_common.skc_family
 #define sk_state		__sk_common.skc_state
 #define sk_reuse		__sk_common.skc_reuse
+#define sk_reuseport		__sk_common.skc_reuseport
 #define sk_bound_dev_if		__sk_common.skc_bound_dev_if
 #define sk_bind_node		__sk_common.skc_bind_node
 #define sk_prot			__sk_common.skc_prot

include/uapi/asm-generic/socket.h

@@ -22,8 +22,7 @@
 #define SO_PRIORITY	12
 #define SO_LINGER	13
 #define SO_BSDCOMPAT	14
-/* To add :#define SO_REUSEPORT 15 */
-
+#define SO_REUSEPORT	15
 #ifndef SO_PASSCRED /* powerpc only differs in these */
 #define SO_PASSCRED	16
 #define SO_PEERCRED	17

net/core/sock.c

@@ -665,6 +665,9 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 	case SO_REUSEADDR:
 		sk->sk_reuse = (valbool ? SK_CAN_REUSE : SK_NO_REUSE);
 		break;
+	case SO_REUSEPORT:
+		sk->sk_reuseport = valbool;
+		break;
 	case SO_TYPE:
 	case SO_PROTOCOL:
 	case SO_DOMAIN:
@@ -972,6 +975,10 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
 		v.val = sk->sk_reuse;
 		break;
 
+	case SO_REUSEPORT:
+		v.val = sk->sk_reuseport;
+		break;
+
 	case SO_KEEPALIVE:
 		v.val = sock_flag(sk, SOCK_KEEPOPEN);
 		break;

net/ipv4/inet_connection_sock.c

@@ -59,6 +59,8 @@ int inet_csk_bind_conflict(const struct sock *sk,
 	struct sock *sk2;
 	struct hlist_node *node;
 	int reuse = sk->sk_reuse;
+	int reuseport = sk->sk_reuseport;
+	kuid_t uid = sock_i_uid((struct sock *)sk);
 
 	/*
 	 * Unlike other sk lookup places we do not check
@@ -73,8 +75,11 @@ int inet_csk_bind_conflict(const struct sock *sk,
 		    (!sk->sk_bound_dev_if ||
 		     !sk2->sk_bound_dev_if ||
 		     sk->sk_bound_dev_if == sk2->sk_bound_dev_if)) {
-			if (!reuse || !sk2->sk_reuse ||
-			    sk2->sk_state == TCP_LISTEN) {
+			if ((!reuse || !sk2->sk_reuse ||
+			    sk2->sk_state == TCP_LISTEN) &&
+			    (!reuseport || !sk2->sk_reuseport ||
+			    (sk2->sk_state != TCP_TIME_WAIT &&
+			     !uid_eq(uid, sock_i_uid(sk2))))) {
 				const __be32 sk2_rcv_saddr = sk_rcv_saddr(sk2);
 				if (!sk2_rcv_saddr || !sk_rcv_saddr(sk) ||
 				    sk2_rcv_saddr == sk_rcv_saddr(sk))
@@ -106,6 +111,7 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
 	int ret, attempts = 5;
 	struct net *net = sock_net(sk);
 	int smallest_size = -1, smallest_rover;
+	kuid_t uid = sock_i_uid(sk);
 
 	local_bh_disable();
 	if (!snum) {
@@ -125,9 +131,12 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
 			spin_lock(&head->lock);
 			inet_bind_bucket_for_each(tb, node, &head->chain)
 				if (net_eq(ib_net(tb), net) && tb->port == rover) {
-					if (tb->fastreuse > 0 &&
-					    sk->sk_reuse &&
-					    sk->sk_state != TCP_LISTEN &&
+					if (((tb->fastreuse > 0 &&
+					      sk->sk_reuse &&
+					      sk->sk_state != TCP_LISTEN) ||
+					     (tb->fastreuseport > 0 &&
+					      sk->sk_reuseport &&
+					      uid_eq(tb->fastuid, uid))) &&
 					    (tb->num_owners < smallest_size || smallest_size == -1)) {
 						smallest_size = tb->num_owners;
 						smallest_rover = rover;
@@ -185,14 +194,17 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
 		if (sk->sk_reuse == SK_FORCE_REUSE)
 			goto success;
 
-		if (tb->fastreuse > 0 &&
-		    sk->sk_reuse && sk->sk_state != TCP_LISTEN &&
+		if (((tb->fastreuse > 0 &&
+		      sk->sk_reuse && sk->sk_state != TCP_LISTEN) ||
+		     (tb->fastreuseport > 0 &&
+		      sk->sk_reuseport && uid_eq(tb->fastuid, uid))) &&
 		    smallest_size == -1) {
 			goto success;
 		} else {
 			ret = 1;
 			if (inet_csk(sk)->icsk_af_ops->bind_conflict(sk, tb, true)) {
-				if (sk->sk_reuse && sk->sk_state != TCP_LISTEN &&
+				if (((sk->sk_reuse && sk->sk_state != TCP_LISTEN) ||
+				     (sk->sk_reuseport && uid_eq(tb->fastuid, uid))) &&
 				    smallest_size != -1 && --attempts >= 0) {
 					spin_unlock(&head->lock);
 					goto again;
@@ -212,9 +224,23 @@ int inet_csk_get_port(struct sock *sk, unsigned short snum)
 			tb->fastreuse = 1;
 		else
 			tb->fastreuse = 0;
-	} else if (tb->fastreuse &&
-		   (!sk->sk_reuse || sk->sk_state == TCP_LISTEN))
-		tb->fastreuse = 0;
+		if (sk->sk_reuseport) {
+			tb->fastreuseport = 1;
+			tb->fastuid = uid;
+		} else {
+			tb->fastreuseport = 0;
+			tb->fastuid = 0;
+		}
+	} else {
+		if (tb->fastreuse &&
+		    (!sk->sk_reuse || sk->sk_state == TCP_LISTEN))
+			tb->fastreuse = 0;
+		if (tb->fastreuseport &&
+		    (!sk->sk_reuseport || !uid_eq(tb->fastuid, uid))) {
+			tb->fastreuseport = 0;
+			tb->fastuid = 0;
+		}
+	}
 success:
 	if (!inet_csk(sk)->icsk_bind_hash)
 		inet_bind_hash(sk, tb, snum);