Merge branch 'net-better-const'

Eric Dumazet says:

====================
net: better const qualifier awareness

This is a follow-up of d27d367d3b78 ("inet: better const qualifier awareness")

Adopting container_of_const() to perform (struct sock *)->(protocol sock *)
operation is allowing us to propagate const qualifier and thus detect
misuses at compile time.

Most conversions are trivial, because most protocols did not adopt yet
const sk pointers where it could make sense.

Only mptcp and tcp patches (end of this series) are requiring small
adjustments.
====================

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

19 files changed, 36 insertions, 57 deletions

diff --git a/include/linux/dccp.h b/include/linux/dccp.h
index 07e547c02fd8..325af611909f 100644
--- a/include/linux/dccp.h
+++ b/include/linux/dccp.h
@@ -305,10 +305,8 @@ struct dccp_sock {
 	struct timer_list		dccps_xmit_timer;
 };
 
-static inline struct dccp_sock *dccp_sk(const struct sock *sk)
-{
-	return (struct dccp_sock *)sk;
-}
+#define dccp_sk(ptr)	container_of_const(ptr, struct dccp_sock, \
+					   dccps_inet_connection.icsk_inet.sk)
 
 static inline const char *dccp_role(const struct sock *sk)
 {
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 37dfdcfcdd54..839247a4f48e 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -336,10 +336,7 @@ static inline struct ipv6_pinfo *inet6_sk(const struct sock *__sk)
 	return sk_fullsock(__sk) ? inet_sk(__sk)->pinet6 : NULL;
 }
 
-static inline struct raw6_sock *raw6_sk(const struct sock *sk)
-{
-	return (struct raw6_sock *)sk;
-}
+#define raw6_sk(ptr) container_of_const(ptr, struct raw6_sock, inet.sk)
 
 #define ipv6_only_sock(sk)	(sk->sk_ipv6only)
 #define ipv6_sk_rxinfo(sk)	((sk)->sk_family == PF_INET6 && \
diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index ca7f05a130d2..b4c08ac86983 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -472,10 +472,12 @@ enum tsq_flags {
 	TCPF_MTU_REDUCED_DEFERRED	= (1UL << TCP_MTU_REDUCED_DEFERRED),
 };
 
-static inline struct tcp_sock *tcp_sk(const struct sock *sk)
-{
-	return (struct tcp_sock *)sk;
-}
+#define tcp_sk(ptr) container_of_const(ptr, struct tcp_sock, inet_conn.icsk_inet.sk)
+
+/* Variant of tcp_sk() upgrading a const sock to a read/write tcp socket.
+ * Used in context of (lockless) tcp listeners.
+ */
+#define tcp_sk_rw(ptr) container_of(ptr, struct tcp_sock, inet_conn.icsk_inet.sk)
 
 struct tcp_timewait_sock {
 	struct inet_timewait_sock tw_sk;
diff --git a/include/linux/udp.h b/include/linux/udp.h
index a2892e151644..43c1fb2d2c21 100644
--- a/include/linux/udp.h
+++ b/include/linux/udp.h
@@ -97,10 +97,7 @@ struct udp_sock {
 
 #define UDP_MAX_SEGMENTS	(1 << 6UL)
 
-static inline struct udp_sock *udp_sk(const struct sock *sk)
-{
-	return (struct udp_sock *)sk;
-}
+#define udp_sk(ptr) container_of_const(ptr, struct udp_sock, inet.sk)
 
 static inline void udp_set_no_check6_tx(struct sock *sk, bool val)
 {
diff --git a/include/net/af_unix.h b/include/net/af_unix.h
index 45ebde587138..824c258143a3 100644
--- a/include/net/af_unix.h
+++ b/include/net/af_unix.h
@@ -74,10 +74,7 @@ struct unix_sock {
 #endif
 };
 
-static inline struct unix_sock *unix_sk(const struct sock *sk)
-{
-	return (struct unix_sock *)sk;
-}
+#define unix_sk(ptr) container_of_const(ptr, struct unix_sock, sk)
 
 #define peer_wait peer_wq.wait
 
diff --git a/include/net/ax25.h b/include/net/ax25.h
index f8cf3629a419..0d939e5aee4e 100644
--- a/include/net/ax25.h
+++ b/include/net/ax25.h
@@ -260,10 +260,7 @@ struct ax25_sock {
 	struct ax25_cb		*cb;
 };
 
-static inline struct ax25_sock *ax25_sk(const struct sock *sk)
-{
-	return (struct ax25_sock *) sk;
-}
+#define ax25_sk(ptr) container_of_const(ptr, struct ax25_sock, sk)
 
 static inline struct ax25_cb *sk_to_ax25(const struct sock *sk)
 {
diff --git a/include/net/raw.h b/include/net/raw.h
index 7ad15830cf38..c215af02f758 100644
--- a/include/net/raw.h
+++ b/include/net/raw.h
@@ -83,10 +83,7 @@ struct raw_sock {
 	u32		   ipmr_table;
 };
 
-static inline struct raw_sock *raw_sk(const struct sock *sk)
-{
-	return (struct raw_sock *)sk;
-}
+#define raw_sk(ptr) container_of_const(ptr, struct raw_sock, inet.sk)
 
 static inline bool raw_sk_bound_dev_eq(struct net *net, int bound_dev_if,
 				       int dif, int sdif)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index db9f828e9d1e..a0a91a988272 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -529,7 +529,7 @@ static inline void tcp_synq_overflow(const struct sock *sk)
 
 	last_overflow = READ_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp);
 	if (!time_between32(now, last_overflow, last_overflow + HZ))
-		WRITE_ONCE(tcp_sk(sk)->rx_opt.ts_recent_stamp, now);
+		WRITE_ONCE(tcp_sk_rw(sk)->rx_opt.ts_recent_stamp, now);
 }
 
 /* syncookies: no recent synqueue overflow on this listening socket? */
diff --git a/include/net/x25.h b/include/net/x25.h
index d7d6c2b4ffa7..597eb53c471e 100644
--- a/include/net/x25.h
+++ b/include/net/x25.h
@@ -177,10 +177,7 @@ struct x25_forward {
 	atomic_t		refcnt;
 };
 
-static inline struct x25_sock *x25_sk(const struct sock *sk)
-{
-	return (struct x25_sock *)sk;
-}
+#define x25_sk(ptr) container_of_const(ptr, struct x25_sock, sk)
 
 /* af_x25.c */
 extern int  sysctl_x25_restart_request_timeout;
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 01569de651b6..fd68d49490f2 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -4570,7 +4570,7 @@ tcp_inbound_md5_hash(const struct sock *sk, const struct sk_buff *skb,
 	const __u8 *hash_location = NULL;
 	struct tcp_md5sig_key *hash_expected;
 	const struct tcphdr *th = tcp_hdr(skb);
-	struct tcp_sock *tp = tcp_sk(sk);
+	const struct tcp_sock *tp = tcp_sk(sk);
 	int genhash, l3index;
 	u8 newhash[16];
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 754ddbe0577f..2b75cd9e2e92 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -458,7 +458,7 @@ static void tcp_sndbuf_expand(struct sock *sk)
 static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb,
 			     unsigned int skbtruesize)
 {
-	struct tcp_sock *tp = tcp_sk(sk);
+	const struct tcp_sock *tp = tcp_sk(sk);
 	/* Optimize this! */
 	int truesize = tcp_win_from_space(sk, skbtruesize) >> 1;
 	int window = tcp_win_from_space(sk, READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_rmem[2])) >> 1;
@@ -5693,7 +5693,7 @@ static void tcp_urg(struct sock *sk, struct sk_buff *skb, const struct tcphdr *t
  */
 static bool tcp_reset_check(const struct sock *sk, const struct sk_buff *skb)
 {
-	struct tcp_sock *tp = tcp_sk(sk);
+	const struct tcp_sock *tp = tcp_sk(sk);
 
 	return unlikely(TCP_SKB_CB(skb)->seq == (tp->rcv_nxt - 1) &&
 			(1 << sk->sk_state) & (TCPF_CLOSE_WAIT | TCPF_LAST_ACK |
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 9a7ef7732c24..dac0d62120e6 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -463,7 +463,7 @@ void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst)
 }
 EXPORT_SYMBOL_GPL(tcp_ca_openreq_child);
 
-static void smc_check_reset_syn_req(struct tcp_sock *oldtp,
+static void smc_check_reset_syn_req(const struct tcp_sock *oldtp,
 				    struct request_sock *req,
 				    struct tcp_sock *newtp)
 {
@@ -492,7 +492,8 @@ struct sock *tcp_create_openreq_child(const struct sock *sk,
 	const struct inet_request_sock *ireq = inet_rsk(req);
 	struct tcp_request_sock *treq = tcp_rsk(req);
 	struct inet_connection_sock *newicsk;
-	struct tcp_sock *oldtp, *newtp;
+	const struct tcp_sock *oldtp;
+	struct tcp_sock *newtp;
 	u32 seq;
 
 	if (!newsk)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index b1e743b39a83..cfe128b81a01 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -4127,8 +4127,13 @@ int tcp_rtx_synack(const struct sock *sk, struct request_sock *req)
 	if (!res) {
 		TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS);
-		if (unlikely(tcp_passive_fastopen(sk)))
-			tcp_sk(sk)->total_retrans++;
+		if (unlikely(tcp_passive_fastopen(sk))) {
+			/* sk has const attribute because listeners are lockless.
+			 * However in this case, we are dealing with a passive fastopen
+			 * socket thus we can change total_retrans value.
+			 */
+			tcp_sk_rw(sk)->total_retrans++;
+		}
 		trace_tcp_retransmit_synack(sk, req);
 	}
 	return res;
diff --git a/net/ipv4/tcp_recovery.c b/net/ipv4/tcp_recovery.c
index 50abaa941387..acf4869c5d3b 100644
--- a/net/ipv4/tcp_recovery.c
+++ b/net/ipv4/tcp_recovery.c
@@ -4,7 +4,7 @@
 
 static u32 tcp_rack_reo_wnd(const struct sock *sk)
 {
-	struct tcp_sock *tp = tcp_sk(sk);
+	const struct tcp_sock *tp = tcp_sk(sk);
 
 	if (!tp->reord_seen) {
 		/* If reordering has not been observed, be aggressive during
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 6738181b2977..2d26b9114373 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -459,7 +459,7 @@ static bool mptcp_pending_data_fin(struct sock *sk, u64 *seq)
 	return false;
 }
 
-static void mptcp_set_datafin_timeout(const struct sock *sk)
+static void mptcp_set_datafin_timeout(struct sock *sk)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
 	u32 retransmits;
diff --git a/net/mptcp/protocol.h b/net/mptcp/protocol.h
index 339a6f072989..e1310bc113be 100644
--- a/net/mptcp/protocol.h
+++ b/net/mptcp/protocol.h
@@ -334,10 +334,7 @@ static inline void msk_owned_by_me(const struct mptcp_sock *msk)
 	sock_owned_by_me((const struct sock *)msk);
 }
 
-static inline struct mptcp_sock *mptcp_sk(const struct sock *sk)
-{
-	return (struct mptcp_sock *)sk;
-}
+#define mptcp_sk(ptr) container_of_const(ptr, struct mptcp_sock, sk.icsk_inet.sk)
 
 /* the msk socket don't use the backlog, also account for the bulk
  * free memory
@@ -371,7 +368,7 @@ static inline struct mptcp_data_frag *mptcp_send_next(struct sock *sk)
 
 static inline struct mptcp_data_frag *mptcp_pending_tail(const struct sock *sk)
 {
-	struct mptcp_sock *msk = mptcp_sk(sk);
+	const struct mptcp_sock *msk = mptcp_sk(sk);
 
 	if (!msk->first_pending)
 		return NULL;
@@ -382,7 +379,7 @@ static inline struct mptcp_data_frag *mptcp_pending_tail(const struct sock *sk)
 	return list_last_entry(&msk->rtx_queue, struct mptcp_data_frag, list);
 }
 
-static inline struct mptcp_data_frag *mptcp_rtx_head(const struct sock *sk)
+static inline struct mptcp_data_frag *mptcp_rtx_head(struct sock *sk)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
 
diff --git a/net/packet/internal.h b/net/packet/internal.h
index 680703dbce5e..e793e99646f1 100644
--- a/net/packet/internal.h
+++ b/net/packet/internal.h
@@ -133,10 +133,7 @@ struct packet_sock {
 	atomic_t		tp_drops ____cacheline_aligned_in_smp;
 };
 
-static inline struct packet_sock *pkt_sk(struct sock *sk)
-{
-	return (struct packet_sock *)sk;
-}
+#define pkt_sk(ptr) container_of_const(ptr, struct packet_sock, sk)
 
 enum packet_sock_flags {
 	PACKET_SOCK_ORIGDEV,
diff --git a/net/smc/smc.h b/net/smc/smc.h
index 5ed765ea0c73..2eeea4cdc718 100644
--- a/net/smc/smc.h
+++ b/net/smc/smc.h
@@ -283,10 +283,7 @@ struct smc_sock {				/* smc sock container */
 						 * */
 };
 
-static inline struct smc_sock *smc_sk(const struct sock *sk)
-{
-	return (struct smc_sock *)sk;
-}
+#define smc_sk(ptr) container_of_const(ptr, struct smc_sock, sk)
 
 static inline void smc_init_saved_callbacks(struct smc_sock *smc)
 {
diff --git a/security/lsm_audit.c b/security/lsm_audit.c
index 00d3bdd386e2..368e77ca43c4 100644
--- a/security/lsm_audit.c
+++ b/security/lsm_audit.c
@@ -310,7 +310,7 @@ static void dump_common_audit_data(struct audit_buffer *ab,
 	case LSM_AUDIT_DATA_NET:
 		if (a->u.net->sk) {
 			const struct sock *sk = a->u.net->sk;
-			struct unix_sock *u;
+			const struct unix_sock *u;
 			struct unix_address *addr;
 			int len = 0;
 			char *p = NULL;