Merge branch 'l2tp-further-checkpatch-pl-cleanups'

Tom Parkin says:

====================
l2tp: further checkpatch.pl cleanups

l2tp hasn't been kept up to date with the static analysis checks offered
by checkpatch.pl.

This patchset builds on the series "l2tp: cleanup checkpatch.pl
warnings".  It includes small refactoring changes which improve code
quality and resolve a subset of the checkpatch warnings for the l2tp
codebase.
====================
Reviewed-by: James Chapman <jchapman@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/l2tp/l2tp_core.c

@@ -412,7 +412,7 @@ static void l2tp_recv_dequeue_skb(struct l2tp_session *session, struct sk_buff *
 	}
 
 	/* call private receive handler */
-	if (session->recv_skb != NULL)
+	if (session->recv_skb)
 		(*session->recv_skb)(session, skb, L2TP_SKB_CB(skb)->length);
 	else
 		kfree_skb(skb);
@@ -683,7 +683,7 @@ void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 		 * check if we sre sending sequence numbers and if not,
 		 * configure it so.
 		 */
-		if ((!session->lns_mode) && (!session->send_seq)) {
+		if (!session->lns_mode && !session->send_seq) {
 			l2tp_info(session, L2TP_MSG_SEQ,
 				  "%s: requested to enable seq numbers by LNS\n",
 				  session->name);
@@ -707,7 +707,7 @@ void l2tp_recv_common(struct l2tp_session *session, struct sk_buff *skb,
 		 * If we're the LNS and we're sending sequence numbers, the
 		 * LAC is broken. Discard the frame.
 		 */
-		if ((!session->lns_mode) && (session->send_seq)) {
+		if (!session->lns_mode && session->send_seq) {
 			l2tp_info(session, L2TP_MSG_SEQ,
 				  "%s: requested to disable seq numbers by LNS\n",
 				  session->name);
@@ -911,7 +911,7 @@ int l2tp_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 	struct l2tp_tunnel *tunnel;
 
 	tunnel = rcu_dereference_sk_user_data(sk);
-	if (tunnel == NULL)
+	if (!tunnel)
 		goto pass_up;
 
 	l2tp_dbg(tunnel, L2TP_MSG_DATA, "%s: received %d bytes\n",
@@ -1150,7 +1150,7 @@ static void l2tp_tunnel_destruct(struct sock *sk)
 {
 	struct l2tp_tunnel *tunnel = l2tp_tunnel(sk);
 
-	if (tunnel == NULL)
+	if (!tunnel)
 		goto end;
 
 	l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: closing...\n", tunnel->name);
@@ -1189,7 +1189,7 @@ static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
 	struct hlist_node *tmp;
 	struct l2tp_session *session;
 
-	BUG_ON(tunnel == NULL);
+	BUG_ON(!tunnel);
 
 	l2tp_info(tunnel, L2TP_MSG_CONTROL, "%s: closing all sessions...\n",
 		  tunnel->name);
@@ -1214,7 +1214,7 @@ static void l2tp_tunnel_closeall(struct l2tp_tunnel *tunnel)
 			__l2tp_session_unhash(session);
 			l2tp_session_queue_purge(session);
 
-			if (session->session_close != NULL)
+			if (session->session_close)
 				(*session->session_close)(session);
 
 			l2tp_session_dec_refcount(session);
@@ -1389,7 +1389,7 @@ static int l2tp_tunnel_sock_create(struct net *net,
 
 out:
 	*sockp = sock;
-	if ((err < 0) && sock) {
+	if (err < 0 && sock) {
 		kernel_sock_shutdown(sock, SHUT_RDWR);
 		sock_release(sock);
 		*sockp = NULL;
@@ -1407,11 +1407,11 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
 	int err;
 	enum l2tp_encap_type encap = L2TP_ENCAPTYPE_UDP;
 
-	if (cfg != NULL)
+	if (cfg)
 		encap = cfg->encap;
 
-	tunnel = kzalloc(sizeof(struct l2tp_tunnel), GFP_KERNEL);
-	if (tunnel == NULL) {
+	tunnel = kzalloc(sizeof(*tunnel), GFP_KERNEL);
+	if (!tunnel) {
 		err = -ENOMEM;
 		goto err;
 	}
@@ -1426,7 +1426,7 @@ int l2tp_tunnel_create(struct net *net, int fd, int version, u32 tunnel_id, u32
 	rwlock_init(&tunnel->hlist_lock);
 	tunnel->acpt_newsess = true;
 
-	if (cfg != NULL)
+	if (cfg)
 		tunnel->debug = cfg->debug;
 
 	tunnel->encap = encap;
@@ -1615,7 +1615,7 @@ int l2tp_session_delete(struct l2tp_session *session)
 
 	__l2tp_session_unhash(session);
 	l2tp_session_queue_purge(session);
-	if (session->session_close != NULL)
+	if (session->session_close)
 		(*session->session_close)(session);
 
 	l2tp_session_dec_refcount(session);
@@ -1647,8 +1647,8 @@ struct l2tp_session *l2tp_session_create(int priv_size, struct l2tp_tunnel *tunn
 {
 	struct l2tp_session *session;
 
-	session = kzalloc(sizeof(struct l2tp_session) + priv_size, GFP_KERNEL);
-	if (session != NULL) {
+	session = kzalloc(sizeof(*session) + priv_size, GFP_KERNEL);
+	if (session) {
 		session->magic = L2TP_SESSION_MAGIC;
 		session->tunnel = tunnel;
 

net/l2tp/l2tp_debugfs.c

@@ -58,7 +58,7 @@ static void l2tp_dfs_next_session(struct l2tp_dfs_seq_data *pd)
 	pd->session = l2tp_session_get_nth(pd->tunnel, pd->session_idx);
 	pd->session_idx++;
 
-	if (pd->session == NULL) {
+	if (!pd->session) {
 		pd->session_idx = 0;
 		l2tp_dfs_next_tunnel(pd);
 	}
@@ -72,16 +72,16 @@ static void *l2tp_dfs_seq_start(struct seq_file *m, loff_t *offs)
 	if (!pos)
 		goto out;
 
-	BUG_ON(m->private == NULL);
+	BUG_ON(!m->private);
 	pd = m->private;
 
-	if (pd->tunnel == NULL)
+	if (!pd->tunnel)
 		l2tp_dfs_next_tunnel(pd);
 	else
 		l2tp_dfs_next_session(pd);
 
 	/* NULL tunnel and session indicates end of list */
-	if ((pd->tunnel == NULL) && (pd->session == NULL))
+	if (!pd->tunnel && !pd->session)
 		pd = NULL;
 
 out:
@@ -146,10 +146,12 @@ static void l2tp_dfs_seq_tunnel_show(struct seq_file *m, void *v)
 
 			seq_printf(m, " from %pI6c to %pI6c\n",
 				   &np->saddr, &tunnel->sock->sk_v6_daddr);
-		} else
+		}
 #endif
-		seq_printf(m, " from %pI4 to %pI4\n",
-			   &inet->inet_saddr, &inet->inet_daddr);
+		if (tunnel->sock->sk_family == AF_INET)
+			seq_printf(m, " from %pI4 to %pI4\n",
+				   &inet->inet_saddr, &inet->inet_daddr);
+
 		if (tunnel->encap == L2TP_ENCAPTYPE_UDP)
 			seq_printf(m, " source port %hu, dest port %hu\n",
 				   ntohs(inet->inet_sport), ntohs(inet->inet_dport));
@@ -221,7 +223,7 @@ static void l2tp_dfs_seq_session_show(struct seq_file *m, void *v)
 		   atomic_long_read(&session->stats.rx_bytes),
 		   atomic_long_read(&session->stats.rx_errors));
 
-	if (session->show != NULL)
+	if (session->show)
 		session->show(m, session);
 }
 
@@ -268,7 +270,7 @@ static int l2tp_dfs_seq_open(struct inode *inode, struct file *file)
 	int rc = -ENOMEM;
 
 	pd = kzalloc(sizeof(*pd), GFP_KERNEL);
-	if (pd == NULL)
+	if (!pd)
 		goto out;
 
 	/* Derive the network namespace from the pid opening the

net/l2tp/l2tp_ip.c

@@ -471,7 +471,7 @@ static int l2tp_ip_sendmsg(struct sock *sk, struct msghdr *msg, size_t len)
 		rt = (struct rtable *)__sk_dst_check(sk, 0);
 
 	rcu_read_lock();
-	if (rt == NULL) {
+	if (!rt) {
 		const struct ip_options_rcu *inet_opt;
 
 		inet_opt = rcu_dereference(inet->inet_opt);

net/l2tp/l2tp_ip6.c

@@ -486,7 +486,7 @@ static int l2tp_ip6_push_pending_frames(struct sock *sk)
 	int err = 0;
 
 	skb = skb_peek(&sk->sk_write_queue);
-	if (skb == NULL)
+	if (!skb)
 		goto out;
 
 	transhdr = (__be32 *)skb_transport_header(skb);

net/l2tp/l2tp_netlink.c

@@ -155,12 +155,38 @@ static int l2tp_session_notify(struct genl_family *family,
 	return ret;
 }
 
+static int l2tp_nl_cmd_tunnel_create_get_addr(struct nlattr **attrs, struct l2tp_tunnel_cfg *cfg)
+{
+	if (attrs[L2TP_ATTR_UDP_SPORT])
+		cfg->local_udp_port = nla_get_u16(attrs[L2TP_ATTR_UDP_SPORT]);
+	if (attrs[L2TP_ATTR_UDP_DPORT])
+		cfg->peer_udp_port = nla_get_u16(attrs[L2TP_ATTR_UDP_DPORT]);
+	cfg->use_udp_checksums = nla_get_flag(attrs[L2TP_ATTR_UDP_CSUM]);
+
+	/* Must have either AF_INET or AF_INET6 address for source and destination */
+#if IS_ENABLED(CONFIG_IPV6)
+	if (attrs[L2TP_ATTR_IP6_SADDR] && attrs[L2TP_ATTR_IP6_DADDR]) {
+		cfg->local_ip6 = nla_data(attrs[L2TP_ATTR_IP6_SADDR]);
+		cfg->peer_ip6 = nla_data(attrs[L2TP_ATTR_IP6_DADDR]);
+		cfg->udp6_zero_tx_checksums = nla_get_flag(attrs[L2TP_ATTR_UDP_ZERO_CSUM6_TX]);
+		cfg->udp6_zero_rx_checksums = nla_get_flag(attrs[L2TP_ATTR_UDP_ZERO_CSUM6_RX]);
+		return 0;
+	}
+#endif
+	if (attrs[L2TP_ATTR_IP_SADDR] && attrs[L2TP_ATTR_IP_DADDR]) {
+		cfg->local_ip.s_addr = nla_get_in_addr(attrs[L2TP_ATTR_IP_SADDR]);
+		cfg->peer_ip.s_addr = nla_get_in_addr(attrs[L2TP_ATTR_IP_DADDR]);
+		return 0;
+	}
+	return -EINVAL;
+}
+
 static int l2tp_nl_cmd_tunnel_create(struct sk_buff *skb, struct genl_info *info)
 {
 	u32 tunnel_id;
 	u32 peer_tunnel_id;
 	int proto_version;
-	int fd;
+	int fd = -1;
 	int ret = 0;
 	struct l2tp_tunnel_cfg cfg = { 0, };
 	struct l2tp_tunnel *tunnel;
@@ -191,33 +217,16 @@ static int l2tp_nl_cmd_tunnel_create(struct sk_buff *skb, struct genl_info *info
 	}
 	cfg.encap = nla_get_u16(attrs[L2TP_ATTR_ENCAP_TYPE]);
 
-	fd = -1;
+	/* Managed tunnels take the tunnel socket from userspace.
+	 * Unmanaged tunnels must call out the source and destination addresses
+	 * for the kernel to create the tunnel socket itself.
+	 */
 	if (attrs[L2TP_ATTR_FD]) {
 		fd = nla_get_u32(attrs[L2TP_ATTR_FD]);
 	} else {
-#if IS_ENABLED(CONFIG_IPV6)
-		if (attrs[L2TP_ATTR_IP6_SADDR] && attrs[L2TP_ATTR_IP6_DADDR]) {
-			cfg.local_ip6 = nla_data(attrs[L2TP_ATTR_IP6_SADDR]);
-			cfg.peer_ip6 = nla_data(attrs[L2TP_ATTR_IP6_DADDR]);
-		} else
-#endif
-		if (attrs[L2TP_ATTR_IP_SADDR] && attrs[L2TP_ATTR_IP_DADDR]) {
-			cfg.local_ip.s_addr = nla_get_in_addr(attrs[L2TP_ATTR_IP_SADDR]);
-			cfg.peer_ip.s_addr = nla_get_in_addr(attrs[L2TP_ATTR_IP_DADDR]);
-		} else {
-			ret = -EINVAL;
+		ret = l2tp_nl_cmd_tunnel_create_get_addr(attrs, &cfg);
+		if (ret < 0)
 			goto out;
-		}
-		if (attrs[L2TP_ATTR_UDP_SPORT])
-			cfg.local_udp_port = nla_get_u16(attrs[L2TP_ATTR_UDP_SPORT]);
-		if (attrs[L2TP_ATTR_UDP_DPORT])
-			cfg.peer_udp_port = nla_get_u16(attrs[L2TP_ATTR_UDP_DPORT]);
-		cfg.use_udp_checksums = nla_get_flag(attrs[L2TP_ATTR_UDP_CSUM]);
-
-#if IS_ENABLED(CONFIG_IPV6)
-		cfg.udp6_zero_tx_checksums = nla_get_flag(attrs[L2TP_ATTR_UDP_ZERO_CSUM6_TX]);
-		cfg.udp6_zero_rx_checksums = nla_get_flag(attrs[L2TP_ATTR_UDP_ZERO_CSUM6_RX]);
-#endif
 	}
 
 	if (attrs[L2TP_ATTR_DEBUG])
@@ -310,16 +319,79 @@ static int l2tp_nl_cmd_tunnel_modify(struct sk_buff *skb, struct genl_info *info
 	return ret;
 }
 
+#if IS_ENABLED(CONFIG_IPV6)
+static int l2tp_nl_tunnel_send_addr6(struct sk_buff *skb, struct sock *sk,
+				     enum l2tp_encap_type encap)
+{
+	struct inet_sock *inet = inet_sk(sk);
+	struct ipv6_pinfo *np = inet6_sk(sk);
+
+	switch (encap) {
+	case L2TP_ENCAPTYPE_UDP:
+		if (udp_get_no_check6_tx(sk) &&
+		    nla_put_flag(skb, L2TP_ATTR_UDP_ZERO_CSUM6_TX))
+			return -1;
+		if (udp_get_no_check6_rx(sk) &&
+		    nla_put_flag(skb, L2TP_ATTR_UDP_ZERO_CSUM6_RX))
+			return -1;
+		if (nla_put_u16(skb, L2TP_ATTR_UDP_SPORT, ntohs(inet->inet_sport)) ||
+		    nla_put_u16(skb, L2TP_ATTR_UDP_DPORT, ntohs(inet->inet_dport)))
+			return -1;
+		fallthrough;
+	case L2TP_ENCAPTYPE_IP:
+		if (nla_put_in6_addr(skb, L2TP_ATTR_IP6_SADDR, &np->saddr) ||
+		    nla_put_in6_addr(skb, L2TP_ATTR_IP6_DADDR, &sk->sk_v6_daddr))
+			return -1;
+		break;
+	}
+	return 0;
+}
+#endif
+
+static int l2tp_nl_tunnel_send_addr4(struct sk_buff *skb, struct sock *sk,
+				     enum l2tp_encap_type encap)
+{
+	struct inet_sock *inet = inet_sk(sk);
+
+	switch (encap) {
+	case L2TP_ENCAPTYPE_UDP:
+		if (nla_put_u8(skb, L2TP_ATTR_UDP_CSUM, !sk->sk_no_check_tx) ||
+		    nla_put_u16(skb, L2TP_ATTR_UDP_SPORT, ntohs(inet->inet_sport)) ||
+		    nla_put_u16(skb, L2TP_ATTR_UDP_DPORT, ntohs(inet->inet_dport)))
+			return -1;
+		fallthrough;
+	case L2TP_ENCAPTYPE_IP:
+		if (nla_put_in_addr(skb, L2TP_ATTR_IP_SADDR, inet->inet_saddr) ||
+		    nla_put_in_addr(skb, L2TP_ATTR_IP_DADDR, inet->inet_daddr))
+			return -1;
+		break;
+	}
+
+	return 0;
+}
+
+/* Append attributes for the tunnel address, handling the different attribute types
+ * used for different tunnel encapsulation and AF_INET v.s. AF_INET6.
+ */
+static int l2tp_nl_tunnel_send_addr(struct sk_buff *skb, struct l2tp_tunnel *tunnel)
+{
+	struct sock *sk = tunnel->sock;
+
+	if (!sk)
+		return 0;
+
+#if IS_ENABLED(CONFIG_IPV6)
+	if (sk->sk_family == AF_INET6)
+		return l2tp_nl_tunnel_send_addr6(skb, sk, tunnel->encap);
+#endif
+	return l2tp_nl_tunnel_send_addr4(skb, sk, tunnel->encap);
+}
+
 static int l2tp_nl_tunnel_send(struct sk_buff *skb, u32 portid, u32 seq, int flags,
 			       struct l2tp_tunnel *tunnel, u8 cmd)
 {
 	void *hdr;
 	struct nlattr *nest;
-	struct sock *sk = NULL;
-	struct inet_sock *inet;
-#if IS_ENABLED(CONFIG_IPV6)
-	struct ipv6_pinfo *np = NULL;
-#endif
 
 	hdr = genlmsg_put(skb, portid, seq, &l2tp_nl_family, flags, cmd);
 	if (!hdr)
@@ -333,7 +405,7 @@ static int l2tp_nl_tunnel_send(struct sk_buff *skb, u32 portid, u32 seq, int fla
 		goto nla_put_failure;
 
 	nest = nla_nest_start_noflag(skb, L2TP_ATTR_STATS);
-	if (nest == NULL)
+	if (!nest)
 		goto nla_put_failure;
 
 	if (nla_put_u64_64bit(skb, L2TP_ATTR_TX_PACKETS,
@@ -363,58 +435,9 @@ static int l2tp_nl_tunnel_send(struct sk_buff *skb, u32 portid, u32 seq, int fla
 		goto nla_put_failure;
 	nla_nest_end(skb, nest);
 
-	sk = tunnel->sock;
-	if (!sk)
-		goto out;
-
-#if IS_ENABLED(CONFIG_IPV6)
-	if (sk->sk_family == AF_INET6)
-		np = inet6_sk(sk);
-#endif
-
-	inet = inet_sk(sk);
-
-	switch (tunnel->encap) {
-	case L2TP_ENCAPTYPE_UDP:
-		switch (sk->sk_family) {
-		case AF_INET:
-			if (nla_put_u8(skb, L2TP_ATTR_UDP_CSUM, !sk->sk_no_check_tx))
-				goto nla_put_failure;
-			break;
-#if IS_ENABLED(CONFIG_IPV6)
-		case AF_INET6:
-			if (udp_get_no_check6_tx(sk) &&
-			    nla_put_flag(skb, L2TP_ATTR_UDP_ZERO_CSUM6_TX))
-				goto nla_put_failure;
-			if (udp_get_no_check6_rx(sk) &&
-			    nla_put_flag(skb, L2TP_ATTR_UDP_ZERO_CSUM6_RX))
-				goto nla_put_failure;
-			break;
-#endif
-		}
-		if (nla_put_u16(skb, L2TP_ATTR_UDP_SPORT, ntohs(inet->inet_sport)) ||
-		    nla_put_u16(skb, L2TP_ATTR_UDP_DPORT, ntohs(inet->inet_dport)))
-			goto nla_put_failure;
-		/* fall through  */
-	case L2TP_ENCAPTYPE_IP:
-#if IS_ENABLED(CONFIG_IPV6)
-		if (np) {
-			if (nla_put_in6_addr(skb, L2TP_ATTR_IP6_SADDR,
-					     &np->saddr) ||
-			    nla_put_in6_addr(skb, L2TP_ATTR_IP6_DADDR,
-					     &sk->sk_v6_daddr))
-				goto nla_put_failure;
-		} else
-#endif
-		if (nla_put_in_addr(skb, L2TP_ATTR_IP_SADDR,
-				    inet->inet_saddr) ||
-		    nla_put_in_addr(skb, L2TP_ATTR_IP_DADDR,
-				    inet->inet_daddr))
-			goto nla_put_failure;
-		break;
-	}
+	if (l2tp_nl_tunnel_send_addr(skb, tunnel))
+		goto nla_put_failure;
 
-out:
 	genlmsg_end(skb, hdr);
 	return 0;
 
@@ -475,7 +498,7 @@ static int l2tp_nl_cmd_tunnel_dump(struct sk_buff *skb, struct netlink_callback
 
 	for (;;) {
 		tunnel = l2tp_tunnel_get_nth(net, ti);
-		if (tunnel == NULL)
+		if (!tunnel)
 			goto out;
 
 		if (l2tp_nl_tunnel_send(skb, NETLINK_CB(cb->skb).portid,
@@ -598,14 +621,13 @@ static int l2tp_nl_cmd_session_create(struct sk_buff *skb, struct genl_info *inf
 		cfg.reorder_timeout = nla_get_msecs(info->attrs[L2TP_ATTR_RECV_TIMEOUT]);
 
 #ifdef CONFIG_MODULES
-	if (l2tp_nl_cmd_ops[cfg.pw_type] == NULL) {
+	if (!l2tp_nl_cmd_ops[cfg.pw_type]) {
 		genl_unlock();
 		request_module("net-l2tp-type-%u", cfg.pw_type);
 		genl_lock();
 	}
 #endif
-	if ((l2tp_nl_cmd_ops[cfg.pw_type] == NULL) ||
-	    (l2tp_nl_cmd_ops[cfg.pw_type]->session_create == NULL)) {
+	if (!l2tp_nl_cmd_ops[cfg.pw_type] || !l2tp_nl_cmd_ops[cfg.pw_type]->session_create) {
 		ret = -EPROTONOSUPPORT;
 		goto out_tunnel;
 	}
@@ -637,7 +659,7 @@ static int l2tp_nl_cmd_session_delete(struct sk_buff *skb, struct genl_info *inf
 	u16 pw_type;
 
 	session = l2tp_nl_session_get(info);
-	if (session == NULL) {
+	if (!session) {
 		ret = -ENODEV;
 		goto out;
 	}
@@ -662,7 +684,7 @@ static int l2tp_nl_cmd_session_modify(struct sk_buff *skb, struct genl_info *inf
 	struct l2tp_session *session;
 
 	session = l2tp_nl_session_get(info);
-	if (session == NULL) {
+	if (!session) {
 		ret = -ENODEV;
 		goto out;
 	}
@@ -729,7 +751,7 @@ static int l2tp_nl_session_send(struct sk_buff *skb, u32 portid, u32 seq, int fl
 		goto nla_put_failure;
 
 	nest = nla_nest_start_noflag(skb, L2TP_ATTR_STATS);
-	if (nest == NULL)
+	if (!nest)
 		goto nla_put_failure;
 
 	if (nla_put_u64_64bit(skb, L2TP_ATTR_TX_PACKETS,
@@ -774,7 +796,7 @@ static int l2tp_nl_cmd_session_get(struct sk_buff *skb, struct genl_info *info)
 	int ret;
 
 	session = l2tp_nl_session_get(info);
-	if (session == NULL) {
+	if (!session) {
 		ret = -ENODEV;
 		goto err;
 	}
@@ -813,14 +835,14 @@ static int l2tp_nl_cmd_session_dump(struct sk_buff *skb, struct netlink_callback
 	int si = cb->args[1];
 
 	for (;;) {
-		if (tunnel == NULL) {
+		if (!tunnel) {
 			tunnel = l2tp_tunnel_get_nth(net, ti);
-			if (tunnel == NULL)
+			if (!tunnel)
 				goto out;
 		}
 
 		session = l2tp_session_get_nth(tunnel, si);
-		if (session == NULL) {
+		if (!session) {
 			ti++;
 			l2tp_tunnel_dec_refcount(tunnel);
 			tunnel = NULL;

net/l2tp/l2tp_ppp.c

@@ -154,12 +154,12 @@ static inline struct l2tp_session *pppol2tp_sock_to_session(struct sock *sk)
 {
 	struct l2tp_session *session;
 
-	if (sk == NULL)
+	if (!sk)
 		return NULL;
 
 	sock_hold(sk);
 	session = (struct l2tp_session *)(sk->sk_user_data);
-	if (session == NULL) {
+	if (!session) {
 		sock_put(sk);
 		goto out;
 	}
@@ -217,7 +217,7 @@ static void pppol2tp_recv(struct l2tp_session *session, struct sk_buff *skb, int
 	 */
 	rcu_read_lock();
 	sk = rcu_dereference(ps->sk);
-	if (sk == NULL)
+	if (!sk)
 		goto no_sock;
 
 	/* If the first two bytes are 0xFF03, consider that it is the PPP's
@@ -285,7 +285,7 @@ static int pppol2tp_sendmsg(struct socket *sock, struct msghdr *m,
 	/* Get session and tunnel contexts */
 	error = -EBADF;
 	session = pppol2tp_sock_to_session(sk);
-	if (session == NULL)
+	if (!session)
 		goto error;
 
 	tunnel = session->tunnel;
@@ -360,7 +360,7 @@ static int pppol2tp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
 
 	/* Get session and tunnel contexts from the socket */
 	session = pppol2tp_sock_to_session(sk);
-	if (session == NULL)
+	if (!session)
 		goto abort;
 
 	tunnel = session->tunnel;
@@ -703,7 +703,7 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
 	 * tunnel id.
 	 */
 	if (!info.session_id && !info.peer_session_id) {
-		if (tunnel == NULL) {
+		if (!tunnel) {
 			struct l2tp_tunnel_cfg tcfg = {
 				.encap = L2TP_ENCAPTYPE_UDP,
 				.debug = 0,
@@ -738,11 +738,11 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
 	} else {
 		/* Error if we can't find the tunnel */
 		error = -ENOENT;
-		if (tunnel == NULL)
+		if (!tunnel)
 			goto end;
 
 		/* Error if socket is not prepped */
-		if (tunnel->sock == NULL)
+		if (!tunnel->sock)
 			goto end;
 	}
 
@@ -802,8 +802,7 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
 	 * the internal context for use by ioctl() and sockopt()
 	 * handlers.
 	 */
-	if ((session->session_id == 0) &&
-	    (session->peer_session_id == 0)) {
+	if (session->session_id == 0 && session->peer_session_id == 0) {
 		error = 0;
 		goto out_no_ppp;
 	}
@@ -911,21 +910,21 @@ static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
 	struct pppol2tp_session *pls;
 
 	error = -ENOTCONN;
-	if (sk == NULL)
+	if (!sk)
 		goto end;
 	if (!(sk->sk_state & PPPOX_CONNECTED))
 		goto end;
 
 	error = -EBADF;
 	session = pppol2tp_sock_to_session(sk);
-	if (session == NULL)
+	if (!session)
 		goto end;
 
 	pls = l2tp_session_priv(session);
 	tunnel = session->tunnel;
 
 	inet = inet_sk(tunnel->sock);
-	if ((tunnel->version == 2) && (tunnel->sock->sk_family == AF_INET)) {
+	if (tunnel->version == 2 && tunnel->sock->sk_family == AF_INET) {
 		struct sockaddr_pppol2tp sp;
 
 		len = sizeof(sp);
@@ -943,8 +942,7 @@ static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
 		sp.pppol2tp.addr.sin_addr.s_addr = inet->inet_daddr;
 		memcpy(uaddr, &sp, len);
 #if IS_ENABLED(CONFIG_IPV6)
-	} else if ((tunnel->version == 2) &&
-		   (tunnel->sock->sk_family == AF_INET6)) {
+	} else if (tunnel->version == 2 && tunnel->sock->sk_family == AF_INET6) {
 		struct sockaddr_pppol2tpin6 sp;
 
 		len = sizeof(sp);
@@ -962,8 +960,7 @@ static int pppol2tp_getname(struct socket *sock, struct sockaddr *uaddr,
 		memcpy(&sp.pppol2tp.addr.sin6_addr, &tunnel->sock->sk_v6_daddr,
 		       sizeof(tunnel->sock->sk_v6_daddr));
 		memcpy(uaddr, &sp, len);
-	} else if ((tunnel->version == 3) &&
-		   (tunnel->sock->sk_family == AF_INET6)) {
+	} else if (tunnel->version == 3 && tunnel->sock->sk_family == AF_INET6) {
 		struct sockaddr_pppol2tpv3in6 sp;
 
 		len = sizeof(sp);
@@ -1179,7 +1176,7 @@ static int pppol2tp_session_setsockopt(struct sock *sk,
 
 	switch (optname) {
 	case PPPOL2TP_SO_RECVSEQ:
-		if ((val != 0) && (val != 1)) {
+		if (val != 0 && val != 1) {
 			err = -EINVAL;
 			break;
 		}
@@ -1190,7 +1187,7 @@ static int pppol2tp_session_setsockopt(struct sock *sk,
 		break;
 
 	case PPPOL2TP_SO_SENDSEQ:
-		if ((val != 0) && (val != 1)) {
+		if (val != 0 && val != 1) {
 			err = -EINVAL;
 			break;
 		}
@@ -1208,7 +1205,7 @@ static int pppol2tp_session_setsockopt(struct sock *sk,
 		break;
 
 	case PPPOL2TP_SO_LNSMODE:
-		if ((val != 0) && (val != 1)) {
+		if (val != 0 && val != 1) {
 			err = -EINVAL;
 			break;
 		}
@@ -1263,19 +1260,18 @@ static int pppol2tp_setsockopt(struct socket *sock, int level, int optname,
 		return -EFAULT;
 
 	err = -ENOTCONN;
-	if (sk->sk_user_data == NULL)
+	if (!sk->sk_user_data)
 		goto end;
 
 	/* Get session context from the socket */
 	err = -EBADF;
 	session = pppol2tp_sock_to_session(sk);
-	if (session == NULL)
+	if (!session)
 		goto end;
 
 	/* Special case: if session_id == 0x0000, treat as operation on tunnel
 	 */
-	if ((session->session_id == 0) &&
-	    (session->peer_session_id == 0)) {
+	if (session->session_id == 0 && session->peer_session_id == 0) {
 		tunnel = session->tunnel;
 		err = pppol2tp_tunnel_setsockopt(sk, tunnel, optname, val);
 	} else {
@@ -1382,18 +1378,17 @@ static int pppol2tp_getsockopt(struct socket *sock, int level, int optname,
 		return -EINVAL;
 
 	err = -ENOTCONN;
-	if (sk->sk_user_data == NULL)
+	if (!sk->sk_user_data)
 		goto end;
 
 	/* Get the session context */
 	err = -EBADF;
 	session = pppol2tp_sock_to_session(sk);
-	if (session == NULL)
+	if (!session)
 		goto end;
 
 	/* Special case: if session_id == 0x0000, treat as operation on tunnel */
-	if ((session->session_id == 0) &&
-	    (session->peer_session_id == 0)) {
+	if (session->session_id == 0 && session->peer_session_id == 0) {
 		tunnel = session->tunnel;
 		err = pppol2tp_tunnel_getsockopt(sk, tunnel, optname, &val);
 		if (err)
@@ -1464,7 +1459,7 @@ static void pppol2tp_next_session(struct net *net, struct pppol2tp_seq_data *pd)
 	pd->session = l2tp_session_get_nth(pd->tunnel, pd->session_idx);
 	pd->session_idx++;
 
-	if (pd->session == NULL) {
+	if (!pd->session) {
 		pd->session_idx = 0;
 		pppol2tp_next_tunnel(net, pd);
 	}
@@ -1479,17 +1474,17 @@ static void *pppol2tp_seq_start(struct seq_file *m, loff_t *offs)
 	if (!pos)
 		goto out;
 
-	BUG_ON(m->private == NULL);
+	BUG_ON(!m->private);
 	pd = m->private;
 	net = seq_file_net(m);
 
-	if (pd->tunnel == NULL)
+	if (!pd->tunnel)
 		pppol2tp_next_tunnel(net, pd);
 	else
 		pppol2tp_next_session(net, pd);
 
 	/* NULL tunnel and session indicates end of list */
-	if ((pd->tunnel == NULL) && (pd->session == NULL))
+	if (!pd->tunnel && !pd->session)
 		pd = NULL;
 
 out: