ipv6: icmp6: avoid indirect call for icmpv6_send()

BugLink: https://bugs.launchpad.net/bugs/1918974

commit cc7a21b upstream.

If IPv6 is builtin, we do not need an expensive indirect call
to reach icmp6_send().

v2: put inline keyword before the type to avoid sparse warnings.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

Author: edumazet

include/linux/icmpv6.h

@@ -13,12 +13,32 @@ static inline struct icmp6hdr *icmp6_hdr(const struct sk_buff *skb)
 #include <linux/netdevice.h>
 
 #if IS_ENABLED(CONFIG_IPV6)
-extern void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info);
 
 typedef void ip6_icmp_send_t(struct sk_buff *skb, u8 type, u8 code, __u32 info,
 			     const struct in6_addr *force_saddr);
+#if IS_BUILTIN(CONFIG_IPV6)
+void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
+		const struct in6_addr *force_saddr);
+static inline void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
+{
+	icmp6_send(skb, type, code, info, NULL);
+}
+static inline int inet6_register_icmp_sender(ip6_icmp_send_t *fn)
+{
+	BUILD_BUG_ON(fn != icmp6_send);
+	return 0;
+}
+static inline int inet6_unregister_icmp_sender(ip6_icmp_send_t *fn)
+{
+	BUILD_BUG_ON(fn != icmp6_send);
+	return 0;
+}
+#else
+extern void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info);
 extern int inet6_register_icmp_sender(ip6_icmp_send_t *fn);
 extern int inet6_unregister_icmp_sender(ip6_icmp_send_t *fn);
+#endif
+
 int ip6_err_gen_icmpv6_unreach(struct sk_buff *skb, int nhs, int type,
 			       unsigned int data_len);
 

net/ipv6/icmp.c

@@ -426,8 +426,8 @@ static int icmp6_iif(const struct sk_buff *skb)
 /*
  *	Send an ICMP message in response to a packet in error
  */
-static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
-		       const struct in6_addr *force_saddr)
+void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
+		const struct in6_addr *force_saddr)
 {
 	struct inet6_dev *idev = NULL;
 	struct ipv6hdr *hdr = ipv6_hdr(skb);
@@ -600,6 +600,7 @@ static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info,
 out_bh_enable:
 	local_bh_enable();
 }
+EXPORT_SYMBOL(icmp6_send);
 
 /* Slightly more convenient version of icmp6_send.
  */

net/ipv6/ip6_icmp.c

@@ -9,6 +9,8 @@
 
 #if IS_ENABLED(CONFIG_IPV6)
 
+#if !IS_BUILTIN(CONFIG_IPV6)
+
 static ip6_icmp_send_t __rcu *ip6_icmp_send;
 
 int inet6_register_icmp_sender(ip6_icmp_send_t *fn)
@@ -37,14 +39,12 @@ void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
 
 	rcu_read_lock();
 	send = rcu_dereference(ip6_icmp_send);
-
-	if (!send)
-		goto out;
-	send(skb, type, code, info, NULL);
-out:
+	if (send)
+		send(skb, type, code, info, NULL);
 	rcu_read_unlock();
 }
 EXPORT_SYMBOL(icmpv6_send);
+#endif
 
 #if IS_ENABLED(CONFIG_NF_NAT)
 #include <net/netfilter/nf_conntrack.h>