[PATCH] netfilter: synproxy: fix building syncookie calls

[Arnd Bergmann <arnd@arndb.de>]

When either CONFIG_IPV6 or CONFIG_SYN_COOKIES are disabled, the kernel
fails to build:

include/linux/netfilter_ipv6.h:180:9: error: implicit declaration of function '__cookie_v6_init_sequence'
      [-Werror,-Wimplicit-function-declaration]
        return __cookie_v6_init_sequence(iph, th, mssp);
include/linux/netfilter_ipv6.h:194:9: error: implicit declaration of function '__cookie_v6_check'
      [-Werror,-Wimplicit-function-declaration]
        return __cookie_v6_check(iph, th, cookie);
net/ipv6/netfilter.c:237:26: error: use of undeclared identifier '__cookie_v6_init_sequence'; did you mean 'cookie_init_sequence'?
net/ipv6/netfilter.c:238:21: error: use of undeclared identifier '__cookie_v6_check'; did you mean '__cookie_v4_check'?

Fix the IS_ENABLED() checks to match the function declaration
and definitions for these.

Fixes: 3006a5224f15 ("netfilter: synproxy: remove module dependency on IPv6 SYNPROXY")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
---
 include/linux/netfilter_ipv6.h | 14 ++++++++------
 net/ipv6/netfilter.c           |  2 ++
 2 files changed, 10 insertions(+), 6 deletions(-)

diff --git a/include/linux/netfilter_ipv6.h b/include/linux/netfilter_ipv6.h
index 1aa3a23744df..7beb681e1ce5 100644
--- a/include/linux/netfilter_ipv6.h
+++ b/include/linux/netfilter_ipv6.h
@@ -171,31 +171,33 @@ static inline u32 nf_ipv6_cookie_init_sequence(const struct ipv6hdr *iph,
 					       const struct tcphdr *th,
 					       u16 *mssp)
 {
+#if IS_ENABLED(CONFIG_SYN_COOKIES)
 #if IS_MODULE(CONFIG_IPV6)
 	const struct nf_ipv6_ops *v6_ops = nf_get_ipv6_ops();
 
 	if (v6_ops)
 		return v6_ops->cookie_init_sequence(iph, th, mssp);
-
-	return 0;
-#else
+#elif IS_BUILTIN(CONFIG_IPV6)
 	return __cookie_v6_init_sequence(iph, th, mssp);
 #endif
+#endif
+	return 0;
 }
 
 static inline int nf_cookie_v6_check(const struct ipv6hdr *iph,
 				     const struct tcphdr *th, __u32 cookie)
 {
+#if IS_ENABLED(CONFIG_SYN_COOKIES)
 #if IS_MODULE(CONFIG_IPV6)
 	const struct nf_ipv6_ops *v6_ops = nf_get_ipv6_ops();
 
 	if (v6_ops)
 		return v6_ops->cookie_v6_check(iph, th, cookie);
-
-	return 0;
-#else
+#elif IS_BUILTIN(CONFIG_IPV6)
 	return __cookie_v6_check(iph, th, cookie);
 #endif
+#endif
+	return 0;
 }
 
 __sum16 nf_ip6_checksum(struct sk_buff *skb, unsigned int hook,
diff --git a/net/ipv6/netfilter.c b/net/ipv6/netfilter.c
index dffb10fdc3e8..61819ed858b1 100644
--- a/net/ipv6/netfilter.c
+++ b/net/ipv6/netfilter.c
@@ -234,8 +234,10 @@ static const struct nf_ipv6_ops ipv6ops = {
 	.route_me_harder	= ip6_route_me_harder,
 	.dev_get_saddr		= ipv6_dev_get_saddr,
 	.route			= __nf_ip6_route,
+#if IS_ENABLED(CONFIG_SYN_COOKIES)
 	.cookie_init_sequence	= __cookie_v6_init_sequence,
 	.cookie_v6_check	= __cookie_v6_check,
+#endif
 #endif
 	.route_input		= ip6_route_input,
 	.fragment		= ip6_fragment,
-- 
2.20.0