netfilter: nf_log_syslog: Consolidate entry checks

Every syslog logging callback has to perform the same check to cover for
rogue containers, introduce a helper for clarity. Drop the FIXME as
there is a viable solution since commit 2851940f ("netfilter: allow
logging from non-init namespaces").
Suggested-by: NFlorian Westphal <fw@strlen.de>
Signed-off-by: NPhil Sutter <phil@nwl.cc>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_log_syslog.c

@@ -40,6 +40,12 @@ struct arppayload {
 	unsigned char ip_dst[4];
 };
 
+/* Guard against containers flooding syslog. */
+static bool nf_log_allowed(const struct net *net)
+{
+	return net_eq(net, &init_net) || sysctl_nf_log_all_netns;
+}
+
 static void nf_log_dump_vlan(struct nf_log_buf *m, const struct sk_buff *skb)
 {
 	u16 vid;
@@ -133,8 +139,7 @@ static void nf_log_arp_packet(struct net *net, u_int8_t pf,
 {
 	struct nf_log_buf *m;
 
-	/* FIXME: Disabled from containers until syslog ns is supported */
-	if (!net_eq(net, &init_net) && !sysctl_nf_log_all_netns)
+	if (!nf_log_allowed(net))
 		return;
 
 	m = nf_log_buf_open();
@@ -831,8 +836,7 @@ static void nf_log_ip_packet(struct net *net, u_int8_t pf,
 {
 	struct nf_log_buf *m;
 
-	/* FIXME: Disabled from containers until syslog ns is supported */
-	if (!net_eq(net, &init_net) && !sysctl_nf_log_all_netns)
+	if (!nf_log_allowed(net))
 		return;
 
 	m = nf_log_buf_open();
@@ -867,8 +871,7 @@ static void nf_log_ip6_packet(struct net *net, u_int8_t pf,
 {
 	struct nf_log_buf *m;
 
-	/* FIXME: Disabled from containers until syslog ns is supported */
-	if (!net_eq(net, &init_net) && !sysctl_nf_log_all_netns)
+	if (!nf_log_allowed(net))
 		return;
 
 	m = nf_log_buf_open();
@@ -904,8 +907,7 @@ static void nf_log_unknown_packet(struct net *net, u_int8_t pf,
 {
 	struct nf_log_buf *m;
 
-	/* FIXME: Disabled from containers until syslog ns is supported */
-	if (!net_eq(net, &init_net) && !sysctl_nf_log_all_netns)
+	if (!nf_log_allowed(net))
 		return;
 
 	m = nf_log_buf_open();