[NETFILTER]: tcp conntrack: accept SYN|URG as valid

Some stacks apparently send packets with SYN|URG set. Linux accepts
these packets, so TCP conntrack should to.

Pointed out by Martijn Posthuma <posthuma@sangine.com>.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/netfilter/ip_conntrack_proto_tcp.c

@@ -812,8 +812,10 @@ void ip_conntrack_tcp_update(struct sk_buff *skb,
 static const u8 tcp_valid_flags[(TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG) + 1] =
 {
 	[TH_SYN]			= 1,
-	[TH_SYN|TH_ACK]			= 1,
 	[TH_SYN|TH_PUSH]		= 1,
+	[TH_SYN|TH_URG]			= 1,
+	[TH_SYN|TH_PUSH|TH_URG]		= 1,
+	[TH_SYN|TH_ACK]			= 1,
 	[TH_SYN|TH_ACK|TH_PUSH]		= 1,
 	[TH_RST]			= 1,
 	[TH_RST|TH_ACK]			= 1,

net/netfilter/nf_conntrack_proto_tcp.c

@@ -769,8 +769,10 @@ EXPORT_SYMBOL_GPL(nf_conntrack_tcp_update);
 static u8 tcp_valid_flags[(TH_FIN|TH_SYN|TH_RST|TH_PUSH|TH_ACK|TH_URG) + 1] =
 {
 	[TH_SYN]			= 1,
-	[TH_SYN|TH_ACK]			= 1,
 	[TH_SYN|TH_PUSH]		= 1,
+	[TH_SYN|TH_URG]			= 1,
+	[TH_SYN|TH_PUSH|TH_URG]		= 1,
+	[TH_SYN|TH_ACK]			= 1,
 	[TH_SYN|TH_ACK|TH_PUSH]		= 1,
 	[TH_RST]			= 1,
 	[TH_RST|TH_ACK]			= 1,