[NETFILTER]: IPv6 capable xt_TOS v1 target

Extends the xt_DSCP target by xt_TOS v1 to add support for selectively
setting and flipping any bit in the IPv4 TOS and IPv6 Priority fields.
(ipt_TOS and xt_DSCP only accepted a limited range of possible
values.)
Signed-off-by: Jan Engelhardt <jengelh@computergmbh.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/netfilter/xt_DSCP.h

@@ -17,4 +17,9 @@ struct xt_DSCP_info {
 	u_int8_t dscp;
 };
 
+struct xt_tos_target_info {
+	u_int8_t tos_value;
+	u_int8_t tos_mask;
+};
+
 #endif /* _XT_DSCP_TARGET_H */

net/netfilter/Kconfig

@@ -304,7 +304,7 @@ config NETFILTER_XT_TARGET_DSCP
 
 	  It also adds the "TOS" target, which allows you to create rules in
 	  the "mangle" table which alter the Type Of Service field of an IPv4
-	  packet prior to routing.
+	  or the Priority field of an IPv6 packet, prior to routing.
 
 	  To compile it as a module, choose M here.  If unsure, say N.
 

net/netfilter/xt_DSCP.c

@@ -26,6 +26,7 @@ MODULE_LICENSE("GPL");
 MODULE_ALIAS("ipt_DSCP");
 MODULE_ALIAS("ip6t_DSCP");
 MODULE_ALIAS("ipt_TOS");
+MODULE_ALIAS("ip6t_TOS");
 
 static unsigned int
 dscp_tg(struct sk_buff *skb, const struct net_device *in,
@@ -117,6 +118,50 @@ tos_tg_check_v0(const char *tablename, const void *e_void,
 	return true;
 }
 
+static unsigned int
+tos_tg(struct sk_buff *skb, const struct net_device *in,
+       const struct net_device *out, unsigned int hooknum,
+       const struct xt_target *target, const void *targinfo)
+{
+	const struct xt_tos_target_info *info = targinfo;
+	struct iphdr *iph = ip_hdr(skb);
+	u_int8_t orig, nv;
+
+	orig = ipv4_get_dsfield(iph);
+	nv   = (orig & info->tos_mask) ^ info->tos_value;
+
+	if (orig != nv) {
+		if (!skb_make_writable(skb, sizeof(struct iphdr)))
+			return NF_DROP;
+		iph = ip_hdr(skb);
+		ipv4_change_dsfield(iph, ~0, nv);
+	}
+
+	return XT_CONTINUE;
+}
+
+static unsigned int
+tos_tg6(struct sk_buff *skb, const struct net_device *in,
+        const struct net_device *out, unsigned int hooknum,
+        const struct xt_target *target, const void *targinfo)
+{
+	const struct xt_tos_target_info *info = targinfo;
+	struct ipv6hdr *iph = ipv6_hdr(skb);
+	u_int8_t orig, nv;
+
+	orig = ipv6_get_dsfield(iph);
+	nv   = (orig & info->tos_mask) ^ info->tos_value;
+
+	if (orig != nv) {
+		if (!skb_make_writable(skb, sizeof(struct iphdr)))
+			return NF_DROP;
+		iph = ipv6_hdr(skb);
+		ipv6_change_dsfield(iph, ~0, nv);
+	}
+
+	return XT_CONTINUE;
+}
+
 static struct xt_target dscp_tg_reg[] __read_mostly = {
 	{
 		.name		= "DSCP",
@@ -146,6 +191,24 @@ static struct xt_target dscp_tg_reg[] __read_mostly = {
 		.checkentry	= tos_tg_check_v0,
 		.me		= THIS_MODULE,
 	},
+	{
+		.name		= "TOS",
+		.revision	= 1,
+		.family		= AF_INET,
+		.table		= "mangle",
+		.target		= tos_tg,
+		.targetsize	= sizeof(struct xt_tos_target_info),
+		.me		= THIS_MODULE,
+	},
+	{
+		.name		= "TOS",
+		.revision	= 1,
+		.family		= AF_INET6,
+		.table		= "mangle",
+		.target		= tos_tg6,
+		.targetsize	= sizeof(struct xt_tos_target_info),
+		.me		= THIS_MODULE,
+	},
 };
 
 static int __init dscp_tg_init(void)