[NETFILTER]: x_tables: replace IPv4 dscp match by address family independent version

This replaces IPv4 dscp match by address family independent version.
This also
	- utilizes dsfield.h to get the DS field in IPv4/IPv6 header, and
	- checks for the DSCP value from user space.
	- fixes Kconfig help text.

Signed-off-by: Yasuyuki Kozakai <yasuyuki.kozakai@toshiba.co.jp>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 125 insertions, 0 deletions

diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index a9894ddfd72a..f781405f5d65 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -263,6 +263,17 @@ config NETFILTER_XT_MATCH_DCCP
           If you want to compile it as a module, say M here and read
           <file:Documentation/modules.txt>.  If unsure, say `N'.
 
+config NETFILTER_XT_MATCH_DSCP
+        tristate '"DSCP" match support'
+        depends on NETFILTER_XTABLES
+        help
+          This option adds a `DSCP' match, which allows you to match against
+          the IPv4/IPv6 header DSCP field (differentiated services codepoint).
+
+          The DSCP field can have any value between 0x0 and 0x3f inclusive.
+
+          To compile it as a module, choose M here.  If unsure, say N.
+
 config NETFILTER_XT_MATCH_ESP
         tristate '"ESP" match support'
         depends on NETFILTER_XTABLES
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index 6fa4b7580458..0b8a70c1df46 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -37,6 +37,7 @@ obj-$(CONFIG_NETFILTER_XT_MATCH_CONNBYTES) += xt_connbytes.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_CONNMARK) += xt_connmark.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_CONNTRACK) += xt_conntrack.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_DCCP) += xt_dccp.o
+obj-$(CONFIG_NETFILTER_XT_MATCH_DSCP) += xt_dscp.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_ESP) += xt_esp.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_HELPER) += xt_helper.o
 obj-$(CONFIG_NETFILTER_XT_MATCH_LENGTH) += xt_length.o
diff --git a/net/netfilter/xt_dscp.c b/net/netfilter/xt_dscp.c
new file mode 100644
index 000000000000..82e250d1f007
--- /dev/null
+++ b/net/netfilter/xt_dscp.c
@@ -0,0 +1,113 @@
+/* IP tables module for matching the value of the IPv4/IPv6 DSCP field
+ *
+ * xt_dscp.c,v 1.3 2002/08/05 19:00:21 laforge Exp
+ *
+ * (C) 2002 by Harald Welte <laforge@netfilter.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ */
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/ip.h>
+#include <linux/ipv6.h>
+#include <net/dsfield.h>
+
+#include <linux/netfilter/xt_dscp.h>
+#include <linux/netfilter/x_tables.h>
+
+MODULE_AUTHOR("Harald Welte <laforge@netfilter.org>");
+MODULE_DESCRIPTION("x_tables DSCP matching module");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("ipt_dscp");
+MODULE_ALIAS("ip6t_dscp");
+
+static int match(const struct sk_buff *skb,
+                 const struct net_device *in,
+                 const struct net_device *out,
+                 const struct xt_match *match,
+                 const void *matchinfo,
+                 int offset,
+                 unsigned int protoff,
+                 int *hotdrop)
+{
+        const struct xt_dscp_info *info = matchinfo;
+        u_int8_t dscp = ipv4_get_dsfield(skb->nh.iph) >> XT_DSCP_SHIFT;
+
+        return (dscp == info->dscp) ^ !!info->invert;
+}
+
+static int match6(const struct sk_buff *skb,
+                  const struct net_device *in,
+                  const struct net_device *out,
+                  const struct xt_match *match,
+                  const void *matchinfo,
+                  int offset,
+                  unsigned int protoff,
+                  int *hotdrop)
+{
+        const struct xt_dscp_info *info = matchinfo;
+        u_int8_t dscp = ipv6_get_dsfield(skb->nh.ipv6h) >> XT_DSCP_SHIFT;
+
+        return (dscp == info->dscp) ^ !!info->invert;
+}
+
+static int checkentry(const char *tablename,
+                      const void *info,
+                      const struct xt_match *match,
+                      void *matchinfo,
+                      unsigned int matchsize,
+                      unsigned int hook_mask)
+{
+        const u_int8_t dscp = ((struct xt_dscp_info *)matchinfo)->dscp;
+
+        if (dscp > XT_DSCP_MAX) {
+                printk(KERN_ERR "xt_dscp: dscp %x out of range\n", dscp);
+                return 0;
+        }
+
+        return 1;
+}
+
+static struct xt_match dscp_match = {
+        .name           = "dscp",
+        .match          = match,
+        .checkentry     = checkentry,
+        .matchsize      = sizeof(struct xt_dscp_info),
+        .family         = AF_INET,
+        .me             = THIS_MODULE,
+};
+
+static struct xt_match dscp6_match = {
+        .name           = "dscp",
+        .match          = match6,
+        .checkentry     = checkentry,
+        .matchsize      = sizeof(struct xt_dscp_info),
+        .family         = AF_INET6,
+        .me             = THIS_MODULE,
+};
+
+static int __init xt_dscp_match_init(void)
+{
+        int ret;
+        ret = xt_register_match(&dscp_match);
+        if (ret)
+                return ret;
+
+        ret = xt_register_match(&dscp6_match);
+        if (ret)
+                xt_unregister_match(&dscp_match);
+
+        return ret;
+}
+
+static void __exit xt_dscp_match_fini(void)
+{
+        xt_unregister_match(&dscp_match);
+        xt_unregister_match(&dscp6_match);
+}
+
+module_init(xt_dscp_match_init);
+module_exit(xt_dscp_match_fini);