[NETFILTER]: Add u32 match
Along comes... xt_u32, a revamped ipt_u32 from POM-NG,
Plus:
* 2007-06-02: added ipv6 support
* 2007-06-05: uses kmalloc for the big buffer
* 2007-06-05: added inversion
* 2007-06-20: use skb_copy_bits() and get rid of the big buffer
and lock (suggested by Pablo Neira Ayuso)
Signed-off-by: Jan Engelhardt <jengelh@gmx.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index a567dae..aa567fa 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -635,6 +635,19 @@
To compile it as a module, choose M here. If unsure, say N.
+config NETFILTER_XT_MATCH_U32
+ tristate '"u32" match support'
+ depends on NETFILTER_XTABLES
+ ---help---
+ u32 allows you to extract quantities of up to 4 bytes from a packet,
+ AND them with specified masks, shift them by specified amounts and
+ test whether the results are in any of a set of specified ranges.
+ The specification of what to extract is general enough to skip over
+ headers with lengths stored in the packet, as in IP or TCP header
+ lengths.
+
+ Details and examples are in the kernel module source.
+
config NETFILTER_XT_MATCH_HASHLIMIT
tristate '"hashlimit" match support'
depends on NETFILTER_XTABLES && (IP6_NF_IPTABLES || IP6_NF_IPTABLES=n)
diff --git a/net/netfilter/Makefile b/net/netfilter/Makefile
index b2b5c75..3cf5b9c 100644
--- a/net/netfilter/Makefile
+++ b/net/netfilter/Makefile
@@ -72,4 +72,5 @@
obj-$(CONFIG_NETFILTER_XT_MATCH_STRING) += xt_string.o
obj-$(CONFIG_NETFILTER_XT_MATCH_TCPMSS) += xt_tcpmss.o
obj-$(CONFIG_NETFILTER_XT_MATCH_PHYSDEV) += xt_physdev.o
+obj-$(CONFIG_NETFILTER_XT_MATCH_U32) += xt_u32.o
obj-$(CONFIG_NETFILTER_XT_MATCH_HASHLIMIT) += xt_hashlimit.o
diff --git a/net/netfilter/xt_u32.c b/net/netfilter/xt_u32.c
new file mode 100644
index 0000000..0706875
--- /dev/null
+++ b/net/netfilter/xt_u32.c
@@ -0,0 +1,135 @@
+/*
+ * xt_u32 - kernel module to match u32 packet content
+ *
+ * Original author: Don Cohen <don@isis.cs3-inc.com>
+ * © Jan Engelhardt <jengelh@gmx.de>, 2007
+ */
+
+#include <linux/module.h>
+#include <linux/moduleparam.h>
+#include <linux/spinlock.h>
+#include <linux/skbuff.h>
+#include <linux/types.h>
+#include <linux/netfilter/x_tables.h>
+#include <linux/netfilter/xt_u32.h>
+
+static bool u32_match_it(const struct xt_u32 *data,
+ const struct sk_buff *skb)
+{
+ const struct xt_u32_test *ct;
+ unsigned int testind;
+ unsigned int nnums;
+ unsigned int nvals;
+ unsigned int i;
+ u_int32_t pos;
+ u_int32_t val;
+ u_int32_t at;
+ int ret;
+
+ /*
+ * Small example: "0 >> 28 == 4 && 8 & 0xFF0000 >> 16 = 6, 17"
+ * (=IPv4 and (TCP or UDP)). Outer loop runs over the "&&" operands.
+ */
+ for (testind = 0; testind < data->ntests; ++testind) {
+ ct = &data->tests[testind];
+ at = 0;
+ pos = ct->location[0].number;
+
+ if (skb->len < 4 || pos > skb->len - 4);
+ return false;
+
+ ret = skb_copy_bits(skb, pos, &val, sizeof(val));
+ BUG_ON(ret < 0);
+ val = ntohl(val);
+ nnums = ct->nnums;
+
+ /* Inner loop runs over "&", "<<", ">>" and "@" operands */
+ for (i = 1; i < nnums; ++i) {
+ u_int32_t number = ct->location[i].number;
+ switch (ct->location[i].nextop) {
+ case XT_U32_AND:
+ val &= number;
+ break;
+ case XT_U32_LEFTSH:
+ val <<= number;
+ break;
+ case XT_U32_RIGHTSH:
+ val >>= number;
+ break;
+ case XT_U32_AT:
+ if (at + val < at)
+ return false;
+ at += val;
+ pos = number;
+ if (at + 4 < at || skb->len < at + 4 ||
+ pos > skb->len - at - 4)
+ return false;
+
+ ret = skb_copy_bits(skb, at + pos, &val,
+ sizeof(val));
+ BUG_ON(ret < 0);
+ val = ntohl(val);
+ break;
+ }
+ }
+
+ /* Run over the "," and ":" operands */
+ nvals = ct->nvalues;
+ for (i = 0; i < nvals; ++i)
+ if (ct->value[i].min <= val && val <= ct->value[i].max)
+ break;
+
+ if (i >= ct->nvalues)
+ return false;
+ }
+
+ return true;
+}
+
+static bool u32_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, bool *hotdrop)
+{
+ const struct xt_u32 *data = matchinfo;
+ bool ret;
+
+ ret = u32_match_it(data, skb);
+ return ret ^ data->invert;
+}
+
+static struct xt_match u32_reg[] = {
+ {
+ .name = "u32",
+ .family = AF_INET,
+ .match = u32_match,
+ .matchsize = sizeof(struct xt_u32),
+ .me = THIS_MODULE,
+ },
+ {
+ .name = "u32",
+ .family = AF_INET6,
+ .match = u32_match,
+ .matchsize = sizeof(struct xt_u32),
+ .me = THIS_MODULE,
+ },
+};
+
+static int __init xt_u32_init(void)
+{
+ return xt_register_matches(u32_reg, ARRAY_SIZE(u32_reg));
+}
+
+static void __exit xt_u32_exit(void)
+{
+ xt_unregister_matches(u32_reg, ARRAY_SIZE(u32_reg));
+}
+
+module_init(xt_u32_init);
+module_exit(xt_u32_exit);
+MODULE_AUTHOR("Jan Engelhardt <jengelh@gmx.de>");
+MODULE_DESCRIPTION("netfilter u32 match module");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("ipt_u32");
+MODULE_ALIAS("ip6t_u32");
