new file mode 100644
@@ -0,0 +1,18 @@
+#ifndef _IPT_COMP_H
+#define _IPT_COMP_H
+
+#include <linux/types.h>
+
+struct ipt_comp {
+ __u32 spis[2]; /* Security Parameter Index */
+ __u8 invflags; /* Inverse flags */
+ __u8 hdrres; /* Test of the Reserved Filed */
+};
+
+
+
+/* Values for "invflags" field in struct ipt_comp. */
+#define IPT_IPCOMP_INV_SPI 0x01 /* Invert the sense of spi. */
+#define IPT_IPCOMP_INV_MASK 0x01 /* All possible flags. */
+
+#endif /*_IPT_COMP_H*/
@@ -81,6 +81,15 @@ config IP_NF_MATCH_AH
To compile it as a module, choose M here. If unsure, say N.
+config IP_NF_MATCH_IPCOMP
+ tristate '"ipcomp" match support'
+ depends on NETFILTER_ADVANCED
+ help
+ This match extension allows you to match a range of SPIs (Actually it's
+ Compression Parameter Index(CPI) inside IPComp header of IPSec packets.
+
+ To compile it as a module, choose M here. If unsure, say N.
+
config IP_NF_MATCH_ECN
tristate '"ecn" match support'
depends on NETFILTER_ADVANCED
@@ -45,6 +45,7 @@ obj-$(CONFIG_IP_NF_SECURITY) += iptable_security.o
# matches
obj-$(CONFIG_IP_NF_MATCH_AH) += ipt_ah.o
+obj-$(CONFIG_IP_NF_MATCH_IPCOMP) += ipt_comp.o
obj-$(CONFIG_IP_NF_MATCH_RPFILTER) += ipt_rpfilter.o
# targets
new file mode 100644
@@ -0,0 +1,101 @@
+/* Kernel module to match IPComp parameters
+ *
+ * Copyright (C) 2013 WindRiver
+ *
+ * Author:
+ * Fan Du <fan.du@windriver.com>
+ *
+ * Based on:
+ * net/ipv4/netfilter/ipt_ah.c
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version
+ * 2 of the License, or (at your option) any later version.
+ */
+
+
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+#include <linux/in.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/ip.h>
+
+#include <linux/netfilter_ipv4/ipt_comp.h>
+#include <linux/netfilter/x_tables.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Fan Du <fan.du@windriver.com>");
+MODULE_DESCRIPTION("Xtables: IPv4 IPsec-IPComp SPI match");
+
+/* Returns 1 if the spi is matched by the range, 0 otherwise */
+static inline bool
+spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, bool invert)
+{
+ bool r;
+ pr_debug("spi_match:%c 0x%x <= 0x%x <= 0x%x\n",
+ invert ? '!' : ' ', min, spi, max);
+ r = (spi >= min && spi <= max) ^ invert;
+ pr_debug(" result %s\n", r ? "PASS" : "FAILED");
+ return r;
+}
+
+static bool comp_mt(const struct sk_buff *skb, struct xt_action_param *par)
+{
+ struct ip_comp_hdr _comphdr;
+ const struct ip_comp_hdr *chdr;
+ const struct ipt_comp *compinfo = par->matchinfo;
+
+ /* Must not be a fragment. */
+ if (par->fragoff != 0)
+ return false;
+
+ chdr = skb_header_pointer(skb, par->thoff, sizeof(_comphdr), &_comphdr);
+ if (chdr == NULL) {
+ /* We've been asked to examine this packet, and we
+ * can't. Hence, no choice but to drop.
+ */
+ pr_debug("Dropping evil IPComp tinygram.\n");
+ par->hotdrop = true;
+ return 0;
+ }
+
+ return spi_match(compinfo->spis[0], compinfo->spis[1],
+ ntohl(chdr->cpi << 16),
+ !!(compinfo->invflags & IPT_IPCOMP_INV_SPI));
+}
+
+static int comp_mt_check(const struct xt_mtchk_param *par)
+{
+ const struct ipt_comp *compinfo = par->matchinfo;
+
+ /* Must specify no unknown invflags */
+ if (compinfo->invflags & ~IPT_IPCOMP_INV_MASK) {
+ pr_debug("unknown flags %X\n", compinfo->invflags);
+ return -EINVAL;
+ }
+ return 0;
+}
+
+static struct xt_match comp_mt_reg __read_mostly = {
+ .name = "ipcomp",
+ .family = NFPROTO_IPV4,
+ .match = comp_mt,
+ .matchsize = sizeof(struct ipt_comp),
+ .proto = IPPROTO_COMP,
+ .checkentry = comp_mt_check,
+ .me = THIS_MODULE,
+};
+
+static int __init comp_mt_init(void)
+{
+ return xt_register_match(&comp_mt_reg);
+}
+
+static void __exit comp_mt_exit(void)
+{
+ xt_unregister_match(&comp_mt_reg);
+}
+
+module_init(comp_mt_init);
+module_exit(comp_mt_exit);
With this plugin, user could specify IPComp tagged with certain CPI that host not interested will be DROPped or any other action. For example: iptables -A INPUT -p 108 -m ipcomp --ipcompspi 0x87 -j DROP Then input IPComp packet with CPI equates 0x87 will not reach upper layer anymore. Signed-off-by: Fan Du <fan.du@windriver.com> --- include/uapi/linux/netfilter_ipv4/ipt_comp.h | 18 +++++ net/ipv4/netfilter/Kconfig | 9 +++ net/ipv4/netfilter/Makefile | 1 + net/ipv4/netfilter/ipt_comp.c | 101 ++++++++++++++++++++++++++ 4 files changed, 129 insertions(+) create mode 100644 include/uapi/linux/netfilter_ipv4/ipt_comp.h create mode 100644 net/ipv4/netfilter/ipt_comp.c