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- /* Kernel module to match AH parameters. */
- /* (C) 1999-2000 Yon Uriarte <yon@astaro.de>
- *
- * 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/in.h>
- #include <linux/module.h>
- #include <linux/skbuff.h>
- #include <linux/ip.h>
- #include <linux/netfilter_ipv4/ipt_ah.h>
- #include <linux/netfilter/x_tables.h>
- MODULE_LICENSE("GPL");
- MODULE_AUTHOR("Yon Uriarte <yon@astaro.de>");
- MODULE_DESCRIPTION("iptables AH SPI match module");
- #ifdef DEBUG_CONNTRACK
- #define duprintf(format, args...) printk(format , ## args)
- #else
- #define duprintf(format, args...)
- #endif
- /* Returns 1 if the spi is matched by the range, 0 otherwise */
- static inline int
- spi_match(u_int32_t min, u_int32_t max, u_int32_t spi, int invert)
- {
- int r=0;
- duprintf("ah spi_match:%c 0x%x <= 0x%x <= 0x%x",invert? '!':' ',
- min,spi,max);
- r=(spi >= min && spi <= max) ^ invert;
- duprintf(" result %s\n",r? "PASS" : "FAILED");
- return r;
- }
- 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)
- {
- struct ip_auth_hdr _ahdr, *ah;
- const struct ipt_ah *ahinfo = matchinfo;
- /* Must not be a fragment. */
- if (offset)
- return 0;
- ah = skb_header_pointer(skb, protoff,
- sizeof(_ahdr), &_ahdr);
- if (ah == NULL) {
- /* We've been asked to examine this packet, and we
- * can't. Hence, no choice but to drop.
- */
- duprintf("Dropping evil AH tinygram.\n");
- *hotdrop = 1;
- return 0;
- }
- return spi_match(ahinfo->spis[0], ahinfo->spis[1],
- ntohl(ah->spi),
- !!(ahinfo->invflags & IPT_AH_INV_SPI));
- }
- /* Called when user tries to insert an entry of this type. */
- static int
- checkentry(const char *tablename,
- const void *ip_void,
- const struct xt_match *match,
- void *matchinfo,
- unsigned int hook_mask)
- {
- const struct ipt_ah *ahinfo = matchinfo;
- /* Must specify no unknown invflags */
- if (ahinfo->invflags & ~IPT_AH_INV_MASK) {
- duprintf("ipt_ah: unknown flags %X\n", ahinfo->invflags);
- return 0;
- }
- return 1;
- }
- static struct xt_match ah_match = {
- .name = "ah",
- .family = AF_INET,
- .match = match,
- .matchsize = sizeof(struct ipt_ah),
- .proto = IPPROTO_AH,
- .checkentry = checkentry,
- .me = THIS_MODULE,
- };
- static int __init ipt_ah_init(void)
- {
- return xt_register_match(&ah_match);
- }
- static void __exit ipt_ah_fini(void)
- {
- xt_unregister_match(&ah_match);
- }
- module_init(ipt_ah_init);
- module_exit(ipt_ah_fini);
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