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Subject2.4.9-ipt_string.patch
Date
This is "iptables --string" patch

diff -urN linux-2.4.9.orig/Documentation/Configure.help linux-2.4.9/Documentation/Configure.help
--- linux-2.4.9.orig/Documentation/Configure.help Mon Aug 13 02:51:41 2001
+++ linux-2.4.9/Documentation/Configure.help Fri Aug 17 12:28:25 2001
@@ -1939,6 +1939,14 @@
If you want to compile it as a module, say M here and read
Documentation/modules.txt. If unsure, say `N'.

+String match support (EXPERIMENTAL)
+CONFIG_IP_NF_MATCH_STRING
+ String matching alows you to match packets which contain a
+ specified string of characters.
+
+ If you want to compile it as a module, say M here and read
+ Documentation/modules.txt. If unsure, say `N'.
+
Unclean match support (EXPERIMENTAL)
CONFIG_IP_NF_MATCH_UNCLEAN
Unclean packet matching matches any strange or invalid packets, by
diff -urN linux-2.4.9.orig/include/linux/netfilter_ipv4/ipt_string.h linux-2.4.9/include/linux/netfilter_ipv4/ipt_string.h
--- linux-2.4.9.orig/include/linux/netfilter_ipv4/ipt_string.h Thu Jan 1 09:00:00 1970
+++ linux-2.4.9/include/linux/netfilter_ipv4/ipt_string.h Sat Aug 11 13:18:32 2001
@@ -0,0 +1,21 @@
+#ifndef _IPT_STRING_H
+#define _IPT_STRING_H
+
+/* *** PERFORMANCE TWEAK ***
+ * Packet size and search string threshold,
+ * above which sublinear searches is used. */
+#define IPT_STRING_HAYSTACK_THRESH 100
+#define IPT_STRING_NEEDLE_THRESH 20
+
+#define BM_MAX_NLEN 256
+#define BM_MAX_HLEN 1024
+
+typedef char *(*proc_ipt_search) (char *, char *, int, int);
+
+struct ipt_string_info {
+ char string[BM_MAX_NLEN];
+ u_int16_t invert;
+ u_int16_t len;
+};
+
+#endif /* _IPT_STRING_H */
diff -urN linux-2.4.9.orig/net/ipv4/netfilter/Config.in linux-2.4.9/net/ipv4/netfilter/Config.in
--- linux-2.4.9.orig/net/ipv4/netfilter/Config.in Wed Mar 7 15:44:16 2001
+++ linux-2.4.9/net/ipv4/netfilter/Config.in Fri Aug 17 12:29:11 2001
@@ -26,6 +26,7 @@
fi
if [ "$CONFIG_EXPERIMENTAL" = "y" ]; then
dep_tristate ' Unclean match support (EXPERIMENTAL)' CONFIG_IP_NF_MATCH_UNCLEAN $CONFIG_IP_NF_IPTABLES
+ dep_tristate ' String match support (EXPERIMENTAL)' CONFIG_IP_NF_MATCH_STRING $CONFIG_IP_NF_IPTABLES
dep_tristate ' Owner match support (EXPERIMENTAL)' CONFIG_IP_NF_MATCH_OWNER $CONFIG_IP_NF_IPTABLES
fi
# The targets
diff -urN linux-2.4.9.orig/net/ipv4/netfilter/Makefile linux-2.4.9/net/ipv4/netfilter/Makefile
--- linux-2.4.9.orig/net/ipv4/netfilter/Makefile Thu Apr 26 07:00:28 2001
+++ linux-2.4.9/net/ipv4/netfilter/Makefile Fri Aug 17 12:28:53 2001
@@ -54,6 +54,7 @@
obj-$(CONFIG_IP_NF_MATCH_TOS) += ipt_tos.o
obj-$(CONFIG_IP_NF_MATCH_STATE) += ipt_state.o
obj-$(CONFIG_IP_NF_MATCH_UNCLEAN) += ipt_unclean.o
+obj-$(CONFIG_IP_NF_MATCH_STRING) += ipt_string.o
obj-$(CONFIG_IP_NF_MATCH_TCPMSS) += ipt_tcpmss.o

# targets
diff -urN linux-2.4.9.orig/net/ipv4/netfilter/ipt_string.c linux-2.4.9/net/ipv4/netfilter/ipt_string.c
--- linux-2.4.9.orig/net/ipv4/netfilter/ipt_string.c Thu Jan 1 09:00:00 1970
+++ linux-2.4.9/net/ipv4/netfilter/ipt_string.c Sat Aug 11 13:18:32 2001
@@ -0,0 +1,156 @@
+/* Kernel module to match a string into a packet.
+ *
+ * Copyright (C) 2000 Emmanuel Roger <winfield@freegates.be>
+ *
+ * ChangeLog
+ * 02.05.2001: Gianni Tedesco <gianni@ecsc.co.uk>
+ * Fixed kernel panic, due to overrunning boyer moore string
+ * tables. Also slightly tweaked heuristic for deciding what
+ * search algo to use.
+ * 27.01.2001: Gianni Tedesco <gianni@ecsc.co.uk>
+ * Implemented Boyer Moore Sublinear search algorithm
+ * alongside the existing linear search based on memcmp().
+ * Also a quick check to decide which method to use on a per
+ * packet basis.
+ */
+
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/file.h>
+#include <net/sock.h>
+
+#include <linux/netfilter_ipv4/ip_tables.h>
+#include <linux/netfilter_ipv4/ipt_string.h>
+
+int skip[BM_MAX_HLEN];
+int shift[BM_MAX_HLEN];
+
+/* Boyer Moore Sublinear string search - VERY FAST */
+char *search_sublinear (char *needle, char *haystack, int needle_len, int haystack_len)
+{
+ int M1, right_end, sk, sh;
+ int ended, j, len[BM_MAX_HLEN];
+ int i;
+
+ /* Setup skip/shift tables */
+ M1 = right_end = needle_len-1;
+ for (i = 0; i < BM_MAX_HLEN; i++) skip[i] = needle_len;
+ for (i = 0; needle[i]; i++) skip[needle[i]] = M1 - i;
+
+ for (i = 1; i < needle_len; i++) {
+ for (j = 0; j < needle_len && needle[M1 - j] == needle[M1 - i - j]; j++);
+ len[i] = j;
+ }
+
+ shift[0] = 1;
+ for (i = 1; i < needle_len; i++) shift[i] = needle_len;
+ for (i = M1; i > 0; i--) shift[len[i]] = i;
+ ended = 0;
+
+ for (i = 0; i < needle_len; i++) {
+ if (len[i] == M1 - i) ended = i;
+ if (ended) shift[i] = ended;
+ }
+
+ /* Do the search*/
+ while (right_end < haystack_len)
+ {
+ for (i = 0; i < needle_len && haystack[right_end - i] == needle[M1 - i]; i++);
+ if (i == needle_len) {
+ return haystack+(right_end - M1);
+ }
+
+ sk = skip[haystack[right_end - i]];
+ sh = shift[i];
+ right_end = max(int, right_end - i + sk, right_end + sh);
+ }
+
+ return NULL;
+}
+
+/* Linear string search based on memcmp() */
+char *search_linear (char *needle, char *haystack, int needle_len, int haystack_len)
+{
+ char *k = haystack + (haystack_len-needle_len);
+ char *t = haystack;
+
+ while ( t++ < k ) {
+ if ( memcmp(t, needle, needle_len) == 0 ) return t;
+ }
+
+ return NULL;
+}
+
+
+static int
+match(const struct sk_buff *skb,
+ const struct net_device *in,
+ const struct net_device *out,
+ const void *matchinfo,
+ int offset,
+ const void *hdr,
+ u_int16_t datalen,
+ int *hotdrop)
+{
+ const struct ipt_string_info *info = matchinfo;
+ struct iphdr *ip = skb->nh.iph;
+ int hlen, nlen;
+ char *needle, *haystack;
+ proc_ipt_search search=search_linear;
+
+ if ( !ip ) return 0;
+
+ /* get lenghts, and validate them */
+ nlen=info->len;
+ hlen=ntohs(ip->tot_len)-(ip->ihl*4);
+ if ( nlen > hlen ) return 0;
+
+ needle=(char *)&info->string;
+ haystack=(char *)ip+(ip->ihl*4);
+
+ /* The sublinear search comes in to its own
+ * on the larger packets */
+ if ( (hlen>IPT_STRING_HAYSTACK_THRESH) &&
+ (nlen>IPT_STRING_NEEDLE_THRESH) ) {
+ if ( hlen < BM_MAX_HLEN ) {
+ search=search_sublinear;
+ }else{
+ if (net_ratelimit())
+ printk(KERN_INFO "ipt_string: Packet too big "
+ "to attempt sublinear string search "
+ "(%d bytes)\n", hlen );
+ }
+ }
+
+ return ((search(needle, haystack, nlen, hlen)!=NULL) ^ info->invert);
+}
+
+static int
+checkentry(const char *tablename,
+ const struct ipt_ip *ip,
+ void *matchinfo,
+ unsigned int matchsize,
+ unsigned int hook_mask)
+{
+
+ if (matchsize != IPT_ALIGN(sizeof(struct ipt_string_info)))
+ return 0;
+
+ return 1;
+}
+
+static struct ipt_match string_match
+= { { NULL, NULL }, "string", &match, &checkentry, NULL, THIS_MODULE };
+
+static int __init init(void)
+{
+ return ipt_register_match(&string_match);
+}
+
+static void __exit fini(void)
+{
+ ipt_unregister_match(&string_match);
+}
+
+module_init(init);
+module_exit(fini);
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