extensions: add rpfilter module

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/extensions/libxt_rpfilter.c b/extensions/libxt_rpfilter.c
new file mode 100644 (file)
index 0000000..168e703
--- /dev/null
+++ b/extensions/libxt_rpfilter.c
@@ -0,0 +1,96 @@
+#include <stdio.h>
+#include <xtables.h>
+#include <linux/netfilter/xt_rpfilter.h>
+
+enum {
+       O_RPF_LOOSE = 0,
+       O_RPF_VMARK = 1,
+       O_RPF_ACCEPT_LOCAL = 2,
+       O_RPF_INVERT = 3,
+};
+
+static void rpfilter_help(void)
+{
+       printf(
+"rpfilter match options:\n"
+"    --loose          permit reverse path via any interface\n"
+"    --validmark      use skb nfmark when performing route lookup\n"
+"    --accept-local   do not reject packets with a local source address\n"
+"    --invert         match packets that failed the reverse path test\n"
+       );
+}
+
+static const struct xt_option_entry rpfilter_opts[] = {
+       {.name = "loose", .id = O_RPF_LOOSE, .type = XTTYPE_NONE, },
+       {.name = "validmark", .id = O_RPF_VMARK, .type = XTTYPE_NONE, },
+       {.name = "accept-local", .id = O_RPF_ACCEPT_LOCAL, .type = XTTYPE_NONE, },
+       {.name = "invert", .id = O_RPF_INVERT, .type = XTTYPE_NONE, },
+       XTOPT_TABLEEND,
+};
+
+static void rpfilter_parse(struct xt_option_call *cb)
+{
+       struct xt_rpfilter_info *rpfinfo = cb->data;
+
+       xtables_option_parse(cb);
+       switch (cb->entry->id) {
+       case O_RPF_LOOSE:
+               rpfinfo->flags |= XT_RPFILTER_LOOSE;
+               break;
+       case O_RPF_VMARK:
+               rpfinfo->flags |= XT_RPFILTER_VALID_MARK;
+               break;
+       case O_RPF_ACCEPT_LOCAL:
+               rpfinfo->flags |= XT_RPFILTER_ACCEPT_LOCAL;
+               break;
+       case O_RPF_INVERT:
+               rpfinfo->flags |= XT_RPFILTER_INVERT;
+               break;
+       }
+}
+
+static void
+rpfilter_print_prefix(const void *ip, const void *matchinfo,
+                       const char *prefix)
+{
+       const struct xt_rpfilter_info *info = matchinfo;
+       if (info->flags & XT_RPFILTER_LOOSE)
+               printf(" %s%s", prefix, rpfilter_opts[O_RPF_LOOSE].name);
+       if (info->flags & XT_RPFILTER_VALID_MARK)
+               printf(" %s%s", prefix, rpfilter_opts[O_RPF_VMARK].name);
+       if (info->flags & XT_RPFILTER_ACCEPT_LOCAL)
+               printf(" %s%s", prefix, rpfilter_opts[O_RPF_ACCEPT_LOCAL].name);
+       if (info->flags & XT_RPFILTER_INVERT)
+               printf(" %s%s", prefix, rpfilter_opts[O_RPF_INVERT].name);
+}
+
+
+static void
+rpfilter_print(const void *ip, const struct xt_entry_match *match, int numeric)
+{
+       printf(" rpfilter");
+       return rpfilter_print_prefix(ip, match->data, "");
+}
+
+static void rpfilter_save(const void *ip, const struct xt_entry_match *match)
+{
+       return rpfilter_print_prefix(ip, match->data, "--");
+}
+
+static struct xtables_match rpfilter_match = {
+       .family         = NFPROTO_UNSPEC,
+       .name           = "rpfilter",
+       .version        = XTABLES_VERSION,
+       .size           = XT_ALIGN(sizeof(struct xt_rpfilter_info)),
+       .userspacesize  = XT_ALIGN(sizeof(struct xt_rpfilter_info)),
+       .help           = rpfilter_help,
+       .print          = rpfilter_print,
+       .save           = rpfilter_save,
+       .x6_parse       = rpfilter_parse,
+       .x6_options     = rpfilter_opts,
+};
+
+void _init(void)
+{
+       xtables_register_match(&rpfilter_match);
+}

diff --git a/extensions/libxt_rpfilter.man b/extensions/libxt_rpfilter.man
new file mode 100644 (file)
index 0000000..aeb4a9d
--- /dev/null
+++ b/extensions/libxt_rpfilter.man
@@ -0,0 +1,38 @@
+Performs a reverse path filter test on a packet.
+If a reply to the packet would be sent via the same interface
+that the packet arrived on, the packet will match.
+Note that, unlike the in-kernel rp_filter, packets protected
+by IPSec are not treated specially.  Combine this match with
+the policy match if you want this.
+Also, packets arriving via the loopback interface are always permitted.
+This match can only be used in the PREROUTING chain of the raw or mangle table.
+.TP
+\fB\-\-loose\fP
+Used to specifiy that the reverse path filter test should match
+even if the selected output device is not the expected one.
+.TP
+\fB\-\-validmark\fP
+Also use the packets' nfmark value when performing the reverse path route lookup.
+.TP
+\fB\-\-accept\-local\fP
+This will permit packets arriving from the network with a source address that is also
+assigned to the local machine.
+\fB\-\-invert\fP
+This will invert the sense of the match.  Instead of matching packets that passed the
+reverse path filter test, match those that have failed it.
+.PP
+Example to log and drop packets failing the reverse path filter test:
+
+iptables \-t raw \-N RPFILTER
+
+iptables \-t raw \-A RPFILTER \-m rpfilter \-j RETURN
+
+iptables \-t raw \-A RPFILTER \-m limit \-\-limit 10/minute \-j NFLOG \-\-nflog\-prefix "rpfilter drop"
+
+iptables \-t raw \-A RPFILTER \-j DROP
+
+iptables \-t raw \-A PREROUTING \-j RPFILTER
+
+Example to drop failed packets, without logging:
+
+iptables \-t raw \-A RPFILTER \-m rpfilter \-\-invert \-j DROP

diff --git a/include/linux/netfilter/xt_rpfilter.h b/include/linux/netfilter/xt_rpfilter.h
new file mode 100644 (file)
index 0000000..672b605
--- /dev/null
+++ b/include/linux/netfilter/xt_rpfilter.h
@@ -0,0 +1,17 @@
+#ifndef _XT_RPATH_H
+#define _XT_RPATH_H
+
+#include <linux/types.h>
+
+enum {
+       XT_RPFILTER_LOOSE = 1 << 0,
+       XT_RPFILTER_VALID_MARK = 1 << 1,
+       XT_RPFILTER_ACCEPT_LOCAL = 1 << 2,
+       XT_RPFILTER_INVERT = 1 << 3,
+};
+
+struct xt_rpfilter_info {
+       __u8 flags;
+};
+
+#endif