conntrackd: helpers: add DHCPv6 helper

This patch adds support for the DHCPv6 helper.

1) nfct helper add dhcpv6 inet6 udp
2) ip6tables -I OUTPUT -t raw -p udp --sport 546 -j CT --helper dhcpv6
3) run conntrackd

You should see:

% conntrack -L exp -f ipv6
279 proto=17 src=:: dst=ff02::1:2 sport=0 dport=546 mask-src=:: mask-dst=ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff sport=0 dport=65535 master-src=fe80::221:ccff:fe4a:7f9c master-dst=ff02::1:2 sport=546 dport=547 PERMANENT class=0 helper=dhcpv6

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 123 insertions, 0 deletions

diff --git a/src/helpers/dhcpv6.c b/src/helpers/dhcpv6.c
new file mode 100644
index 0000000..73632ec
--- /dev/null
+++ b/src/helpers/dhcpv6.c
@@ -0,0 +1,123 @@
+/*
+ * (C) 2013 by Pablo Neira Ayuso <pablo@netfilter.org>
+ *
+ * Adapted from:
+ *
+ * DHCPv6 multicast connection tracking helper.
+ *
+ * (c) 2012 Google Inc.
+ *
+ * Original author: Darren Willis <djw@google.com>
+ *
+ * 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.
+ */
+
+#include "conntrackd.h"
+#include "helper.h"
+#include "myct.h"
+#include "log.h"
+#include <errno.h>
+#include <netinet/ip.h>
+#include <netinet/ip6.h>
+#include <netinet/udp.h>
+#include <libmnl/libmnl.h>
+#include <libnetfilter_conntrack/libnetfilter_conntrack.h>
+#include <libnetfilter_queue/libnetfilter_queue.h>
+#include <libnetfilter_queue/libnetfilter_queue_udp.h>
+#include <libnetfilter_queue/pktbuff.h>
+#include <linux/netfilter.h>
+
+#define DHCPV6_CLIENT_PORT 546
+
+static uint16_t dhcpv6_port;
+
+/* Timeouts for DHCPv6 replies, in seconds, indexed by message type. */
+static const int dhcpv6_timeouts[] = {
+	0,	/* No message has type 0. */
+	120,	/* Solicit. */
+	0,	/* Advertise. */
+	30,	/* Request. */
+	4,	/* Confirm. */
+	600,	/* Renew. */
+	600,	/* Rebind. */
+	0,	/* Reply. */
+	1,	/* Release. */
+	1,	/* Decline. */
+	0,	/* Reconfigure. */
+	120,	/* Information Request. */
+	0,	/* Relay-forward. */
+	0	/* Relay-reply. */
+};
+
+static inline int ipv6_addr_is_multicast(const struct in6_addr *addr)
+{
+	return (addr->s6_addr32[0] & htonl(0xFF000000)) == htonl(0xFF000000);
+}
+
+static int
+dhcpv6_helper_cb(struct pkt_buff *pkt, uint32_t protoff,
+		 struct myct *myct, uint32_t ctinfo)
+{
+	struct iphdr *iph = (struct iphdr *)pktb_network_header(pkt);
+	struct ip6_hdr *ip6h = (struct ip6_hdr *)pktb_network_header(pkt);
+	int dir = CTINFO2DIR(ctinfo);
+	union nfct_attr_grp_addr addr;
+	struct nf_expect *exp;
+	uint8_t *dhcpv6_msg_type;
+
+	if (iph->version != 6 || !ipv6_addr_is_multicast(&ip6h->ip6_dst))
+		return NF_ACCEPT;
+
+	dhcpv6_msg_type = pktb_network_header(pkt) + protoff + sizeof(struct udphdr);
+	if (*dhcpv6_msg_type > ARRAY_SIZE(dhcpv6_timeouts)) {
+		printf("Dropping DHCPv6 message with bad type %u\n",
+			*dhcpv6_msg_type);
+		return NF_DROP;
+	}
+
+	exp = nfexp_new();
+	if (exp == NULL)
+		return NF_ACCEPT;
+
+	cthelper_get_addr_src(myct->ct, dir, &addr);
+
+	if (cthelper_expect_init(exp, myct->ct, 0, NULL, &addr,
+				 IPPROTO_UDP, NULL, &dhcpv6_port,
+				 NF_CT_EXPECT_PERMANENT)) {
+		nfexp_destroy(exp);
+		return NF_DROP;
+	}
+
+	myct->exp = exp;
+
+	if (dhcpv6_timeouts[*dhcpv6_msg_type] > 0) {
+		nfct_set_attr_u32(myct->ct, ATTR_TIMEOUT,
+				  dhcpv6_timeouts[*dhcpv6_msg_type]);
+	}
+
+	return NF_ACCEPT;
+}
+
+static struct ctd_helper dhcpv6_helper = {
+	.name		= "dhcpv6",
+	.l4proto	= IPPROTO_UDP,
+	.cb		= dhcpv6_helper_cb,
+	.policy		= {
+		[0] = {
+			.name			= "dhcpv6",
+			.expect_max		= 1,
+			.expect_timeout		= 300,
+		},
+	},
+};
+
+void __attribute__ ((constructor)) dhcpv6_init(void);
+
+void dhcpv6_init(void)
+{
+	dhcpv6_port = htons(DHCPV6_CLIENT_PORT);
+	helper_register(&dhcpv6_helper);
+}