1 files changed, 532 insertions, 0 deletions

diff --git a/src/ndp.c b/src/ndp.c
new file mode 100644
index 0000000..89bcd3c
--- /dev/null
+++ b/src/ndp.c
@@ -0,0 +1,532 @@
+/**
+ * Copyright (C) 2012-2013 Steven Barth <steven@midlink.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License v2 as published by
+ * the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <errno.h>
+
+#include <arpa/inet.h>
+#include <sys/socket.h>
+#include <net/ethernet.h>
+#include <netinet/ip6.h>
+#include <netinet/icmp6.h>
+#include <netpacket/packet.h>
+
+#include <linux/rtnetlink.h>
+#include <linux/filter.h>
+#include "router.h"
+#include "ndp.h"
+
+
+
+static void handle_solicit(void *addr, void *data, size_t len,
+		struct interface *iface);
+static void handle_rtnetlink(void *addr, void *data, size_t len,
+		struct interface *iface);
+static struct ndp_neighbor* find_neighbor(struct in6_addr *addr, bool strict);
+static void modify_neighbor(struct in6_addr *addr, struct interface *iface,
+		bool add);
+static ssize_t ping6(struct in6_addr *addr,
+		const struct interface *iface);
+
+static struct list_head neighbors = LIST_HEAD_INIT(neighbors);
+static size_t neighbor_count = 0;
+static uint32_t rtnl_seqid = 0;
+
+static int ping_socket = -1;
+static struct odhcpd_event ndp_event = {{.fd = -1}, handle_solicit};
+static struct odhcpd_event rtnl_event = {{.fd = -1}, handle_rtnetlink};
+
+
+// Filter ICMPv6 messages of type neighbor soliciation
+static struct sock_filter bpf[] = {
+	BPF_STMT(BPF_LD | BPF_B | BPF_ABS, offsetof(struct ip6_hdr, ip6_nxt)),
+	BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, IPPROTO_ICMPV6, 0, 3),
+	BPF_STMT(BPF_LD | BPF_B | BPF_ABS, sizeof(struct ip6_hdr) +
+			offsetof(struct icmp6_hdr, icmp6_type)),
+	BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ND_NEIGHBOR_SOLICIT, 0, 1),
+	BPF_STMT(BPF_RET | BPF_K, 0xffffffff),
+	BPF_STMT(BPF_RET | BPF_K, 0),
+};
+static const struct sock_fprog bpf_prog = {sizeof(bpf) / sizeof(*bpf), bpf};
+
+
+// Initialize NDP-proxy
+int init_ndp(void)
+{
+	// Setup netlink socket
+	if ((rtnl_event.uloop.fd = odhcpd_open_rtnl()) < 0)
+		return -1;
+
+	// Receive netlink neighbor and ip-address events
+	uint32_t group = RTNLGRP_IPV6_IFADDR;
+	setsockopt(rtnl_event.uloop.fd, SOL_NETLINK,
+			NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
+	group = RTNLGRP_IPV6_ROUTE;
+	setsockopt(rtnl_event.uloop.fd, SOL_NETLINK,
+			NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
+
+	// Synthesize initial address events
+	struct {
+		struct nlmsghdr nh;
+		struct ifaddrmsg ifa;
+	} req2 = {
+		{sizeof(req2), RTM_GETADDR, NLM_F_REQUEST | NLM_F_DUMP,
+				++rtnl_seqid, 0},
+		{.ifa_family = AF_INET6}
+	};
+	send(rtnl_event.uloop.fd, &req2, sizeof(req2), MSG_DONTWAIT);
+	odhcpd_register(&rtnl_event);
+
+
+	// Create socket for intercepting NDP
+	int sock = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC | SOCK_NONBLOCK,
+			htons(ETH_P_ALL)); // ETH_P_ALL for ingress + egress
+	if (sock < 0) {
+		syslog(LOG_ERR, "Unable to open packet socket: %s",
+				strerror(errno));
+		return -1;
+	}
+
+	if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER,
+			&bpf_prog, sizeof(bpf_prog))) {
+		syslog(LOG_ERR, "Failed to set BPF: %s", strerror(errno));
+		return -1;
+	}
+
+	ndp_event.uloop.fd = sock;
+	odhcpd_register(&ndp_event);
+
+	// Open ICMPv6 socket
+	ping_socket = socket(AF_INET6, SOCK_RAW | SOCK_CLOEXEC, IPPROTO_ICMPV6);
+
+	int val = 2;
+	setsockopt(ping_socket, IPPROTO_RAW, IPV6_CHECKSUM, &val, sizeof(val));
+
+	// This is required by RFC 4861
+	val = 255;
+	setsockopt(ping_socket, IPPROTO_IPV6, IPV6_MULTICAST_HOPS, &val, sizeof(val));
+	setsockopt(ping_socket, IPPROTO_IPV6, IPV6_UNICAST_HOPS, &val, sizeof(val));
+
+	// Filter all packages, we only want to send
+	struct icmp6_filter filt;
+	ICMP6_FILTER_SETBLOCKALL(&filt);
+	setsockopt(ping_socket, IPPROTO_ICMPV6, ICMP6_FILTER, &filt, sizeof(filt));
+
+
+	// Netlink socket, continued...
+	group = RTNLGRP_NEIGH;
+	setsockopt(rtnl_event.uloop.fd, SOL_NETLINK, NETLINK_ADD_MEMBERSHIP, &group, sizeof(group));
+
+	// Synthesize initial neighbor events
+	struct {
+		struct nlmsghdr nh;
+		struct ndmsg ndm;
+	} req = {
+		{sizeof(req), RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP,
+				++rtnl_seqid, 0},
+		{.ndm_family = AF_INET6}
+	};
+	send(rtnl_event.uloop.fd, &req, sizeof(req), MSG_DONTWAIT);
+
+	return 0;
+}
+
+
+int setup_ndp_interface(struct interface *iface, bool enable)
+{
+	struct packet_mreq mreq = {iface->ifindex, PACKET_MR_ALLMULTI, ETH_ALEN, {0}};
+	setsockopt(ndp_event.uloop.fd, SOL_PACKET, PACKET_DROP_MEMBERSHIP, &mreq, sizeof(mreq));
+
+	struct ndp_neighbor *c, *n;
+	list_for_each_entry_safe(c, n, &neighbors, head)
+		if (c->iface == iface && (c->timeout == 0 || iface->ndp != RELAYD_RELAY || !enable))
+			modify_neighbor(&c->addr, c->iface, false);
+
+	if (enable && iface->ndp == RELAYD_RELAY) {
+		setsockopt(ndp_event.uloop.fd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
+
+		if (iface->static_ndp_len) {
+			char *entry = alloca(iface->static_ndp_len), *saveptr;
+			memcpy(entry, iface->static_ndp, iface->static_ndp_len);
+
+			for (entry = strtok_r(entry, " ", &saveptr); entry; entry = strtok_r(NULL, " ", &saveptr)) {
+				struct ndp_neighbor *n = malloc(sizeof(*n));
+				n->iface = iface;
+				n->timeout = 0;
+
+				char ipbuf[INET6_ADDRSTRLEN];
+				if (sscanf(entry, "%45s/%hhu", ipbuf, &n->len) < 2
+						|| n->len > 128 || inet_pton(AF_INET6, ipbuf, &n->addr) != 1) {
+					syslog(LOG_ERR, "Invalid static NDP-prefix %s", entry);
+					return -1;
+				}
+
+				list_add(&n->head, &neighbors);
+			}
+		}
+	}
+
+	return 0;
+}
+
+
+// Send an ICMP-ECHO. This is less for actually pinging but for the
+// neighbor cache to be kept up-to-date.
+static ssize_t ping6(struct in6_addr *addr,
+		const struct interface *iface)
+{
+	struct sockaddr_in6 dest = {AF_INET6, 0, 0, *addr, 0};
+	struct icmp6_hdr echo = {.icmp6_type = ICMP6_ECHO_REQUEST};
+	struct iovec iov = {&echo, sizeof(echo)};
+
+	// Linux seems to not honor IPV6_PKTINFO on raw-sockets, so work around
+	setsockopt(ping_socket, SOL_SOCKET, SO_BINDTODEVICE,
+			iface->ifname, sizeof(iface->ifname));
+	return odhcpd_send(ping_socket, &dest, &iov, 1, iface);
+}
+
+
+// Handle solicitations
+static void handle_solicit(void *addr, void *data, size_t len,
+		struct interface *iface)
+{
+	struct ip6_hdr *ip6 = data;
+	struct nd_neighbor_solicit *req = (struct nd_neighbor_solicit*)&ip6[1];
+	struct sockaddr_ll *ll = addr;
+
+	// Solicitation is for duplicate address detection
+	bool ns_is_dad = IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src);
+
+	// Don't forward any non-DAD solicitation for external ifaces
+	// TODO: check if we should even forward DADs for them
+	if (iface->external && !ns_is_dad)
+		return;
+
+	if (len < sizeof(*ip6) + sizeof(*req))
+		return; // Invalid reqicitation
+
+	if (IN6_IS_ADDR_LINKLOCAL(&req->nd_ns_target) ||
+			IN6_IS_ADDR_LOOPBACK(&req->nd_ns_target) ||
+			IN6_IS_ADDR_MULTICAST(&req->nd_ns_target))
+		return; // Invalid target
+
+	char ipbuf[INET6_ADDRSTRLEN];
+	inet_ntop(AF_INET6, &req->nd_ns_target, ipbuf, sizeof(ipbuf));
+	syslog(LOG_NOTICE, "Got a NS for %s", ipbuf);
+
+	uint8_t mac[6];
+	odhcpd_get_mac(iface, mac);
+	if (!memcmp(ll->sll_addr, mac, sizeof(mac)) &&
+			ll->sll_pkttype != PACKET_OUTGOING)
+		return; // Looped back
+
+	time_t now = time(NULL);
+
+	struct ndp_neighbor *n = find_neighbor(&req->nd_ns_target, false);
+	if (n && (n->iface || abs(n->timeout - now) < 5)) {
+		syslog(LOG_NOTICE, "%s is on %s", ipbuf,
+				(n->iface) ? n->iface->ifname : "<pending>");
+		if (!n->iface || n->iface == iface)
+			return;
+
+		// Found on other interface, answer with advertisement
+		struct {
+			struct nd_neighbor_advert body;
+			struct nd_opt_hdr opt_ll_hdr;
+			uint8_t mac[6];
+		} advert = {
+			.body = {
+				.nd_na_hdr = {ND_NEIGHBOR_ADVERT,
+					0, 0, {{0}}},
+				.nd_na_target = req->nd_ns_target,
+			},
+			.opt_ll_hdr = {ND_OPT_TARGET_LINKADDR, 1},
+		};
+
+		memcpy(advert.mac, mac, sizeof(advert.mac));
+		advert.body.nd_na_flags_reserved = ND_NA_FLAG_ROUTER |
+				ND_NA_FLAG_SOLICITED;
+
+		struct sockaddr_in6 dest = {AF_INET6, 0, 0, ALL_IPV6_NODES, 0};
+		if (!ns_is_dad) // If not DAD, then unicast to source
+			dest.sin6_addr = ip6->ip6_src;
+
+		// Linux seems to not honor IPV6_PKTINFO on raw-sockets, so work around
+		setsockopt(ping_socket, SOL_SOCKET, SO_BINDTODEVICE,
+					iface->ifname, sizeof(iface->ifname));
+		struct iovec iov = {&advert, sizeof(advert)};
+		odhcpd_send(ping_socket, &dest, &iov, 1, iface);
+	} else {
+		// Send echo to all other interfaces to see where target is on
+		// This will trigger neighbor discovery which is what we want.
+		// We will observe the neighbor cache to see results.
+
+		ssize_t sent = 0;
+		struct interface *c;
+		list_for_each_entry(c, &interfaces, head)
+			if (iface->ndp == RELAYD_RELAY && iface != c &&
+					(!ns_is_dad || !c->external == false))
+				sent += ping6(&req->nd_ns_target, c);
+
+		if (sent > 0) // Sent a ping, add pending neighbor entry
+			modify_neighbor(&req->nd_ns_target, NULL, true);
+	}
+}
+
+
+void odhcpd_setup_route(const struct in6_addr *addr, int prefixlen,
+		const struct interface *iface, const struct in6_addr *gw, bool add)
+{
+	struct req {
+		struct nlmsghdr nh;
+		struct rtmsg rtm;
+		struct rtattr rta_dst;
+		struct in6_addr dst_addr;
+		struct rtattr rta_oif;
+		uint32_t ifindex;
+		struct rtattr rta_table;
+		uint32_t table;
+		struct rtattr rta_gw;
+		struct in6_addr gw;
+	} req = {
+		{sizeof(req), 0, NLM_F_REQUEST, ++rtnl_seqid, 0},
+		{AF_INET6, prefixlen, 0, 0, 0, 0, 0, 0, 0},
+		{sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_DST},
+		*addr,
+		{sizeof(struct rtattr) + sizeof(uint32_t), RTA_OIF},
+		iface->ifindex,
+		{sizeof(struct rtattr) + sizeof(uint32_t), RTA_TABLE},
+		RT_TABLE_MAIN,
+		{sizeof(struct rtattr) + sizeof(struct in6_addr), RTA_GATEWAY},
+		IN6ADDR_ANY_INIT,
+	};
+
+	if (gw)
+		req.gw = *gw;
+
+	if (add) {
+		req.nh.nlmsg_type = RTM_NEWROUTE;
+		req.nh.nlmsg_flags |= (NLM_F_CREATE | NLM_F_REPLACE);
+		req.rtm.rtm_protocol = RTPROT_BOOT;
+		req.rtm.rtm_scope = (gw) ? RT_SCOPE_UNIVERSE : RT_SCOPE_LINK;
+		req.rtm.rtm_type = RTN_UNICAST;
+	} else {
+		req.nh.nlmsg_type = RTM_DELROUTE;
+		req.rtm.rtm_scope = RT_SCOPE_NOWHERE;
+	}
+
+	size_t reqlen = (gw) ? sizeof(req) : offsetof(struct req, rta_gw);
+	send(rtnl_event.uloop.fd, &req, reqlen, MSG_DONTWAIT);
+}
+
+// Use rtnetlink to modify kernel routes
+static void setup_route(struct in6_addr *addr, struct interface *iface,
+		bool add)
+{
+	char namebuf[INET6_ADDRSTRLEN];
+	inet_ntop(AF_INET6, addr, namebuf, sizeof(namebuf));
+	syslog(LOG_NOTICE, "%s about %s on %s", (add) ? "Learned" : "Forgot",
+			namebuf, (iface) ? iface->ifname : "<pending>");
+
+	if (!iface || !iface->learn_routes)
+		return;
+
+	odhcpd_setup_route(addr, 128, iface, NULL, add);
+}
+
+static void free_neighbor(struct ndp_neighbor *n)
+{
+	setup_route(&n->addr, n->iface, false);
+	list_del(&n->head);
+	free(n);
+	--neighbor_count;
+}
+
+
+static bool match_neighbor(struct ndp_neighbor *n, struct in6_addr *addr)
+{
+	if (n->len <= 32)
+		return ntohl(n->addr.s6_addr32[0]) >> (32 - n->len) ==
+				ntohl(addr->s6_addr32[0]) >> (32 - n->len);
+
+	if (n->addr.s6_addr32[0] != addr->s6_addr32[0])
+		return false;
+
+	if (n->len <= 64)
+		return ntohl(n->addr.s6_addr32[1]) >> (64 - n->len) ==
+				ntohl(addr->s6_addr32[1]) >> (64 - n->len);
+
+	if (n->addr.s6_addr32[1] != addr->s6_addr32[1])
+		return false;
+
+	if (n->len <= 96)
+		return ntohl(n->addr.s6_addr32[2]) >> (96 - n->len) ==
+				ntohl(addr->s6_addr32[2]) >> (96 - n->len);
+
+	if (n->addr.s6_addr32[2] != addr->s6_addr32[2])
+		return false;
+
+	return ntohl(n->addr.s6_addr32[3]) >> (128 - n->len) ==
+			ntohl(addr->s6_addr32[3]) >> (128 - n->len);
+}
+
+
+static struct ndp_neighbor* find_neighbor(struct in6_addr *addr, bool strict)
+{
+	time_t now = time(NULL);
+	struct ndp_neighbor *n, *e;
+	list_for_each_entry_safe(n, e, &neighbors, head) {
+		if ((!strict && match_neighbor(n, addr)) ||
+				(n->len == 128 && IN6_ARE_ADDR_EQUAL(&n->addr, addr)))
+			return n;
+
+		if (!n->iface && abs(n->timeout - now) >= 5)
+			free_neighbor(n);
+	}
+	return NULL;
+}
+
+
+// Modified our own neighbor-entries
+static void modify_neighbor(struct in6_addr *addr,
+		struct interface *iface, bool add)
+{
+	if (!addr || (void*)addr == (void*)iface)
+		return;
+
+	struct ndp_neighbor *n = find_neighbor(addr, true);
+	if (!add) { // Delete action
+		if (n && (!n->iface || n->iface == iface))
+			free_neighbor(n);
+	} else if (!n) { // No entry yet, add one if possible
+		if (neighbor_count >= NDP_MAX_NEIGHBORS ||
+				!(n = malloc(sizeof(*n))))
+			return;
+
+		n->len = 128;
+		n->addr = *addr;
+		n->iface = iface;
+		if (!n->iface)
+			time(&n->timeout);
+		list_add(&n->head, &neighbors);
+		++neighbor_count;
+		setup_route(addr, n->iface, add);
+	} else if (n->iface == iface) {
+		if (!n->iface)
+			time(&n->timeout);
+	} else if (iface && (!n->iface ||
+			(!iface->external && n->iface->external))) {
+		setup_route(addr, n->iface, false);
+		n->iface = iface;
+		setup_route(addr, n->iface, add);
+	}
+	// TODO: In case a host switches interfaces we might want
+	// to set its old neighbor entry to NUD_STALE and ping it
+	// on the old interface to confirm if the MACs match.
+}
+
+
+// Handler for neighbor cache entries from the kernel. This is our source
+// to learn and unlearn hosts on interfaces.
+static void handle_rtnetlink(_unused void *addr, void *data, size_t len,
+		_unused struct interface *iface)
+{
+	for (struct nlmsghdr *nh = data; NLMSG_OK(nh, len);
+			nh = NLMSG_NEXT(nh, len)) {
+		struct rtmsg *rtm = NLMSG_DATA(nh);
+		if ((nh->nlmsg_type == RTM_NEWROUTE ||
+				nh->nlmsg_type == RTM_DELROUTE) &&
+				rtm->rtm_dst_len == 0)
+			raise(SIGUSR1); // Inform about a change in default route
+
+		struct ndmsg *ndm = NLMSG_DATA(nh);
+		struct ifaddrmsg *ifa = NLMSG_DATA(nh);
+		if (nh->nlmsg_type != RTM_NEWNEIGH
+				&& nh->nlmsg_type != RTM_DELNEIGH
+				&& nh->nlmsg_type != RTM_NEWADDR
+				&& nh->nlmsg_type != RTM_DELADDR)
+			continue; // Unrelated message type
+		bool is_addr = (nh->nlmsg_type == RTM_NEWADDR
+				|| nh->nlmsg_type == RTM_DELADDR);
+
+		// Family and ifindex are on the same offset for NEIGH and ADDR
+		if (NLMSG_PAYLOAD(nh, 0) < sizeof(*ndm)
+				|| ndm->ndm_family != AF_INET6)
+			continue; //
+
+		// Lookup interface
+		struct interface *iface;
+		if (!(iface = odhcpd_get_interface_by_index(ndm->ndm_ifindex)))
+			continue;
+
+		// Data to retrieve
+		size_t rta_offset = (is_addr) ? sizeof(*ifa) : sizeof(*ndm);
+		uint16_t atype = (is_addr) ? IFA_ADDRESS : NDA_DST;
+		ssize_t alen = NLMSG_PAYLOAD(nh, rta_offset);
+		struct in6_addr *addr = NULL;
+
+		for (struct rtattr *rta = (void*)(((uint8_t*)ndm) + rta_offset);
+				RTA_OK(rta, alen); rta = RTA_NEXT(rta, alen))
+			if (rta->rta_type == atype &&
+					RTA_PAYLOAD(rta) >= sizeof(*addr))
+				addr = RTA_DATA(rta);
+
+		// Address not specified or unrelated
+		if (!addr || IN6_IS_ADDR_LINKLOCAL(addr) ||
+				IN6_IS_ADDR_MULTICAST(addr))
+			continue;
+
+		// Check for states
+		bool add;
+		if (is_addr)
+			add = (nh->nlmsg_type == RTM_NEWADDR);
+		else
+			add = (nh->nlmsg_type == RTM_NEWNEIGH && (ndm->ndm_state &
+				(NUD_REACHABLE | NUD_STALE | NUD_DELAY | NUD_PROBE
+						| NUD_PERMANENT | NUD_NOARP)));
+
+		if (iface->ndp == RELAYD_RELAY)
+			modify_neighbor(addr, iface, add);
+
+		if (is_addr && iface->ra == RELAYD_SERVER)
+			raise(SIGUSR1); // Inform about a change in addresses
+
+		if (is_addr && iface->dhcpv6 == RELAYD_SERVER)
+			iface->ia_reconf = true;
+
+		if (iface->ndp == RELAYD_RELAY && is_addr && iface->master) {
+			// Replay address changes on all slave interfaces
+			nh->nlmsg_flags = NLM_F_REQUEST;
+
+			if (nh->nlmsg_type == RTM_NEWADDR)
+				nh->nlmsg_flags |= NLM_F_CREATE | NLM_F_REPLACE;
+
+			struct interface *c;
+			list_for_each_entry(c, &interfaces, head) {
+				if (c->ndp == RELAYD_RELAY && !c->master) {
+					ifa->ifa_index = c->ifindex;
+					send(rtnl_event.uloop.fd, nh, nh->nlmsg_len, MSG_DONTWAIT);
+				}
+			}
+		}
+
+		/* TODO: See if this is required for optimal operation
+		// Keep neighbor entries alive so we don't loose routes
+		if (add && (ndm->ndm_state & NUD_STALE))
+			ping6(addr, iface);
+		*/
+	}
+}