Add experimental and unfinished bfd ping work

1 files changed, 231 insertions, 0 deletions

diff --git a/src/bfd.c b/src/bfd.c
new file mode 100644
index 0000000..be71361
--- /dev/null
+++ b/src/bfd.c
@@ -0,0 +1,231 @@
+#include <syslog.h>
+#include <signal.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <netinet/ip6.h>
+#include <netinet/icmp6.h>
+
+#include <sys/socket.h>
+#include <net/ethernet.h>
+#include <netpacket/packet.h>
+#include <linux/rtnetlink.h>
+#include <linux/filter.h>
+
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "odhcp6c.h"
+
+static int sock = -1, rtnl = -1;
+static int if_index = -1;
+static int bfd_failed = 0, bfd_limit = 0, bfd_interval = 0;
+static bool bfd_armed = false;
+
+
+static void bfd_send(int signal)
+{
+	struct {
+		struct ip6_hdr ip6;
+		struct icmp6_hdr icmp6;
+	} ping;
+	memset(&ping, 0, sizeof(ping));
+
+	ping.ip6.ip6_vfc = 6 << 4;
+	ping.ip6.ip6_plen = htons(8);
+	ping.ip6.ip6_nxt = IPPROTO_ICMPV6;
+	ping.ip6.ip6_hlim = 255;
+
+	ping.icmp6.icmp6_type = ICMP6_ECHO_REQUEST;
+	ping.icmp6.icmp6_data32[0] = htonl(0xbfd0bfd);
+
+	size_t pdlen, rtlen;
+	struct odhcp6c_entry *pd = odhcp6c_get_state(STATE_IA_PD, &pdlen), *cpd = NULL;
+	struct odhcp6c_entry *rt = odhcp6c_get_state(STATE_RA_ROUTE, &rtlen), *crt = NULL;
+	bool crt_found = false;
+
+	// Detect PD-Prefix
+	for (size_t i = 0; i < pdlen / sizeof(*pd); ++i)
+		if (!cpd || ((cpd->target.s6_addr[0] & 7) == 0xfc) > ((pd[i].target.s6_addr[0] & 7) == 0xfc)
+				|| cpd->preferred < pd[i].preferred)
+			cpd = &pd[i];
+
+	// Detect default router
+	for (size_t i = 0; i < rtlen / sizeof(*rt); ++i)
+		if (IN6_IS_ADDR_UNSPECIFIED(&rt[i].target) && (!crt || crt->priority > rt[i].priority))
+			crt = &rt[i];
+
+	struct sockaddr_ll dest = {
+		.sll_family = AF_PACKET,
+		.sll_protocol = htons(ETH_P_IPV6),
+		.sll_ifindex = if_index,
+		.sll_halen = ETH_ALEN,
+	};
+
+	if (crt) {
+		struct {
+			struct nlmsghdr hdr;
+			struct ndmsg ndm;
+		} req = {
+			.hdr = {sizeof(req), RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP, 1, 0},
+			.ndm = {.ndm_family = AF_INET6, .ndm_ifindex = if_index}
+		};
+		send(rtnl, &req, sizeof(req), 0);
+
+		uint8_t buf[8192];
+		struct nlmsghdr *nhm;
+		do {
+			ssize_t read = recv(rtnl, buf, sizeof(buf), 0);
+			nhm = (struct nlmsghdr*)buf;
+			if (read < 0 || !NLMSG_OK(nhm, (size_t)read))
+				continue;
+
+			for (; read > 0 && NLMSG_OK(nhm, (size_t)read); nhm = NLMSG_NEXT(nhm, read)) {
+				ssize_t attrlen = NLMSG_PAYLOAD(nhm, sizeof(struct ndmsg));
+				if (nhm->nlmsg_type != RTM_NEWNEIGH || attrlen <= 0) {
+					nhm = NULL;
+					break;
+				}
+
+				// Already have our MAC
+				if (crt_found)
+					continue;
+
+				struct ndmsg *ndm = NLMSG_DATA(nhm);
+				for (struct rtattr *rta = (struct rtattr*)&ndm[1];
+						attrlen > 0 && RTA_OK(rta, (size_t)attrlen);
+						rta = RTA_NEXT(rta, attrlen)) {
+					if (rta->rta_type == NDA_DST) {
+						crt_found = IN6_ARE_ADDR_EQUAL(RTA_DATA(rta), &crt->router);
+					} else if (rta->rta_type == NDA_LLADDR) {
+						memcpy(dest.sll_addr, RTA_DATA(rta), ETH_ALEN);
+					}
+				}
+			}
+		} while (nhm);
+	}
+
+	if (!crt_found || !cpd)
+		return;
+
+	ping.ip6.ip6_src = cpd->target;
+	ping.ip6.ip6_dst = cpd->target;
+
+	if (bfd_armed) {
+		if (bfd_failed++ > bfd_limit) {
+			raise(SIGUSR2);
+			return;
+		}
+	}
+
+/*
+	uint16_t sum = cksum(&ping.ip6.ip6_src, sizeof(ping.ip6.ip6_src), 0);
+	sum = cksum(&ping.ip6.ip6_dst, sizeof(ping.ip6.ip6_dst), ~sum);
+	sum = cksum(&ping.ip6.ip6_plen, sizeof(ping.ip6.ip6_plen), ~sum);
+
+	uint8_t next[4] = {0, 0, 0, ping.ip6.ip6_nxt};
+	sum = cksum(next, sizeof(next), ~sum);
+
+	ping.icmp6.icmp6_cksum = cksum(&ping.icmp6, sizeof(ping.icmp6), ~sum);
+*/
+
+	struct sock_filter bpf[] = {
+		BPF_STMT(BPF_LD | BPF_W | BPF_ABS, offsetof(struct ip6_hdr, ip6_plen)),
+		BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htonl(8 << 16 | IPPROTO_ICMPV6 << 8 | 254), 0, 13),
+		BPF_STMT(BPF_LD | BPF_W | BPF_ABS, offsetof(struct ip6_hdr, ip6_dst)),
+		BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ping.ip6.ip6_dst.s6_addr32[0], 0, 11),
+		BPF_STMT(BPF_LD | BPF_W | BPF_ABS, offsetof(struct ip6_hdr, ip6_dst) + 4),
+		BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ping.ip6.ip6_dst.s6_addr32[1], 0, 9),
+		BPF_STMT(BPF_LD | BPF_W | BPF_ABS, offsetof(struct ip6_hdr, ip6_dst) + 8),
+		BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ping.ip6.ip6_dst.s6_addr32[2], 0, 7),
+		BPF_STMT(BPF_LD | BPF_W | BPF_ABS, offsetof(struct ip6_hdr, ip6_dst) + 12),
+		BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ping.ip6.ip6_dst.s6_addr32[3], 0, 5),
+		BPF_STMT(BPF_LD | BPF_W | BPF_ABS, sizeof(struct ip6_hdr) +
+				offsetof(struct icmp6_hdr, icmp6_type)),
+		BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, htonl(ICMP6_ECHO_REQUEST << 24), 0, 3),
+		BPF_STMT(BPF_LD | BPF_W | BPF_ABS, sizeof(struct ip6_hdr) +
+				offsetof(struct icmp6_hdr, icmp6_data32)),
+		BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ping.icmp6.icmp6_data32[0], 0, 1),
+		BPF_STMT(BPF_RET | BPF_K, 0xffffffff),
+		BPF_STMT(BPF_RET | BPF_K, 0),
+	};
+	struct sock_fprog bpf_prog = {sizeof(bpf) / sizeof(*bpf), bpf};
+
+	setsockopt(sock, SOL_SOCKET, SO_DETACH_FILTER, &bpf_prog, sizeof(bpf_prog));
+	if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &bpf_prog, sizeof(bpf_prog))) {
+		close(sock);
+		return;
+	}
+
+
+	if (!signal) {
+		bind(sock, (struct sockaddr*)&dest, sizeof(dest));
+		uint8_t dummy[8];
+		while (recv(sock, dummy, sizeof(dummy), MSG_DONTWAIT | MSG_TRUNC) > 0);
+	}
+	sendto(sock, &ping, sizeof(ping), MSG_DONTWAIT,
+			(struct sockaddr*)&dest, sizeof(dest));
+	alarm(bfd_interval);
+}
+
+
+void bfd_receive(void)
+{
+	uint8_t dummy[8];
+	while (recv(sock, dummy, sizeof(dummy), MSG_DONTWAIT | MSG_TRUNC) > 0) {
+		bfd_failed = 0;
+		bfd_armed = true;
+	}
+}
+
+
+int bfd_start(int ifindex, int limit, int interval)
+{
+	if_index = ifindex;
+	bfd_armed = false;
+	bfd_failed = 0;
+	bfd_limit = limit;
+	bfd_interval = interval;
+
+	if (limit < 1 || interval < 1)
+		return 0;
+
+	rtnl = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
+	struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
+	connect(rtnl, (const struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel));
+
+	sock = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC, htons(ETH_P_IPV6));
+	bfd_send(0);
+
+	fcntl(sock, F_SETOWN, getpid());
+	fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
+
+	signal(SIGALRM, bfd_send);
+	return 0;
+}
+
+
+void bfd_stop(void)
+{
+	alarm(0);
+	close(sock);
+	close(rtnl);
+}
+
+/*
+
+uint16_t cksum(const uint16_t *addr, size_t count, uint16_t start)
+{
+	uint32_t sum = start;
+
+	while (count > 1) {
+		sum += *addr++;
+		count -= 2;
+	}
+
+	while (sum >> 16)
+		sum = (sum & 0xffff) + (sum >> 16);
+
+	return ~sum;
+}
+
+*/