5 #include <netinet/ip6.h>
6 #include <netinet/icmp6.h>
8 #include <sys/socket.h>
10 #include <net/ethernet.h>
11 #include <netpacket/packet.h>
12 #include <linux/rtnetlink.h>
13 #include <linux/filter.h>
20 static int sock = -1, rtnl = -1;
21 static int if_index = -1;
22 static int bfd_failed = 0, bfd_limit = 0, bfd_interval = 0;
23 static bool bfd_armed = false;
26 static void bfd_send(int signal __attribute__((unused)))
30 struct icmp6_hdr icmp6;
32 memset(&ping, 0, sizeof(ping));
34 ping.ip6.ip6_vfc = 6 << 4;
35 ping.ip6.ip6_plen = htons(8);
36 ping.ip6.ip6_nxt = IPPROTO_ICMPV6;
37 ping.ip6.ip6_hlim = 255;
39 ping.icmp6.icmp6_type = ICMP6_ECHO_REQUEST;
40 ping.icmp6.icmp6_data32[0] = htonl(0xbfd0bfd);
43 struct odhcp6c_entry *pd = odhcp6c_get_state(STATE_IA_PD, &pdlen), *cpd = NULL;
44 struct odhcp6c_entry *rt = odhcp6c_get_state(STATE_RA_ROUTE, &rtlen), *crt = NULL;
45 bool crt_found = false;
50 if (++bfd_failed > bfd_limit) {
57 for (size_t i = 0; i < pdlen / sizeof(*pd); ++i)
58 if (!cpd || ((cpd->target.s6_addr[0] & 7) == 0xfc) > ((pd[i].target.s6_addr[0] & 7) == 0xfc)
59 || cpd->preferred < pd[i].preferred)
62 // Detect default router
63 for (size_t i = 0; i < rtlen / sizeof(*rt); ++i)
64 if (IN6_IS_ADDR_UNSPECIFIED(&rt[i].target) && (!crt || crt->priority > rt[i].priority))
67 struct sockaddr_ll dest = {
68 .sll_family = AF_PACKET,
69 .sll_protocol = htons(ETH_P_IPV6),
70 .sll_ifindex = if_index,
71 .sll_halen = ETH_ALEN,
79 .hdr = {sizeof(req), RTM_GETNEIGH, NLM_F_REQUEST | NLM_F_DUMP, 1, 0},
80 .ndm = {.ndm_family = AF_INET6, .ndm_ifindex = if_index}
82 send(rtnl, &req, sizeof(req), 0);
87 ssize_t read = recv(rtnl, buf, sizeof(buf), 0);
88 nhm = (struct nlmsghdr*)buf;
89 if (read < 0 || !NLMSG_OK(nhm, (size_t)read))
92 for (; read > 0 && NLMSG_OK(nhm, (size_t)read); nhm = NLMSG_NEXT(nhm, read)) {
93 ssize_t attrlen = NLMSG_PAYLOAD(nhm, sizeof(struct ndmsg));
94 if (nhm->nlmsg_type != RTM_NEWNEIGH || attrlen <= 0) {
99 // Already have our MAC
103 struct ndmsg *ndm = NLMSG_DATA(nhm);
104 for (struct rtattr *rta = (struct rtattr*)&ndm[1];
105 attrlen > 0 && RTA_OK(rta, (size_t)attrlen);
106 rta = RTA_NEXT(rta, attrlen)) {
107 if (rta->rta_type == NDA_DST) {
108 crt_found = IN6_ARE_ADDR_EQUAL(RTA_DATA(rta), &crt->router);
109 } else if (rta->rta_type == NDA_LLADDR) {
110 memcpy(dest.sll_addr, RTA_DATA(rta), ETH_ALEN);
117 if (!crt_found || !cpd)
120 ping.ip6.ip6_src = cpd->target;
121 ping.ip6.ip6_dst = cpd->target;
124 uint16_t sum = cksum(&ping.ip6.ip6_src, sizeof(ping.ip6.ip6_src), 0);
125 sum = cksum(&ping.ip6.ip6_dst, sizeof(ping.ip6.ip6_dst), ~sum);
126 sum = cksum(&ping.ip6.ip6_plen, sizeof(ping.ip6.ip6_plen), ~sum);
128 uint8_t next[4] = {0, 0, 0, ping.ip6.ip6_nxt};
129 sum = cksum(next, sizeof(next), ~sum);
131 ping.icmp6.icmp6_cksum = cksum(&ping.icmp6, sizeof(ping.icmp6), ~sum);
134 struct sock_filter bpf[] = {
135 BPF_STMT(BPF_LD | BPF_W | BPF_ABS, offsetof(struct ip6_hdr, ip6_plen)),
136 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, 8 << 16 | IPPROTO_ICMPV6 << 8 | 254, 0, 13),
137 BPF_STMT(BPF_LD | BPF_W | BPF_ABS, offsetof(struct ip6_hdr, ip6_dst)),
138 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ntohl(ping.ip6.ip6_dst.s6_addr32[0]), 0, 11),
139 BPF_STMT(BPF_LD | BPF_W | BPF_ABS, offsetof(struct ip6_hdr, ip6_dst) + 4),
140 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ntohl(ping.ip6.ip6_dst.s6_addr32[1]), 0, 9),
141 BPF_STMT(BPF_LD | BPF_W | BPF_ABS, offsetof(struct ip6_hdr, ip6_dst) + 8),
142 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ntohl(ping.ip6.ip6_dst.s6_addr32[2]), 0, 7),
143 BPF_STMT(BPF_LD | BPF_W | BPF_ABS, offsetof(struct ip6_hdr, ip6_dst) + 12),
144 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ntohl(ping.ip6.ip6_dst.s6_addr32[3]), 0, 5),
145 BPF_STMT(BPF_LD | BPF_W | BPF_ABS, sizeof(struct ip6_hdr) +
146 offsetof(struct icmp6_hdr, icmp6_type)),
147 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ICMP6_ECHO_REQUEST << 24, 0, 3),
148 BPF_STMT(BPF_LD | BPF_W | BPF_ABS, sizeof(struct ip6_hdr) +
149 offsetof(struct icmp6_hdr, icmp6_data32)),
150 BPF_JUMP(BPF_JMP | BPF_JEQ | BPF_K, ntohl(ping.icmp6.icmp6_data32[0]), 0, 1),
151 BPF_STMT(BPF_RET | BPF_K, 0xffffffff),
152 BPF_STMT(BPF_RET | BPF_K, 0),
154 struct sock_fprog bpf_prog = {sizeof(bpf) / sizeof(*bpf), bpf};
158 sock = socket(AF_PACKET, SOCK_DGRAM | SOCK_CLOEXEC, htons(ETH_P_IPV6));
159 bind(sock, (struct sockaddr*)&dest, sizeof(dest));
161 fcntl(sock, F_SETOWN, getpid());
162 fcntl(sock, F_SETFL, fcntl(sock, F_GETFL) | O_ASYNC);
165 setsockopt(sock, SOL_SOCKET, SO_DETACH_FILTER, &bpf_prog, sizeof(bpf_prog));
166 if (setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &bpf_prog, sizeof(bpf_prog))) {
173 while (recv(sock, dummy, sizeof(dummy), MSG_DONTWAIT | MSG_TRUNC) > 0);
175 sendto(sock, &ping, sizeof(ping), MSG_DONTWAIT,
176 (struct sockaddr*)&dest, sizeof(dest));
180 void bfd_receive(void)
183 while (recv(sock, dummy, sizeof(dummy), MSG_DONTWAIT | MSG_TRUNC) > 0) {
190 int bfd_start(const char *ifname, int limit, int interval)
192 if_index = if_nametoindex(ifname);
196 bfd_interval = interval;
198 if (limit < 1 || interval < 1)
201 rtnl = socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_ROUTE);
202 struct sockaddr_nl rtnl_kernel = { .nl_family = AF_NETLINK };
203 connect(rtnl, (const struct sockaddr*)&rtnl_kernel, sizeof(rtnl_kernel));
205 signal(SIGALRM, bfd_send);
223 uint16_t cksum(const uint16_t *addr, size_t count, uint16_t start)
225 uint32_t sum = start;
233 sum = (sum & 0xffff) + (sum >> 16);