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#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;
}
*/
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