From c792b89ce22cca9b6eca3dc9156bdccb1ea46653 Mon Sep 17 00:00:00 2001 From: Steven Barth Date: Tue, 5 Nov 2013 08:56:29 +0100 Subject: [PATCH] Add experimental and unfinished bfd ping work --- src/bfd.c | 231 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 231 insertions(+) create mode 100644 src/bfd.c 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 +#include +#include +#include +#include +#include + +#include +#include +#include +#include +#include + +#include +#include + +#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; +} + +*/ -- 2.25.1