| /* vi: set sw=4 ts=4: */ |
| /* |
| * RFC3927 ZeroConf IPv4 Link-Local addressing |
| * (see <http://www.zeroconf.org/>) |
| * |
| * Copyright (C) 2003 by Arthur van Hoff (avh@strangeberry.com) |
| * Copyright (C) 2004 by David Brownell |
| * |
| * Licensed under GPLv2 or later, see file LICENSE in this source tree. |
| */ |
| |
| /* |
| * ZCIP just manages the 169.254.*.* addresses. That network is not |
| * routed at the IP level, though various proxies or bridges can |
| * certainly be used. Its naming is built over multicast DNS. |
| */ |
| |
| //#define DEBUG |
| |
| // TODO: |
| // - more real-world usage/testing, especially daemon mode |
| // - kernel packet filters to reduce scheduling noise |
| // - avoid silent script failures, especially under load... |
| // - link status monitoring (restart on link-up; stop on link-down) |
| |
| //usage:#define zcip_trivial_usage |
| //usage: "[OPTIONS] IFACE SCRIPT" |
| //usage:#define zcip_full_usage "\n\n" |
| //usage: "Manage a ZeroConf IPv4 link-local address\n" |
| //usage: "\n -f Run in foreground" |
| //usage: "\n -q Quit after obtaining address" |
| //usage: "\n -r 169.254.x.x Request this address first" |
| //usage: "\n -l x.x.0.0 Use this range instead of 169.254" |
| //usage: "\n -v Verbose" |
| //usage: "\n" |
| //usage: "\n$LOGGING=none Suppress logging" |
| //usage: "\n$LOGGING=syslog Log to syslog" |
| //usage: "\n" |
| //usage: "\nWith no -q, runs continuously monitoring for ARP conflicts," |
| //usage: "\nexits only on I/O errors (link down etc)" |
| |
| #include "libbb.h" |
| #include <netinet/ether.h> |
| #include <net/if.h> |
| #include <net/if_arp.h> |
| #include <linux/sockios.h> |
| |
| #include <syslog.h> |
| |
| /* We don't need more than 32 bits of the counter */ |
| #define MONOTONIC_US() ((unsigned)monotonic_us()) |
| |
| struct arp_packet { |
| struct ether_header eth; |
| struct ether_arp arp; |
| } PACKED; |
| |
| enum { |
| /* 0-1 seconds before sending 1st probe */ |
| PROBE_WAIT = 1, |
| /* 1-2 seconds between probes */ |
| PROBE_MIN = 1, |
| PROBE_MAX = 2, |
| PROBE_NUM = 3, /* total probes to send */ |
| ANNOUNCE_INTERVAL = 2, /* 2 seconds between announces */ |
| ANNOUNCE_NUM = 3, /* announces to send */ |
| /* if probe/announce sees a conflict, multiply RANDOM(NUM_CONFLICT) by... */ |
| CONFLICT_MULTIPLIER = 2, |
| /* if we monitor and see a conflict, how long is defend state? */ |
| DEFEND_INTERVAL = 10, |
| }; |
| |
| /* States during the configuration process. */ |
| enum { |
| PROBE = 0, |
| ANNOUNCE, |
| MONITOR, |
| DEFEND |
| }; |
| |
| #define VDBG(...) do { } while (0) |
| |
| |
| enum { |
| sock_fd = 3 |
| }; |
| |
| struct globals { |
| struct sockaddr iface_sockaddr; |
| struct ether_addr our_ethaddr; |
| uint32_t localnet_ip; |
| } FIX_ALIASING; |
| #define G (*(struct globals*)&bb_common_bufsiz1) |
| #define INIT_G() do { } while (0) |
| |
| |
| /** |
| * Pick a random link local IP address on 169.254/16, except that |
| * the first and last 256 addresses are reserved. |
| */ |
| static uint32_t pick_nip(void) |
| { |
| unsigned tmp; |
| |
| do { |
| tmp = rand() & IN_CLASSB_HOST; |
| } while (tmp > (IN_CLASSB_HOST - 0x0200)); |
| return htonl((G.localnet_ip + 0x0100) + tmp); |
| } |
| |
| static const char *nip_to_a(uint32_t nip) |
| { |
| struct in_addr in; |
| in.s_addr = nip; |
| return inet_ntoa(in); |
| } |
| |
| /** |
| * Broadcast an ARP packet. |
| */ |
| static void send_arp_request( |
| /* int op, - always ARPOP_REQUEST */ |
| /* const struct ether_addr *source_eth, - always &G.our_ethaddr */ |
| uint32_t source_nip, |
| const struct ether_addr *target_eth, uint32_t target_nip) |
| { |
| enum { op = ARPOP_REQUEST }; |
| #define source_eth (&G.our_ethaddr) |
| |
| struct arp_packet p; |
| memset(&p, 0, sizeof(p)); |
| |
| // ether header |
| p.eth.ether_type = htons(ETHERTYPE_ARP); |
| memcpy(p.eth.ether_shost, source_eth, ETH_ALEN); |
| memset(p.eth.ether_dhost, 0xff, ETH_ALEN); |
| |
| // arp request |
| p.arp.arp_hrd = htons(ARPHRD_ETHER); |
| p.arp.arp_pro = htons(ETHERTYPE_IP); |
| p.arp.arp_hln = ETH_ALEN; |
| p.arp.arp_pln = 4; |
| p.arp.arp_op = htons(op); |
| memcpy(&p.arp.arp_sha, source_eth, ETH_ALEN); |
| memcpy(&p.arp.arp_spa, &source_nip, 4); |
| memcpy(&p.arp.arp_tha, target_eth, ETH_ALEN); |
| memcpy(&p.arp.arp_tpa, &target_nip, 4); |
| |
| // send it |
| // Even though sock_fd is already bound to G.iface_sockaddr, just send() |
| // won't work, because "socket is not connected" |
| // (and connect() won't fix that, "operation not supported"). |
| // Thus we sendto() to G.iface_sockaddr. I wonder which sockaddr |
| // (from bind() or from sendto()?) kernel actually uses |
| // to determine iface to emit the packet from... |
| xsendto(sock_fd, &p, sizeof(p), &G.iface_sockaddr, sizeof(G.iface_sockaddr)); |
| #undef source_eth |
| } |
| |
| /** |
| * Run a script. |
| * argv[0]:intf argv[1]:script_name argv[2]:junk argv[3]:NULL |
| */ |
| static int run(char *argv[3], const char *param, uint32_t nip) |
| { |
| int status; |
| const char *addr = addr; /* for gcc */ |
| const char *fmt = "%s %s %s" + 3; |
| |
| argv[2] = (char*)param; |
| |
| VDBG("%s run %s %s\n", argv[0], argv[1], argv[2]); |
| |
| if (nip != 0) { |
| addr = nip_to_a(nip); |
| xsetenv("ip", addr); |
| fmt -= 3; |
| } |
| bb_info_msg(fmt, argv[2], argv[0], addr); |
| |
| status = spawn_and_wait(argv + 1); |
| if (status < 0) { |
| bb_perror_msg("%s %s %s" + 3, argv[2], argv[0]); |
| return -errno; |
| } |
| if (status != 0) |
| bb_error_msg("script %s %s failed, exitcode=%d", argv[1], argv[2], status & 0xff); |
| return status; |
| } |
| |
| /** |
| * Return milliseconds of random delay, up to "secs" seconds. |
| */ |
| static ALWAYS_INLINE unsigned random_delay_ms(unsigned secs) |
| { |
| return (unsigned)rand() % (secs * 1000); |
| } |
| |
| /** |
| * main program |
| */ |
| int zcip_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
| int zcip_main(int argc UNUSED_PARAM, char **argv) |
| { |
| char *r_opt; |
| const char *l_opt = "169.254.0.0"; |
| int state; |
| int nsent; |
| unsigned opts; |
| |
| // Ugly trick, but I want these zeroed in one go |
| struct { |
| const struct ether_addr null_ethaddr; |
| struct ifreq ifr; |
| uint32_t chosen_nip; |
| int conflicts; |
| int timeout_ms; // must be signed |
| int verbose; |
| } L; |
| #define null_ethaddr (L.null_ethaddr) |
| #define ifr (L.ifr ) |
| #define chosen_nip (L.chosen_nip ) |
| #define conflicts (L.conflicts ) |
| #define timeout_ms (L.timeout_ms ) |
| #define verbose (L.verbose ) |
| |
| memset(&L, 0, sizeof(L)); |
| INIT_G(); |
| |
| #define FOREGROUND (opts & 1) |
| #define QUIT (opts & 2) |
| // Parse commandline: prog [options] ifname script |
| // exactly 2 args; -v accumulates and implies -f |
| opt_complementary = "=2:vv:vf"; |
| opts = getopt32(argv, "fqr:l:v", &r_opt, &l_opt, &verbose); |
| #if !BB_MMU |
| // on NOMMU reexec early (or else we will rerun things twice) |
| if (!FOREGROUND) |
| bb_daemonize_or_rexec(0 /*was: DAEMON_CHDIR_ROOT*/, argv); |
| #endif |
| // Open an ARP socket |
| // (need to do it before openlog to prevent openlog from taking |
| // fd 3 (sock_fd==3)) |
| xmove_fd(xsocket(AF_PACKET, SOCK_PACKET, htons(ETH_P_ARP)), sock_fd); |
| if (!FOREGROUND) { |
| // do it before all bb_xx_msg calls |
| openlog(applet_name, 0, LOG_DAEMON); |
| logmode |= LOGMODE_SYSLOG; |
| } |
| bb_logenv_override(); |
| |
| { // -l n.n.n.n |
| struct in_addr net; |
| if (inet_aton(l_opt, &net) == 0 |
| || (net.s_addr & htonl(IN_CLASSB_NET)) != net.s_addr |
| ) { |
| bb_error_msg_and_die("invalid network address"); |
| } |
| G.localnet_ip = ntohl(net.s_addr); |
| } |
| if (opts & 4) { // -r n.n.n.n |
| struct in_addr ip; |
| if (inet_aton(r_opt, &ip) == 0 |
| || (ntohl(ip.s_addr) & IN_CLASSB_NET) != G.localnet_ip |
| ) { |
| bb_error_msg_and_die("invalid link address"); |
| } |
| chosen_nip = ip.s_addr; |
| } |
| argv += optind - 1; |
| |
| /* Now: argv[0]:junk argv[1]:intf argv[2]:script argv[3]:NULL */ |
| /* We need to make space for script argument: */ |
| argv[0] = argv[1]; |
| argv[1] = argv[2]; |
| /* Now: argv[0]:intf argv[1]:script argv[2]:junk argv[3]:NULL */ |
| #define argv_intf (argv[0]) |
| |
| xsetenv("interface", argv_intf); |
| |
| // Initialize the interface (modprobe, ifup, etc) |
| if (run(argv, "init", 0)) |
| return EXIT_FAILURE; |
| |
| // Initialize G.iface_sockaddr |
| // G.iface_sockaddr is: { u16 sa_family; u8 sa_data[14]; } |
| //memset(&G.iface_sockaddr, 0, sizeof(G.iface_sockaddr)); |
| //TODO: are we leaving sa_family == 0 (AF_UNSPEC)?! |
| safe_strncpy(G.iface_sockaddr.sa_data, argv_intf, sizeof(G.iface_sockaddr.sa_data)); |
| |
| // Bind to the interface's ARP socket |
| xbind(sock_fd, &G.iface_sockaddr, sizeof(G.iface_sockaddr)); |
| |
| // Get the interface's ethernet address |
| //memset(&ifr, 0, sizeof(ifr)); |
| strncpy_IFNAMSIZ(ifr.ifr_name, argv_intf); |
| xioctl(sock_fd, SIOCGIFHWADDR, &ifr); |
| memcpy(&G.our_ethaddr, &ifr.ifr_hwaddr.sa_data, ETH_ALEN); |
| |
| // Start with some stable ip address, either a function of |
| // the hardware address or else the last address we used. |
| // we are taking low-order four bytes, as top-order ones |
| // aren't random enough. |
| // NOTE: the sequence of addresses we try changes only |
| // depending on when we detect conflicts. |
| { |
| uint32_t t; |
| move_from_unaligned32(t, ((char *)&G.our_ethaddr + 2)); |
| srand(t); |
| } |
| // FIXME cases to handle: |
| // - zcip already running! |
| // - link already has local address... just defend/update |
| |
| // Daemonize now; don't delay system startup |
| if (!FOREGROUND) { |
| #if BB_MMU |
| bb_daemonize(0 /*was: DAEMON_CHDIR_ROOT*/); |
| #endif |
| bb_info_msg("start, interface %s", argv_intf); |
| } |
| |
| // Run the dynamic address negotiation protocol, |
| // restarting after address conflicts: |
| // - start with some address we want to try |
| // - short random delay |
| // - arp probes to see if another host uses it |
| // 00:04:e2:64:23:c2 > ff:ff:ff:ff:ff:ff arp who-has 169.254.194.171 tell 0.0.0.0 |
| // - arp announcements that we're claiming it |
| // 00:04:e2:64:23:c2 > ff:ff:ff:ff:ff:ff arp who-has 169.254.194.171 (00:04:e2:64:23:c2) tell 169.254.194.171 |
| // - use it |
| // - defend it, within limits |
| // exit if: |
| // - address is successfully obtained and -q was given: |
| // run "<script> config", then exit with exitcode 0 |
| // - poll error (when does this happen?) |
| // - read error (when does this happen?) |
| // - sendto error (in send_arp_request()) (when does this happen?) |
| // - revents & POLLERR (link down). run "<script> deconfig" first |
| if (chosen_nip == 0) { |
| new_nip_and_PROBE: |
| chosen_nip = pick_nip(); |
| } |
| nsent = 0; |
| state = PROBE; |
| while (1) { |
| struct pollfd fds[1]; |
| unsigned deadline_us; |
| struct arp_packet p; |
| int ip_conflict; |
| int n; |
| |
| fds[0].fd = sock_fd; |
| fds[0].events = POLLIN; |
| fds[0].revents = 0; |
| |
| // Poll, being ready to adjust current timeout |
| if (!timeout_ms) { |
| timeout_ms = random_delay_ms(PROBE_WAIT); |
| // FIXME setsockopt(sock_fd, SO_ATTACH_FILTER, ...) to |
| // make the kernel filter out all packets except |
| // ones we'd care about. |
| } |
| // Set deadline_us to the point in time when we timeout |
| deadline_us = MONOTONIC_US() + timeout_ms * 1000; |
| |
| VDBG("...wait %d %s nsent=%u\n", |
| timeout_ms, argv_intf, nsent); |
| |
| n = safe_poll(fds, 1, timeout_ms); |
| if (n < 0) { |
| //bb_perror_msg("poll"); - done in safe_poll |
| return EXIT_FAILURE; |
| } |
| if (n == 0) { // timed out? |
| VDBG("state:%d\n", state); |
| switch (state) { |
| case PROBE: |
| // No conflicting ARP packets were seen: |
| // we can progress through the states |
| if (nsent < PROBE_NUM) { |
| nsent++; |
| VDBG("probe/%u %s@%s\n", |
| nsent, argv_intf, nip_to_a(chosen_nip)); |
| timeout_ms = PROBE_MIN * 1000; |
| timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN); |
| send_arp_request(0, &null_ethaddr, chosen_nip); |
| continue; |
| } |
| // Switch to announce state |
| nsent = 0; |
| state = ANNOUNCE; |
| goto send_announce; |
| case ANNOUNCE: |
| // No conflicting ARP packets were seen: |
| // we can progress through the states |
| if (nsent < ANNOUNCE_NUM) { |
| send_announce: |
| nsent++; |
| VDBG("announce/%u %s@%s\n", |
| nsent, argv_intf, nip_to_a(chosen_nip)); |
| timeout_ms = ANNOUNCE_INTERVAL * 1000; |
| send_arp_request(chosen_nip, &G.our_ethaddr, chosen_nip); |
| continue; |
| } |
| // Switch to monitor state |
| // FIXME update filters |
| run(argv, "config", chosen_nip); |
| // NOTE: all other exit paths should deconfig... |
| if (QUIT) |
| return EXIT_SUCCESS; |
| // fall through: switch to MONITOR |
| default: |
| // case DEFEND: |
| // case MONITOR: (shouldn't happen, MONITOR timeout is infinite) |
| // Defend period ended with no ARP replies - we won |
| timeout_ms = -1; // never timeout in monitor state |
| state = MONITOR; |
| continue; |
| } |
| } |
| |
| // Packet arrived, or link went down. |
| // We need to adjust the timeout in case we didn't receive |
| // a conflicting packet. |
| if (timeout_ms > 0) { |
| unsigned diff = deadline_us - MONOTONIC_US(); |
| if ((int)(diff) < 0) { |
| // Current time is greater than the expected timeout time. |
| diff = 0; |
| } |
| VDBG("adjusting timeout\n"); |
| timeout_ms = (diff / 1000) | 1; // never 0 |
| } |
| |
| if ((fds[0].revents & POLLIN) == 0) { |
| if (fds[0].revents & POLLERR) { |
| // FIXME: links routinely go down; |
| // this shouldn't necessarily exit. |
| bb_error_msg("iface %s is down", argv_intf); |
| if (state >= MONITOR) { |
| // Only if we are in MONITOR or DEFEND |
| run(argv, "deconfig", chosen_nip); |
| } |
| return EXIT_FAILURE; |
| } |
| continue; |
| } |
| |
| // Read ARP packet |
| if (safe_read(sock_fd, &p, sizeof(p)) < 0) { |
| bb_perror_msg_and_die(bb_msg_read_error); |
| } |
| |
| if (p.eth.ether_type != htons(ETHERTYPE_ARP)) |
| continue; |
| if (p.arp.arp_op != htons(ARPOP_REQUEST) |
| && p.arp.arp_op != htons(ARPOP_REPLY) |
| ) { |
| continue; |
| } |
| #ifdef DEBUG |
| { |
| struct ether_addr *sha = (struct ether_addr *) p.arp.arp_sha; |
| struct ether_addr *tha = (struct ether_addr *) p.arp.arp_tha; |
| struct in_addr *spa = (struct in_addr *) p.arp.arp_spa; |
| struct in_addr *tpa = (struct in_addr *) p.arp.arp_tpa; |
| VDBG("source=%s %s\n", ether_ntoa(sha), inet_ntoa(*spa)); |
| VDBG("target=%s %s\n", ether_ntoa(tha), inet_ntoa(*tpa)); |
| } |
| #endif |
| ip_conflict = 0; |
| if (memcmp(&p.arp.arp_sha, &G.our_ethaddr, ETH_ALEN) != 0) { |
| if (memcmp(p.arp.arp_spa, &chosen_nip, 4) == 0) { |
| // A probe or reply with source_ip == chosen ip |
| ip_conflict = 1; |
| } |
| if (p.arp.arp_op == htons(ARPOP_REQUEST) |
| && memcmp(p.arp.arp_spa, &const_int_0, 4) == 0 |
| && memcmp(p.arp.arp_tpa, &chosen_nip, 4) == 0 |
| ) { |
| // A probe with source_ip == 0.0.0.0, target_ip == chosen ip: |
| // another host trying to claim this ip! |
| ip_conflict |= 2; |
| } |
| } |
| VDBG("state:%d ip_conflict:%d\n", state, ip_conflict); |
| if (!ip_conflict) |
| continue; |
| |
| // Either src or target IP conflict exists |
| if (state <= ANNOUNCE) { |
| // PROBE or ANNOUNCE |
| conflicts++; |
| timeout_ms = PROBE_MIN * 1000 |
| + CONFLICT_MULTIPLIER * random_delay_ms(conflicts); |
| goto new_nip_and_PROBE; |
| } |
| |
| // MONITOR or DEFEND: only src IP conflict is a problem |
| if (ip_conflict & 1) { |
| if (state == MONITOR) { |
| // Src IP conflict, defend with a single ARP probe |
| VDBG("monitor conflict - defending\n"); |
| timeout_ms = DEFEND_INTERVAL * 1000; |
| state = DEFEND; |
| send_arp_request(chosen_nip, &G.our_ethaddr, chosen_nip); |
| continue; |
| } |
| // state == DEFEND |
| // Another src IP conflict, start over |
| VDBG("defend conflict - starting over\n"); |
| run(argv, "deconfig", chosen_nip); |
| conflicts = 0; |
| timeout_ms = 0; |
| goto new_nip_and_PROBE; |
| } |
| // Note: if we only have a target IP conflict here (ip_conflict & 2), |
| // IOW: if we just saw this sort of ARP packet: |
| // aa:bb:cc:dd:ee:ff > xx:xx:xx:xx:xx:xx arp who-has <chosen_nip> tell 0.0.0.0 |
| // we expect _kernel_ to respond to that, because <chosen_nip> |
| // is (expected to be) configured on this iface. |
| } // while (1) |
| #undef argv_intf |
| } |