| /* 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 the GPL v2 or later, see the file LICENSE in this tarball. |
| */ |
| |
| /* |
| * 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) |
| |
| #include <syslog.h> |
| #include <poll.h> |
| #include <sys/wait.h> |
| #include <netinet/ether.h> |
| #include <net/ethernet.h> |
| #include <net/if.h> |
| #include <net/if_arp.h> |
| #include <linux/if_packet.h> |
| #include <linux/sockios.h> |
| |
| #include "libbb.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; |
| } ATTRIBUTE_PACKED; |
| |
| enum { |
| /* 169.254.0.0 */ |
| LINKLOCAL_ADDR = 0xa9fe0000, |
| |
| /* protocol timeout parameters, specified in seconds */ |
| PROBE_WAIT = 1, |
| PROBE_MIN = 1, |
| PROBE_MAX = 2, |
| PROBE_NUM = 3, |
| MAX_CONFLICTS = 10, |
| RATE_LIMIT_INTERVAL = 60, |
| ANNOUNCE_WAIT = 2, |
| ANNOUNCE_NUM = 2, |
| ANNOUNCE_INTERVAL = 2, |
| DEFEND_INTERVAL = 10 |
| }; |
| |
| /* States during the configuration process. */ |
| enum { |
| PROBE = 0, |
| RATE_LIMIT_PROBE, |
| ANNOUNCE, |
| MONITOR, |
| DEFEND |
| }; |
| |
| #define VDBG(...) do { } while (0) |
| |
| |
| enum { |
| sock_fd = 3 |
| }; |
| |
| struct globals { |
| char *intf; |
| struct sockaddr saddr; |
| }; |
| #define G (*(struct globals*)&bb_common_bufsiz1) |
| #define intf (G.intf ) |
| #define saddr (G.saddr) |
| |
| |
| /** |
| * Pick a random link local IP address on 169.254/16, except that |
| * the first and last 256 addresses are reserved. |
| */ |
| static void pick(struct in_addr *ip) |
| { |
| unsigned tmp; |
| |
| do { |
| tmp = rand() & IN_CLASSB_HOST; |
| } while (tmp > (IN_CLASSB_HOST - 0x0200)); |
| ip->s_addr = htonl((LINKLOCAL_ADDR + 0x0100) + tmp); |
| } |
| |
| /** |
| * Broadcast an ARP packet. |
| */ |
| static void arp(int op, |
| const struct ether_addr *source_eth, struct in_addr source_ip, |
| const struct ether_addr *target_eth, struct in_addr target_ip) |
| { |
| 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_ip, sizeof(p.arp.arp_spa)); |
| memcpy(&p.arp.arp_tha, target_eth, ETH_ALEN); |
| memcpy(&p.arp.arp_tpa, &target_ip, sizeof(p.arp.arp_tpa)); |
| |
| // send it |
| xsendto(sock_fd, &p, sizeof(p), &saddr, sizeof(saddr)); |
| |
| // Currently all callers ignore errors, that's why returns are |
| // commented out... |
| //return 0; |
| } |
| |
| /** |
| * Run a script. argv[2] is already NULL. |
| */ |
| static int run(char *argv[3], struct in_addr *ip) |
| { |
| int status; |
| char *addr = addr; /* for gcc */ |
| const char *fmt = "%s %s %s" + 3; |
| |
| VDBG("%s run %s %s\n", intf, argv[0], argv[1]); |
| |
| if (ip) { |
| addr = inet_ntoa(*ip); |
| setenv("ip", addr, 1); |
| fmt -= 3; |
| } |
| bb_info_msg(fmt, argv[1], intf, addr); |
| |
| status = wait4pid(spawn(argv)); |
| if (status < 0) { |
| bb_perror_msg("%s %s %s" + 3, argv[1], intf); |
| return -errno; |
| } |
| if (status != 0) |
| bb_error_msg("script %s %s failed, exitcode=%d", argv[0], argv[1], status); |
| return status; |
| } |
| |
| /** |
| * Return milliseconds of random delay, up to "secs" seconds. |
| */ |
| static unsigned ALWAYS_INLINE random_delay_ms(unsigned secs) |
| { |
| return rand() % (secs * 1000); |
| } |
| |
| /** |
| * main program |
| */ |
| int zcip_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE; |
| int zcip_main(int argc, char **argv) |
| { |
| int state = PROBE; |
| struct ether_addr eth_addr; |
| char *r_opt; |
| unsigned opts; |
| |
| /* Ugly trick, but I want these zeroed in one go */ |
| struct { |
| const struct in_addr null_ip; |
| const struct ether_addr null_addr; |
| struct in_addr ip; |
| struct ifreq ifr; |
| char *script_av[3]; |
| int timeout_ms; /* must be signed */ |
| unsigned conflicts; |
| unsigned nprobes; |
| unsigned nclaims; |
| int ready; |
| int verbose; |
| } L; |
| #define null_ip (L.null_ip ) |
| #define null_addr (L.null_addr ) |
| #define ip (L.ip ) |
| #define ifr (L.ifr ) |
| #define script_av (L.script_av ) |
| #define timeout_ms (L.timeout_ms) |
| #define conflicts (L.conflicts ) |
| #define nprobes (L.nprobes ) |
| #define nclaims (L.nclaims ) |
| #define ready (L.ready ) |
| #define verbose (L.verbose ) |
| |
| memset(&L, 0, sizeof(L)); |
| |
| #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:v", &r_opt, &verbose); |
| if (!FOREGROUND) { |
| /* Do it early, before all bb_xx_msg calls */ |
| openlog(applet_name, 0, LOG_DAEMON); |
| logmode |= LOGMODE_SYSLOG; |
| } |
| if (opts & 4) { // -r n.n.n.n |
| if (inet_aton(r_opt, &ip) == 0 |
| || (ntohl(ip.s_addr) & IN_CLASSB_NET) != LINKLOCAL_ADDR |
| ) { |
| bb_error_msg_and_die("invalid link address"); |
| } |
| } |
| // On NOMMU reexec early (or else we will rerun things twice) |
| #if !BB_MMU |
| if (!FOREGROUND) |
| bb_daemonize_or_rexec(DAEMON_CHDIR_ROOT, argv); |
| #endif |
| argc -= optind; |
| argv += optind; |
| |
| intf = argv[0]; |
| script_av[0] = argv[1]; |
| setenv("interface", intf, 1); |
| |
| // initialize the interface (modprobe, ifup, etc) |
| script_av[1] = (char*)"init"; |
| if (run(script_av, NULL)) |
| return EXIT_FAILURE; |
| |
| // initialize saddr |
| // saddr is: { u16 sa_family; u8 sa_data[14]; } |
| //memset(&saddr, 0, sizeof(saddr)); |
| //TODO: are we leaving sa_family == 0 (AF_UNSPEC)?! |
| safe_strncpy(saddr.sa_data, intf, sizeof(saddr.sa_data)); |
| |
| // open an ARP socket |
| xmove_fd(xsocket(AF_PACKET, SOCK_PACKET, htons(ETH_P_ARP)), sock_fd); |
| // bind to the interface's ARP socket |
| xbind(sock_fd, &saddr, sizeof(saddr)); |
| |
| // get the interface's ethernet address |
| //memset(&ifr, 0, sizeof(ifr)); |
| strncpy(ifr.ifr_name, intf, sizeof(ifr.ifr_name)); |
| xioctl(sock_fd, SIOCGIFHWADDR, &ifr); |
| memcpy(ð_addr, &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; |
| memcpy(&t, (char*)ð_addr + 2, 4); |
| srand(t); |
| } |
| if (ip.s_addr == 0) |
| pick(&ip); |
| |
| // 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(DAEMON_CHDIR_ROOT); |
| #endif |
| bb_info_msg("start, interface %s", 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 else uses it |
| // - arp announcements that we're claiming it |
| // - use it |
| // - defend it, within limits |
| while (1) { |
| struct pollfd fds[1]; |
| unsigned deadline_us; |
| struct arp_packet p; |
| int source_ip_conflict; |
| int target_ip_conflict; |
| |
| 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 nprobes=%u, nclaims=%u\n", |
| timeout_ms, intf, nprobes, nclaims); |
| |
| switch (safe_poll(fds, 1, timeout_ms)) { |
| |
| default: |
| /*bb_perror_msg("poll"); - done in safe_poll */ |
| return EXIT_FAILURE; |
| |
| // timeout |
| case 0: |
| VDBG("state = %d\n", state); |
| switch (state) { |
| case PROBE: |
| // timeouts in the PROBE state mean no conflicting ARP packets |
| // have been received, so we can progress through the states |
| if (nprobes < PROBE_NUM) { |
| nprobes++; |
| VDBG("probe/%u %s@%s\n", |
| nprobes, intf, inet_ntoa(ip)); |
| arp(ARPOP_REQUEST, |
| ð_addr, null_ip, |
| &null_addr, ip); |
| timeout_ms = PROBE_MIN * 1000; |
| timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN); |
| } |
| else { |
| // Switch to announce state. |
| state = ANNOUNCE; |
| nclaims = 0; |
| VDBG("announce/%u %s@%s\n", |
| nclaims, intf, inet_ntoa(ip)); |
| arp(ARPOP_REQUEST, |
| ð_addr, ip, |
| ð_addr, ip); |
| timeout_ms = ANNOUNCE_INTERVAL * 1000; |
| } |
| break; |
| case RATE_LIMIT_PROBE: |
| // timeouts in the RATE_LIMIT_PROBE state mean no conflicting ARP packets |
| // have been received, so we can move immediately to the announce state |
| state = ANNOUNCE; |
| nclaims = 0; |
| VDBG("announce/%u %s@%s\n", |
| nclaims, intf, inet_ntoa(ip)); |
| arp(ARPOP_REQUEST, |
| ð_addr, ip, |
| ð_addr, ip); |
| timeout_ms = ANNOUNCE_INTERVAL * 1000; |
| break; |
| case ANNOUNCE: |
| // timeouts in the ANNOUNCE state mean no conflicting ARP packets |
| // have been received, so we can progress through the states |
| if (nclaims < ANNOUNCE_NUM) { |
| nclaims++; |
| VDBG("announce/%u %s@%s\n", |
| nclaims, intf, inet_ntoa(ip)); |
| arp(ARPOP_REQUEST, |
| ð_addr, ip, |
| ð_addr, ip); |
| timeout_ms = ANNOUNCE_INTERVAL * 1000; |
| } |
| else { |
| // Switch to monitor state. |
| state = MONITOR; |
| // link is ok to use earlier |
| // FIXME update filters |
| script_av[1] = (char*)"config"; |
| run(script_av, &ip); |
| ready = 1; |
| conflicts = 0; |
| timeout_ms = -1; // Never timeout in the monitor state. |
| |
| // NOTE: all other exit paths |
| // should deconfig ... |
| if (QUIT) |
| return EXIT_SUCCESS; |
| } |
| break; |
| case DEFEND: |
| // We won! No ARP replies, so just go back to monitor. |
| state = MONITOR; |
| timeout_ms = -1; |
| conflicts = 0; |
| break; |
| default: |
| // Invalid, should never happen. Restart the whole protocol. |
| state = PROBE; |
| pick(&ip); |
| timeout_ms = 0; |
| nprobes = 0; |
| nclaims = 0; |
| break; |
| } // switch (state) |
| break; // case 0 (timeout) |
| |
| // packets arriving, or link went down |
| case 1: |
| // 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. |
| // Should never happen. |
| VDBG("missed an expected timeout\n"); |
| timeout_ms = 0; |
| } else { |
| 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", intf); |
| if (ready) { |
| script_av[1] = (char*)"deconfig"; |
| run(script_av, &ip); |
| } |
| 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; |
| #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("%s recv arp type=%d, op=%d,\n", |
| intf, ntohs(p.eth.ether_type), |
| ntohs(p.arp.arp_op)); |
| VDBG("\tsource=%s %s\n", |
| ether_ntoa(sha), |
| inet_ntoa(*spa)); |
| VDBG("\ttarget=%s %s\n", |
| ether_ntoa(tha), |
| inet_ntoa(*tpa)); |
| } |
| #endif |
| if (p.arp.arp_op != htons(ARPOP_REQUEST) |
| && p.arp.arp_op != htons(ARPOP_REPLY)) |
| continue; |
| |
| source_ip_conflict = 0; |
| target_ip_conflict = 0; |
| |
| if (memcmp(p.arp.arp_spa, &ip.s_addr, sizeof(struct in_addr)) == 0 |
| && memcmp(&p.arp.arp_sha, ð_addr, ETH_ALEN) != 0 |
| ) { |
| source_ip_conflict = 1; |
| } |
| if (p.arp.arp_op == htons(ARPOP_REQUEST) |
| && memcmp(p.arp.arp_tpa, &ip.s_addr, sizeof(struct in_addr)) == 0 |
| && memcmp(&p.arp.arp_tha, ð_addr, ETH_ALEN) != 0 |
| ) { |
| target_ip_conflict = 1; |
| } |
| |
| VDBG("state = %d, source ip conflict = %d, target ip conflict = %d\n", |
| state, source_ip_conflict, target_ip_conflict); |
| switch (state) { |
| case PROBE: |
| case ANNOUNCE: |
| // When probing or announcing, check for source IP conflicts |
| // and other hosts doing ARP probes (target IP conflicts). |
| if (source_ip_conflict || target_ip_conflict) { |
| conflicts++; |
| if (conflicts >= MAX_CONFLICTS) { |
| VDBG("%s ratelimit\n", intf); |
| timeout_ms = RATE_LIMIT_INTERVAL * 1000; |
| state = RATE_LIMIT_PROBE; |
| } |
| |
| // restart the whole protocol |
| pick(&ip); |
| timeout_ms = 0; |
| nprobes = 0; |
| nclaims = 0; |
| } |
| break; |
| case MONITOR: |
| // If a conflict, we try to defend with a single ARP probe. |
| if (source_ip_conflict) { |
| VDBG("monitor conflict -- defending\n"); |
| state = DEFEND; |
| timeout_ms = DEFEND_INTERVAL * 1000; |
| arp(ARPOP_REQUEST, |
| ð_addr, ip, |
| ð_addr, ip); |
| } |
| break; |
| case DEFEND: |
| // Well, we tried. Start over (on conflict). |
| if (source_ip_conflict) { |
| state = PROBE; |
| VDBG("defend conflict -- starting over\n"); |
| ready = 0; |
| script_av[1] = (char*)"deconfig"; |
| run(script_av, &ip); |
| |
| // restart the whole protocol |
| pick(&ip); |
| timeout_ms = 0; |
| nprobes = 0; |
| nclaims = 0; |
| } |
| break; |
| default: |
| // Invalid, should never happen. Restart the whole protocol. |
| VDBG("invalid state -- starting over\n"); |
| state = PROBE; |
| pick(&ip); |
| timeout_ms = 0; |
| nprobes = 0; |
| nclaims = 0; |
| break; |
| } // switch state |
| break; // case 1 (packets arriving) |
| } // switch poll |
| } // while (1) |
| } |