/* vi: set sw=4 ts=4: */ /* * RFC3927 ZeroConf IPv4 Link-Local addressing * (see ) * * 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 #include #include #include #include #include #include "libbb.h" #include /* 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 { /* 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 { struct sockaddr saddr; struct ether_addr eth_addr; }; #define G (*(struct globals*)&bb_common_bufsiz1) #define saddr (G.saddr ) #define eth_addr (G.eth_addr) /** * 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(void) { unsigned tmp; do { tmp = rand() & IN_CLASSB_HOST; } while (tmp > (IN_CLASSB_HOST - 0x0200)); return htonl((LINKLOCAL_ADDR + 0x0100) + tmp); } /** * Broadcast an ARP packet. */ static void arp( /* int op, - always ARPOP_REQUEST */ /* const struct ether_addr *source_eth, - always ð_addr */ struct in_addr source_ip, const struct ether_addr *target_eth, struct in_addr target_ip) { enum { op = ARPOP_REQUEST }; #define source_eth (ð_addr) 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 // Even though sock_fd is already bound to saddr, just send() // won't work, because "socket is not connected" // (and connect() won't fix that, "operation not supported"). // Thus we sendto() to saddr. 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), &saddr, sizeof(saddr)); #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, struct in_addr *ip) { int status; 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 (ip) { addr = inet_ntoa(*ip); xsetenv("ip", addr); fmt -= 3; } bb_info_msg(fmt, argv[2], argv[0], addr); status = wait4pid(spawn(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); return status; } /** * Return milliseconds of random delay, up to "secs" seconds. */ static ALWAYS_INLINE unsigned 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; 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; 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 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 !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; } 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"); } } argc -= optind; 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", 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, argv_intf, sizeof(saddr.sa_data)); // 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_IFNAMSIZ(ifr.ifr_name, argv_intf); 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 = get_unaligned_u32p((uint32_t *) ((char *)ð_addr + 2)); srand(t); } if (ip.s_addr == 0) ip.s_addr = pick(); // 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 // - arp announcements that we're claiming it // - use it // - defend it, within limits // exit if: // - address is successfully obtained and -q was given: // run "