diff options
Diffstat (limited to 'networking/zcip.c')
| -rw-r--r-- | networking/zcip.c | 546 |
1 files changed, 546 insertions, 0 deletions
diff --git a/networking/zcip.c b/networking/zcip.c new file mode 100644 index 0000000..27e281c --- /dev/null +++ b/networking/zcip.c @@ -0,0 +1,546 @@ +/* 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 "busybox.h" +#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> + + +struct arp_packet { + struct ether_header hdr; + 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(fmt,args...) \ + do { } while (0) + +static unsigned opts; +#define FOREGROUND (opts & 1) +#define QUIT (opts & 2) + +/** + * 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; + + /* use cheaper math than lrand48() mod N */ + do { + tmp = (lrand48() >> 16) & IN_CLASSB_HOST; + } while (tmp > (IN_CLASSB_HOST - 0x0200)); + ip->s_addr = htonl((LINKLOCAL_ADDR + 0x0100) + tmp); +} + +/* TODO: we need a flag to direct bb_[p]error_msg output to stderr. */ + +/** + * Broadcast an ARP packet. + */ +static void arp(int fd, struct sockaddr *saddr, int op, + const struct ether_addr *source_addr, struct in_addr source_ip, + const struct ether_addr *target_addr, struct in_addr target_ip) +{ + struct arp_packet p; + memset(&p, 0, sizeof(p)); + + // ether header + p.hdr.ether_type = htons(ETHERTYPE_ARP); + memcpy(p.hdr.ether_shost, source_addr, ETH_ALEN); + memset(p.hdr.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_addr, ETH_ALEN); + memcpy(&p.arp.arp_spa, &source_ip, sizeof (p.arp.arp_spa)); + memcpy(&p.arp.arp_tha, target_addr, ETH_ALEN); + memcpy(&p.arp.arp_tpa, &target_ip, sizeof (p.arp.arp_tpa)); + + // send it + if (sendto(fd, &p, sizeof (p), 0, saddr, sizeof (*saddr)) < 0) { + bb_perror_msg("sendto"); + //return -errno; + } + // Currently all callers ignore errors, that's why returns are + // commented out... + //return 0; +} + +/** + * Run a script. + */ +static int run(char *script, char *arg, char *intf, struct in_addr *ip) +{ + int pid, status; + char *why; + + if(1) { //always true: if (script != NULL) + VDBG("%s run %s %s\n", intf, script, arg); + if (ip != NULL) { + char *addr = inet_ntoa(*ip); + setenv("ip", addr, 1); + bb_info_msg("%s %s %s", arg, intf, addr); + } + + pid = vfork(); + if (pid < 0) { // error + why = "vfork"; + goto bad; + } else if (pid == 0) { // child + execl(script, script, arg, NULL); + bb_perror_msg("execl"); + _exit(EXIT_FAILURE); + } + + if (waitpid(pid, &status, 0) <= 0) { + why = "waitpid"; + goto bad; + } + if (WEXITSTATUS(status) != 0) { + bb_error_msg("script %s failed, exit=%d", + script, WEXITSTATUS(status)); + return -errno; + } + } + return 0; +bad: + status = -errno; + bb_perror_msg("%s %s, %s", arg, intf, why); + return status; +} + + +/** + * Return milliseconds of random delay, up to "secs" seconds. + */ +static unsigned ATTRIBUTE_ALWAYS_INLINE ms_rdelay(unsigned secs) +{ + return lrand48() % (secs * 1000); +} + +/** + * main program + */ + +/* Used to be auto variables on main() stack, but + * most of them were zero-inited. Moving them to bss + * is more space-efficient. + */ +static const struct in_addr null_ip; // = { 0 }; +static const struct ether_addr null_addr; // = { {0, 0, 0, 0, 0, 0} }; + +static struct sockaddr saddr; // memset(0); +static struct in_addr ip; // = { 0 }; +static struct ifreq ifr; //memset(0); + +static char *intf; // = NULL; +static char *script; // = NULL; +static suseconds_t timeout; // = 0; // milliseconds +static unsigned conflicts; // = 0; +static unsigned nprobes; // = 0; +static unsigned nclaims; // = 0; +static int ready; // = 0; +static int verbose; // = 0; +static int state = PROBE; + +int zcip_main(int argc, char *argv[]) +{ + struct ether_addr eth_addr; + char *why; + int fd; + + // parse commandline: prog [options] ifname script + char *r_opt; + opt_complementary = "vv:vf"; // -v accumulates and implies -f + opts = getopt32(argc, argv, "fqr:v", &r_opt, &verbose); + if (!FOREGROUND) { + /* Do it early, before all bb_xx_msg calls */ + logmode = LOGMODE_SYSLOG; + openlog(applet_name, 0, LOG_DAEMON); + } + 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; + if (argc != 2) + bb_show_usage(); + intf = argv[0]; + script = argv[1]; + setenv("interface", intf, 1); + + // initialize the interface (modprobe, ifup, etc) + if (run(script, "init", intf, NULL) < 0) + return EXIT_FAILURE; + + // initialize saddr + //memset(&saddr, 0, sizeof (saddr)); + safe_strncpy(saddr.sa_data, intf, sizeof (saddr.sa_data)); + + // open an ARP socket + fd = xsocket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP)); + // bind to the interface's ARP socket + xbind(fd, &saddr, sizeof (saddr)); + + // get the interface's ethernet address + //memset(&ifr, 0, sizeof (ifr)); + strncpy(ifr.ifr_name, intf, sizeof (ifr.ifr_name)); + if (ioctl(fd, SIOCGIFHWADDR, &ifr) < 0) { + bb_perror_msg_and_die("get ethernet address"); + } + 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. + // NOTE: the sequence of addresses we try changes only + // depending on when we detect conflicts. + // (SVID 3 bogon: who says that "short" is always 16 bits?) + seed48( (unsigned short*)&ifr.ifr_hwaddr.sa_data ); + 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) { + setsid(); + xdaemon(0, 0); + 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]; + struct timeval tv1; + struct arp_packet p; + + int source_ip_conflict = 0; + int target_ip_conflict = 0; + + fds[0].fd = fd; + fds[0].events = POLLIN; + fds[0].revents = 0; + + // poll, being ready to adjust current timeout + if (!timeout) { + timeout = ms_rdelay(PROBE_WAIT); + // FIXME setsockopt(fd, SO_ATTACH_FILTER, ...) to + // make the kernel filter out all packets except + // ones we'd care about. + } + // set tv1 to the point in time when we timeout + gettimeofday(&tv1, NULL); + tv1.tv_usec += (timeout % 1000) * 1000; + while (tv1.tv_usec > 1000000) { + tv1.tv_usec -= 1000000; + tv1.tv_sec++; + } + tv1.tv_sec += timeout / 1000; + + VDBG("...wait %ld %s nprobes=%d, nclaims=%d\n", + timeout, intf, nprobes, nclaims); + switch (poll(fds, 1, timeout)) { + + // 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/%d %s@%s\n", + nprobes, intf, inet_ntoa(ip)); + arp(fd, &saddr, ARPOP_REQUEST, + ð_addr, null_ip, + &null_addr, ip); + timeout = PROBE_MIN * 1000; + timeout += ms_rdelay(PROBE_MAX + - PROBE_MIN); + } + else { + // Switch to announce state. + state = ANNOUNCE; + nclaims = 0; + VDBG("announce/%d %s@%s\n", + nclaims, intf, inet_ntoa(ip)); + arp(fd, &saddr, ARPOP_REQUEST, + ð_addr, ip, + ð_addr, ip); + timeout = 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/%d %s@%s\n", + nclaims, intf, inet_ntoa(ip)); + arp(fd, &saddr, ARPOP_REQUEST, + ð_addr, ip, + ð_addr, ip); + timeout = 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/%d %s@%s\n", + nclaims, intf, inet_ntoa(ip)); + arp(fd, &saddr, ARPOP_REQUEST, + ð_addr, ip, + ð_addr, ip); + timeout = ANNOUNCE_INTERVAL * 1000; + } + else { + // Switch to monitor state. + state = MONITOR; + // link is ok to use earlier + // FIXME update filters + run(script, "config", intf, &ip); + ready = 1; + conflicts = 0; + timeout = -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 = -1; + conflicts = 0; + break; + default: + // Invalid, should never happen. Restart the whole protocol. + state = PROBE; + pick(&ip); + timeout = 0; + nprobes = 0; + nclaims = 0; + break; + } // switch (state) + break; // case 0 (timeout) + // packets arriving + case 1: + // We need to adjust the timeout in case we didn't receive + // a conflicting packet. + if (timeout > 0) { + struct timeval tv2; + + gettimeofday(&tv2, NULL); + if (timercmp(&tv1, &tv2, <)) { + // Current time is greater than the expected timeout time. + // Should never happen. + VDBG("missed an expected timeout\n"); + timeout = 0; + } else { + VDBG("adjusting timeout\n"); + timersub(&tv1, &tv2, &tv1); + timeout = 1000 * tv1.tv_sec + + tv1.tv_usec / 1000; + } + } + + if ((fds[0].revents & POLLIN) == 0) { + if (fds[0].revents & POLLERR) { + // FIXME: links routinely go down; + // this shouldn't necessarily exit. + bb_error_msg("%s: poll error", intf); + if (ready) { + run(script, "deconfig", + intf, &ip); + } + return EXIT_FAILURE; + } + continue; + } + + // read ARP packet + if (recv(fd, &p, sizeof (p), 0) < 0) { + why = "recv"; + goto bad; + } + if (p.hdr.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.hdr.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; + + if (memcmp(p.arp.arp_spa, &ip.s_addr, sizeof(struct in_addr)) == 0 && + memcmp(ð_addr, &p.arp.arp_sha, ETH_ALEN) != 0) { + source_ip_conflict = 1; + } + if (memcmp(p.arp.arp_tpa, &ip.s_addr, sizeof(struct in_addr)) == 0 && + p.arp.arp_op == htons(ARPOP_REQUEST) && + memcmp(ð_addr, &p.arp.arp_tha, 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 = RATE_LIMIT_INTERVAL * 1000; + state = RATE_LIMIT_PROBE; + } + + // restart the whole protocol + pick(&ip); + timeout = 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 = DEFEND_INTERVAL * 1000; + arp(fd, &saddr, + 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; + run(script, "deconfig", intf, &ip); + + // restart the whole protocol + pick(&ip); + timeout = 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 = 0; + nprobes = 0; + nclaims = 0; + break; + } // switch state + + break; // case 1 (packets arriving) + default: + why = "poll"; + goto bad; + } // switch poll + } +bad: + bb_perror_msg("%s, %s", intf, why); + return EXIT_FAILURE; +} |