diff options
| -rw-r--r-- | examples/zcip.script | 38 | ||||
| -rw-r--r-- | include/applets.h | 3 | ||||
| -rw-r--r-- | include/usage.h | 10 | ||||
| -rw-r--r-- | networking/Config.in | 11 | ||||
| -rw-r--r-- | networking/Makefile.in | 1 | ||||
| -rw-r--r-- | networking/zcip.c | 550 |
6 files changed, 613 insertions, 0 deletions
diff --git a/examples/zcip.script b/examples/zcip.script new file mode 100644 index 0000000..988e542 --- /dev/null +++ b/examples/zcip.script @@ -0,0 +1,38 @@ +#!/bin/sh + +# only for use as a "zcip" callback script +if [ "x$interface" = x ] +then + exit 1 +fi + +# zcip should start on boot/resume and various media changes +case "$1" in +init) + # for now, zcip requires the link to be already up, + # and it drops links when they go down. that isn't + # the most robust model... + exit 0 + ;; +config) + if [ "x$ip" = x ] + then + exit 1 + fi + # remember $ip for $interface, to use on restart + if [ "x$IP" != x -a -w "$IP.$interface" ] + then + echo $ip > "$IP.$interface" + fi + exec ip address add dev $interface \ + scope link local "$ip/16" broadcast + + ;; +deconfig) + if [ x$ip = x ] + then + exit 1 + fi + exec ip address del dev $interface local $ip + ;; +esac +exit 1 diff --git a/include/applets.h b/include/applets.h index 755eb01..7f6f758 100644 --- a/include/applets.h +++ b/include/applets.h @@ -692,6 +692,9 @@ #ifdef CONFIG_GUNZIP APPLET(zcat, gunzip_main, _BB_DIR_BIN, _BB_SUID_NEVER) #endif +#ifdef CONFIG_ZCIP + APPLET(zcip, zcip_main, _BB_DIR_SBIN, _BB_SUID_NEVER) +#endif #if !defined(PROTOTYPES) && !defined(MAKE_USAGE) { 0,NULL,0 } diff --git a/include/usage.h b/include/usage.h index 04d6ff4..b57644b 100644 --- a/include/usage.h +++ b/include/usage.h @@ -3038,4 +3038,14 @@ #define zcat_full_usage \ "Uncompress to stdout." +#define zcip_trivial_usage \ + "[OPTIONS] ifname script" +#define zcip_full_usage \ + "zcip manages a ZeroConf IPv4 link-local address.\n" \ + "Options:\n" \ + "\t-f foreground mode\n" \ + "\t-q quit after address (no daemon)\n" \ + "\t-r 169.254.x.x request this address first\n" \ + "\t-v verbose; show version\n" + #endif /* __BB_USAGE_H__ */ diff --git a/networking/Config.in b/networking/Config.in index cf2f1dc..418ef4b 100644 --- a/networking/Config.in +++ b/networking/Config.in @@ -637,5 +637,16 @@ config CONFIG_FEATURE_WGET_IP6_LITERAL source networking/udhcp/Config.in +config CONFIG_ZCIP + bool "zcip" + default n + help + ZCIP provides ZeroConf IPv4 address selection, according to RFC 3927. + It's a daemon that allocates and defends a dynamically assigned + address on the 169.254/16 network, requiring no system administrator. + + See http://www.zeroconf.org for further details, and "zcip.script" + in the busybox examples. + endmenu diff --git a/networking/Makefile.in b/networking/Makefile.in index 4e27dbc..778d0ba 100644 --- a/networking/Makefile.in +++ b/networking/Makefile.in @@ -51,6 +51,7 @@ NETWORKING-$(CONFIG_TFTP) += tftp.o NETWORKING-$(CONFIG_TRACEROUTE) += traceroute.o NETWORKING-$(CONFIG_VCONFIG) += vconfig.o NETWORKING-$(CONFIG_WGET) += wget.o +NETWORKING-$(CONFIG_ZCIP) += zcip.o libraries-y+=$(NETWORKING_DIR)$(NETWORKING_AR) diff --git a/networking/zcip.c b/networking/zcip.c new file mode 100644 index 0000000..ccf399b --- /dev/null +++ b/networking/zcip.c @@ -0,0 +1,550 @@ +/* + * 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 + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA + * 02111-1307 USA + */ + +/* + * This can build as part of BusyBox or by itself: + * + * $(CROSS_COMPILE)cc -Os -Wall -DNO_BUSYBOX -DDEBUG -o zcip zcip.c + * + * 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 <errno.h> +#include <stdlib.h> +#include <stdio.h> +#include <string.h> +#include <syslog.h> +#include <poll.h> +#include <time.h> +#include <unistd.h> + +#include <sys/ioctl.h> +#include <sys/types.h> +#include <sys/wait.h> +#include <sys/time.h> +#include <sys/socket.h> + +#include <arpa/inet.h> +#include <netinet/in.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; + // FIXME this part is netinet/if_ether.h "struct ether_arp" + struct arphdr arp; + struct ether_addr source_addr; + struct in_addr source_ip; + struct ether_addr target_addr; + struct in_addr target_ip; +} __attribute__ ((__packed__)); + +/* 169.254.0.0 */ +static const uint32_t LINKLOCAL_ADDR = 0xa9fe0000; + +/* protocol timeout parameters, specified in seconds */ +static const unsigned PROBE_WAIT = 1; +static const unsigned PROBE_MIN = 1; +static const unsigned PROBE_MAX = 2; +static const unsigned PROBE_NUM = 3; +static const unsigned MAX_CONFLICTS = 10; +static const unsigned RATE_LIMIT_INTERVAL = 60; +static const unsigned ANNOUNCE_WAIT = 2; +static const unsigned ANNOUNCE_NUM = 2; +static const unsigned ANNOUNCE_INTERVAL = 2; +static const time_t DEFEND_INTERVAL = 10; + +static const unsigned char ZCIP_VERSION[] = "0.75 (18 April 2005)"; +static char *prog; + +static const struct in_addr null_ip = { 0 }; +static const struct ether_addr null_addr = { {0, 0, 0, 0, 0, 0} }; + +static int verbose = 0; + +#ifdef DEBUG + +#define DBG(fmt,args...) \ + fprintf(stderr, "%s: " fmt , prog , ## args) +#define VDBG(fmt,args...) do { \ + if (verbose) fprintf(stderr, "%s: " fmt , prog ,## args); \ + } while (0) +#else + +#define DBG(fmt,args...) \ + do { } while (0) +#define VDBG DBG +#endif /* DEBUG */ + +/** + * 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); +} + +/** + * Broadcast an ARP packet. + */ +static int +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; + + // 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.ar_hrd = htons(ARPHRD_ETHER); + p.arp.ar_pro = htons(ETHERTYPE_IP); + p.arp.ar_hln = ETH_ALEN; + p.arp.ar_pln = 4; + p.arp.ar_op = htons(op); + memcpy(&p.source_addr, source_addr, ETH_ALEN); + memcpy(&p.source_ip, &source_ip, sizeof (p.source_ip)); + memcpy(&p.target_addr, target_addr, ETH_ALEN); + memcpy(&p.target_ip, &target_ip, sizeof (p.target_ip)); + + // send it + if (sendto(fd, &p, sizeof (p), 0, saddr, sizeof (*saddr)) < 0) { + perror("sendto"); + return -errno; + } + return 0; +} + +/** + * Run a script. + */ +static int +run(char *script, char *arg, char *intf, struct in_addr *ip) +{ + int pid, status; + char *why; + + if (script != NULL) { + VDBG("%s run %s %s\n", intf, script, arg); + if (ip != NULL) { + char *addr = inet_ntoa(*ip); + setenv("ip", addr, 1); + syslog(LOG_INFO, "%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); + perror("execl"); + _exit(EXIT_FAILURE); + } + + if (waitpid(pid, &status, 0) <= 0) { + why = "waitpid"; + goto bad; + } + if (WEXITSTATUS(status) != 0) { + fprintf(stderr, "%s: script %s failed, exit=%d\n", + prog, script, WEXITSTATUS(status)); + return -errno; + } + } + return 0; +bad: + status = -errno; + syslog(LOG_ERR, "%s %s, %s error: %s", + arg, intf, why, strerror(errno)); + return status; +} + +#ifndef NO_BUSYBOX +#include "busybox.h" +#endif + +/** + * Print usage information. + */ +static void __attribute__ ((noreturn)) +usage(const char *msg) +{ + fprintf(stderr, "%s: %s\n", prog, msg); +#ifdef NO_BUSYBOX + fprintf(stderr, "Usage: %s [OPTIONS] ifname script\n" + "\t-f foreground mode (implied by -v)\n" + "\t-q quit after address (no daemon)\n" + "\t-r 169.254.x.x request this address first\n" + "\t-v verbose; show version\n", + prog); + exit(0); +#else + bb_show_usage(); +#endif +} + +/** + * Return milliseconds of random delay, up to "secs" seconds. + */ +static inline unsigned +ms_rdelay(unsigned secs) +{ + return lrand48() % (secs * 1000); +} + +/** + * main program + */ +int +main(int argc, char *argv[]) + __attribute__ ((weak, alias ("zcip_main"))); + +int zcip_main(int argc, char *argv[]) +{ + char *intf = NULL; + char *script = NULL; + int quit = 0; + int foreground = 0; + + char *why; + struct sockaddr saddr; + struct ether_addr addr; + struct in_addr ip = { 0 }; + int fd; + int ready = 0; + suseconds_t timeout = 0; // milliseconds + time_t defend = 0; + unsigned conflicts = 0; + unsigned nprobes = 0; + unsigned nclaims = 0; + int t; + + // parse commandline: prog [options] ifname script + prog = argv[0]; + while ((t = getopt(argc, argv, "fqr:v")) != EOF) { + switch (t) { + case 'f': + foreground = 1; + continue; + case 'q': + quit = 1; + continue; + case 'r': + if (inet_aton(optarg, &ip) == 0 + || (ntohl(ip.s_addr) & IN_CLASSB_NET) + != LINKLOCAL_ADDR) { + usage("invalid link address"); + } + continue; + case 'v': + if (!verbose) + printf("%s: version %s\n", prog, ZCIP_VERSION); + verbose++; + foreground = 1; + continue; + default: + usage("bad option"); + } + } + if (optind < argc - 1) { + intf = argv[optind++]; + setenv("interface", intf, 1); + script = argv[optind++]; + } + if (optind != argc || !intf) + usage("wrong number of arguments"); + openlog(prog, 0, LOG_DAEMON); + + // initialize the interface (modprobe, ifup, etc) + if (run(script, "init", intf, NULL) < 0) + return EXIT_FAILURE; + + // initialize saddr + memset(&saddr, 0, sizeof (saddr)); + strncpy(saddr.sa_data, intf, sizeof (saddr.sa_data)); + + // open an ARP socket + if ((fd = socket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP))) < 0) { + why = "open"; +fail: + foreground = 1; + goto bad; + } + // bind to the interface's ARP socket + if (bind(fd, &saddr, sizeof (saddr)) < 0) { + why = "bind"; + goto fail; + } else { + struct ifreq ifr; + short seed[3]; + + // 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) { + why = "get ethernet address"; + goto fail; + } + memcpy(&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. + memcpy(seed, &ifr.ifr_hwaddr.sa_data, ETH_ALEN); + seed48(seed); + 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 (daemon(0, verbose) < 0) { + why = "daemon"; + goto bad; + } + syslog(LOG_INFO, "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; + + fds[0].fd = fd; + fds[0].events = POLLIN; + fds[0].revents = 0; + + // poll, being ready to adjust current timeout + if (timeout > 0) { + 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; + } else if (timeout == 0) { + 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. + } + VDBG("...wait %ld %s nprobes=%d, nclaims=%d\n", + timeout, intf, nprobes, nclaims); + switch (poll(fds, 1, timeout)) { + + // timeouts trigger protocol transitions + case 0: + // probes + if (nprobes < PROBE_NUM) { + nprobes++; + VDBG("probe/%d %s@%s\n", + nprobes, intf, inet_ntoa(ip)); + (void)arp(fd, &saddr, ARPOP_REQUEST, + &addr, null_ip, + &null_addr, ip); + if (nprobes < PROBE_NUM) { + timeout = PROBE_MIN * 1000; + timeout += ms_rdelay(PROBE_MAX + - PROBE_MIN); + } else + timeout = ANNOUNCE_WAIT * 1000; + } + // then announcements + else if (nclaims < ANNOUNCE_NUM) { + nclaims++; + VDBG("announce/%d %s@%s\n", + nclaims, intf, inet_ntoa(ip)); + (void)arp(fd, &saddr, ARPOP_REQUEST, + &addr, ip, + &addr, ip); + if (nclaims < ANNOUNCE_NUM) { + timeout = ANNOUNCE_INTERVAL * 1000; + } else { + // link is ok to use earlier + run(script, "config", intf, &ip); + ready = 1; + conflicts = 0; + timeout = -1; + + // NOTE: all other exit paths + // should deconfig ... + if (quit) + return EXIT_SUCCESS; + // FIXME update filters + } + } + break; + + // packets arriving + case 1: + // maybe adjust timeout + if (timeout > 0) { + struct timeval tv2; + + gettimeofday(&tv2, NULL); + if (timercmp(&tv1, &tv2, <)) { + timeout = -1; + } else { + 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. + fprintf(stderr, "%s %s: poll error\n", + prog, 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; + + VDBG("%s recv arp type=%d, op=%d,\n", + intf, ntohs(p.hdr.ether_type), + ntohs(p.arp.ar_op)); + VDBG("\tsource=%s %s\n", + ether_ntoa(&p.source_addr), + inet_ntoa(p.source_ip)); + VDBG("\ttarget=%s %s\n", + ether_ntoa(&p.target_addr), + inet_ntoa(p.target_ip)); + if (p.arp.ar_op != htons(ARPOP_REQUEST) + && p.arp.ar_op != htons(ARPOP_REPLY)) + continue; + + // some cases are always conflicts + if ((p.source_ip.s_addr == ip.s_addr) + && (memcmp(&addr, &p.source_addr, + ETH_ALEN) != 0)) { +collision: + VDBG("%s ARP conflict from %s\n", intf, + ether_ntoa(&p.source_addr)); + if (ready) { + time_t now = time(0); + + if ((defend + DEFEND_INTERVAL) + < now) { + defend = now; + (void)arp(fd, &saddr, + ARPOP_REQUEST, + &addr, ip, + &addr, ip); + VDBG("%s defend\n", intf); + timeout = -1; + continue; + } + defend = now; + ready = 0; + run(script, "deconfig", intf, &ip); + // FIXME rm filters: setsockopt(fd, + // SO_DETACH_FILTER, ...) + } + conflicts++; + if (conflicts >= MAX_CONFLICTS) { + VDBG("%s ratelimit\n", intf); + sleep(RATE_LIMIT_INTERVAL); + } + // restart the whole protocol + pick(&ip); + timeout = 0; + nprobes = 0; + nclaims = 0; + } + // two hosts probing one address is a collision too + else if (p.target_ip.s_addr == ip.s_addr + && nclaims == 0 + && p.arp.ar_op == htons(ARPOP_REQUEST) + && memcmp(&addr, &p.target_addr, + ETH_ALEN) != 0) { + goto collision; + } + break; + + default: + why = "poll"; + goto bad; + } + } +bad: + if (foreground) + perror(why); + else + syslog(LOG_ERR, "%s %s, %s error: %s", + prog, intf, why, strerror(errno)); + return EXIT_FAILURE; +} |