8445a9ff99
> Hi, > this is a first attempt of size optimization for zcip taking into account all > the hints given so far on the list. > I've applied just the more obvious busyboxifications so maybe it could be > optimized more. BTW: I've ripped out a lot of debug code and changed c++ // comments to /* */ as both were rather confusing for a newbie like me. ;-) Sorry to the author for that. I know that this makes mantaining the code easier, but I'm simple minded....
474 lines
12 KiB
C
474 lines
12 KiB
C
/*
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* RFC3927 ZeroConf IPv4 Link-Local addressing
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* (see <http://www.zeroconf.org/>)
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*
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* Copyright (C) 2003 by Arthur van Hoff (avh@strangeberry.com)
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* Copyright (C) 2004 by David Brownell
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
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* 02111-1307 USA
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*/
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/*
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* This can build as part of BusyBox or by itself:
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*
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* $(CROSS_COMPILE)cc -Os -Wall -DNO_BUSYBOX -DDEBUG -o zcip zcip.c
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*
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* ZCIP just manages the 169.254.*.* addresses. That network is not
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* routed at the IP level, though various proxies or bridges can
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* certainly be used. Its naming is built over multicast DNS.
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*/
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/* TODO:
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- more real-world usage/testing, especially daemon mode
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- kernel packet filters to reduce scheduling noise
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- avoid silent script failures, especially under load...
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- link status monitoring (restart on link-up; stop on link-down)
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*/
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#include <errno.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <string.h>
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#include <syslog.h>
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#include <poll.h>
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#include <time.h>
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#include <unistd.h>
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#include <sys/ioctl.h>
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#include <sys/types.h>
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#include <sys/wait.h>
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#include <sys/time.h>
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#include <sys/socket.h>
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#include <arpa/inet.h>
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#include <netinet/in.h>
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#include <netinet/ether.h>
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#include <net/ethernet.h>
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#include <net/if.h>
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#include <net/if_arp.h>
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#include <linux/if_packet.h>
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#include <linux/sockios.h>
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#include "busybox.h"
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#include "libbb.h"
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struct arp_packet {
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struct ether_header hdr;
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/* FIXME this part is netinet/if_ether.h "struct ether_arp" */
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struct arphdr arp;
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struct ether_addr source_addr;
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struct in_addr source_ip;
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struct ether_addr target_addr;
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struct in_addr target_ip;
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} __attribute__ ((__packed__));
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/* 169.254.0.0 */
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static const uint32_t LINKLOCAL_ADDR = 0xa9fe0000;
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/* protocol timeout parameters, specified in seconds */
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static const unsigned PROBE_WAIT = 1;
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static const unsigned PROBE_MIN = 1;
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static const unsigned PROBE_MAX = 2;
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static const unsigned PROBE_NUM = 3;
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static const unsigned MAX_CONFLICTS = 10;
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static const unsigned RATE_LIMIT_INTERVAL = 60;
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static const unsigned ANNOUNCE_WAIT = 2;
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static const unsigned ANNOUNCE_NUM = 2;
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static const unsigned ANNOUNCE_INTERVAL = 2;
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static const time_t DEFEND_INTERVAL = 10;
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#define ZCIP_VERSION "0.75 (18 April 2005)"
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static const struct in_addr null_ip = { 0 };
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static const struct ether_addr null_addr = { {0, 0, 0, 0, 0, 0} };
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/*
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* Pick a random link local IP address on 169.254/16, except that
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* the first and last 256 addresses are reserved.
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*/
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static void
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pick(struct in_addr *ip)
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{
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unsigned tmp;
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/* use cheaper math than lrand48() mod N */
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do {
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tmp = (lrand48() >> 16) & IN_CLASSB_HOST;
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} while (tmp > (IN_CLASSB_HOST - 0x0200));
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ip->s_addr = htonl((LINKLOCAL_ADDR + 0x0100) + tmp);
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}
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/*
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* Broadcast an ARP packet.
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*/
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static int
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arp(int fd, struct sockaddr *saddr, int op,
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const struct ether_addr *source_addr, struct in_addr source_ip,
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const struct ether_addr *target_addr, struct in_addr target_ip)
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{
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struct arp_packet p;
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/* ether header */
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p.hdr.ether_type = htons(ETHERTYPE_ARP);
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memcpy(p.hdr.ether_shost, source_addr, ETH_ALEN);
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memset(p.hdr.ether_dhost, 0xff, ETH_ALEN);
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/* arp request */
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p.arp.ar_hrd = htons(ARPHRD_ETHER);
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p.arp.ar_pro = htons(ETHERTYPE_IP);
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p.arp.ar_hln = ETH_ALEN;
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p.arp.ar_pln = 4;
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p.arp.ar_op = htons(op);
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memcpy(&p.source_addr, source_addr, ETH_ALEN);
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memcpy(&p.source_ip, &source_ip, sizeof (p.source_ip));
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memcpy(&p.target_addr, target_addr, ETH_ALEN);
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memcpy(&p.target_ip, &target_ip, sizeof (p.target_ip));
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/* send it */
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if (sendto(fd, &p, sizeof (p), 0, saddr, sizeof (*saddr)) < 0) {
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bb_perror_msg("sendto");
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return -errno;
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}
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return 0;
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}
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/*
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* Run a script.
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*/
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static int
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run(char *script, char *arg, char *intf, struct in_addr *ip)
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{
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int pid, status;
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char *why;
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if (script != NULL) {
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if (ip != NULL) {
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char *addr = inet_ntoa(*ip);
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xsetenv("ip", addr);
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syslog(LOG_INFO, "%s %s %s", arg, intf, addr);
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}
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pid = vfork();
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if (pid < 0) { /* error */
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why = "vfork";
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goto bad;
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} else if (pid == 0) { /* child */
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execl(script, script, arg, NULL);
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bb_perror_msg_and_die("execl");
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}
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if (waitpid(pid, &status, 0) <= 0) {
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why = "waitpid";
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goto bad;
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}
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if (WEXITSTATUS(status) != 0) {
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bb_perror_msg("script %s failed, exit=%d", script, WEXITSTATUS(status));
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return -errno;
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}
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}
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return 0;
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bad:
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status = -errno;
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syslog(LOG_ERR, "%s %s, %s error: %s",
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arg, intf, why, strerror(errno));
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return status;
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}
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/*
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* Return milliseconds of random delay, up to "secs" seconds.
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*/
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static inline unsigned
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ms_rdelay(unsigned secs)
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{
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return lrand48() % (secs * 1000);
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}
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/*
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* main program
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*/
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#define FOREGROUND 1
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#define QUIT 2
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#define REQUEST 4
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#define VERBOSE 8
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int zcip_main(int argc, char *argv[])
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{
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char *intf = NULL;
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char *script = NULL;
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char *why;
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struct sockaddr saddr;
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struct ether_addr addr;
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struct in_addr ip = { 0 };
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int fd;
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int ready = 0;
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suseconds_t timeout = 0; /* milliseconds */
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time_t defend = 0;
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unsigned conflicts = 0;
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unsigned nprobes = 0;
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unsigned nclaims = 0;
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unsigned long t;
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bb_opt_complementaly = "vf";
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/* parse commandline: prog [options] ifname script */
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t = bb_getopt_ulflags(argc, argv, "fqr:v", &why); /* reuse char* why */
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argc -= optind;
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argv += optind;
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if ((t & 0x80000000UL) || (argc < 1) || (argc > 2)) {
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bb_show_usage();
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}
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if (t & VERBOSE) {
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bb_printf("%s: version %s\n", bb_applet_name, ZCIP_VERSION);
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}
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if ((t & REQUEST) && (inet_aton(why, &ip) == 0 || (ntohl(ip.s_addr) & IN_CLASSB_NET) != LINKLOCAL_ADDR)) {
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bb_perror_msg_and_die("invalid link address");
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}
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intf = argv[0];
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xsetenv("interface", intf);
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script = argv[1]; /* Could be NULL ? */
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openlog(bb_applet_name, 0, LOG_DAEMON);
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/* initialize the interface (modprobe, ifup, etc) */
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if (run(script, "init", intf, NULL) < 0)
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return EXIT_FAILURE;
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/* initialize saddr */
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memset(&saddr, 0, sizeof (saddr));
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strncpy(saddr.sa_data, intf, sizeof (saddr.sa_data));
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/* open an ARP socket */
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if ((fd = socket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP))) < 0) {
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why = "open";
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fail:
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t |= FOREGROUND;
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goto bad;
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}
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/* bind to the interface's ARP socket */
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if (bind(fd, &saddr, sizeof (saddr)) < 0) {
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why = "bind";
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goto fail;
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} else {
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struct ifreq ifr;
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short seed[3];
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/* get the interface's ethernet address */
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memset(&ifr, 0, sizeof (ifr));
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strncpy(ifr.ifr_name, intf, sizeof (ifr.ifr_name));
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if (ioctl(fd, SIOCGIFHWADDR, &ifr) < 0) {
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why = "get ethernet address";
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goto fail;
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}
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memcpy(&addr, &ifr.ifr_hwaddr.sa_data, ETH_ALEN);
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/* start with some stable ip address, either a function of
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the hardware address or else the last address we used.
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NOTE: the sequence of addresses we try changes only
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depending on when we detect conflicts. */
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memcpy(seed, &ifr.ifr_hwaddr.sa_data, ETH_ALEN);
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seed48(seed);
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if (ip.s_addr == 0)
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pick(&ip);
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}
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/* FIXME cases to handle:
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- zcip already running!
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- link already has local address... just defend/update */
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/* daemonize now; don't delay system startup */
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if (!(t & FOREGROUND)) {
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if (daemon(0, (t & VERBOSE)) < 0) {
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why = "daemon";
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goto bad;
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}
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syslog(LOG_INFO, "start, interface %s", intf);
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}
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/* run the dynamic address negotiation protocol,
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restarting after address conflicts:
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- start with some address we want to try
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- short random delay
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- arp probes to see if another host else uses it
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- arp announcements that we're claiming it
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- use it
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- defend it, within limits */
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while (1) {
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struct pollfd fds[1];
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struct timeval tv1;
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struct arp_packet p;
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fds[0].fd = fd;
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fds[0].events = POLLIN;
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fds[0].revents = 0;
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/* poll, being ready to adjust current timeout */
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if (timeout > 0) {
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gettimeofday(&tv1, NULL);
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tv1.tv_usec += (timeout % 1000) * 1000;
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while (tv1.tv_usec > 1000000) {
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tv1.tv_usec -= 1000000;
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tv1.tv_sec++;
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}
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tv1.tv_sec += timeout / 1000;
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} else if (timeout == 0) {
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timeout = ms_rdelay(PROBE_WAIT);
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/* FIXME setsockopt(fd, SO_ATTACH_FILTER, ...) to
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make the kernel filter out all packets except
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ones we'd care about. */
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}
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switch (poll(fds, 1, timeout)) {
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/* timeouts trigger protocol transitions */
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case 0:
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/* probes */
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if (nprobes < PROBE_NUM) {
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nprobes++;
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(void)arp(fd, &saddr, ARPOP_REQUEST,
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&addr, null_ip,
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&null_addr, ip);
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if (nprobes < PROBE_NUM) {
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timeout = PROBE_MIN * 1000;
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timeout += ms_rdelay(PROBE_MAX
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- PROBE_MIN);
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} else
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timeout = ANNOUNCE_WAIT * 1000;
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}
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/* then announcements */
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else if (nclaims < ANNOUNCE_NUM) {
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nclaims++;
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(void)arp(fd, &saddr, ARPOP_REQUEST,
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&addr, ip,
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&addr, ip);
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if (nclaims < ANNOUNCE_NUM) {
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timeout = ANNOUNCE_INTERVAL * 1000;
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} else {
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/* link is ok to use earlier */
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run(script, "config", intf, &ip);
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ready = 1;
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conflicts = 0;
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timeout = -1;
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/* NOTE: all other exit paths
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should deconfig ... */
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if (t & QUIT)
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return EXIT_SUCCESS;
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/* FIXME update filters */
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}
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}
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break;
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/* packets arriving */
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case 1:
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/* maybe adjust timeout */
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if (timeout > 0) {
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struct timeval tv2;
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gettimeofday(&tv2, NULL);
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if (timercmp(&tv1, &tv2, <)) {
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timeout = -1;
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} else {
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timersub(&tv1, &tv2, &tv1);
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timeout = 1000 * tv1.tv_sec
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+ tv1.tv_usec / 1000;
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}
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}
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if ((fds[0].revents & POLLIN) == 0) {
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if (fds[0].revents & POLLERR) {
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/* FIXME: links routinely go down;
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this shouldn't necessarily exit. */
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bb_perror_msg("%s: poll error", intf);
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if (ready) {
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run(script, "deconfig", intf, &ip);
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}
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return EXIT_FAILURE;
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}
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continue;
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}
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/* read ARP packet */
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if (recv(fd, &p, sizeof (p), 0) < 0) {
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why = "recv";
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goto bad;
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}
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if (p.hdr.ether_type != htons(ETHERTYPE_ARP))
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continue;
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if (p.arp.ar_op != htons(ARPOP_REQUEST)
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&& p.arp.ar_op != htons(ARPOP_REPLY))
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continue;
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/* some cases are always conflicts */
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if ((p.source_ip.s_addr == ip.s_addr)
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&& (memcmp(&addr, &p.source_addr,
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ETH_ALEN) != 0)) {
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collision:
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if (ready) {
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time_t now = time(0);
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if ((defend + DEFEND_INTERVAL)
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< now) {
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defend = now;
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(void)arp(fd, &saddr,
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ARPOP_REQUEST,
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&addr, ip,
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&addr, ip);
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timeout = -1;
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continue;
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}
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defend = now;
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ready = 0;
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run(script, "deconfig", intf, &ip);
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/* FIXME rm filters: setsockopt(fd,
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SO_DETACH_FILTER, ...) */
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}
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conflicts++;
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if (conflicts >= MAX_CONFLICTS) {
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sleep(RATE_LIMIT_INTERVAL);
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}
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/* restart the whole protocol */
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pick(&ip);
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timeout = 0;
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nprobes = 0;
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nclaims = 0;
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}
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/* two hosts probing one address is a collision too */
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else if (p.target_ip.s_addr == ip.s_addr
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&& nclaims == 0
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&& p.arp.ar_op == htons(ARPOP_REQUEST)
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&& memcmp(&addr, &p.target_addr,
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ETH_ALEN) != 0) {
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goto collision;
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}
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break;
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default:
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why = "poll";
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goto bad;
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}
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}
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bad:
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if ( t & FOREGROUND) {
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bb_perror_msg(why);
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} else {
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syslog(LOG_ERR, "%s %s, %s error: %s",
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bb_applet_name, intf, why, strerror(errno));
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}
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return EXIT_FAILURE;
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}
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