[BusyBox] ZeroConf IP (ZCIP) for BusyBox

Pantelis Antoniou panto at intracom.gr
Mon Oct 25 06:55:12 UTC 2004


David Brownell wrote:

>Hi,
>
>There's an IETF working group that's been working on how IP networks would
>work with "zero configuration" effort required.  Summary:  use 169.254/16
>and multicast DNS, and your devices can be "network admins R optional"
>(within certain constraints).  Also, see Apple's "Rendezvous" stuff.
>
>I know several folk have wanted embeddable versions of the IP addressing
>code, so here's a version that fits in less than 3KB code on ARM, as part
>of BusyBox.  Add multicast DNS (one person said 38KB on XScale) and
>your system can start to offer some interesting capabilities ...
>
>Drop a line if you find this code useful, especially if you have patches.
>The code is a bit young for my taste, I expect it'll need some tweaks
>to work better on busy networks (with lots of ARP traffic).
>
>Tested on Linux 2.6.recent, on ARM and (standalone, no BusyBox) x86.
>
>- Dave
>
>
>
>
>  
>
>------------------------------------------------------------------------
>
>This patch adds ZeroConf IP address allocation support to BusyBox, adding
>less than 3KB ARM code.  Run by
>
>	zcip eth0 /etc/zcip.script
>
>A sample script is included.
>
>It's a pretty close match to draft-ietf-zeroconf-ipv4-linklocal-17.txt (the
>July 2004 version) but this version has only had light testing so far: no
>busy networks, in particular.  For now, avoid large deployments relying on
>this implementation without additional testing.
>
>
>
>--- busybox-1.00/docs/busybox_header.pod	2004-08-16 03:29:29.000000000 -0700
>+++ busybox/docs/busybox_header.pod	2004-10-18 15:33:42.000000000 -0700
>@@ -102,7 +102,7 @@
> 	touch, tr, traceroute, true, tty, udhcpc, udhcpd, umount, uname,
> 	uncompress, uniq, unix2dos, unzip, uptime, usleep, uudecode, uuencode,
> 	vconfig, vi, vlock, watch, watchdog, wc, wget, which, who, whoami, xargs,
>-	yes, zcat
>+	yes, zcat, zcip
> 
> =head1 COMMAND DESCRIPTIONS
> 
>--- busybox-1.00/examples/zcip.script	1969-12-31 16:00:00.000000000 -0800
>+++ busybox/examples/zcip.script	2004-10-18 15:33:42.000000000 -0700
>@@ -0,0 +1,34 @@
>+#!/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 "$1" in
>+init)
>+	# for now, zcip requires the link to be already up,
>+	# and it drops links when they go down.  that may
>+	# not be the most robust model.
>+	exit 0
>+	;;
>+config)
>+	if [ x$ip = x ]
>+	then
>+		exit 1
>+	fi
>+	# FIXME remember $ip for $interface, to use on restart
>+	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 $ip
>+	;;
>+esac
>+exit 1
>--- busybox-1.00/include/applets.h	2004-08-26 16:01:34.000000000 -0700
>+++ busybox/include/applets.h	2004-10-18 15:33:42.000000000 -0700
>@@ -670,6 +670,9 @@
> #ifdef CONFIG_GUNZIP
> 	APPLET(zcat, gunzip_main, _BB_DIR_BIN, _BB_SUID_NEVER)
> #endif
>+#ifdef CONFIG_ZCIP
>+	APPLET(zcip, zcip_main, _BB_DIR_SBIN, _BB_SUID_NEVER)
>+#endif
> 
> #if !defined(PROTOTYPES) && !defined(MAKE_USAGE)
> 	{ 0,NULL,0 }
>--- busybox-1.00/include/usage.h	2004-09-14 09:23:56.000000000 -0700
>+++ busybox/include/usage.h	2004-10-18 15:33:42.000000000 -0700
>@@ -2882,4 +2882,14 @@
> #define zcat_full_usage \
> 	"Uncompress to stdout."
> 
>+#define zcip_trivial_usage \
>+	"[OPTIONS] ifname script"
>+#define zcip_full_usage \
>+	"zcip manages a ZeroConf IPv4 link-local address.\n" \
>+	"Options:\n" \
>+	"\t-f              foreground mode\n" \
>+	"\t-q              quit after address (no daemon)\n" \
>+	"\t-r 169.254.x.x  request this address first\n" \
>+	"\t-v              verbose; show version\n"
>+
> #endif /* __BB_USAGE_H__ */
>--- busybox-1.00/networking/Config.in	2004-09-23 13:08:46.000000000 -0700
>+++ busybox/networking/Config.in	2004-10-18 15:33:42.000000000 -0700
>@@ -630,5 +630,14 @@
> 
> source networking/udhcp/Config.in
> 
>+config CONFIG_ZCIP
>+	bool "zcip"
>+	default n
>+	help
>+	  zcip supports ZeroConf IPv4 address selection:
>+	  it manages an address on the 169.254/16 network.
>+
>+	  See http://www.zeroconf.org for further details.
>+
> endmenu
> 
>--- busybox-1.00/networking/Makefile.in	2004-10-08 00:45:43.000000000 -0700
>+++ busybox/networking/Makefile.in	2004-10-20 01:48:43.504468768 -0700
>@@ -50,6 +50,7 @@
> NETWORKING-$(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)
> 
>--- busybox-1.00/networking/zcip.c	1969-12-31 16:00:00.000000000 -0800
>+++ busybox/networking/zcip.c	2004-10-20 02:18:13.390405208 -0700
>@@ -0,0 +1,558 @@
>+/*
>+ * ZeroConf IPv4 Link-Local addressing (see <http://www.zeroconf.org/>)
>+ *
>+ * Copyright (C) 2003 by Arthur van Hoff (avh at 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 is a user-mode implementation that's a pretty close match to
>+ * draft-ietf-zeroconf-ipv4-linklocal-17.txt (the July 2004 version).
>+ * It can build as part of BusyBox or by itself:
>+ *
>+ *	cc -Os -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 scripts failures, especially under load...
>+	// - implement some syslog option '-s'
>+	// - link status monitoring
>+
>+#include <errno.h>
>+#include <stdlib.h>
>+#include <stdio.h>
>+#include <string.h>
>+#include <time.h>
>+#include <unistd.h>
>+
>+#include <sys/ioctl.h>
>+#include <sys/types.h>
>+#include <sys/poll.h>
>+#include <sys/wait.h>
>+#include <sys/time.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;
>+	struct arphdr arp;
>+	struct ether_addr source_addr;
>+	struct in_addr source_ip;
>+	struct ether_addr target_addr;
>+	struct in_addr target_ip;
>+	unsigned char pad[18];
>+} __attribute__ ((__packed__));
>+
>+/* 169.254.0.0 */
>+static uint32_t LINKLOCAL_ADDR = 0xa9fe0000;
>+static uint32_t LINKLOCAL_MASK = 0xFFFF0000;
>+
>+/* 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_COLLISIONS = 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 unsigned DEFEND_INTERVAL = 10;
>+
>+static const unsigned char ZCIP_VERSION[] = "0.7 (20 October 2004)";
>+static char *prog;
>+
>+static struct in_addr null_ip = { 0 };
>+static 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)
>+
>+/**
>+ * Convert an ethernet address to a printable string.
>+ */
>+static char *
>+ether2str(const struct ether_addr *addr)
>+{
>+	static char str[32];
>+
>+	snprintf(str, sizeof (str), "%02x:%02x:%02x:%02x:%02x:%02x",
>+			addr->ether_addr_octet[0], addr->ether_addr_octet[1],
>+			addr->ether_addr_octet[2], addr->ether_addr_octet[3],
>+			addr->ether_addr_octet[4], addr->ether_addr_octet[5]);
>+	return str;
>+}
>+
>+#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)
>+{
>+	ip->s_addr = htonl(LINKLOCAL_ADDR |
>+			((abs(lrand48()) % 0xFD00) + 0x0100));
>+}
>+
>+/**
>+ * Broadcast an ARP packet.
>+ */
>+static int
>+arp(int fd, struct sockaddr *saddr, int op,
>+		struct ether_addr *source_addr, struct in_addr source_ip,
>+		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.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.
>+ */
>+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);
>+#ifdef __uClinux__
>+#error	need to use vfork/execle
>+#else
>+		pid = fork();
>+		if (pid < 0) {
>+			why = "fork";
>+			goto bad;
>+		}
>+		if (pid == 0) {
>+			// child process
>+			setenv("interface", intf, 1);
>+			if (ip != NULL) {
>+				setenv("ip", inet_ntoa(*ip), 1);
>+// FIXME syslog these calls
>+			}
>+			execl(script, script, arg, NULL);
>+			why = "execl";
>+			goto bad;
>+		}
>+#endif
>+		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:
>+// FIXME syslog errors here
>+	perror(why);
>+	return -errno;
>+}
>+
>+#ifndef	NO_BUSYBOX
>+#include "busybox.h"
>+#define main zcip_main
>+#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\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[])
>+{
>+	char *intf = NULL;
>+	char *script = NULL;
>+	char *why;
>+	struct sockaddr saddr;
>+	struct arp_packet p;
>+	struct ether_addr addr;
>+	struct in_addr ip = { 0 };
>+	int fd;
>+	int quit = 0;
>+	int ready = 0;
>+	int foreground = 0;
>+	suseconds_t timeout = 0;	// milliseconds
>+	time_t defend = 0;
>+	int collisions = 0;
>+	int nprobes = 0;
>+	int 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) & LINKLOCAL_MASK)
>+						!= LINKLOCAL_ADDR) {
>+				usage("invalid link address");
>+			}
>+			continue;
>+		case 'v':
>+			if (!verbose)
>+				printf("%s: version %s\n", prog, ZCIP_VERSION);
>+			verbose++;
>+			continue;
>+		default:
>+			usage("bad option");
>+		}
>+	}
>+	if (optind < argc - 1) {
>+		intf = argv[optind++];
>+		script = argv[optind++];
>+	}
>+	if (optind != argc || !intf)
>+		usage("wrong number of arguments");
>+
>+	// 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";
>+		goto bad;
>+	}
>+	// bind to the interface's ARP socket
>+	if (bind(fd, &saddr, sizeof (saddr)) < 0) {
>+		why = "bind";
>+		goto bad;
>+	} 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 bad;
>+		}
>+		memcpy(&addr, &ifr.ifr_hwaddr.sa_data, ETHER_ADDR_LEN);
>+
>+		// start with some stable ip address, either a function of
>+		// the hardware address or else the last address we used.
>+		// retry timers and new addresses shouldn't be predictable.
>+		memcpy(seed, &ifr.ifr_hwaddr.sa_data, ETHER_ADDR_LEN);
>+		if (ip.s_addr == 0) {
>+			seed48(seed);
>+			pick(&ip);
>+		}
>+		t = time(0);
>+		seed[0] ^= t;
>+		seed[1] ^= t >> 16;
>+		seed48(seed);
>+	}
>+
>+	// 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;
>+		}
>+	}
>+
>+	// run the dynamic address negotiation protocol,
>+	// restarting after address collisions:
>+	//  - 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;
>+
>+		fds[0].fd = fd;
>+		fds[0].events = POLLIN | POLLERR;
>+		fds[0].revents = 0;
>+
>+		// poll, being ready to adjust current timeout 
>+		if (timeout > 0) {
>+			gettimeofday(&tv1, NULL);
>+			tv1.tv_usec += (timeout % 1000) * 1000;
>+			if (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;
>+					collisions = 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) {
>+// FIXME stderr may be bad here (syslog)
>+				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",
>+					ether2str(&p.source_addr),
>+					inet_ntoa(p.source_ip));
>+			VDBG("\ttarget=%s %s\n",
>+					ether2str(&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 collisions 
>+			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,
>+						ether2str(&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, ...)
>+				}
>+				collisions++;
>+				if (collisions >= MAX_COLLISIONS) {
>+					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:
>+// FIXME stderr may be bad here (syslog)
>+			why = "poll";
>+			goto bad;
>+		}
>+	}
>+bad:
>+	perror(why);
>+	return EXIT_FAILURE;
>+}
>  
>
>------------------------------------------------------------------------
>
>#!/bin/sh
>
>PATH=$PATH
>ZCIP=/sbin/zcip
>IFNAME=eth0
>SCRIPT=/etc/zcip.script
>
># SHOULD use "-r 169.254.x.x" to reclaim the last value
># it should have been saved away somewhere by $SCRIPT
>FLAGS=""
>
>case "$1" in
>start|restart)
>	ip link set $IFNAME up
>	exec $ZCIP $FLAGS $IFNAME $SCRIPT
>	;;
>stop)
>	# FIXME should probably save and use daemon's PID
>	;;
>status)
>	;;
>*)
>	echo "Usage: $0 {start|stop|status|restart}"
>	exit 1
>	;;
>esac
>  
>
>------------------------------------------------------------------------
>
>_______________________________________________
>busybox mailing list
>busybox at mail.busybox.net
>http://busybox.net/mailman/listinfo/busybox
>  
>
Hi David.

This sure is interesting.

Will get back to you when I test it on my ppc based board.

Regards

Pantelis




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