David Brownell submitted a new applet, zcip, based on RFC 3927. This is

version 0418b.  It compiled.

1 files changed, 550 insertions, 0 deletions

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;
+}