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 000000000..ccf399bb7
--- /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;
+}