/* vi: set sw=4 ts=4: */
/*
* RFC3927 ZeroConf IPv4 Link-Local addressing
* (see )
*
* Copyright (C) 2003 by Arthur van Hoff (avh@strangeberry.com)
* Copyright (C) 2004 by David Brownell
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
/*
* 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)
//usage:#define zcip_trivial_usage
//usage: "[OPTIONS] IFACE SCRIPT"
//usage:#define zcip_full_usage "\n\n"
//usage: "Manage a ZeroConf IPv4 link-local address\n"
//usage: "\n -f Run in foreground"
//usage: "\n -q Quit after obtaining address"
//usage: "\n -r 169.254.x.x Request this address first"
//usage: "\n -v Verbose"
//usage: "\n"
//usage: "\nWith no -q, runs continuously monitoring for ARP conflicts,"
//usage: "\nexits only on I/O errors (link down etc)"
#include "libbb.h"
#include
#include
#include
#include
#include
/* We don't need more than 32 bits of the counter */
#define MONOTONIC_US() ((unsigned)monotonic_us())
struct arp_packet {
struct ether_header eth;
struct ether_arp arp;
} PACKED;
enum {
/* 169.254.0.0 */
LINKLOCAL_ADDR = 0xa9fe0000,
/* protocol timeout parameters, specified in seconds */
PROBE_WAIT = 1,
PROBE_MIN = 1,
PROBE_MAX = 2,
PROBE_NUM = 3,
MAX_CONFLICTS = 10,
RATE_LIMIT_INTERVAL = 60,
ANNOUNCE_WAIT = 2,
ANNOUNCE_NUM = 2,
ANNOUNCE_INTERVAL = 2,
DEFEND_INTERVAL = 10
};
/* States during the configuration process. */
enum {
PROBE = 0,
RATE_LIMIT_PROBE,
ANNOUNCE,
MONITOR,
DEFEND
};
#define VDBG(...) do { } while (0)
enum {
sock_fd = 3
};
struct globals {
struct sockaddr saddr;
struct ether_addr eth_addr;
} FIX_ALIASING;
#define G (*(struct globals*)&bb_common_bufsiz1)
#define saddr (G.saddr )
#define eth_addr (G.eth_addr)
#define INIT_G() do { } while (0)
/**
* Pick a random link local IP address on 169.254/16, except that
* the first and last 256 addresses are reserved.
*/
static uint32_t pick(void)
{
unsigned tmp;
do {
tmp = rand() & IN_CLASSB_HOST;
} while (tmp > (IN_CLASSB_HOST - 0x0200));
return htonl((LINKLOCAL_ADDR + 0x0100) + tmp);
}
/**
* Broadcast an ARP packet.
*/
static void arp(
/* int op, - always ARPOP_REQUEST */
/* const struct ether_addr *source_eth, - always ð_addr */
struct in_addr source_ip,
const struct ether_addr *target_eth, struct in_addr target_ip)
{
enum { op = ARPOP_REQUEST };
#define source_eth (ð_addr)
struct arp_packet p;
memset(&p, 0, sizeof(p));
// ether header
p.eth.ether_type = htons(ETHERTYPE_ARP);
memcpy(p.eth.ether_shost, source_eth, ETH_ALEN);
memset(p.eth.ether_dhost, 0xff, ETH_ALEN);
// arp request
p.arp.arp_hrd = htons(ARPHRD_ETHER);
p.arp.arp_pro = htons(ETHERTYPE_IP);
p.arp.arp_hln = ETH_ALEN;
p.arp.arp_pln = 4;
p.arp.arp_op = htons(op);
memcpy(&p.arp.arp_sha, source_eth, ETH_ALEN);
memcpy(&p.arp.arp_spa, &source_ip, sizeof(p.arp.arp_spa));
memcpy(&p.arp.arp_tha, target_eth, ETH_ALEN);
memcpy(&p.arp.arp_tpa, &target_ip, sizeof(p.arp.arp_tpa));
// send it
// Even though sock_fd is already bound to saddr, just send()
// won't work, because "socket is not connected"
// (and connect() won't fix that, "operation not supported").
// Thus we sendto() to saddr. I wonder which sockaddr
// (from bind() or from sendto()?) kernel actually uses
// to determine iface to emit the packet from...
xsendto(sock_fd, &p, sizeof(p), &saddr, sizeof(saddr));
#undef source_eth
}
/**
* Run a script.
* argv[0]:intf argv[1]:script_name argv[2]:junk argv[3]:NULL
*/
static int run(char *argv[3], const char *param, struct in_addr *ip)
{
int status;
char *addr = addr; /* for gcc */
const char *fmt = "%s %s %s" + 3;
argv[2] = (char*)param;
VDBG("%s run %s %s\n", argv[0], argv[1], argv[2]);
if (ip) {
addr = inet_ntoa(*ip);
xsetenv("ip", addr);
fmt -= 3;
}
bb_info_msg(fmt, argv[2], argv[0], addr);
status = spawn_and_wait(argv + 1);
if (status < 0) {
bb_perror_msg("%s %s %s" + 3, argv[2], argv[0]);
return -errno;
}
if (status != 0)
bb_error_msg("script %s %s failed, exitcode=%d", argv[1], argv[2], status & 0xff);
return status;
}
/**
* Return milliseconds of random delay, up to "secs" seconds.
*/
static ALWAYS_INLINE unsigned random_delay_ms(unsigned secs)
{
return rand() % (secs * 1000);
}
/**
* main program
*/
int zcip_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int zcip_main(int argc UNUSED_PARAM, char **argv)
{
int state;
char *r_opt;
unsigned opts;
// ugly trick, but I want these zeroed in one go
struct {
const struct in_addr null_ip;
const struct ether_addr null_addr;
struct in_addr ip;
struct ifreq ifr;
int timeout_ms; /* must be signed */
unsigned conflicts;
unsigned nprobes;
unsigned nclaims;
int ready;
int verbose;
} L;
#define null_ip (L.null_ip )
#define null_addr (L.null_addr )
#define ip (L.ip )
#define ifr (L.ifr )
#define timeout_ms (L.timeout_ms)
#define conflicts (L.conflicts )
#define nprobes (L.nprobes )
#define nclaims (L.nclaims )
#define ready (L.ready )
#define verbose (L.verbose )
memset(&L, 0, sizeof(L));
INIT_G();
#define FOREGROUND (opts & 1)
#define QUIT (opts & 2)
// parse commandline: prog [options] ifname script
// exactly 2 args; -v accumulates and implies -f
opt_complementary = "=2:vv:vf";
opts = getopt32(argv, "fqr:v", &r_opt, &verbose);
#if !BB_MMU
// on NOMMU reexec early (or else we will rerun things twice)
if (!FOREGROUND)
bb_daemonize_or_rexec(0 /*was: DAEMON_CHDIR_ROOT*/, argv);
#endif
// open an ARP socket
// (need to do it before openlog to prevent openlog from taking
// fd 3 (sock_fd==3))
xmove_fd(xsocket(AF_PACKET, SOCK_PACKET, htons(ETH_P_ARP)), sock_fd);
if (!FOREGROUND) {
// do it before all bb_xx_msg calls
openlog(applet_name, 0, LOG_DAEMON);
logmode |= LOGMODE_SYSLOG;
}
if (opts & 4) { // -r n.n.n.n
if (inet_aton(r_opt, &ip) == 0
|| (ntohl(ip.s_addr) & IN_CLASSB_NET) != LINKLOCAL_ADDR
) {
bb_error_msg_and_die("invalid link address");
}
}
argv += optind - 1;
/* Now: argv[0]:junk argv[1]:intf argv[2]:script argv[3]:NULL */
/* We need to make space for script argument: */
argv[0] = argv[1];
argv[1] = argv[2];
/* Now: argv[0]:intf argv[1]:script argv[2]:junk argv[3]:NULL */
#define argv_intf (argv[0])
xsetenv("interface", argv_intf);
// initialize the interface (modprobe, ifup, etc)
if (run(argv, "init", NULL))
return EXIT_FAILURE;
// initialize saddr
// saddr is: { u16 sa_family; u8 sa_data[14]; }
//memset(&saddr, 0, sizeof(saddr));
//TODO: are we leaving sa_family == 0 (AF_UNSPEC)?!
safe_strncpy(saddr.sa_data, argv_intf, sizeof(saddr.sa_data));
// bind to the interface's ARP socket
xbind(sock_fd, &saddr, sizeof(saddr));
// get the interface's ethernet address
//memset(&ifr, 0, sizeof(ifr));
strncpy_IFNAMSIZ(ifr.ifr_name, argv_intf);
xioctl(sock_fd, SIOCGIFHWADDR, &ifr);
memcpy(ð_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.
// we are taking low-order four bytes, as top-order ones
// aren't random enough.
// NOTE: the sequence of addresses we try changes only
// depending on when we detect conflicts.
{
uint32_t t;
move_from_unaligned32(t, ((char *)ð_addr + 2));
srand(t);
}
if (ip.s_addr == 0)
ip.s_addr = pick();
// 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 BB_MMU
bb_daemonize(0 /*was: DAEMON_CHDIR_ROOT*/);
#endif
bb_info_msg("start, interface %s", argv_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 uses it
// - arp announcements that we're claiming it
// - use it
// - defend it, within limits
// exit if:
// - address is successfully obtained and -q was given:
// run "