From 4aca87515a5083ae0e31ce3177189fd43b6d05ac Mon Sep 17 00:00:00 2001
From: Andreas Baumann <mail@andreasbaumann.cc>
Date: Sat, 3 Jan 2015 13:58:15 +0100
Subject: patch to Vanilla Tomato 1.28

---
 release/src/router/busybox/networking/zcip.c | 567 +++++++++++++++++++++++++++
 1 file changed, 567 insertions(+)
 create mode 100644 release/src/router/busybox/networking/zcip.c

(limited to 'release/src/router/busybox/networking/zcip.c')

diff --git a/release/src/router/busybox/networking/zcip.c b/release/src/router/busybox/networking/zcip.c
new file mode 100644
index 00000000..df4c0ec2
--- /dev/null
+++ b/release/src/router/busybox/networking/zcip.c
@@ -0,0 +1,567 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * 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
+ *
+ * Licensed under the GPL v2 or later, see the file LICENSE in this tarball.
+ */
+
+/*
+ * 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 <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>
+
+#include "libbb.h"
+#include <syslog.h>
+
+/* 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;
+};
+#define G (*(struct globals*)&bb_common_bufsiz1)
+#define saddr    (G.saddr   )
+#define eth_addr (G.eth_addr)
+
+
+/**
+ * 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 &eth_addr */
+					struct in_addr source_ip,
+	const struct ether_addr *target_eth, struct in_addr target_ip)
+{
+	enum { op = ARPOP_REQUEST };
+#define source_eth (&eth_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 = wait4pid(spawn(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);
+	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, 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));
+
+#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");
+		}
+	}
+	argc -= optind;
+	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(&eth_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 *)&eth_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 "<script> config", then exit with exitcode 0
+	// - poll error (when does this happen?)
+	// - read error (when does this happen?)
+	// - sendto error (in arp()) (when does this happen?)
+	// - revents & POLLERR (link down). run "<script> deconfig" first
+	state = PROBE;
+	while (1) {
+		struct pollfd fds[1];
+		unsigned deadline_us;
+		struct arp_packet p;
+		int source_ip_conflict;
+		int target_ip_conflict;
+
+		fds[0].fd = sock_fd;
+		fds[0].events = POLLIN;
+		fds[0].revents = 0;
+
+		// poll, being ready to adjust current timeout
+		if (!timeout_ms) {
+			timeout_ms = random_delay_ms(PROBE_WAIT);
+			// FIXME setsockopt(sock_fd, SO_ATTACH_FILTER, ...) to
+			// make the kernel filter out all packets except
+			// ones we'd care about.
+		}
+		// set deadline_us to the point in time when we timeout
+		deadline_us = MONOTONIC_US() + timeout_ms * 1000;
+
+		VDBG("...wait %d %s nprobes=%u, nclaims=%u\n",
+				timeout_ms, argv_intf, nprobes, nclaims);
+
+		switch (safe_poll(fds, 1, timeout_ms)) {
+
+		default:
+			//bb_perror_msg("poll"); - done in safe_poll
+			return EXIT_FAILURE;
+
+		// timeout
+		case 0:
+			VDBG("state = %d\n", state);
+			switch (state) {
+			case PROBE:
+				// timeouts in the PROBE state mean no conflicting ARP packets
+				// have been received, so we can progress through the states
+				if (nprobes < PROBE_NUM) {
+					nprobes++;
+					VDBG("probe/%u %s@%s\n",
+							nprobes, argv_intf, inet_ntoa(ip));
+					arp(/* ARPOP_REQUEST, */
+							/* &eth_addr, */ null_ip,
+							&null_addr, ip);
+					timeout_ms = PROBE_MIN * 1000;
+					timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN);
+				}
+				else {
+					// Switch to announce state.
+					state = ANNOUNCE;
+					nclaims = 0;
+					VDBG("announce/%u %s@%s\n",
+							nclaims, argv_intf, inet_ntoa(ip));
+					arp(/* ARPOP_REQUEST, */
+							/* &eth_addr, */ ip,
+							&eth_addr, ip);
+					timeout_ms = ANNOUNCE_INTERVAL * 1000;
+				}
+				break;
+			case RATE_LIMIT_PROBE:
+				// timeouts in the RATE_LIMIT_PROBE state mean no conflicting ARP packets
+				// have been received, so we can move immediately to the announce state
+				state = ANNOUNCE;
+				nclaims = 0;
+				VDBG("announce/%u %s@%s\n",
+						nclaims, argv_intf, inet_ntoa(ip));
+				arp(/* ARPOP_REQUEST, */
+						/* &eth_addr, */ ip,
+						&eth_addr, ip);
+				timeout_ms = ANNOUNCE_INTERVAL * 1000;
+				break;
+			case ANNOUNCE:
+				// timeouts in the ANNOUNCE state mean no conflicting ARP packets
+				// have been received, so we can progress through the states
+				if (nclaims < ANNOUNCE_NUM) {
+					nclaims++;
+					VDBG("announce/%u %s@%s\n",
+							nclaims, argv_intf, inet_ntoa(ip));
+					arp(/* ARPOP_REQUEST, */
+							/* &eth_addr, */ ip,
+							&eth_addr, ip);
+					timeout_ms = ANNOUNCE_INTERVAL * 1000;
+				}
+				else {
+					// Switch to monitor state.
+					state = MONITOR;
+					// link is ok to use earlier
+					// FIXME update filters
+					run(argv, "config", &ip);
+					ready = 1;
+					conflicts = 0;
+					timeout_ms = -1; // Never timeout in the monitor state.
+
+					// NOTE: all other exit paths
+					// should deconfig ...
+					if (QUIT)
+						return EXIT_SUCCESS;
+				}
+				break;
+			case DEFEND:
+				// We won!  No ARP replies, so just go back to monitor.
+				state = MONITOR;
+				timeout_ms = -1;
+				conflicts = 0;
+				break;
+			default:
+				// Invalid, should never happen.  Restart the whole protocol.
+				state = PROBE;
+				ip.s_addr = pick();
+				timeout_ms = 0;
+				nprobes = 0;
+				nclaims = 0;
+				break;
+			} // switch (state)
+			break; // case 0 (timeout)
+
+		// packets arriving, or link went down
+		case 1:
+			// We need to adjust the timeout in case we didn't receive
+			// a conflicting packet.
+			if (timeout_ms > 0) {
+				unsigned diff = deadline_us - MONOTONIC_US();
+				if ((int)(diff) < 0) {
+					// Current time is greater than the expected timeout time.
+					// Should never happen.
+					VDBG("missed an expected timeout\n");
+					timeout_ms = 0;
+				} else {
+					VDBG("adjusting timeout\n");
+					timeout_ms = (diff / 1000) | 1; /* never 0 */
+				}
+			}
+
+			if ((fds[0].revents & POLLIN) == 0) {
+				if (fds[0].revents & POLLERR) {
+					// FIXME: links routinely go down;
+					// this shouldn't necessarily exit.
+					bb_error_msg("iface %s is down", argv_intf);
+					if (ready) {
+						run(argv, "deconfig", &ip);
+					}
+					return EXIT_FAILURE;
+				}
+				continue;
+			}
+
+			// read ARP packet
+			if (safe_read(sock_fd, &p, sizeof(p)) < 0) {
+				bb_perror_msg_and_die(bb_msg_read_error);
+			}
+			if (p.eth.ether_type != htons(ETHERTYPE_ARP))
+				continue;
+#ifdef DEBUG
+			{
+				struct ether_addr *sha = (struct ether_addr *) p.arp.arp_sha;
+				struct ether_addr *tha = (struct ether_addr *) p.arp.arp_tha;
+				struct in_addr *spa = (struct in_addr *) p.arp.arp_spa;
+				struct in_addr *tpa = (struct in_addr *) p.arp.arp_tpa;
+				VDBG("%s recv arp type=%d, op=%d,\n",
+					argv_intf, ntohs(p.eth.ether_type),
+					ntohs(p.arp.arp_op));
+				VDBG("\tsource=%s %s\n",
+					ether_ntoa(sha),
+					inet_ntoa(*spa));
+				VDBG("\ttarget=%s %s\n",
+					ether_ntoa(tha),
+					inet_ntoa(*tpa));
+			}
+#endif
+			if (p.arp.arp_op != htons(ARPOP_REQUEST)
+			 && p.arp.arp_op != htons(ARPOP_REPLY))
+				continue;
+
+			source_ip_conflict = 0;
+			target_ip_conflict = 0;
+
+			if (memcmp(p.arp.arp_spa, &ip.s_addr, sizeof(struct in_addr)) == 0
+			 && memcmp(&p.arp.arp_sha, &eth_addr, ETH_ALEN) != 0
+			) {
+				source_ip_conflict = 1;
+			}
+			if (p.arp.arp_op == htons(ARPOP_REQUEST)
+			 && memcmp(p.arp.arp_tpa, &ip.s_addr, sizeof(struct in_addr)) == 0
+			 && memcmp(&p.arp.arp_tha, &eth_addr, ETH_ALEN) != 0
+			) {
+				target_ip_conflict = 1;
+			}
+
+			VDBG("state = %d, source ip conflict = %d, target ip conflict = %d\n",
+				state, source_ip_conflict, target_ip_conflict);
+			switch (state) {
+			case PROBE:
+			case ANNOUNCE:
+				// When probing or announcing, check for source IP conflicts
+				// and other hosts doing ARP probes (target IP conflicts).
+				if (source_ip_conflict || target_ip_conflict) {
+					conflicts++;
+					if (conflicts >= MAX_CONFLICTS) {
+						VDBG("%s ratelimit\n", argv_intf);
+						timeout_ms = RATE_LIMIT_INTERVAL * 1000;
+						state = RATE_LIMIT_PROBE;
+					}
+
+					// restart the whole protocol
+					ip.s_addr = pick();
+					timeout_ms = 0;
+					nprobes = 0;
+					nclaims = 0;
+				}
+				break;
+			case MONITOR:
+				// If a conflict, we try to defend with a single ARP probe.
+				if (source_ip_conflict) {
+					VDBG("monitor conflict -- defending\n");
+					state = DEFEND;
+					timeout_ms = DEFEND_INTERVAL * 1000;
+					arp(/* ARPOP_REQUEST, */
+						/* &eth_addr, */ ip,
+						&eth_addr, ip);
+				}
+				break;
+			case DEFEND:
+				// Well, we tried.  Start over (on conflict).
+				if (source_ip_conflict) {
+					state = PROBE;
+					VDBG("defend conflict -- starting over\n");
+					ready = 0;
+					run(argv, "deconfig", &ip);
+
+					// restart the whole protocol
+					ip.s_addr = pick();
+					timeout_ms = 0;
+					nprobes = 0;
+					nclaims = 0;
+				}
+				break;
+			default:
+				// Invalid, should never happen.  Restart the whole protocol.
+				VDBG("invalid state -- starting over\n");
+				state = PROBE;
+				ip.s_addr = pick();
+				timeout_ms = 0;
+				nprobes = 0;
+				nclaims = 0;
+				break;
+			} // switch state
+			break; // case 1 (packets arriving)
+		} // switch poll
+	} // while (1)
+#undef argv_intf
+}
-- 
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