net: Add link-local addressing support

Code based on networking/zcip.c in busybox
commit 8531d76a15890c2c535908ce888b2e2aed35b172

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>

README

@@ -785,6 +785,8 @@ The following options need to be configured:
 		CONFIG_CMD_JFFS2	* JFFS2 Support
 		CONFIG_CMD_KGDB		* kgdb
 		CONFIG_CMD_LDRINFO	  ldrinfo (display Blackfin loader)
+		CONFIG_CMD_LINK_LOCAL	* link-local IP address auto-configuration
+					  (169.254.*.*)
 		CONFIG_CMD_LOADB	  loadb
 		CONFIG_CMD_LOADS	  loads
 		CONFIG_CMD_MD5SUM	  print md5 message digest
@@ -1633,6 +1635,14 @@ The following options need to be configured:
 		the DHCP timeout and retry process takes a longer than
 		this delay.
 
+ - Link-local IP address negotiation:
+		Negotiate with other link-local clients on the local network
+		for an address that doesn't require explicit configuration.
+		This is especially useful if a DHCP server cannot be guaranteed
+		to exist in all environments that the device must operate.
+
+		See doc/README.link-local for more information.
+
  - CDP Options:
 		CONFIG_CDP_DEVICE_ID
 

common/cmd_net.c

@@ -428,3 +428,34 @@ U_BOOT_CMD(
 );
 
 #endif	/* CONFIG_CMD_DNS */
+
+#if defined(CONFIG_CMD_LINK_LOCAL)
+static int do_link_local(cmd_tbl_t *cmdtp, int flag, int argc,
+			char * const argv[])
+{
+	char tmp[22];
+
+	if (NetLoop(LINKLOCAL) < 0)
+		return 1;
+
+	NetOurGatewayIP = 0;
+	ip_to_string(NetOurGatewayIP, tmp);
+	setenv("gatewayip", tmp);
+
+	ip_to_string(NetOurSubnetMask, tmp);
+	setenv("netmask", tmp);
+
+	ip_to_string(NetOurIP, tmp);
+	setenv("ipaddr", tmp);
+	setenv("llipaddr", tmp); /* store this for next time */
+
+	return 0;
+}
+
+U_BOOT_CMD(
+	linklocal,	1,	1,	do_link_local,
+	"acquire a network IP address using the link-local protocol",
+	""
+);
+
+#endif  /* CONFIG_CMD_LINK_LOCAL */

doc/README.link-local

@@ -0,0 +1,76 @@
+------------------------------------------
+ Link-local IP address auto-configuration
+------------------------------------------
+
+Negotiate with other link-local clients on the local network
+for an address that doesn't require explicit configuration.
+This is especially useful if a DHCP server cannot be guaranteed
+to exist in all environments that the device must operate.
+
+This is an implementation of RFC3927.
+
+----------
+ Commands
+----------
+
+When CONFIG_CMD_LINK_LOCAL is defined in the board config file,
+the "linklocal" command is available.  This running this will
+take approximately 5 seconds while the address is negotiated.
+
+------------------------
+ Environment interation
+------------------------
+
+The "llipaddr" variable is set with the most recently
+negotiated address and is preferred in future negotiations.
+
+The "ipaddr", "netmask", and "gatewayip" variables are set
+after successful negotiation to enable network access.
+
+-------------
+ Limitations
+-------------
+
+RFC3927 requires that addresses are continuously checked to
+avoid conflicts, however this can only happen when the NetLoop
+is getting called.  It is possible for a conflict to go undetected
+until a command that accesses the network is executed.
+
+Using NetConsole is one way to ensure that NetLoop is always
+processing packets and monitoring for conflicts.
+
+This is also not a concern if the feature is use to connect
+directly to another machine that may not be running a DHCP server.
+
+----------------
+ Example script
+----------------
+
+This script allows use of DHCP and/or Link-local controlled
+by env variables.  It depends on CONFIG_CMD_LINK_LOCAL, CONFIG_CMD_DHCP,
+and CONFIG_BOOTP_MAY_FAIL.
+If both fail or are disabled, static settings are used.
+
+#define CONFIG_EXTRA_ENV_SETTINGS \
+	"ipconfigcmd=if test \\\"$dhcpenabled\\\" -ne 0;"		\
+		"then "							\
+			"dhcpfail=0;dhcp || dhcpfail=1;"		\
+		"else "							\
+			"dhcpfail=-1;"					\
+		"fi;"							\
+		"if test \\\"$linklocalenabled\\\" -ne 0 -a "		\
+			"\\\"$dhcpfail\\\" -ne 0;"			\
+		"then "							\
+			"linklocal;"					\
+			"llfail=0;"					\
+		"else "							\
+			"llfail=-1;"					\
+		"fi;"							\
+		"if test \\\"$llfail\\\" -ne 0 -a "			\
+			"\\\"$dhcpfail\\\" -ne 0; "			\
+		"then "							\
+			"setenv ipaddr $sipaddr; "			\
+			"setenv netmask $snetmask; "			\
+			"setenv gatewayip $sgatewayip; "		\
+		"fi;\0"							\
+

include/net.h

@@ -395,7 +395,7 @@ extern int		NetRestartWrap;		/* Tried all network devices */
 
 enum proto_t {
 	BOOTP, RARP, ARP, TFTPGET, DHCP, PING, DNS, NFS, CDP, NETCONS, SNTP,
-	TFTPSRV, TFTPPUT
+	TFTPSRV, TFTPPUT, LINKLOCAL
 };
 
 /* from net/net.c */

net/Makefile

@@ -32,15 +32,17 @@ COBJS-$(CONFIG_CMD_NET)  += bootp.o
 COBJS-$(CONFIG_CMD_CDP)  += cdp.o
 COBJS-$(CONFIG_CMD_DNS)  += dns.o
 COBJS-$(CONFIG_CMD_NET)  += eth.o
+COBJS-$(CONFIG_CMD_LINK_LOCAL) += link_local.o
 COBJS-$(CONFIG_CMD_NET)  += net.o
 COBJS-$(CONFIG_BOOTP_RANDOM_DELAY) += net_rand.o
+COBJS-$(CONFIG_CMD_LINK_LOCAL) += net_rand.o
 COBJS-$(CONFIG_CMD_NFS)  += nfs.o
 COBJS-$(CONFIG_CMD_PING) += ping.o
 COBJS-$(CONFIG_CMD_RARP) += rarp.o
 COBJS-$(CONFIG_CMD_SNTP) += sntp.o
 COBJS-$(CONFIG_CMD_NET)  += tftp.o
 
-COBJS	:= $(COBJS-y)
+COBJS	:= $(sort $(COBJS-y))
 SRCS	:= $(COBJS:.o=.c)
 OBJS	:= $(addprefix $(obj),$(COBJS))
 

net/link_local.c

@@ -0,0 +1,332 @@
+/*
+ * RFC3927 ZeroConf IPv4 Link-Local addressing
+ * (see <http://www.zeroconf.org/>)
+ *
+ * Copied from BusyBox - networking/zcip.c
+ *
+ * Copyright (C) 2003 by Arthur van Hoff (avh@strangeberry.com)
+ * Copyright (C) 2004 by David Brownell
+ * Copyright (C) 2010 by Joe Hershberger
+ *
+ * Licensed under the GPL v2 or later
+ */
+
+#include <common.h>
+#include <net.h>
+#include "arp.h"
+#include "net_rand.h"
+
+/* We don't need more than 32 bits of the counter */
+#define MONOTONIC_MS() ((unsigned)get_timer(0) * (1000 / CONFIG_SYS_HZ))
+
+enum {
+/* 169.254.0.0 */
+	LINKLOCAL_ADDR = 0xa9fe0000,
+
+	IN_CLASSB_NET = 0xffff0000,
+	IN_CLASSB_HOST = 0x0000ffff,
+
+/* 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. */
+static enum ll_state_t {
+	PROBE = 0,
+	RATE_LIMIT_PROBE,
+	ANNOUNCE,
+	MONITOR,
+	DEFEND,
+	DISABLED
+} state = DISABLED;
+
+static IPaddr_t ip;
+static int timeout_ms = -1;
+static unsigned deadline_ms;
+static unsigned conflicts;
+static unsigned nprobes;
+static unsigned nclaims;
+static int ready;
+
+static void link_local_timeout(void);
+
+/**
+ * Pick a random link local IP address on 169.254/16, except that
+ * the first and last 256 addresses are reserved.
+ */
+static IPaddr_t pick(void)
+{
+	unsigned tmp;
+
+	do {
+		tmp = rand() & IN_CLASSB_HOST;
+	} while (tmp > (IN_CLASSB_HOST - 0x0200));
+	return (IPaddr_t) htonl((LINKLOCAL_ADDR + 0x0100) + tmp);
+}
+
+/**
+ * Return milliseconds of random delay, up to "secs" seconds.
+ */
+static inline unsigned random_delay_ms(unsigned secs)
+{
+	return rand() % (secs * 1000);
+}
+
+static void configure_wait(void)
+{
+	if (timeout_ms == -1)
+		return;
+
+	/* poll, being ready to adjust current timeout */
+	if (!timeout_ms)
+		timeout_ms = random_delay_ms(PROBE_WAIT);
+
+	/* set deadline_ms to the point in time when we timeout */
+	deadline_ms = MONOTONIC_MS() + timeout_ms;
+
+	debug("...wait %d %s nprobes=%u, nclaims=%u\n",
+			timeout_ms, eth_get_name(), nprobes, nclaims);
+
+	NetSetTimeout(timeout_ms, link_local_timeout);
+}
+
+void link_local_start(void)
+{
+	ip = getenv_IPaddr("llipaddr");
+	if (ip != 0 && (ip & IN_CLASSB_NET) != LINKLOCAL_ADDR) {
+		puts("invalid link address");
+		net_set_state(NETLOOP_FAIL);
+		return;
+	}
+	NetOurSubnetMask = IN_CLASSB_NET;
+
+	srand_mac();
+	if (ip == 0)
+		ip = pick();
+
+	state = PROBE;
+	timeout_ms = 0;
+	conflicts = 0;
+	nprobes = 0;
+	nclaims = 0;
+	ready = 0;
+
+	configure_wait();
+}
+
+static void link_local_timeout(void)
+{
+	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++;
+			debug("probe/%u %s@%pI4\n",
+					nprobes, eth_get_name(), &ip);
+			arp_raw_request(0, NetEtherNullAddr, ip);
+			timeout_ms = PROBE_MIN * 1000;
+			timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN);
+		} else {
+			/* Switch to announce state */
+			state = ANNOUNCE;
+			nclaims = 0;
+			debug("announce/%u %s@%pI4\n",
+					nclaims, eth_get_name(), &ip);
+			arp_raw_request(ip, NetOurEther, 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;
+		debug("announce/%u %s@%pI4\n",
+				nclaims, eth_get_name(), &ip);
+		arp_raw_request(ip, NetOurEther, 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++;
+			debug("announce/%u %s@%pI4\n",
+					nclaims, eth_get_name(), &ip);
+			arp_raw_request(ip, NetOurEther, ip);
+			timeout_ms = ANNOUNCE_INTERVAL * 1000;
+		} else {
+			/* Switch to monitor state */
+			state = MONITOR;
+			printf("Successfully assigned %pI4\n", &ip);
+			NetCopyIP(&NetOurIP, &ip);
+			ready = 1;
+			conflicts = 0;
+			timeout_ms = -1;
+			/* Never timeout in the monitor state */
+			NetSetTimeout(0, NULL);
+
+			/* NOTE: all other exit paths should deconfig ... */
+			net_set_state(NETLOOP_SUCCESS);
+			return;
+		}
+		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 = pick();
+		timeout_ms = 0;
+		nprobes = 0;
+		nclaims = 0;
+		break;
+	}
+	configure_wait();
+}
+
+void link_local_receive_arp(struct arp_hdr *arp, int len)
+{
+	int source_ip_conflict;
+	int target_ip_conflict;
+
+	if (state == DISABLED)
+		return;
+
+	/* We need to adjust the timeout in case we didn't receive a
+	   conflicting packet. */
+	if (timeout_ms > 0) {
+		unsigned diff = deadline_ms - MONOTONIC_MS();
+		if ((int)(diff) < 0) {
+			/* Current time is greater than the expected timeout
+			   time. This should never happen */
+			debug("missed an expected timeout\n");
+			timeout_ms = 0;
+		} else {
+			debug("adjusting timeout\n");
+			timeout_ms = diff | 1; /* never 0 */
+		}
+	}
+/*
+ * XXX Don't bother with ethernet link just yet
+	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", eth_get_name());
+			if (ready) {
+				run(argv, "deconfig", &ip);
+			}
+			return EXIT_FAILURE;
+		}
+		continue;
+	}
+*/
+
+	debug("%s recv arp type=%d, op=%d,\n",
+		eth_get_name(), ntohs(arp->ar_pro),
+		ntohs(arp->ar_op));
+	debug("\tsource=%pM %pI4\n",
+		&arp->ar_sha,
+		&arp->ar_spa);
+	debug("\ttarget=%pM %pI4\n",
+		&arp->ar_tha,
+		&arp->ar_tpa);
+
+	if (arp->ar_op != htons(ARPOP_REQUEST)
+	 && arp->ar_op != htons(ARPOP_REPLY)
+	) {
+		configure_wait();
+		return;
+	}
+
+	source_ip_conflict = 0;
+	target_ip_conflict = 0;
+
+	if (memcmp(&arp->ar_spa, &ip, ARP_PLEN) == 0
+	 && memcmp(&arp->ar_sha, NetOurEther, ARP_HLEN) != 0
+	) {
+		source_ip_conflict = 1;
+	}
+	if (arp->ar_op == htons(ARPOP_REQUEST)
+	 && memcmp(&arp->ar_tpa, &ip, ARP_PLEN) == 0
+	 && memcmp(&arp->ar_tha, NetOurEther, ARP_HLEN) != 0
+	) {
+		target_ip_conflict = 1;
+	}
+
+	debug("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++;
+			state = PROBE;
+			if (conflicts >= MAX_CONFLICTS) {
+				debug("%s ratelimit\n", eth_get_name());
+				timeout_ms = RATE_LIMIT_INTERVAL * 1000;
+				state = RATE_LIMIT_PROBE;
+			}
+
+			/* restart the whole protocol */
+			ip = 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) {
+			debug("monitor conflict -- defending\n");
+			state = DEFEND;
+			timeout_ms = DEFEND_INTERVAL * 1000;
+			arp_raw_request(ip, NetOurEther, ip);
+		}
+		break;
+	case DEFEND:
+		/* Well, we tried.  Start over (on conflict) */
+		if (source_ip_conflict) {
+			state = PROBE;
+			debug("defend conflict -- starting over\n");
+			ready = 0;
+			NetOurIP = 0;
+
+			/* restart the whole protocol */
+			ip = pick();
+			timeout_ms = 0;
+			nprobes = 0;
+			nclaims = 0;
+		}
+		break;
+	default:
+		/* Invalid, should never happen.  Restart the whole protocol */
+		debug("invalid state -- starting over\n");
+		state = PROBE;
+		ip = pick();
+		timeout_ms = 0;
+		nprobes = 0;
+		nclaims = 0;
+		break;
+	}
+	configure_wait();
+}

net/link_local.h

@@ -0,0 +1,24 @@
+/*
+ * RFC3927 ZeroConf IPv4 Link-Local addressing
+ * (see <http://www.zeroconf.org/>)
+ *
+ * Copied from BusyBox - networking/zcip.c
+ *
+ * Copyright (C) 2003 by Arthur van Hoff (avh@strangeberry.com)
+ * Copyright (C) 2004 by David Brownell
+ *
+ * Licensed under the GPL v2 or later
+ */
+
+#if defined(CONFIG_CMD_LINK_LOCAL)
+
+#ifndef __LINK_LOCAL_H__
+#define __LINK_LOCAL_H__
+
+#include <common.h>
+
+void link_local_receive_arp(struct arp_hdr *arp, int len);
+void link_local_start(void);
+
+#endif /* __LINK_LOCAL_H__ */
+#endif

net/net.c

@@ -23,6 +23,12 @@
  *			- name of bootfile
  *	Next step:	ARP
  *
+ * LINK_LOCAL:
+ *
+ *	Prerequisites:	- own ethernet address
+ *	We want:	- own IP address
+ *	Next step:	ARP
+ *
  * RARP:
  *
  *	Prerequisites:	- own ethernet address
@@ -89,6 +95,7 @@
 #if defined(CONFIG_CMD_DNS)
 #include "dns.h"
 #endif
+#include "link_local.h"
 #include "nfs.h"
 #include "ping.h"
 #include "rarp.h"
@@ -401,6 +408,11 @@ restart:
 		case DNS:
 			DnsStart();
 			break;
+#endif
+#if defined(CONFIG_CMD_LINK_LOCAL)
+		case LINKLOCAL:
+			link_local_start();
+			break;
 #endif
 		default:
 			break;
@@ -1194,6 +1206,7 @@ common:
 	case BOOTP:
 	case CDP:
 	case DHCP:
+	case LINKLOCAL:
 		if (memcmp(NetOurEther, "\0\0\0\0\0\0", 6) == 0) {
 			int num = eth_get_dev_index();