add the 'ead' package (emergency access daemon), which can provide remote access to your device, even if the ip and firewall settings are broken

SVN-Revision: 13738

1 files changed, 931 insertions, 0 deletions

diff --git a/package/ead/src/ead.c b/package/ead/src/ead.c
new file mode 100644
index 0000000000..7367c38658
--- /dev/null
+++ b/package/ead/src/ead.c
@@ -0,0 +1,931 @@
+/*
+ * Emergency Access Daemon
+ * Copyright (C) 2008 Felix Fietkau <nbd@openwrt.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2
+ * as published by the Free Software Foundation
+ *
+ * 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.
+ */
+
+#include <sys/types.h>
+#include <sys/time.h>
+#include <sys/select.h>
+#include <stdio.h>
+#include <stddef.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdbool.h>
+#include <fcntl.h>
+#include <signal.h>
+#include <pcap.h>
+#include <pcap-bpf.h>
+#include <t_pwd.h>
+#include <t_read.h>
+#include <t_sha.h>
+#include <t_defines.h>
+#include <t_server.h>
+
+#include "list.h"
+#include "ead.h"
+#include "ead-pcap.h"
+#include "ead-crypt.h"
+
+#include "filter.c"
+
+#ifdef linux
+#include "libbridge_init.c"
+#endif
+
+#define PASSWD_FILE	"/etc/passwd"
+
+#ifndef DEFAULT_IFNAME
+#define DEFAULT_IFNAME "eth0"
+#endif
+
+#ifndef DEFAULT_DEVNAME
+#define DEFAULT_DEVNAME "Unknown"
+#endif
+
+#define PCAP_MRU		1600
+#define PCAP_TIMEOUT	200
+
+#if EAD_DEBUGLEVEL >= 1
+#define DEBUG(n, format, ...) do { \
+	if (EAD_DEBUGLEVEL >= n) \
+		fprintf(stderr, format, ##__VA_ARGS__); \
+} while (0);
+
+#else
+#define DEBUG(n, format, ...) do {} while(0)
+#endif
+
+static char ethmac[6] = "\x00\x13\x37\x00\x00\x00"; /* last 3 bytes will be randomized */
+static pcap_t *pcap_fp = NULL;
+static pcap_t *pcap_fp_rx = NULL;
+static const char *ifname = DEFAULT_IFNAME;
+static char pktbuf_b[PCAP_MRU];
+static struct ead_packet *pktbuf = (struct ead_packet *)pktbuf_b;
+static u16_t nid = 0xffff; /* node id */
+static char username[32] = "";
+static int state = EAD_TYPE_SET_USERNAME;
+static const char *passwd_file = PASSWD_FILE;
+static const char password[MAXPARAMLEN];
+static bool child_pending = false;
+
+static unsigned char abuf[MAXPARAMLEN + 1];
+static unsigned char pwbuf[MAXPARAMLEN];
+static unsigned char saltbuf[MAXSALTLEN];
+static unsigned char pw_saltbuf[MAXSALTLEN];
+static struct list_head instances;
+static const char *dev_name = DEFAULT_DEVNAME;
+static bool nonfork = false;
+
+#ifdef linux
+static const char *brname = NULL;
+#endif
+
+struct ead_instance {
+	struct list_head list;
+	char name[16];
+	int pid;
+#ifdef linux
+	char bridge[16];
+	bool br_check;
+#endif
+};
+
+static struct t_pwent tpe = {
+	.name = username,
+	.index = 1,
+	.password.data = pwbuf,
+	.password.len = 0,
+	.salt.data = saltbuf,
+	.salt.len = 0,
+};
+struct t_confent *tce = NULL;
+static struct t_server *ts = NULL;
+static struct t_num A, *B = NULL;
+unsigned char *skey;
+
+static bool
+prepare_password(void)
+{
+	static char lbuf[1024];
+	unsigned char dig[SHA_DIGESTSIZE];
+	BigInteger x, v, n, g;
+	SHA1_CTX ctxt;
+	int ulen = strlen(username);
+	FILE *f;
+
+	lbuf[sizeof(lbuf) - 1] = 0;
+
+	f = fopen(passwd_file, "r");
+	if (!f)
+		return false;
+
+	while (fgets(lbuf, sizeof(lbuf) - 1, f) != NULL) {
+		char *str, *s2;
+
+		if (strncmp(lbuf, username, ulen) != 0)
+			continue;
+
+		if (lbuf[ulen] != ':')
+			continue;
+
+		str = &lbuf[ulen + 1];
+
+		if (strncmp(str, "$1$", 3) != 0)
+			continue;
+
+		s2 = strchr(str + 3, '$');
+		if (!s2)
+			continue;
+
+		if (s2 - str >= MAXSALTLEN)
+			continue;
+
+		strncpy((char *) pw_saltbuf, str, s2 - str);
+		pw_saltbuf[s2 - str] = 0;
+
+		s2 = strchr(s2, ':');
+		if (!s2)
+			continue;
+
+		*s2 = 0;
+		if (s2 - str >= MAXPARAMLEN)
+			continue;
+
+		strncpy((char *)password, str, MAXPARAMLEN);
+		fclose(f);
+		goto hash_password;
+	}
+
+	/* not found */
+	fclose(f);
+	return false;
+
+hash_password:
+	tce = gettcid(tpe.index);
+	do {
+		t_random(tpe.password.data, SALTLEN);
+	} while (memcmp(saltbuf, (char *)dig, sizeof(saltbuf)) == 0);
+	if (saltbuf[0] == 0)
+		saltbuf[0] = 0xff;
+
+	n = BigIntegerFromBytes(tce->modulus.data, tce->modulus.len);
+	g = BigIntegerFromBytes(tce->generator.data, tce->generator.len);
+	v = BigIntegerFromInt(0);
+
+	SHA1Init(&ctxt);
+	SHA1Update(&ctxt, (unsigned char *) username, strlen(username));
+	SHA1Update(&ctxt, (unsigned char *) ":", 1);
+	SHA1Update(&ctxt, (unsigned char *) password, strlen(password));
+	SHA1Final(dig, &ctxt);
+
+	SHA1Init(&ctxt);
+	SHA1Update(&ctxt, saltbuf, tpe.salt.len);
+	SHA1Update(&ctxt, dig, sizeof(dig));
+	SHA1Final(dig, &ctxt);
+
+	/* x = H(s, H(u, ':', p)) */
+	x = BigIntegerFromBytes(dig, sizeof(dig));
+
+	BigIntegerModExp(v, g, x, n);
+	tpe.password.len = BigIntegerToBytes(v, (unsigned char *)pwbuf);
+
+	BigIntegerFree(v);
+	BigIntegerFree(x);
+	BigIntegerFree(g);
+	BigIntegerFree(n);
+	return true;
+}
+
+static u16_t
+chksum(u16_t sum, const u8_t *data, u16_t len)
+{
+	u16_t t;
+	const u8_t *dataptr;
+	const u8_t *last_byte;
+
+	dataptr = data;
+	last_byte = data + len - 1;
+
+	while(dataptr < last_byte) {	/* At least two more bytes */
+		t = (dataptr[0] << 8) + dataptr[1];
+		sum += t;
+		if(sum < t) {
+			sum++;		/* carry */
+		}
+		dataptr += 2;
+	}
+
+	if(dataptr == last_byte) {
+		t = (dataptr[0] << 8) + 0;
+		sum += t;
+		if(sum < t) {
+			sum++;		/* carry */
+		}
+	}
+
+	/* Return sum in host byte order. */
+	return sum;
+}
+
+static void
+ead_send_packet_clone(struct ead_packet *pkt)
+{
+	u16_t len, sum;
+
+	memcpy(pktbuf, pkt, offsetof(struct ead_packet, msg));
+	memcpy(pktbuf->eh.ether_shost, ethmac, 6);
+	memcpy(pktbuf->eh.ether_dhost, pkt->eh.ether_shost, 6);
+
+	/* ip header */
+	len = sizeof(struct ead_packet) - sizeof(struct ether_header) + ntohl(pktbuf->msg.len);
+	pktbuf->len[0] = len >> 8;
+	pktbuf->len[1] = len & 0xff;
+	memcpy(pktbuf->srcipaddr, pkt->destipaddr, 4);
+	memcpy(pktbuf->destipaddr, pkt->srcipaddr, 4);
+
+	/* ip checksum */
+	pktbuf->ipchksum = 0;
+	sum = chksum(0, (void *) &pktbuf->vhl, UIP_IPH_LEN);
+	if (sum == 0)
+		sum = 0xffff;
+	pktbuf->ipchksum = htons(~sum);
+
+	/* udp header */
+	pktbuf->srcport = pkt->destport;
+	pktbuf->destport = pkt->srcport;
+
+	/* udp checksum */
+	len -= UIP_IPH_LEN;
+	pktbuf->udplen = htons(len);
+	pktbuf->udpchksum = 0;
+	sum = len + UIP_PROTO_UDP;
+	sum = chksum(sum, (void *) &pktbuf->srcipaddr[0], 8); /* src, dest ip */
+	sum = chksum(sum, (void *) &pktbuf->srcport, len);
+	if (sum == 0)
+		sum = 0xffff;
+	pktbuf->udpchksum = htons(~sum);
+	pcap_sendpacket(pcap_fp, (void *) pktbuf, sizeof(struct ead_packet) + ntohl(pktbuf->msg.len));
+}
+
+static void
+set_state(int nstate)
+{
+	if (state == nstate)
+		return;
+
+	if (nstate < state) {
+		if ((nstate < EAD_TYPE_GET_PRIME) &&
+			(state >= EAD_TYPE_GET_PRIME)) {
+			t_serverclose(ts);
+			ts = NULL;
+		}
+		goto done;
+	}
+
+	switch(state) {
+	case EAD_TYPE_SET_USERNAME:
+		if (!prepare_password())
+			goto error;
+		ts = t_serveropenraw(&tpe, tce);
+		if (!ts)
+			goto error;
+		break;
+	case EAD_TYPE_GET_PRIME:
+		B = t_servergenexp(ts);
+		break;
+	case EAD_TYPE_SEND_A:
+		skey = t_servergetkey(ts, &A);
+		if (!skey)
+			goto error;
+
+		ead_set_key(skey);
+		break;
+	}
+done:
+	state = nstate;
+error:
+	return;
+}
+
+static bool
+handle_ping(struct ead_packet *pkt, int len, int *nstate)
+{
+	struct ead_msg *msg = &pktbuf->msg;
+	struct ead_msg_pong *pong = EAD_DATA(msg, pong);
+	int slen;
+
+	slen = strlen(dev_name);
+	if (slen > 1024)
+		slen = 1024;
+
+	msg->len = htonl(sizeof(struct ead_msg_pong) + slen);
+	strncpy(pong->name, dev_name, slen);
+	pong->name[len] = 0;
+	pong->auth_type = htons(EAD_AUTH_MD5);
+
+	return true;
+}
+
+static bool
+handle_set_username(struct ead_packet *pkt, int len, int *nstate)
+{
+	struct ead_msg *msg = &pkt->msg;
+	struct ead_msg_user *user = EAD_DATA(msg, user);
+
+	set_state(EAD_TYPE_SET_USERNAME); /* clear old state */
+	strncpy(username, user->username, sizeof(username));
+	username[sizeof(username)] = 0;
+
+	msg = &pktbuf->msg;
+	msg->len = 0;
+
+	*nstate = EAD_TYPE_GET_PRIME;
+	return true;
+}
+
+static bool
+handle_get_prime(struct ead_packet *pkt, int len, int *nstate)
+{
+	struct ead_msg *msg = &pktbuf->msg;
+	struct ead_msg_salt *salt = EAD_DATA(msg, salt);
+
+	msg->len = htonl(sizeof(struct ead_msg_salt));
+	salt->prime = tce->index - 1;
+	salt->len = ts->s.len;
+	memcpy(salt->salt, ts->s.data, ts->s.len);
+	memcpy(salt->ext_salt, pw_saltbuf, MAXSALTLEN);
+
+	*nstate = EAD_TYPE_SEND_A;
+	return true;
+}
+
+static bool
+handle_send_a(struct ead_packet *pkt, int len, int *nstate)
+{
+	struct ead_msg *msg = &pkt->msg;
+	struct ead_msg_number *number = EAD_DATA(msg, number);
+	len = ntohl(msg->len) - sizeof(struct ead_msg_number);
+
+	if (len > MAXPARAMLEN + 1)
+		return false;
+
+	A.len = len;
+	A.data = abuf;
+	memcpy(A.data, number->data, len);
+
+	msg = &pktbuf->msg;
+	number = EAD_DATA(msg, number);
+	msg->len = htonl(sizeof(struct ead_msg_number) + B->len);
+	memcpy(number->data, B->data, B->len);
+
+	*nstate = EAD_TYPE_SEND_AUTH;
+	return true;
+}
+
+static bool
+handle_send_auth(struct ead_packet *pkt, int len, int *nstate)
+{
+	struct ead_msg *msg = &pkt->msg;
+	struct ead_msg_auth *auth = EAD_DATA(msg, auth);
+
+	if (t_serververify(ts, auth->data) != 0) {
+		DEBUG(2, "Client authentication failed\n");
+		*nstate = EAD_TYPE_SET_USERNAME;
+		return false;
+	}
+
+	msg = &pktbuf->msg;
+	auth = EAD_DATA(msg, auth);
+	msg->len = htonl(sizeof(struct ead_msg_auth));
+
+	DEBUG(2, "Client authentication successful\n");
+	memcpy(auth->data, t_serverresponse(ts), sizeof(auth->data));
+
+	*nstate = EAD_TYPE_SEND_CMD;
+	return true;
+}
+
+static bool
+handle_send_cmd(struct ead_packet *pkt, int len, int *nstate)
+{
+	struct ead_msg *msg = &pkt->msg;
+	struct ead_msg_cmd *cmd = EAD_ENC_DATA(msg, cmd);
+	struct ead_msg_cmd_data *cmddata;
+	struct timeval tv, to, tn;
+	int pfd[2], fd;
+	fd_set fds;
+	pid_t pid;
+	bool stream = false;
+	int timeout;
+	int type;
+	int datalen;
+
+	datalen = ead_decrypt_message(msg) - sizeof(struct ead_msg_cmd);
+	if (datalen <= 0)
+		return false;
+
+	type = ntohs(cmd->type);
+	timeout = ntohs(cmd->timeout);
+
+	FD_ZERO(&fds);
+	cmd->data[datalen] = 0;
+	switch(type) {
+	case EAD_CMD_NORMAL:
+		if (pipe(pfd) < 0)
+			return false;
+
+		fcntl(pfd[0], F_SETFL, O_NONBLOCK | fcntl(pfd[0], F_GETFL));
+		child_pending = true;
+		pid = fork();
+		if (pid == 0) {
+			close(pfd[0]);
+			fd = open("/dev/null", O_RDWR);
+			if (fd > 0) {
+				dup2(fd, 0);
+				dup2(pfd[1], 1);
+				dup2(pfd[1], 2);
+			}
+			system((char *)cmd->data);
+			exit(0);
+		} else if (pid > 0) {
+			close(pfd[1]);
+			if (!timeout)
+				timeout = EAD_CMD_TIMEOUT;
+
+			stream = true;
+			break;
+		}
+		return false;
+	case EAD_CMD_BACKGROUND:
+		pid = fork();
+		if (pid == 0) {
+			/* close stdin, stdout, stderr, replace with fd to /dev/null */
+			fd = open("/dev/null", O_RDWR);
+			if (fd > 0) {
+				dup2(fd, 0);
+				dup2(fd, 1);
+				dup2(fd, 2);
+			}
+			system((char *)cmd->data);
+			exit(0);
+		} else if (pid > 0) {
+			break;
+		}
+		return false;
+	default:
+		return false;
+	}
+
+	msg = &pktbuf->msg;
+	cmddata = EAD_ENC_DATA(msg, cmd_data);
+
+	if (stream) {
+		int nfds, bytes;
+
+		/* send keepalive packets every 200 ms so that the client doesn't timeout */
+		gettimeofday(&to, NULL);
+		memcpy(&tn, &to, sizeof(tn));
+		tv.tv_usec = PCAP_TIMEOUT * 1000;
+		tv.tv_sec = 0;
+		do {
+			cmddata->done = 0;
+			FD_SET(pfd[0], &fds);
+			nfds = select(pfd[0] + 1, &fds, NULL, NULL, &tv);
+			bytes = 0;
+			if (nfds > 0) {
+				bytes = read(pfd[0], cmddata->data, 1024);
+				if (bytes < 0)
+					bytes = 0;
+			}
+			if (!bytes && !child_pending)
+				break;
+			DEBUG(3, "Sending %d bytes of console data, type=%d, timeout=%d\n", bytes, ntohl(msg->type), timeout);
+			ead_encrypt_message(msg, sizeof(struct ead_msg_cmd_data) + bytes);
+			ead_send_packet_clone(pkt);
+			gettimeofday(&tn, NULL);
+		} while (tn.tv_sec < to.tv_sec + timeout);
+		if (child_pending) {
+			kill(pid, SIGKILL);
+			return false;
+		}
+	}
+	cmddata->done = 1;
+	ead_encrypt_message(msg, sizeof(struct ead_msg_cmd_data));
+
+	return true;
+}
+
+
+
+static void
+parse_message(struct ead_packet *pkt, int len)
+{
+	bool (*handler)(struct ead_packet *pkt, int len, int *nstate);
+	int min_len = sizeof(struct ead_packet);
+	int nstate = state;
+	int type = ntohl(pkt->msg.type);
+
+	if ((type >= EAD_TYPE_GET_PRIME) &&
+		(state != type))
+		return;
+
+	switch(type) {
+	case EAD_TYPE_PING:
+		handler = handle_ping;
+		break;
+	case EAD_TYPE_SET_USERNAME:
+		handler = handle_set_username;
+		min_len += sizeof(struct ead_msg_user);
+		break;
+	case EAD_TYPE_GET_PRIME:
+		handler = handle_get_prime;
+		break;
+	case EAD_TYPE_SEND_A:
+		handler = handle_send_a;
+		min_len += sizeof(struct ead_msg_number);
+		break;
+	case EAD_TYPE_SEND_AUTH:
+		handler = handle_send_auth;
+		min_len += sizeof(struct ead_msg_auth);
+		break;
+	case EAD_TYPE_SEND_CMD:
+		handler = handle_send_cmd;
+		min_len += sizeof(struct ead_msg_cmd) + sizeof(struct ead_msg_encrypted);
+		break;
+	default:
+		return;
+	}
+
+	if (len < min_len) {
+		DEBUG(2, "discarding packet: message too small\n");
+		return;
+	}
+
+	pktbuf->msg.magic = htonl(EAD_MAGIC);
+	pktbuf->msg.type = htonl(type + 1);
+	pktbuf->msg.nid = htons(nid);
+	pktbuf->msg.len = 0;
+
+	if (handler(pkt, len, &nstate)) {
+		DEBUG(2, "sending response to packet type %d: %d\n", type + 1, ntohl(pktbuf->msg.len));
+		/* format response packet */
+		ead_send_packet_clone(pkt);
+	}
+	set_state(nstate);
+}
+
+static void
+handle_packet(u_char *user, const struct pcap_pkthdr *h, const u_char *bytes)
+{
+	struct ead_packet *pkt = (struct ead_packet *) bytes;
+
+	if (h->len < sizeof(struct ead_packet))
+		return;
+
+	if (pkt->eh.ether_type != htons(ETHERTYPE_IP))
+		return;
+
+	if (memcmp(pkt->eh.ether_dhost, "\xff\xff\xff\xff\xff\xff", 6) != 0)
+		return;
+
+	if (pkt->proto != UIP_PROTO_UDP)
+		return;
+
+	if (pkt->destport != htons(EAD_PORT))
+		return;
+
+	if (pkt->msg.magic != htonl(EAD_MAGIC))
+		return;
+
+	if (h->len < sizeof(struct ead_packet) + ntohl(pkt->msg.len))
+		return;
+
+	if ((pkt->msg.nid != 0xffff) &&
+		(pkt->msg.nid != htons(nid)))
+		return;
+
+	parse_message(pkt, h->len);
+}
+
+static void
+ead_pcap_reopen(bool first)
+{
+	static char errbuf[PCAP_ERRBUF_SIZE] = "";
+
+	if (pcap_fp_rx != pcap_fp)
+		pcap_close(pcap_fp_rx);
+
+	if (pcap_fp)
+		pcap_close(pcap_fp);
+
+	pcap_fp_rx = pcap_fp;
+	do {
+		pcap_fp = pcap_open_live(ifname, PCAP_MRU, 1, PCAP_TIMEOUT, errbuf);
+#ifdef linux
+		if (brname) {
+			pcap_fp_rx = pcap_open_live(brname, PCAP_MRU, 1, PCAP_TIMEOUT, errbuf);
+			if (!pcap_fp_rx)
+				pcap_fp_rx = pcap_fp;
+		}
+#endif
+		pcap_setfilter(pcap_fp_rx, &pktfilter);
+		if (first && !pcap_fp) {
+			DEBUG(1, "WARNING: unable to open interface '%s'\n", ifname);
+			first = false;
+		}
+		if (!pcap_fp)
+			sleep(1);
+	} while (!pcap_fp);
+}
+
+
+static void
+ead_pktloop(void)
+{
+	while (1) {
+		if (pcap_dispatch(pcap_fp_rx, 1, handle_packet, NULL) < 0) {
+			ead_pcap_reopen(false);
+			continue;
+		}
+	}
+}
+
+
+static int
+usage(const char *prog)
+{
+	fprintf(stderr, "Usage: %s [<options>]\n"
+		"Options:\n"
+		"\t-B             Run in background mode\n"
+		"\t-d <device>    Set the device to listen on\n"
+		"\t-D <name>      Set the name of the device visible to clients\n"
+		"\t-p <file>      Set the password file for authenticating\n"
+		"\t-P <file>      Write a pidfile\n"
+		"\n", prog);
+	return -1;
+}
+
+static void
+server_handle_sigchld(int sig)
+{
+	struct ead_instance *in;
+	struct list_head *p;
+	int pid = 0;
+	wait(&pid);
+
+	list_for_each(p, &instances) {
+		in = list_entry(p, struct ead_instance, list);
+		if (pid != in->pid)
+			continue;
+
+		in->pid = 0;
+		break;
+	}
+}
+
+static void
+instance_handle_sigchld(int sig)
+{
+	int pid = 0;
+	wait(&pid);
+	child_pending = false;
+}
+
+static void
+start_server(struct ead_instance *i)
+{
+	if (!nonfork) {
+		i->pid = fork();
+		if (i->pid != 0) {
+			if (i->pid < 0)
+				i->pid = 0;
+			return;
+		}
+	}
+
+	signal(SIGCHLD, instance_handle_sigchld);
+	ifname = i->name;
+#ifdef linux
+	if (i->bridge[0])
+		brname = i->bridge;
+#endif
+	ead_pcap_reopen(true);
+	ead_pktloop();
+	pcap_close(pcap_fp);
+	if (pcap_fp_rx != pcap_fp)
+		pcap_close(pcap_fp_rx);
+
+	exit(0);
+}
+
+
+static void
+start_servers(bool restart)
+{
+	struct ead_instance *in;
+	struct list_head *p;
+
+	list_for_each(p, &instances) {
+		in = list_entry(p, struct ead_instance, list);
+		if (in->pid > 0)
+			continue;
+
+		sleep(1);
+		start_server(in);
+	}
+}
+
+static void
+stop_server(struct ead_instance *in, bool do_free)
+{
+	if (in->pid > 0)
+		kill(in->pid, SIGKILL);
+	in->pid = 0;
+	if (do_free) {
+		list_del(&in->list);
+		free(in);
+	}
+}
+
+static void
+server_handle_sigint(int sig)
+{
+	struct ead_instance *in;
+	struct list_head *p, *tmp;
+
+	list_for_each_safe(p, tmp, &instances) {
+		in = list_entry(p, struct ead_instance, list);
+		stop_server(in, true);
+	}
+	exit(1);
+}
+
+#ifdef linux
+static int
+check_bridge_port(const char *br, const char *port, void *arg)
+{
+	struct ead_instance *in;
+	struct list_head *p, *tmp;
+
+	list_for_each(p, &instances) {
+		in = list_entry(p, struct ead_instance, list);
+
+		if (strcmp(in->name, port) != 0)
+			continue;
+
+		in->br_check = true;
+		if (strcmp(in->bridge, br) == 0)
+			break;
+
+		strncpy(in->bridge, br, sizeof(in->bridge));
+		DEBUG(2, "assigning port %s to bridge %s\n", in->name, in->bridge);
+		stop_server(in, false);
+	}
+	return 0;
+}
+
+static int
+check_bridge(const char *name, void *arg)
+{
+	br_foreach_port(name, check_bridge_port, arg);
+	return 0;
+}
+#endif
+
+static void
+check_all_interfaces(void)
+{
+#ifdef linux
+	struct ead_instance *in;
+	struct list_head *p, *tmp;
+
+	br_foreach_bridge(check_bridge, NULL);
+
+	/* look for interfaces that are no longer part of a bridge */
+	list_for_each(p, &instances) {
+		in = list_entry(p, struct ead_instance, list);
+
+		if (in->br_check) {
+			in->br_check = false;
+		} else if (in->bridge[0]) {
+			DEBUG(2, "removing port %s from bridge %s\n", in->name, in->bridge);
+			in->bridge[0] = 0;
+			stop_server(in, false);
+		}
+	}
+#endif
+}
+
+
+int main(int argc, char **argv)
+{
+	struct ead_instance *in;
+	struct timeval tv;
+	int fd, ch;
+	const char *pidfile = NULL;
+	bool background = false;
+	int n_iface = 0;
+
+	if (argc == 1)
+		return usage(argv[0]);
+
+	INIT_LIST_HEAD(&instances);
+	while ((ch = getopt(argc, argv, "Bd:D:fhp:P:")) != -1) {
+		switch(ch) {
+		case 'B':
+			background = true;
+			break;
+		case 'f':
+			nonfork = true;
+			break;
+		case 'h':
+			return usage(argv[0]);
+		case 'd':
+			in = malloc(sizeof(struct ead_instance));
+			memset(in, 0, sizeof(struct ead_instance));
+			INIT_LIST_HEAD(&in->list);
+			strncpy(in->name, optarg, sizeof(in->name) - 1);
+			list_add(&in->list, &instances);
+			n_iface++;
+			break;
+		case 'D':
+			dev_name = optarg;
+			break;
+		case 'p':
+			passwd_file = optarg;
+			break;
+		case 'P':
+			pidfile = optarg;
+			break;
+		}
+	}
+	signal(SIGCHLD, server_handle_sigchld);
+	signal(SIGINT, server_handle_sigint);
+	signal(SIGTERM, server_handle_sigint);
+	signal(SIGKILL, server_handle_sigint);
+
+	if (!n_iface) {
+		fprintf(stderr, "Error: ead needs at least one interface\n");
+		return -1;
+	}
+
+	if (background) {
+		if (fork() > 0)
+			exit(0);
+
+		fd = open("/dev/null", O_RDWR);
+		dup2(fd, 0);
+		dup2(fd, 1);
+		dup2(fd, 2);
+	}
+
+	if (pidfile) {
+		char pid[8];
+		int len;
+
+		unlink(pidfile);
+		fd = open(pidfile, O_CREAT|O_WRONLY|O_EXCL, 0644);
+		if (fd > 0) {
+			len = sprintf(pid, "%d\n", getpid());
+			write(fd, pid, len);
+			close(fd);
+		}
+	}
+
+	/* randomize the mac address */
+	fd = open("/dev/urandom", O_RDONLY);
+	if (fd < 0) {
+		perror("open");
+		exit(1);
+	}
+	read(fd, ethmac + 3, 3);
+	close(fd);
+	nid = *(((u16_t *) ethmac) + 2);
+
+	start_servers(false);
+#ifdef linux
+	br_init();
+#endif
+	tv.tv_sec = 1;
+	tv.tv_usec = 0;
+	while (1) {
+		check_all_interfaces();
+		start_servers(true);
+		sleep(1);
+	}
+#ifdef linux
+	br_shutdown();
+#endif
+
+	return 0;
+}