/* See LICENSE file for copyright and license details. */
#include <sys/auxv.h>
#include <sys/epoll.h>
#include <sys/timerfd.h>
#include <libblake.h>
#include <libsimple.h>
#include <libsimple-arg.h>

USAGE("[-a unix-address] [-c config-file] [-p udp-port]");


#define UDP_PORT 42712
#define LOCAL_ADDRESS_PREFIX "@oikobus-"

#define LOCAL_ADDRESS_BUFSIZE (sizeof(LOCAL_ADDRESS_PREFIX) + 3u * sizeof(uintmax_t))
#define LOCAL_ADDRESS(UID) "%s%ju", LOCAL_ADDRESS_PREFIX, (uintmax_t)(UID)

#define SOCKADDR(ADDR) ((void *)&(ADDR)), ((socklen_t)sizeof(ADDR))
#define ALPHA64 "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz{}"
#define MIN_REALM_LEN 1u
#define MAX_REALM_LEN 510u
#define CHALLENGE_SIZE 64u /* must be within [1 64] (BLAKE2b key bounds) */
#define PROOF_SIZE 64u /* must be within [1 64] (BLAKE2b digest bounds) */
#define CHALLENGE_PEPPER "\xa1\x7d\xcc\x75\x51\xd9\xc2\x2b\x63\xf9\x45\x83\x4b\x4d\xae\x4c"


union file;


enum file_type {
	TIMER_FILE,
	BROADCAST_FILE,
	NETWORK_FILE,
	LOCAL_FILE,
	PEER_FILE,
	CLIENT_FILE
};

#define FILE_COMMON\
	enum file_type type;\
	int fd;\
	void (*on_event)(union file *this, uint32_t epoll_events)

struct timer_file {
	FILE_COMMON;
	union file *owner;
};

struct broadcast_file {
	FILE_COMMON;
	struct sockaddr_in addr;
	struct timer_file timer;
	int64_t timer_inc;
	struct timespec alarm_time;
};

struct network_file {
	FILE_COMMON;
};

struct local_file {
	FILE_COMMON;
};

struct peer_file {
	FILE_COMMON;
	uint64_t id;
	struct sockaddr_in addr;
	uint8_t *realms;
	struct handshake_state {
#define HANDSHAKE_A_INIT HANDSHAKE_A_SEND_ID
#define HANDSHAKE_B_INIT HANDSHAKE_B_SEND_ID
		enum handshake_status {
			HANDSHAKE_A_SEND_ID,
			HANDSHAKE_A_RECV_ID,
			HANDSHAKE_A_SEND_REALM,
			HANDSHAKE_A_RECV_CHALLENGE,
			HANDSHAKE_A_SEND_PROOF,
			HANDSHAKE_A_RECV_ACCEPTANCE,
			HANDSHAKE_B_SEND_ID,
			HANDSHAKE_B_RECV_ID,
			HANDSHAKE_B_RECV_REALM,
			HANDSHAKE_B_SEND_CHALLENGE,
			HANDSHAKE_B_RECV_PROOF,
			HANDSHAKE_B_SEND_ACCEPTANCE
		} status;
		size_t realm;
		uint16_t off;
		uint16_t len;
		uint16_t head;
		uint16_t tail;
		unsigned char buf[512];
		unsigned char sbuf[512];
	} *handshake_state;
};

struct client_file {
	FILE_COMMON;
	struct client_file *prev;
	struct client_file *next;
};

union file {
	struct { FILE_COMMON; };
	struct timer_file timer;
	struct broadcast_file broadcast;
	struct network_file network;
	struct local_file local;
	struct peer_file peer;
	struct client_file client;
};


struct broadcast_message {
#define BROADCAST_MESSAGE_SIZE 10
	uint64_t id;
	uint16_t port;
};


struct realm {
	char *name;
	char *key;
};


static struct realm *realms = NULL;
static size_t nrealms = 0u;
static struct broadcast_message server_identity;
static int epoll;
static struct epoll_event *events;
static int events_size;
static struct local_file *lsock;
static struct network_file *nsock;
static struct broadcast_file *bsock;
static struct peer_file **peers;
static size_t npeers;
static size_t peers_size;
static uid_t uid;
static struct client_file clients_head;
static struct client_file clients_tail;


static void
remove_peer(struct peer_file *peer)
{
	size_t i;
	for (i = 0u; i < npeers; i++) {
		if (peers[i] == peer) {
			peers[i] = peers[--npeers];
			break;
		}
	}
	close(peer->fd);
	free(peer->handshake_state);
	free(peer->realms);
	free(peer);
}


static struct peer_file *
add_peer(int fd, uint64_t id, const struct sockaddr_in *addr,
         enum handshake_status status, void (*on_event)(union file *, uint32_t))
{
	struct peer_file *file;
	struct epoll_event ev;

	file = emalloc(sizeof(*file));
	file->type = PEER_FILE;
	file->fd = fd;
	file->id = id;
	file->addr = *addr;
	file->on_event = on_event;
	file->realms = nrealms ? ecalloc((nrealms + 7u) / 8u, sizeof(uint8_t)) : NULL;
	file->handshake_state = ecalloc(1u, sizeof(*file->handshake_state));
	file->handshake_state->status = status;

	memset(&ev, 0, sizeof(ev));
	ev.events = EPOLLIN | EPOLLOUT;
	ev.data.ptr = file;
	if (epoll_ctl(epoll, EPOLL_CTL_ADD, file->fd, &ev))
		eprintf("epoll_ctl <epoll> EPOLL_CTL_ADD <peer tcp socket> {EPOLLIN|EPOLLOUT}:");

	if (npeers == peers_size)
		peers = ereallocarray(peers, ++peers_size, sizeof(*peers));
	peers[npeers++] = file;

	return file;
}


static void
on_client_event(union file *this, uint32_t epoll_events)
{
	(void) this;
	(void) epoll_events;
	/* TODO */
}


static void
on_peer_event(union file *this, uint32_t epoll_events)
{
	(void) this;
	(void) epoll_events;
	/* TODO */
}


static unsigned char *
handshake_prepare(struct peer_file *this, size_t len)
{
	uint16_t n;
	if (len > sizeof(this->handshake_state->sbuf) - 2u)
		abort();
	len += 2u;
	n = (uint16_t)len;
	this->handshake_state->off = 0u;
	this->handshake_state->len = n;
	n = htons(n);
	memcpy(&this->handshake_state->sbuf[0u], &n, 2u);
	return &this->handshake_state->sbuf[2u];
}


static int
handshake_continue(struct peer_file *this)
{
	size_t rem;
	ssize_t r;
	while ((rem = this->handshake_state->len - this->handshake_state->off)) {
		r = send(this->fd, &this->handshake_state->sbuf[this->handshake_state->off], rem, MSG_NOSIGNAL | MSG_DONTWAIT);
		if (r < 0) {
			if (errno == EINTR)
				continue;
			if (errno == ECONNRESET || errno == EPIPE)
				return -1;
			if (errno == EAGAIN)
				return 0;
#if EAGAIN != EWOULDBLOCK
			if (errno == EWOULDBLOCK)
				return 0;
#endif
			weprintf("send <peer tcp socket>:");
			return -1;
		}
		this->handshake_state->off += (uint16_t)r;
	}
	this->handshake_state->off = 0u;
	this->handshake_state->len = 0u;
	return 1;
}


static int
handshake_send(struct peer_file *this, const void *message, size_t len)
{
	if (!this->handshake_state->len)
		memcpy(handshake_prepare(this, len), message, len);
	return handshake_continue(this);
}


static int
handshake_receive(struct peer_file *this)
{
	ssize_t r;
	uint16_t len = 0u;

	if (this->handshake_state->head != this->handshake_state->tail) {
		memmove(&this->handshake_state->buf[0u],
		        &this->handshake_state->buf[this->handshake_state->head],
		        this->handshake_state->tail -= this->handshake_state->head);
		this->handshake_state->off += this->handshake_state->tail;
		this->handshake_state->tail = this->handshake_state->head = 0u;
	}

	for (;;) {
		if (len) {
			goto check_done;
		} else if (this->handshake_state->off >= 2u) {
			memcpy(&len, &this->handshake_state->buf[0u], 2u);
			len = ntohs(len);
		check_done:
			if (this->handshake_state->off >= len)
				break;
		}

		r = recv(this->fd, &this->handshake_state->buf[this->handshake_state->off],
		         sizeof(this->handshake_state->buf) - this->handshake_state->off,
		         MSG_DONTWAIT);
		if (r <= 0) {
			if (!r)
				return -1;
			if (errno == EINTR)
				continue;
			if (errno == ECONNRESET || errno == EPIPE)
				return -1;
			if (errno == EAGAIN)
				return 0;
#if EAGAIN != EWOULDBLOCK
			if (errno == EWOULDBLOCK)
				return 0;
#endif
			weprintf("recv <peer tcp socket>:");
			return -1;
		}
		this->handshake_state->off += (uint16_t)r;
	}

	this->handshake_state->tail = this->handshake_state->off;
	this->handshake_state->head = this->handshake_state->off = len;
	return 1;
}


static void
generate_proof(const struct realm *realm, const void *challenge, unsigned char *buf)
{
	unsigned char block[LIBBLAKE_BLAKE2B_BLOCK_SIZE];
	struct libblake_blake2b_params params;
	struct libblake_blake2b_state state;
	size_t salt_len;
	size_t key_len = strlen(realm->key);
	size_t off = 0u;

	salt_len = strlen(realm->name);
	salt_len = salt_len < 16u ? salt_len : 16u;
	memset(&params, 0, sizeof(params));
	params.digest_len = PROOF_SIZE;
	params.key_len = CHALLENGE_SIZE;
	params.fanout = 1u;
	params.depth = 1u;
	memcpy(params.salt, realm->name, salt_len);
	memcpy(params.pepper, CHALLENGE_PEPPER, 16u);

	libblake_blake2b_init(&state, &params);

	memcpy(&block[0u], challenge, CHALLENGE_SIZE);
	memset(&block[CHALLENGE_SIZE], 0, sizeof(block) - CHALLENGE_SIZE);
	libblake_blake2b_force_update(&state, block, sizeof(block));

	off = key_len & ~(sizeof(block) - 1u);
	if (off == key_len)
		off -= sizeof(block);
	if (off)
		off = libblake_blake2b_force_update(&state, realm->key, off);
	memcpy(&block[0u], realm->key, key_len - off);
	libblake_blake2b_digest(&state, block, key_len - off, 0, PROOF_SIZE, buf);
}


static void
peer_handshake(union file *this_, uint32_t epoll_events)
{
	unsigned char proof_buf[PROOF_SIZE];
	struct peer_file *this = &this_->peer;
	struct epoll_event ev;
	uint16_t len;
	size_t i;
	int r;

#define SEND(...) CHECKED(handshake_send(this, __VA_ARGS__)) goto wait_write
#define RECV() CHECKED(handshake_receive(this)) goto wait_read
#define CONT() CHECKED(handshake_continue(this)) goto wait_write
#define CHECKED(COMMAND)\
	r = (COMMAND);\
	if (r < 0) goto remove;\
	if (r == 0)

	(void) epoll_events;

	switch (this->handshake_state->status) {
	case HANDSHAKE_A_SEND_ID:
		SEND(&server_identity.id, 8u);
		this->handshake_state->status++;
		/* fall-through */

	case HANDSHAKE_A_RECV_ID:
		RECV();
		len = this->handshake_state->off;
		this->handshake_state->off = 0u;
		if (len != 10u || memcmp(&this->handshake_state->buf[2u], &this->id, 8u))
			goto remove;
		this->handshake_state->status++;
		/* fall-through */

	case HANDSHAKE_A_SEND_REALM:
	send_realm:
		if (this->handshake_state->realm == nrealms) {
			SEND("", 0u);
			break;
		}
		SEND(realms[this->handshake_state->realm].name,
		     strlen(realms[this->handshake_state->realm].name));
		this->handshake_state->status++;
		/* fall-through */

	case HANDSHAKE_A_RECV_CHALLENGE:
		RECV();
		len = this->handshake_state->off;
		this->handshake_state->off = 0u;
		if (len == 2u) {
			this->handshake_state->status = HANDSHAKE_A_SEND_REALM;
			goto send_realm;
		}
		if (len != CHALLENGE_SIZE + 2u) {
			goto remove;
		}
		generate_proof(&realms[this->handshake_state->realm],
		               &this->handshake_state->buf[2u],
		               handshake_prepare(this, PROOF_SIZE));
		this->handshake_state->status++;
		/* fall-through */

	case HANDSHAKE_A_SEND_PROOF:
		CONT();
		this->handshake_state->status++;
		/* fall-through */

	case HANDSHAKE_A_RECV_ACCEPTANCE:
		RECV();
		len = this->handshake_state->off;
		this->handshake_state->off = 0u;
		if (len != 3u || this->handshake_state->buf[2u] > 1u)
			goto remove;
		if (this->handshake_state->buf[2u]) {
			uint8_t bit = (uint8_t)(1u << (this->handshake_state->realm % 8u));
			this->realms[this->handshake_state->realm / 8u] |= bit;
		}
		this->handshake_state->realm++;
		this->handshake_state->status = HANDSHAKE_A_SEND_REALM;
		goto send_realm;


	case HANDSHAKE_B_SEND_ID:
		if (!handshake_send(this, &server_identity.id, 8u))
			goto wait_write;
		this->handshake_state->status++;
		/* fall-through */

	case HANDSHAKE_B_RECV_ID:
		RECV();
		len = this->handshake_state->off;
		this->handshake_state->off = 0u;
		if (len != 10u)
			goto remove;
		memcpy(&this->id, &this->handshake_state->buf[2u], 8u);
		if (this->id == server_identity.id)
			goto remove;
		for (i = 0u; i < npeers; i++)
			if (peers[i]->id == this->id && peers[i] != this)
				goto remove;
		this->handshake_state->status++;
		/* fall-through */

	case HANDSHAKE_B_RECV_REALM:
	recv_realm:
		RECV();
		len = this->handshake_state->off;
		this->handshake_state->off = 0u;
		if (len <= 2u) {
			if (len == 2u)
				break;
			goto remove;
		}
		len = (uint16_t)(len - 2u);
		for (i = 0u; i < nrealms; i++) {
			if (memcmp(realms[i].name, &this->handshake_state->buf[2u], len))
				continue;
			if (realms[i].name[len])
				continue;
			break;
		}
		this->handshake_state->realm = i;
		if (this->handshake_state->realm == nrealms) {
			handshake_prepare(this, 0u);
		} else {
			unsigned char *m = handshake_prepare(this, CHALLENGE_SIZE);
			for (i = 0u; i < CHALLENGE_SIZE; i++)
				m[i] = (unsigned char)(rand() & 255);
		}
		this->handshake_state->status++;
		/* fall-through */

	case HANDSHAKE_B_SEND_CHALLENGE:
		CONT();
		if (this->handshake_state->realm == nrealms) {
			this->handshake_state->status = HANDSHAKE_B_RECV_REALM;
			goto recv_realm;
		}
		this->handshake_state->status++;
		/* fall-through */

	case HANDSHAKE_B_RECV_PROOF:
		RECV();
		len = this->handshake_state->off;
		this->handshake_state->off = 0u;
		if (len != PROOF_SIZE + 2u)
			goto remove;
		generate_proof(&realms[this->handshake_state->realm],
		               &this->handshake_state->sbuf[2u], proof_buf);
		if (!memcmp(&this->handshake_state->buf[2u], proof_buf, PROOF_SIZE)) {
			uint8_t bit = (uint8_t)(1u << (this->handshake_state->realm % 8u));
			this->realms[this->handshake_state->realm / 8u] |= bit;
			handshake_prepare(this, 1u)[0u] = 1u;
			/* TODO we should send a realm index instead, so we can
			 *      encode reals as indicies rather than names
			 *      (index 0 should be reserved for the local-only
			 *      realm: a default realm that can only be accessed
			 *      on the same machine by the same user) */
		} else {
			handshake_prepare(this, 1u)[0u] = 0u;
		}
		this->handshake_state->status++;
		/* fall-through */

	case HANDSHAKE_B_SEND_ACCEPTANCE:
		CONT();
		this->handshake_state->status = HANDSHAKE_B_RECV_REALM;
		goto recv_realm;

	default:
		abort();
	}

	for (i = 0u; i < (nrealms + 7u) / 8u; i++)
		if (this->realms[i])
			goto have_a_realm;
remove:
	remove_peer(this);
	return;

have_a_realm:
	epoll_events = EPOLLIN;
	this->on_event = &on_peer_event;
	/* TODO copy over handshake recv buf */
	free(this->handshake_state);
	this->handshake_state = NULL;

config_epoll:
	memset(&ev, 0, sizeof(ev));
	ev.events = epoll_events;
	ev.data.ptr = this;
	if (epoll_ctl(epoll, EPOLL_CTL_MOD, this->fd, &ev))
		eprintf("epoll_ctl <epoll> EPOLL_CTL_MOD <peer tcp socket> {%s}:",
		        epoll_events == EPOLLIN ? "EPOLLIN" : "EPOLLOUT");
	return;

wait_write:
	epoll_events = EPOLLOUT;
	goto config_epoll;
wait_read:
	epoll_events = EPOLLIN;
	goto config_epoll;

#undef SEND
#undef RECV
#undef CONT
#undef CHECKED
}


static void
peer_connection_done(union file *this, uint32_t epoll_events)
{
	int err = 0;
	socklen_t len = (socklen_t)sizeof(err);

	if (getsockopt(this->fd, SOL_SOCKET, SO_ERROR, &err, &len))
		eprintf("getsockopt <peer tcp socket> SOL_SOCKET SO_ERROR");
	if (len > (socklen_t)sizeof(err))
		abort();

	if (err && err != EINTR) {
		weprintf("connect(async) <tcp socket> %s:%u\n",
		         inet_ntoa(this->peer.addr.sin_addr), ntohs(this->peer.addr.sin_port));
		remove_peer(&this->peer);
		return;
	}

	this->on_event = &peer_handshake;
	peer_handshake(this, epoll_events);
}


static void
on_network_socket_event(union file *this, uint32_t epoll_events)
{
	struct sockaddr_in addr;
	socklen_t addrlen = (socklen_t)sizeof(addr);
	struct peer_file *file;
	int fd;

	(void) epoll_events;

retry:
	fd = accept4(this->fd, (void *)&addr, &addrlen, SOCK_NONBLOCK);
	if (fd < 0) {
		switch (errno) {
		case EINTR:
			goto retry;
		case ECONNABORTED:
		case ECONNRESET:
		case EPERM:
			return;
		default:
			eprintf("accept4 <tcp server socket> SOCK_NONBLOCK:");
		}
	}
	if (addrlen > (socklen_t)sizeof(addr)) {
		weprintf("TCP socket peer name overlong\n");
		close(fd);
		return;
	}

	file = add_peer(fd, 0u, &addr, HANDSHAKE_B_INIT, &peer_handshake);
	peer_handshake((void *)file, EPOLLOUT);
}


static void
on_broadcast_socket_event(union file *this, uint32_t epoll_events)
{
	struct broadcast_message msg;
	struct sockaddr_in addr;
	socklen_t addrlen = (socklen_t)sizeof(addr);
	ssize_t r;
	int fd, in_progress;
	struct peer_file *file;
	size_t i;

	(void) epoll_events;

retry_recv:
	r = recvfrom(this->fd, &msg, sizeof(msg), MSG_TRUNC, &addr, &addrlen);
	if (r < 0) {
		if (errno == EINTR)
			goto retry_recv;
		if (errno == ECONNREFUSED)
			return;
		eprintf("recvfrom <broadcast socket>:");
	}
	if (addrlen > (socklen_t)sizeof(addr)) {
		weprintf("TCP socket peer name overlong\n");
		return;
	}
	if (r != BROADCAST_MESSAGE_SIZE || msg.id == server_identity.id)
		return;
	for (i = 0u; i < npeers; i++)
		if (msg.id == peers[i]->id)
			return;

	fd = socket(PF_INET, SOCK_STREAM | SOCK_NONBLOCK, 0);
	if (fd < 0) {
		weprintf("socket PF_INET SOCK_STREAM|SOCK_NONBLOCK 0:");
		return;
	}

	addr.sin_port = msg.port;
retry_connect:
	if (!connect(fd, (void *)&addr, addrlen)) {
		in_progress = 0;
	} else if (errno == EINPROGRESS) {
		in_progress = 1;
	} else if (errno == EINTR) {
		goto retry_connect;
	} else {
		weprintf("connect <tcp socket> %s:%u\n", inet_ntoa(addr.sin_addr), ntohs(msg.port));
		if (errno != ENETUNREACH && errno != ETIMEDOUT && errno != ECONNREFUSED)
			exit(1);
		close(fd);
		return;
	}

	file = add_peer(fd, msg.id, &addr, HANDSHAKE_A_INIT,
	                in_progress ? &peer_connection_done : &peer_handshake);
	if (!in_progress)
		peer_handshake((void *)file, EPOLLOUT);
}


static void
broadcast_identity(struct broadcast_file *file)
{
	long int rnd;
	struct itimerspec its;

	if (sendto(file->fd, &server_identity, BROADCAST_MESSAGE_SIZE, 0, SOCKADDR(file->addr)) != BROADCAST_MESSAGE_SIZE)
		weprintf("sendto <broadcast socket>:");

	file->alarm_time.tv_sec += file->timer_inc;
	file->timer_inc *= 2;
	rnd = rand() & 255;
	rnd *= 1000000l;
	file->alarm_time.tv_nsec += rnd;
	if (file->alarm_time.tv_nsec >= 1000000000l) {
		file->alarm_time.tv_nsec -= 1000000000l;
		file->alarm_time.tv_sec += 1;
	}

	memset(&its, 0, sizeof(its));
	its.it_value = file->alarm_time;
	if (timerfd_settime(file->timer.fd, 0, &its, NULL))
		weprintf("timerfd_settime <timerfd for broadcast socket> 0 <single expiry> NULL:");
}


static void
on_broadcast_timer_event(union file *this, uint32_t epoll_events)
{
	(void) epoll_events;
	broadcast_identity(&this->timer.owner->broadcast);
}


static void
on_local_socket_event(union file *this, uint32_t epoll_events)
{
	struct ucred cred;
	socklen_t len = (socklen_t)sizeof(cred);
	int fd;
	struct client_file *file;
	struct epoll_event ev;

	(void) epoll_events;

retry:
	fd = accept4(this->fd, NULL, NULL, SOCK_NONBLOCK | SOCK_CLOEXEC);
	if (fd < 0) {
		switch (errno) {
		case EINTR:
			goto retry;
		case ECONNABORTED:
		case ECONNRESET:
		case EPERM:
			return;
		default:
			eprintf("accept4 <local socket> NULL NULL SOCK_NONBLOCK|SOCK_CLOEXEC:");
		}
	}

	if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &cred, &len)) {
		weprintf("getsockopt <local client socket> SOL_SOCKET SO_PEERCRED:");
		close(fd);
		return;
	}
	if (len != (socklen_t)sizeof(cred))
		abort();
	if (cred.uid != uid) {
		/* TODO maybe it should be possible to open up realms to specific/all
		 *      users so they don't need a separate instance running */
		close(fd);
		return;
	}

	file = emalloc(sizeof(*file));
	file->type = CLIENT_FILE;
	file->fd = fd;
	file->on_event = &on_client_event;

	file->next = &clients_tail;
	file->prev = clients_tail.prev;
	clients_tail.prev->next = file;
	clients_tail.prev = file;

	memset(&ev, 0, sizeof(ev));
	ev.events = EPOLLIN;
	ev.data.ptr = file;
	if (epoll_ctl(epoll, EPOLL_CTL_ADD, file->fd, &ev))
		eprintf("epoll_ctl <epoll> EPOLL_CTL_ADD <client local socket> {EPOLLIN}:");
}


static struct network_file *
create_network_socket(void)
{
	struct sockaddr_in addr;
	socklen_t addrlen = (socklen_t)sizeof(addr);
	struct network_file *file;
	struct epoll_event ev;

	file = emalloc(sizeof(*file));
	file->type = NETWORK_FILE;
	file->on_event = &on_network_socket_event;

	file->fd = socket(PF_INET, SOCK_STREAM, 0);
	if (file->fd < 0)
		eprintf("socket PF_INET SOCK_STREAM 0:");

	memset(&addr, 0, sizeof(addr));
	addr.sin_family = AF_INET;
	addr.sin_addr.s_addr = htonl(INADDR_ANY);

	if (bind(file->fd, (const void *)&addr, addrlen))
		eprintf("bind <tcp socket> &{AF_INET, 0.0.0.0:0}:");

	if (getsockname(file->fd, &addr, &addrlen))
		eprintf("getsockname <tcp socket>:");
	if (addrlen < (socklen_t)(offsetof(struct sockaddr_in, sin_port) + sizeof(addr.sin_port)))
		abort();
	server_identity.port = addr.sin_port;

	if (listen(file->fd, SOMAXCONN))
		eprintf("listen <tcp socket> SOMAXCONN:");

	memset(&ev, 0, sizeof(ev));
	ev.events = EPOLLIN;
	ev.data.ptr = file;
	if (epoll_ctl(epoll, EPOLL_CTL_ADD, file->fd, &ev))
		eprintf("epoll_ctl <epoll> EPOLL_CTL_ADD <tcp server socket> {EPOLLIN}:");

	return file;
}


static struct broadcast_file *
create_broadcast_socket(uint16_t port)
{
	struct broadcast_file *file;
	struct epoll_event ev;

	file = emalloc(sizeof(*file));
	memset(file, 0, sizeof(*file));
	file->type = BROADCAST_FILE;
	file->on_event = &on_broadcast_socket_event;
	file->timer_inc = 1;
	file->timer.type = TIMER_FILE;
	file->timer.owner = (void *)file;
	file->timer.on_event = &on_broadcast_timer_event;

	file->fd = socket(PF_INET, SOCK_DGRAM, 0);
	if (file->fd < 0)
		eprintf("socket PF_INET SOCK_DGRAM 0:");

	/* TODO switch to multicast (for portability) */
	if (setsockopt(file->fd, SOL_SOCKET, SO_REUSEADDR, &(int){1}, (socklen_t)sizeof(int)))
		eprintf("setsockopt <udp socket> SOL_SOCKET SO_REUSEADDR &{1}:");

	if (setsockopt(file->fd, SOL_SOCKET, SO_BROADCAST, &(int){1}, (socklen_t)sizeof(int)))
		eprintf("setsockopt <udp socket> SOL_SOCKET SO_BROADCAST &{1}:");

	memset(&file->addr, 0, sizeof(file->addr));
	file->addr.sin_family = AF_INET;
	file->addr.sin_port = htons(port);
	file->addr.sin_addr.s_addr = htonl(INADDR_ANY);

	if (bind(file->fd, SOCKADDR(file->addr)))
		eprintf("bind <broadcast socket> &{AF_INET, 0.0.0.0:%i}:", port);

	file->addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);

	file->timer.fd = timerfd_create(CLOCK_BOOTTIME, 0);
	if (file->timer.fd < 0)
		eprintf("timerfd_create CLOCK_BOOTTIME 0:");

	memset(&ev, 0, sizeof(ev));
	ev.events = EPOLLIN;
	ev.data.ptr = file;
	if (epoll_ctl(epoll, EPOLL_CTL_ADD, file->fd, &ev))
		eprintf("epoll_ctl <epoll> EPOLL_CTL_ADD <broadcast socket> {EPOLLIN}:");
	ev.data.ptr = &file->timer;
	if (epoll_ctl(epoll, EPOLL_CTL_ADD, file->timer.fd, &ev))
		eprintf("epoll_ctl <epoll> EPOLL_CTL_ADD <timerfd for broadcast socket> {EPOLLIN}:");

	return file;
}


static struct local_file *
create_local_socket(const char *address)
{
	struct sockaddr_un addr;
	socklen_t addrlen = (socklen_t)sizeof(addr);
	struct local_file *file;
	struct epoll_event ev;
	size_t len;
	int print_sockname = 0;

	len = strlen(address);
	if (len > sizeof(addr.sun_path))
		eprintf("local address overlong: %s", address);

	file = emalloc(sizeof(*file));
	file->type = LOCAL_FILE;
	file->on_event = &on_local_socket_event;

	file->fd = socket(PF_LOCAL, SOCK_SEQPACKET, 0);
	if (file->fd < 0)
		eprintf("socket PF_LOCAL SOCK_SEQPACKET 0:");

	memset(&addr, 0, sizeof(addr));
	addr.sun_family = AF_LOCAL;
	memcpy(addr.sun_path, address, len);
	if (!len || addr.sun_path[0u] == '@') {
		addr.sun_path[0u] = '\0';
		if (len <= 1u) {
			for (len = 1u; len < sizeof(addr.sun_path); len++)
				addr.sun_path[len] = ALPHA64[rand() & 63];
			print_sockname = 1;
		} else {
			addrlen = (socklen_t)(offsetof(struct sockaddr_un, sun_path) + len);
		}
	}

	if (bind(file->fd, (const void *)&addr, addrlen)) 
		eprintf("bind <local socket> &{AF_LOCAL, %c%.*s}:",
		        addr.sun_path[0u] ? addr.sun_path[0u] : '@',
		        (int)len - 1, &addr.sun_path[1u]);

	if (listen(file->fd, SOMAXCONN))
		eprintf("listen <local socket> SOMAXCONN:");

	memset(&ev, 0, sizeof(ev));
	ev.events = EPOLLIN;
	ev.data.ptr = file;
	if (epoll_ctl(epoll, EPOLL_CTL_ADD, file->fd, &ev))
		eprintf("epoll_ctl <epoll> EPOLL_CTL_ADD <tcp server socket> {EPOLLIN}:");

	if (print_sockname) {
		if (printf("@%.*s\n", (int)len - 1, &addr.sun_path[1u]) < 0 || fflush(stdout))
			eprintf("printf:");
	}

	return file;
}


static void
init_process(void)
{
	struct timespec ts;
	unsigned long int auxval;
	unsigned seed = 0;
	size_t i;
	int fd;

	do {
		fd = open("/dev/null", O_RDWR);
		if (fd < 0)
			eprintf("open /dev/null O_RDWR:");
		if (fd > STDERR_FILENO)
			close(fd);
	} while (fd < STDERR_FILENO);

	uid = getuid();

	libblake_init();

	clients_head.prev = NULL;
	clients_head.next = &clients_tail;
	clients_tail.prev = &clients_head;
	clients_tail.next = NULL;

	auxval = getauxval(AT_RANDOM);
	if (auxval) {
		unsigned char *r = (unsigned char *)(uintptr_t)auxval;
		for (i = 0u; i < 16u; i++)
			seed = seed * 131u + r[i];
	}
	if (!clock_gettime(CLOCK_REALTIME, &ts)) {
		seed ^= (unsigned)ts.tv_sec;
		seed ^= (unsigned)ts.tv_nsec;
	}
	if (!clock_gettime(CLOCK_MONOTONIC, &ts)) {
		seed ^= (unsigned)ts.tv_sec * (unsigned)2654435761lu;
		seed ^= (unsigned)ts.tv_nsec;
	}
	srand(seed);
}


static void
load_config(const char *config_file, char **local_address, uint16_t *udp_port)
{
	FILE *f;
	ssize_t r;
	char *key, *value;
	char *line = NULL;
	size_t size = 0u;
	size_t len, off, i;
	int fd, old_fd;
	int udp_set = 0;
	long int li;
	unsigned long int lu;
	char *end, *start;
	const char *env;
	char *config_file_free = NULL;
	size_t config_file_size = 0u;

	if (!config_file) {
#define SET_PREFIX(PREFIX) SET_PREFIXN(PREFIX, strlen(PREFIX))
#define SET_PREFIXN(PREFIX, LEN)\
		do {\
			if (config_file_size < (LEN) + 32u) {\
				config_file_size = (LEN) + 32u;\
				config_file_free = erealloc(config_file_free, config_file_size);\
			}\
			start = stpcpy(config_file_free, (PREFIX));\
		} while (0)
#define TEST_CONFIG(PATH)\
		do {\
			if (!access(PATH, F_OK)) {\
				config_file = (PATH);\
				goto open_file;\
			}\
		} while (0)

		env = getenv("OIKOBUS_CONFIG");
		if (env && *env) {
			config_file = env;
			goto open_file;
		}

		env = getenv("XDG_CONFIG_HOME");
		if (env && *env) {
			SET_PREFIX(env);
			stpcpy(start, "/oikobus/config");
			TEST_CONFIG(config_file_free);
			stpcpy(start, "/oikobus.conf");
			TEST_CONFIG(config_file_free);
		}

		env = getenv("HOME");
		if (env && *env) {
			SET_PREFIX(env);
		} else {
			struct passwd *pw;
		retry_getpwuid:
			pw = getpwuid(uid);
			if (!pw) {
				if (errno == EINTR)
					goto retry_getpwuid;
				eprintf("getpwuid <real uid>:");
			}
			if (!pw->pw_dir || !*pw->pw_dir)
				goto no_home;
			SET_PREFIX(pw->pw_dir);
		}
		stpcpy(start, "/.config/oikobus/config");
		TEST_CONFIG(config_file_free);
		stpcpy(start, "/.config/oikobus.conf");
		TEST_CONFIG(config_file_free);
		stpcpy(start, "/.oikobus/config");
		TEST_CONFIG(config_file_free);
		stpcpy(start, "/.oikobus.conf");
		TEST_CONFIG(config_file_free);

	no_home:
		env = getenv("XDG_CONFIG_DIRS");
		if (env && *env) {
			for (off = 0u; env[off]; off = i) {
				for (i = off; env[i] && env[i] != ':'; i++);
				len = i - off;
				if (env[i])
					i++;
				if (!len)
					continue;
				SET_PREFIXN(&env[off], len);
				stpcpy(start, "/oikobus/config");
				TEST_CONFIG(config_file_free);
				stpcpy(start, "/oikobus.conf");
				TEST_CONFIG(config_file_free);
			}
		}

		TEST_CONFIG("/etc/oikobus/config");
		TEST_CONFIG("/etc/oikobus.conf");

		eprintf("no configuration file found, use -c/dev/null if you don't want to load one");

#undef SET_PREFIXN
#undef SET_PREFIX
#undef TEST_CONFIG
	} else {
		if (!strcmp(config_file, "-")) {
			config_file = "/dev/stdin";
			fd = STDIN_FILENO;
			goto open_fd;
		} else if (!strcmp(config_file, "/dev/stdin")) {
			fd = STDIN_FILENO;
			goto open_fd;
		} else if (!strcmp(config_file, "/dev/stdout")) {
			fd = STDOUT_FILENO;
			goto open_fd;
		} else if (!strcmp(config_file, "/dev/stderr")) {
			fd = STDERR_FILENO;
			goto open_fd;
		}

		if (strstarts(config_file, "/dev/fd/")) {
			off = sizeof("/dev/fd/") - 1u;
		} else if (strstarts(config_file, "/proc/self/fd/")) {
			off = sizeof("/proc/self/fd/") - 1u;
		} else {
			goto open_file;
		}

		if ('0' > config_file[off] || config_file[off] > '9')
			goto open_file;
		errno = 0;
		li = strtol(&config_file[off], &end, 10);
		if (errno || li < 0 || li > INT_MAX || *end)
			goto open_file;
		fd = (int)li;
		if (fd <= STDERR_FILENO) {
		open_fd:
			fd = dup(old_fd = fd);
			if (fd < 0)
				eprintf("dup %i:", old_fd);
		}
		f = fdopen(fd, "r");
		goto file_opened;
	}

open_file:
	f = fopen(config_file, "r");
file_opened:
	if (!f)
		eprintf("%s:", config_file);

	while ((r = getdelim(&line, &size, '\n', f)) != -1) {
		len = (size_t)r;
		if (len && line[len - 1u] == '\n')
			line[--len] = '\0';
		if (len && line[len - 1u] == '\r')
			line[--len] = '\0';

		off = 0u;
		while (isspace(line[off]))
			off++;
		key = &line[off];
		value = NULL;
		for (i = off; line[i]; i++) {
			if (line[i] == '#' || line[i] == ';') {
				if (i == off || isspace(line[i - 1u])) {
					line[i] = '\0';
					len = i;
					break;
				}
			} else if ((line[i] == ':' || line[i] == '=') && !value) {
				value = &line[i];
			}
		}

		while (len && isspace(line[len - 1u]))
			line[--len] = '\0';

		if (value) {
			i = (size_t)(value - key);
			*value++ = '\0';
			while (isspace(*value))
				value++;
			while (i-- && isspace(line[i]))
				line[i] = '\0';
		}

		if (nrealms) {
			if (!strcmp(key, "password")) {
				if (!value)
					goto value_missing;
				if (realms[nrealms - 1u].key)
					goto duplicate_realm_option;
				realms[nrealms - 1u].key = estrdup(value);
			} else {
				eprintf("%s: realm option '%s' not recognised", config_file, key);
			}
		} else if (!value && key[0] == '[' && (end = strchr(key, '\0'))[-1] == ']') {
			key++;
			*--end = '\0';
			len = (size_t)(end - key);
			if (len < MIN_REALM_LEN || len > MAX_REALM_LEN)
				eprintf("%s: invalid realm name length: '%s', must "
				        "be between %u and %u bytes (inclusively)",
				        config_file, key, MIN_REALM_LEN, MAX_REALM_LEN);
			for (i = 0u; i < nrealms; i++)
				if (!strcmp(key, realms[i].name))
					eprintf("%s: duplicate section for realm '%s'", config_file, key);
			realms = ereallocarray(realms, ++nrealms, sizeof(*realms));
			realms[nrealms - 1u].name = estrdup(key);
			realms[nrealms - 1u].key = NULL;
		} else {
			if (!strcmp(key, "udp-port")) {
				if (!value)
					goto value_missing;
				if (udp_set++)
					goto duplicate_global_option;
				errno = 0;
				lu = strtoul(value, &end, 10);
				if (errno || lu == 0u || lu > UINT16_MAX || *end)
					eprintf("%s: global option '%s' not recognised requires a "
					        "non-zero, unsigned 16-bit integer", config_file, key);
				*udp_port = (uint16_t)lu;
			} else if (!strcmp(key, "unix-address")) {
				if (!value)
					goto value_missing;
				if (*local_address)
					goto duplicate_global_option;
				*local_address = estrdup(value);
			} else {
				eprintf("%s: global option '%s' not recognised", config_file, key);
			}
		}
	}
	if (ferror(f) || fclose(f))
		eprintf("getline %s:", config_file);

	free(line);
	free(config_file_free);
	return;

duplicate_realm_option:
	eprintf("%s: realm option '%s' configured twice for realm '%s'", config_file, key, realms[nrealms - 1u].name);
duplicate_global_option:
	eprintf("%s: global option '%s' configured twice", config_file, key);
value_missing:
	eprintf("%s: option '%s' requires a value", config_file, key);
}


static void
init_server(const char *config_file, const char *local_address_cmdline, uint16_t udp_port_cmdline)
{
	uint16_t udp_port = UDP_PORT;
	const char *local_address = NULL;
	char *local_address_free = NULL;
	char local_address_buf[LOCAL_ADDRESS_BUFSIZE];
	size_t i;

	load_config(config_file, &local_address_free, &udp_port);
	local_address = local_address_free;
	if (udp_port_cmdline)
		udp_port = udp_port_cmdline;
	if (local_address_cmdline)
		local_address = local_address_cmdline;

	if (!local_address) {
		sprintf(local_address_buf, LOCAL_ADDRESS(getuid()));
		local_address = local_address_buf;
	}

	for (i = 0u; i < sizeof(server_identity.id); i++)
		((unsigned char *)&server_identity.id)[i] = (unsigned char)(rand() & 255);

	events_size = 32;
	events = ecalloc((size_t)events_size, sizeof(*events));

	epoll = epoll_create1(0);
	if (epoll < 0)
		eprintf("create_epoll1 0:");

	lsock = create_local_socket(local_address);
	nsock = create_network_socket();
	bsock = create_broadcast_socket(udp_port);

	free(local_address_free);
}


static void
signal_inited(void)
{
	if (dup2(STDERR_FILENO, STDIN_FILENO) != STDIN_FILENO)
		eprintf("dup2 STDERR_FILENO STDIN_FILENO:");
	if (dup2(STDERR_FILENO, STDOUT_FILENO) != STDOUT_FILENO)
		eprintf("dup2 STDERR_FILENO STDOUT_FILENO:");
}


int
main(int argc, char *argv[])
{
	uint16_t udp_port_cmdline = 0u;
	const char *config_file = NULL;
	const char *local_address_cmdline = NULL;
	char *arg;
	unsigned long int lu;
	union file *file;
	int n;

	ARGBEGIN {
	/* TODO add daemonisation options */
	/* TODO add realm options */
	case 'a':
		if (local_address_cmdline)
			usage();
		local_address_cmdline = ARG();
		if (!*local_address_cmdline)
			usage();
		break;
	case 'c':
		if (config_file)
			usage();
		config_file = ARG();
		if (!*config_file)
			usage();
		break;
	case 'p':
		arg = ARG();
		if ('0' > arg[0u] || arg[0u] > '9' || udp_port_cmdline)
			usage();
		errno = 0;
		lu = strtoul(arg, &arg, 10);
		if (errno || *arg || lu > UINT16_MAX || !lu)
			usage();
		udp_port_cmdline = (uint16_t)lu;
		break;
	default:
		usage();
	} ARGEND;
	/* -W is reserved for vendor options */

	if (argc)
		usage();

	init_process();
	init_server(config_file, local_address_cmdline, udp_port_cmdline);
	broadcast_identity(bsock);
	signal_inited();

	for (;;) {
		n = epoll_wait(epoll, events, events_size, -1);
		if (n < 0) {
			if (errno == EINTR)
				continue;
			eprintf("epoll_wait <epoll> <buffer> %i -1:", events_size);
		}

		while (n--) {
			file = events[n].data.ptr;
			(*file->on_event)(file, events[n].events);
		}
	}
}