/*
 * This file is part of OpenTTD.
 * OpenTTD is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, version 2.
 * OpenTTD 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. You should have received a copy of the GNU General Public License along with OpenTTD. If not, see <http://www.gnu.org/licenses/>.
 */

/** @file core/address.cpp Implementation of the address. */

#include "../../stdafx.h"

#include "address.h"
#include "../../debug.h"

#include "../../safeguards.h"

static const int DEFAULT_CONNECT_TIMEOUT_SECONDS = 3; ///< Allow connect() three seconds to connect.

/**
 * Get the hostname; in case it wasn't given the
 * IPv4 dotted representation is given.
 * @return the hostname
 */
const char *NetworkAddress::GetHostname()
{
	if (StrEmpty(this->hostname) && this->address.ss_family != AF_UNSPEC) {
		assert(this->address_length != 0);
		getnameinfo((struct sockaddr *)&this->address, this->address_length, this->hostname, sizeof(this->hostname), nullptr, 0, NI_NUMERICHOST);
	}
	return this->hostname;
}

/**
 * Get the port.
 * @return the port.
 */
uint16 NetworkAddress::GetPort() const
{
	switch (this->address.ss_family) {
		case AF_UNSPEC:
		case AF_INET:
			return ntohs(((const struct sockaddr_in *)&this->address)->sin_port);

		case AF_INET6:
			return ntohs(((const struct sockaddr_in6 *)&this->address)->sin6_port);

		default:
			NOT_REACHED();
	}
}

/**
 * Set the port.
 * @param port set the port number.
 */
void NetworkAddress::SetPort(uint16 port)
{
	switch (this->address.ss_family) {
		case AF_UNSPEC:
		case AF_INET:
			((struct sockaddr_in*)&this->address)->sin_port = htons(port);
			break;

		case AF_INET6:
			((struct sockaddr_in6*)&this->address)->sin6_port = htons(port);
			break;

		default:
			NOT_REACHED();
	}
}

/**
 * Get the address as a string, e.g. 127.0.0.1:12345.
 * @param buffer the buffer to write to
 * @param last the last element in the buffer
 * @param with_family whether to add the family (e.g. IPvX).
 */
void NetworkAddress::GetAddressAsString(char *buffer, const char *last, bool with_family)
{
	if (this->GetAddress()->ss_family == AF_INET6) buffer = strecpy(buffer, "[", last);
	buffer = strecpy(buffer, this->GetHostname(), last);
	if (this->GetAddress()->ss_family == AF_INET6) buffer = strecpy(buffer, "]", last);
	buffer += seprintf(buffer, last, ":%d", this->GetPort());

	if (with_family) {
		char family;
		switch (this->address.ss_family) {
			case AF_INET:  family = '4'; break;
			case AF_INET6: family = '6'; break;
			default:       family = '?'; break;
		}
		seprintf(buffer, last, " (IPv%c)", family);
	}
}

/**
 * Get the address as a string, e.g. 127.0.0.1:12345.
 * @param with_family whether to add the family (e.g. IPvX).
 * @return the address
 */
std::string NetworkAddress::GetAddressAsString(bool with_family)
{
	/* 6 = for the : and 5 for the decimal port number */
	char buf[NETWORK_HOSTNAME_LENGTH + 6 + 7];
	this->GetAddressAsString(buf, lastof(buf), with_family);
	return buf;
}

/**
 * Helper function to resolve without opening a socket.
 * @param runp information about the socket to try not
 * @return the opened socket or INVALID_SOCKET
 */
static SOCKET ResolveLoopProc(addrinfo *runp)
{
	/* We just want the first 'entry', so return a valid socket. */
	return !INVALID_SOCKET;
}

/**
 * Get the address in its internal representation.
 * @return the address
 */
const sockaddr_storage *NetworkAddress::GetAddress()
{
	if (!this->IsResolved()) {
		/* Here we try to resolve a network address. We use SOCK_STREAM as
		 * socket type because some stupid OSes, like Solaris, cannot be
		 * bothered to implement the specifications and allow '0' as value
		 * that means "don't care whether it is SOCK_STREAM or SOCK_DGRAM".
		 */
		this->Resolve(this->address.ss_family, SOCK_STREAM, AI_ADDRCONFIG, nullptr, ResolveLoopProc);
		this->resolved = true;
	}
	return &this->address;
}

/**
 * Checks of this address is of the given family.
 * @param family the family to check against
 * @return true if it is of the given family
 */
bool NetworkAddress::IsFamily(int family)
{
	if (!this->IsResolved()) {
		this->Resolve(family, SOCK_STREAM, AI_ADDRCONFIG, nullptr, ResolveLoopProc);
	}
	return this->address.ss_family == family;
}

/**
 * Checks whether this IP address is contained by the given netmask.
 * @param netmask the netmask in CIDR notation to test against.
 * @note netmask without /n assumes all bits need to match.
 * @return true if this IP is within the netmask.
 */
bool NetworkAddress::IsInNetmask(const char *netmask)
{
	/* Resolve it if we didn't do it already */
	if (!this->IsResolved()) this->GetAddress();

	int cidr = this->address.ss_family == AF_INET ? 32 : 128;

	NetworkAddress mask_address;

	/* Check for CIDR separator */
	const char *chr_cidr = strchr(netmask, '/');
	if (chr_cidr != nullptr) {
		int tmp_cidr = atoi(chr_cidr + 1);

		/* Invalid CIDR, treat as single host */
		if (tmp_cidr > 0 || tmp_cidr < cidr) cidr = tmp_cidr;

		/* Remove the / so that NetworkAddress works on the IP portion */
		std::string ip_str(netmask, chr_cidr - netmask);
		mask_address = NetworkAddress(ip_str.c_str(), 0, this->address.ss_family);
	} else {
		mask_address = NetworkAddress(netmask, 0, this->address.ss_family);
	}

	if (mask_address.GetAddressLength() == 0) return false;

	uint32 *ip;
	uint32 *mask;
	switch (this->address.ss_family) {
		case AF_INET:
			ip = (uint32*)&((struct sockaddr_in*)&this->address)->sin_addr.s_addr;
			mask = (uint32*)&((struct sockaddr_in*)&mask_address.address)->sin_addr.s_addr;
			break;

		case AF_INET6:
			ip = (uint32*)&((struct sockaddr_in6*)&this->address)->sin6_addr;
			mask = (uint32*)&((struct sockaddr_in6*)&mask_address.address)->sin6_addr;
			break;

		default:
			NOT_REACHED();
	}

	while (cidr > 0) {
		uint32 msk = cidr >= 32 ? (uint32)-1 : htonl(-(1 << (32 - cidr)));
		if ((*mask++ & msk) != (*ip++ & msk)) return false;

		cidr -= 32;
	}

	return true;
}

/**
 * Resolve this address into a socket
 * @param family the type of 'protocol' (IPv4, IPv6)
 * @param socktype the type of socket (TCP, UDP, etc)
 * @param flags the flags to send to getaddrinfo
 * @param sockets the list of sockets to add the sockets to
 * @param func the inner working while looping over the address info
 * @return the resolved socket or INVALID_SOCKET.
 */
SOCKET NetworkAddress::Resolve(int family, int socktype, int flags, SocketList *sockets, LoopProc func)
{
	struct addrinfo *ai;
	struct addrinfo hints;
	memset(&hints, 0, sizeof (hints));
	hints.ai_family   = family;
	hints.ai_flags    = flags;
	hints.ai_socktype = socktype;

	/* The port needs to be a string. Six is enough to contain all characters + '\0'. */
	char port_name[6];
	seprintf(port_name, lastof(port_name), "%u", this->GetPort());

	bool reset_hostname = false;
	/* Setting both hostname to nullptr and port to 0 is not allowed.
	 * As port 0 means bind to any port, the other must mean that
	 * we want to bind to 'all' IPs. */
	if (StrEmpty(this->hostname) && this->address_length == 0 && this->GetPort() == 0) {
		reset_hostname = true;
		int fam = this->address.ss_family;
		if (fam == AF_UNSPEC) fam = family;
		strecpy(this->hostname, fam == AF_INET ? "0.0.0.0" : "::", lastof(this->hostname));
	}

	static bool _resolve_timeout_error_message_shown = false;
	auto start = std::chrono::steady_clock::now();
	int e = getaddrinfo(StrEmpty(this->hostname) ? nullptr : this->hostname, port_name, &hints, &ai);
	auto end = std::chrono::steady_clock::now();
	std::chrono::seconds duration = std::chrono::duration_cast<std::chrono::seconds>(end - start);
	if (!_resolve_timeout_error_message_shown && duration >= std::chrono::seconds(5)) {
		DEBUG(net, 0, "getaddrinfo for hostname \"%s\", port %s, address family %s and socket type %s took %i seconds",
				this->hostname, port_name, AddressFamilyAsString(family), SocketTypeAsString(socktype), (int)duration.count());
		DEBUG(net, 0, "  this is likely an issue in the DNS name resolver's configuration causing it to time out");
		_resolve_timeout_error_message_shown = true;
	}


	if (reset_hostname) strecpy(this->hostname, "", lastof(this->hostname));

	if (e != 0) {
		if (func != ResolveLoopProc) {
			DEBUG(net, 0, "getaddrinfo for hostname \"%s\", port %s, address family %s and socket type %s failed: %s",
				this->hostname, port_name, AddressFamilyAsString(family), SocketTypeAsString(socktype), FS2OTTD(gai_strerror(e)).c_str());
		}
		return INVALID_SOCKET;
	}

	SOCKET sock = INVALID_SOCKET;
	for (struct addrinfo *runp = ai; runp != nullptr; runp = runp->ai_next) {
		/* When we are binding to multiple sockets, make sure we do not
		 * connect to one with exactly the same address twice. That's
		 * of course totally unneeded ;) */
		if (sockets != nullptr) {
			NetworkAddress address(runp->ai_addr, (int)runp->ai_addrlen);
			if (sockets->Contains(address)) continue;
		}
		sock = func(runp);
		if (sock == INVALID_SOCKET) continue;

		if (sockets == nullptr) {
			this->address_length = (int)runp->ai_addrlen;
			assert(sizeof(this->address) >= runp->ai_addrlen);
			memcpy(&this->address, runp->ai_addr, runp->ai_addrlen);
#ifdef __EMSCRIPTEN__
			/* Emscripten doesn't zero sin_zero, but as we compare addresses
			 * to see if they are the same address, we need them to be zero'd.
			 * Emscripten is, as far as we know, the only OS not doing this.
			 *
			 * https://github.com/emscripten-core/emscripten/issues/12998
			 */
			if (this->address.ss_family == AF_INET) {
				sockaddr_in *address_ipv4 = (sockaddr_in *)&this->address;
				memset(address_ipv4->sin_zero, 0, sizeof(address_ipv4->sin_zero));
			}
#endif
			break;
		}

		NetworkAddress addr(runp->ai_addr, (int)runp->ai_addrlen);
		(*sockets)[addr] = sock;
		sock = INVALID_SOCKET;
	}
	freeaddrinfo (ai);

	return sock;
}

/**
 * Helper function to resolve a connected socket.
 * @param runp information about the socket to try not
 * @return the opened socket or INVALID_SOCKET
 */
static SOCKET ConnectLoopProc(addrinfo *runp)
{
	const char *type = NetworkAddress::SocketTypeAsString(runp->ai_socktype);
	const char *family = NetworkAddress::AddressFamilyAsString(runp->ai_family);
	char address[NETWORK_HOSTNAME_LENGTH + 6 + 7];
	NetworkAddress(runp->ai_addr, (int)runp->ai_addrlen).GetAddressAsString(address, lastof(address));

	SOCKET sock = socket(runp->ai_family, runp->ai_socktype, runp->ai_protocol);
	if (sock == INVALID_SOCKET) {
		DEBUG(net, 1, "[%s] could not create %s socket: %s", type, family, NetworkGetLastErrorString());
		return INVALID_SOCKET;
	}

	if (!SetNoDelay(sock)) DEBUG(net, 1, "[%s] setting TCP_NODELAY failed", type);

	if (!SetNonBlocking(sock)) DEBUG(net, 0, "[%s] setting non-blocking mode failed", type);

	int err = connect(sock, runp->ai_addr, (int)runp->ai_addrlen);
	if (err != 0 && NetworkGetLastError() != EINPROGRESS) {
		DEBUG(net, 1, "[%s] could not connect to %s over %s: %s", type, address, family, NetworkGetLastErrorString());
		closesocket(sock);
		return INVALID_SOCKET;
	}

	fd_set write_fd;
	struct timeval tv;

	FD_ZERO(&write_fd);
	FD_SET(sock, &write_fd);

	/* Wait for connect() to either connect, timeout or fail. */
	tv.tv_usec = 0;
	tv.tv_sec = DEFAULT_CONNECT_TIMEOUT_SECONDS;
	int n = select(FD_SETSIZE, NULL, &write_fd, NULL, &tv);
	if (n < 0) {
		DEBUG(net, 1, "[%s] could not connect to %s: %s", type, address, NetworkGetLastErrorString());
		closesocket(sock);
		return INVALID_SOCKET;
	}

	/* If no fd is selected, the timeout has been reached. */
	if (n == 0) {
		DEBUG(net, 1, "[%s] timed out while connecting to %s", type, address);
		closesocket(sock);
		return INVALID_SOCKET;
	}

	/* Retrieve last error, if any, on the socket. */
	err = GetSocketError(sock);
	if (err != 0) {
		DEBUG(net, 1, "[%s] could not connect to %s: %s", type, address, NetworkGetErrorString(err));
		closesocket(sock);
		return INVALID_SOCKET;
	}

	/* Connection succeeded. */
	DEBUG(net, 1, "[%s] connected to %s", type, address);

	return sock;
}

/**
 * Connect to the given address.
 * @return the connected socket or INVALID_SOCKET.
 */
SOCKET NetworkAddress::Connect()
{
	DEBUG(net, 1, "Connecting to %s", this->GetAddressAsString().c_str());

	return this->Resolve(AF_UNSPEC, SOCK_STREAM, AI_ADDRCONFIG, nullptr, ConnectLoopProc);
}

/**
 * Helper function to resolve a listening.
 * @param runp information about the socket to try not
 * @return the opened socket or INVALID_SOCKET
 */
static SOCKET ListenLoopProc(addrinfo *runp)
{
	const char *type = NetworkAddress::SocketTypeAsString(runp->ai_socktype);
	const char *family = NetworkAddress::AddressFamilyAsString(runp->ai_family);
	char address[NETWORK_HOSTNAME_LENGTH + 6 + 7];
	NetworkAddress(runp->ai_addr, (int)runp->ai_addrlen).GetAddressAsString(address, lastof(address));

	SOCKET sock = socket(runp->ai_family, runp->ai_socktype, runp->ai_protocol);
	if (sock == INVALID_SOCKET) {
		DEBUG(net, 0, "[%s] could not create %s socket on port %s: %s", type, family, address, NetworkGetLastErrorString());
		return INVALID_SOCKET;
	}

	if (runp->ai_socktype == SOCK_STREAM && !SetNoDelay(sock)) {
		DEBUG(net, 3, "[%s] setting TCP_NODELAY failed for port %s", type, address);
	}

	int on = 1;
	/* The (const char*) cast is needed for windows!! */
	if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (const char*)&on, sizeof(on)) == -1) {
		DEBUG(net, 3, "[%s] could not set reusable %s sockets for port %s: %s", type, family, address, NetworkGetLastErrorString());
	}

#ifndef __OS2__
	if (runp->ai_family == AF_INET6 &&
			setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, (const char*)&on, sizeof(on)) == -1) {
		DEBUG(net, 3, "[%s] could not disable IPv4 over IPv6 on port %s: %s", type, address, NetworkGetLastErrorString());
	}
#endif

	if (bind(sock, runp->ai_addr, (int)runp->ai_addrlen) != 0) {
		DEBUG(net, 1, "[%s] could not bind on %s port %s: %s", type, family, address, NetworkGetLastErrorString());
		closesocket(sock);
		return INVALID_SOCKET;
	}

	if (runp->ai_socktype != SOCK_DGRAM && listen(sock, 1) != 0) {
		DEBUG(net, 1, "[%s] could not listen at %s port %s: %s", type, family, address, NetworkGetLastErrorString());
		closesocket(sock);
		return INVALID_SOCKET;
	}

	/* Connection succeeded */
	if (!SetNonBlocking(sock)) DEBUG(net, 0, "[%s] setting non-blocking mode failed for %s port %s", type, family, address);

	DEBUG(net, 1, "[%s] listening on %s port %s", type, family, address);
	return sock;
}

/**
 * Make the given socket listen.
 * @param socktype the type of socket (TCP, UDP, etc)
 * @param sockets the list of sockets to add the sockets to
 */
void NetworkAddress::Listen(int socktype, SocketList *sockets)
{
	assert(sockets != nullptr);

	/* Setting both hostname to nullptr and port to 0 is not allowed.
	 * As port 0 means bind to any port, the other must mean that
	 * we want to bind to 'all' IPs. */
	if (this->address_length == 0 && this->address.ss_family == AF_UNSPEC &&
			StrEmpty(this->hostname) && this->GetPort() == 0) {
		this->Resolve(AF_INET,  socktype, AI_ADDRCONFIG | AI_PASSIVE, sockets, ListenLoopProc);
		this->Resolve(AF_INET6, socktype, AI_ADDRCONFIG | AI_PASSIVE, sockets, ListenLoopProc);
	} else {
		this->Resolve(AF_UNSPEC, socktype, AI_ADDRCONFIG | AI_PASSIVE, sockets, ListenLoopProc);
	}
}

/**
 * Convert the socket type into a string
 * @param socktype the socket type to convert
 * @return the string representation
 * @note only works for SOCK_STREAM and SOCK_DGRAM
 */
/* static */ const char *NetworkAddress::SocketTypeAsString(int socktype)
{
	switch (socktype) {
		case SOCK_STREAM: return "tcp";
		case SOCK_DGRAM:  return "udp";
		default:          return "unsupported";
	}
}

/**
 * Convert the address family into a string
 * @param family the family to convert
 * @return the string representation
 * @note only works for AF_INET, AF_INET6 and AF_UNSPEC
 */
/* static */ const char *NetworkAddress::AddressFamilyAsString(int family)
{
	switch (family) {
		case AF_UNSPEC: return "either IPv4 or IPv6";
		case AF_INET:   return "IPv4";
		case AF_INET6:  return "IPv6";
		default:        return "unsupported";
	}
}