/*
 * Copyright (C) 2009 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *	  http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
 
#ifndef IFADDRS_ANDROID_H_included
#define IFADDRS_ANDROID_H_included

#include <arpa/inet.h>
#include <cstring>
#include <errno.h>
#include <net/if.h>
#include <netinet/in.h>
#include <new>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <linux/netlink.h>
#include <linux/rtnetlink.h>
#include <unistd.h>

#include <Containers/SmallVector.h>

// Source-compatible subset of the BSD struct.
struct ifaddrs {
	// Pointer to next struct in list, or NULL at end.
	ifaddrs* ifa_next;
	
	// Interface name.
	char* ifa_name;
	
	// Interface flags.
	unsigned int ifa_flags;
	
	// Interface network address.
	sockaddr* ifa_addr;
	
	// Interface netmask.
	sockaddr* ifa_netmask;
	
	ifaddrs(ifaddrs* next)
	: ifa_next(next), ifa_name(NULL), ifa_flags(0), ifa_addr(NULL), ifa_netmask(NULL) {}
	
	~ifaddrs() {
		delete ifa_next;
		delete[] ifa_name;
		delete ifa_addr;
		delete ifa_netmask;
	}
	
	// Sadly, we can't keep the interface index for portability with BSD.
	// We'll have to keep the name instead, and re-query the index when
	// we need it later.
	bool setNameAndFlagsByIndex(int interfaceIndex) {
		// Get the name.
		char buf[IFNAMSIZ];
		char* name = if_indextoname(interfaceIndex, buf);
		if (name == NULL) {
			return false;
		}
		ifa_name = new char[strlen(name) + 1];
		strcpy(ifa_name, name);
		
		// Get the flags.
		int fd = socket(AF_INET, SOCK_DGRAM, 0);
		if (fd == -1) {
			return false;
		}
		ifreq ifr;
		memset(&ifr, 0, sizeof(ifr));
		strcpy(ifr.ifr_name, name);
		int rc = ioctl(fd, SIOCGIFFLAGS, &ifr);
		close(fd);
		if (rc == -1) {
			return false;
		}
		ifa_flags = ifr.ifr_flags;
		return true;
	}
	
	// Netlink gives us the address family in the header, and the
	// sockaddr_in or sockaddr_in6 bytes as the payload. We need to
	// stitch the two bits together into the sockaddr that's part of
	// our portable interface.
	void setAddress(int family, void* data, size_t byteCount) {
		// Set the address proper...
		sockaddr_storage* ss = new sockaddr_storage;
		memset(ss, 0, sizeof(*ss));
		ifa_addr = reinterpret_cast<sockaddr*>(ss);
		ss->ss_family = family;
		uint8_t* dst = sockaddrBytes(family, ss);
		memcpy(dst, data, byteCount);
	}
	
	// Netlink gives us the prefix length as a bit count. We need to turn
	// that into a BSD-compatible netmask represented by a sockaddr*.
	void setNetmask(int family, size_t prefixLength) {
		// ...and work out the netmask from the prefix length.
		sockaddr_storage* ss = new sockaddr_storage;
		memset(ss, 0, sizeof(*ss));
		ifa_netmask = reinterpret_cast<sockaddr*>(ss);
		ss->ss_family = family;
		uint8_t* dst = sockaddrBytes(family, ss);
		memset(dst, 0xff, prefixLength / 8);
		if ((prefixLength % 8) != 0) {
			dst[prefixLength/8] = (0xff << (8 - (prefixLength % 8)));
		}
	}
	
	// Returns a pointer to the first byte in the address data (which is
	// stored in network byte order).
	uint8_t* sockaddrBytes(int family, sockaddr_storage* ss) {
		if (family == AF_INET) {
			sockaddr_in* ss4 = reinterpret_cast<sockaddr_in*>(ss);
			return reinterpret_cast<uint8_t*>(&ss4->sin_addr);
		} else if (family == AF_INET6) {
			sockaddr_in6* ss6 = reinterpret_cast<sockaddr_in6*>(ss);
			return reinterpret_cast<uint8_t*>(&ss6->sin6_addr);
		}
		return NULL;
	}
	
private:
	// Disallow copy and assignment.
	ifaddrs(const ifaddrs&);
	void operator=(const ifaddrs&);
};

// FIXME: use iovec instead.
struct addrReq_struct {
	nlmsghdr netlinkHeader;
	ifaddrmsg msg;
};

inline bool sendNetlinkMessage(int fd, const void* data, size_t byteCount) {
	ssize_t sentByteCount = TEMP_FAILURE_RETRY(send(fd, data, byteCount, 0));
	return (sentByteCount == static_cast<ssize_t>(byteCount));
}

inline ssize_t recvNetlinkMessage(int fd, char* buf, size_t byteCount) {
	return TEMP_FAILURE_RETRY(recv(fd, buf, byteCount, 0));
}

// Source-compatible with the BSD function.
inline int getifaddrs(ifaddrs** result) {
	// Simplify cleanup for callers.
	*result = NULL;
	// Create a netlink socket.
	int fd = socket(AF_NETLINK, SOCK_DGRAM, NETLINK_ROUTE);
	if (fd < 0) {
		return -1;
	}
	// Ask for the address information.
	addrReq_struct addrRequest;
	memset(&addrRequest, 0, sizeof(addrRequest));
	addrRequest.netlinkHeader.nlmsg_flags = NLM_F_REQUEST | NLM_F_MATCH;
	addrRequest.netlinkHeader.nlmsg_type = RTM_GETADDR;
	addrRequest.netlinkHeader.nlmsg_len = NLMSG_ALIGN(NLMSG_LENGTH(sizeof(addrRequest)));
	addrRequest.msg.ifa_family = AF_UNSPEC; // All families.
	addrRequest.msg.ifa_index = 0; // All interfaces.
	if (!sendNetlinkMessage(fd, &addrRequest, addrRequest.netlinkHeader.nlmsg_len)) {
		close(fd);
		return -1;
	}
	
	// Read the responses.
	Death::Containers::SmallVector<char, 0> buf(65536);
	ssize_t bytesRead;
	while ((bytesRead = recvNetlinkMessage(fd, &buf[0], buf.size())) > 0) {
		nlmsghdr* hdr = reinterpret_cast<nlmsghdr*>(&buf[0]);
		for (; NLMSG_OK(hdr, (size_t)bytesRead); hdr = NLMSG_NEXT(hdr, bytesRead)) {
			switch (hdr->nlmsg_type) {
			case NLMSG_DONE:
				close(fd);
				return 0;
			case NLMSG_ERROR:
				close(fd);
				return -1;
			case RTM_NEWADDR:
				{
					ifaddrmsg* address = reinterpret_cast<ifaddrmsg*>(NLMSG_DATA(hdr));
					rtattr* rta = IFA_RTA(address);
					size_t ifaPayloadLength = IFA_PAYLOAD(hdr);
					while (RTA_OK(rta, ifaPayloadLength)) {
						if (rta->rta_type == IFA_LOCAL) {
							int family = address->ifa_family;
							if (family == AF_INET || family == AF_INET6) {
								*result = new ifaddrs(*result);
								if (!(*result)->setNameAndFlagsByIndex(address->ifa_index)) {
									close(fd);
									return -1;
								}
								(*result)->setAddress(family, RTA_DATA(rta), RTA_PAYLOAD(rta));
								(*result)->setNetmask(family, address->ifa_prefixlen);
							}
						}
						rta = RTA_NEXT(rta, ifaPayloadLength);
					}
				}
				break;
			}
		}
	}
	
	// We only get here if recv fails before we see a NLMSG_DONE.
	close(fd);
	return -1;
}

// Source-compatible with the BSD function.
inline void freeifaddrs(ifaddrs* addresses) {
	delete addresses;
}

#endif