ip_address.c

/*
 * Copyright 2013-2015 Google Inc.
 *
 * This program 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; either version 2
 * of the License, or (at your option) any later version.
 *
 * 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.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
 * 02110-1301, USA.
 */
/*
 * Author: ncardwell@google.com (Neal Cardwell)
 *
 * Implementation for operations for IPv4 and IPv6 addresses.
 */

#include "ip_address.h"

#include <ifaddrs.h>
#include <net/if.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>

#include "logging.h"

/* IPv6 prefix for IPv4-mapped addresses. These are in the
 * ::FFFF:0:0/96 space, i.e. 10 bytes of 0x00 and 2 bytes of 0xFF. See
 * RFC 4291 ("IPv6 Addressing Architecture") section 2.5.5.2
 * ("IPv4-Mapped IPv6 Address").
 */
const u8 ipv4_mapped_prefix[] = { 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0xFF, 0xFF };

int ip_address_length(int address_family)
{
	switch (address_family) {
	case AF_INET:
		return sizeof(struct in_addr);
	case AF_INET6:
		return sizeof(struct in6_addr);
	default:
		die("ip_address_length: bad address family: %d\n",
		    address_family);
		break;
	}
	return 0;  /* not reached */
}

int sockaddr_length(int address_family)
{
	switch (address_family) {
	case AF_INET:
		return sizeof(struct sockaddr_in);
	case AF_INET6:
		return sizeof(struct sockaddr_in6);
	default:
		die("sockaddr_length: bad address family: %d\n",
		    address_family);
		break;
	}
	return 0;  /* not reached */
}

static void ipv4_init(struct ip_address *ipv4)
{
	memset(ipv4, 0, sizeof(*ipv4));
	ipv4->address_family = AF_INET;
}

static void ipv6_init(struct ip_address *ipv6)
{
	memset(ipv6, 0, sizeof(*ipv6));
	ipv6->address_family = AF_INET6;
}

void ip_from_ipv4(const struct in_addr *ipv4, struct ip_address *ip)
{
	ipv4_init(ip);
	ip->ip.v4 = *ipv4;
}

void ip_from_ipv6(const struct in6_addr *ipv6, struct ip_address *ip)
{
	ipv6_init(ip);
	ip->ip.v6 = *ipv6;
}

void ip_to_ipv4(const struct ip_address *ip, struct in_addr *ipv4)
{
	*ipv4 = ip->ip.v4;
}

void ip_to_ipv6(const struct ip_address *ip, struct in6_addr *ipv6)
{
	*ipv6 = ip->ip.v6;
}

struct ip_address ipv4_parse(const char *ip_string)
{
	struct ip_address ipv4;
	ipv4_init(&ipv4);

	if (inet_pton(AF_INET, ip_string, &ipv4.ip.v4) != 1)
		die("bad IPv4 address: %s\n", ip_string);

	return ipv4;
}

struct ip_address ipv6_parse(const char *ip_string)
{
	struct ip_address ipv6;
	ipv6_init(&ipv6);

	if (inet_pton(AF_INET6, ip_string, &ipv6.ip.v6) != 1)
		die("bad IPv6 address: %s\n", ip_string);

	return ipv6;
}

const char *ip_to_string(const struct ip_address *ip, char *buffer)
{
	if (!inet_ntop(ip->address_family, &ip->ip, buffer, ADDR_STR_LEN))
		die_perror("inet_ntop");

	return buffer;
}

struct ip_address ipv6_map_from_ipv4(const struct ip_address ipv4)
{
	struct ip_address ipv6;
	ipv6_init(&ipv6);

	assert(sizeof(ipv4.ip.v4) + sizeof(ipv4_mapped_prefix) ==
	       sizeof(ipv6.ip.v6));
	memcpy(ipv6.ip.v6.s6_addr, ipv4_mapped_prefix,
	       sizeof(ipv4_mapped_prefix));
	memcpy(ipv6.ip.v6.s6_addr + sizeof(ipv4_mapped_prefix),
	       &ipv4.ip.v4, sizeof(ipv4.ip.v4));
	return ipv6;
}

int ipv6_map_to_ipv4(const struct ip_address ipv6, struct ip_address *ipv4)
{
	if (memcmp(&ipv6.ip.v6.s6_addr,
		   ipv4_mapped_prefix, sizeof(ipv4_mapped_prefix)) == 0) {
		ipv4_init(ipv4);
		memcpy(&ipv4->ip.v4,
		       ipv6.ip.v6.s6_addr + sizeof(ipv4_mapped_prefix),
		       sizeof(ipv4->ip.v4));
		return STATUS_OK;
	} else {
		return STATUS_ERR;
	}
}

/* Fill in a sockaddr struct and socklen_t using the given IPv4
 * address and port.
 */
static void ipv4_to_sockaddr(const struct ip_address *ipv4, u16 port,
			     struct sockaddr *address, socklen_t *length)
{
	struct sockaddr_in sa_v4;
	memset(&sa_v4, 0, sizeof(sa_v4));
#ifndef linux
	sa_v4.sin_len = sizeof(sa_v4);
#endif
	sa_v4.sin_family = AF_INET;
	sa_v4.sin_port = htons(port);
	memcpy(&sa_v4.sin_addr, &ipv4->ip.v4, sizeof(sa_v4.sin_addr));
	*length = sizeof(sa_v4);
	memcpy(address, &sa_v4, *length);
}

/* Fill in a sockaddr struct and socklen_t using the given IPv6
 * address and port.
 */
static void ipv6_to_sockaddr(const struct ip_address *ipv6, u16 port,
			     struct sockaddr *address, socklen_t *length)
{
	struct sockaddr_in6 sa_v6;
	memset(&sa_v6, 0, sizeof(sa_v6));
#ifndef linux
	sa_v6.sin6_len = sizeof(sa_v6);
#endif
	sa_v6.sin6_family = AF_INET6;
	sa_v6.sin6_port = htons(port);
	memcpy(&sa_v6.sin6_addr, &ipv6->ip.v6, sizeof(sa_v6.sin6_addr));
	*length = sizeof(sa_v6);
	memcpy(address, &sa_v6, *length);
}

void ip_to_sockaddr(const struct ip_address *ip, u16 port,
		    struct sockaddr *address, socklen_t *length)
{
	switch (ip->address_family) {
	case AF_INET:
		ipv4_to_sockaddr(ip, port, address, length);
		break;
	case AF_INET6:
		ipv6_to_sockaddr(ip, port, address, length);
		break;
	default:
		die("ip_to_sockaddr: bad address family: %d\n",
		    ip->address_family);
		break;
	}
}

/* Extract and return the IPv4 address and port from the given sockaddr. */
static void ipv4_from_sockaddr(const struct sockaddr *address, socklen_t length,
			       struct ip_address *ipv4, u16 *port)
{
	assert(address->sa_family == AF_INET);
	ipv4_init(ipv4);

	struct sockaddr_in sa_v4;
	assert(length == sizeof(sa_v4));
	memcpy(&sa_v4, address, length);  /* to avoid aliasing issues */
	ipv4->ip.v4 = sa_v4.sin_addr;
	*port = ntohs(sa_v4.sin_port);
}

/* Extract and return the IPv6 address and port from the given sockaddr. */
static void ipv6_from_sockaddr(const struct sockaddr *address, socklen_t length,
			       struct ip_address *ipv4, u16 *port)
{
	assert(address->sa_family == AF_INET6);
	ipv6_init(ipv4);

	struct sockaddr_in6 sa_v6;
	assert(length == sizeof(sa_v6));
	memcpy(&sa_v6, address, length);  /* to avoid aliasing issues */
	ipv4->ip.v6 = sa_v6.sin6_addr;
	*port = ntohs(sa_v6.sin6_port);
}

void ip_from_sockaddr(const struct sockaddr *address, socklen_t length,
		      struct ip_address *ip, u16 *port)
{
	switch (address->sa_family) {
	case AF_INET:
		ipv4_from_sockaddr(address, length, ip, port);
		break;
	case AF_INET6:
		ipv6_from_sockaddr(address, length, ip, port);
		break;
	default:
		die("ip_from_sockaddr: bad address family: %d\n",
		    address->sa_family);
		break;
	}
}

int get_ip_device(const struct ip_address *ip, char *dev_name)
{
	struct ifaddrs *ifaddr_list, *ifaddr;
	bool is_local = false;

	if (getifaddrs(&ifaddr_list))
		die_perror("getifaddrs");

	for (ifaddr = ifaddr_list; ifaddr != NULL; ifaddr = ifaddr->ifa_next) {
		int family;
		struct ip_address interface_ip;
		u16 port;

		if (ifaddr->ifa_addr == NULL)
			continue;

		family = ifaddr->ifa_addr->sa_family;
		if (family != ip->address_family)
			continue;

		ip_from_sockaddr(ifaddr->ifa_addr, sockaddr_length(family),
				 &interface_ip, &port);
		if (is_equal_ip(ip, &interface_ip)) {
			assert(ifaddr->ifa_name);
			assert(strlen(ifaddr->ifa_name) < IFNAMSIZ);
			strcpy(dev_name, ifaddr->ifa_name);
			is_local = true;
			break;
		}
	}

	freeifaddrs(ifaddr_list);

	return is_local;
}

int is_ip_local(const struct ip_address *ip)
{
	char dev_name[IFNAMSIZ];

	return get_ip_device(ip, dev_name);
}

int netmask_to_prefix(const char *netmask)
{
	int pos;
	struct ip_address mask = ipv4_parse(netmask);
	u32 mask_addr = ntohl(mask.ip.v4.s_addr);
	int prefix_len = 0;

	for (pos = 31; pos >= 0; --pos) {
		if (!(mask_addr & (1<<pos)))
			break;
		++prefix_len;
	}
	return prefix_len;
}

static int urandom_read(void *buffer, int sz)
{
	static int fd_urandom = -1;

	if (fd_urandom == -1)
		fd_urandom = open("/dev/urandom", O_RDONLY);
	return read(fd_urandom, buffer, sz);
}

void generate_random_ipv4_addr(char *result, const char *base,
			       const char *netmask)
{
	int prefix_len = netmask_to_prefix(netmask);
	struct ip_address addr = ipv4_parse(base);

	if (prefix_len < 31) {
		unsigned int rnd;

		if (urandom_read(&rnd, sizeof(rnd)) == sizeof(rnd)) {
			if (prefix_len) {
				u32 mask = (1U << (32 - prefix_len)) - 1;

				rnd &= mask;
				/* .0 is reserved for network address.
				 * .1 is reserved for the gateway
				 */
				if (rnd < 2)
					rnd = 2;
				/* .255.255 is reserved for net broadcast */
				if (rnd == mask)
					rnd--;
			}
			addr.ip.v4.s_addr |= htonl(rnd);
		}
	}
	ip_to_string(&addr, result);
}

/* In this version, we randomize last 32bits (or less) of the address.
 * There is no need to fully use RFC 4193 range.
 * ( fd3d:fa7b:d17d::/48 in unique local address space )
 */
void generate_random_ipv6_addr(char *result, const char *base, int prefixlen)
{
	struct ip_address addr = ipv6_parse(base);
	unsigned int mask = ~0U, rnd = 0;

	urandom_read(&rnd, sizeof(rnd));
	if (prefixlen > 128 - 32) {
		mask = (1U << (128 - prefixlen)) - 1;
		rnd &= mask;
	}
	if (!rnd)
		rnd++;
	if (rnd == mask)
		rnd--;
	addr.ip.v6.s6_addr32[3] |= htonl(rnd);
	ip_to_string(&addr, result);
}