net.c

/* 
 * dhcpcd - DHCP client daemon
 * Copyright 2006-2008 Roy Marples <roy@marples.name>
 * All rights reserved

 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <sys/time.h>

#include <net/if.h>
#include <net/if_arp.h>
#include <arpa/inet.h>
#include <netinet/in_systm.h>
#ifdef __linux__
#include <netinet/ether.h>
#include <netpacket/packet.h>
#endif
#include <netinet/in.h>
#include <netinet/ip.h>
#define __FAVOR_BSD /* Nasty glibc hack so we can use BSD semantics for UDP */
#include <netinet/udp.h>
#undef __FAVOR_BSD
#ifdef SIOCGIFMEDIA
#include <net/if_media.h>
#endif
#include <arpa/inet.h>
#ifdef AF_LINK
# include <net/if_dl.h>
#endif

#include <ctype.h>
#include <errno.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "config.h"
#include "common.h"
#include "dhcp.h"
#include "logger.h"
#include "net.h"
#include "signals.h"

int
inet_ntocidr(struct in_addr address)
{
	int cidr = 0;
	uint32_t mask = htonl(address.s_addr);

	while (mask) {
		cidr++;
		mask <<= 1;
	}

	return cidr;
}

int
inet_cidrtoaddr(int cidr, struct in_addr *addr)
{
	int ocets;

	if (cidr < 0 || cidr > 32) {
		errno = EINVAL;
		return -1;
	}
	ocets = (cidr + 7) / 8;

	addr->s_addr = 0;
	if (ocets > 0) {
		memset(&addr->s_addr, 255, (size_t)ocets - 1);
		memset((unsigned char *)&addr->s_addr + (ocets - 1),
		       (256 - (1 << (32 - cidr) % 8)), 1);
	}

	return 0;
}

uint32_t
get_netmask(uint32_t addr)
{
	uint32_t dst;

	if (addr == 0)
		return 0;

	dst = htonl(addr);
	if (IN_CLASSA(dst))
		return ntohl(IN_CLASSA_NET);
	if (IN_CLASSB(dst))
		return ntohl(IN_CLASSB_NET);
	if (IN_CLASSC(dst))
		return ntohl(IN_CLASSC_NET);

	return 0;
}

char *
hwaddr_ntoa(const unsigned char *hwaddr, size_t hwlen)
{
	static char buffer[(HWADDR_LEN * 3) + 1];
	char *p = buffer;
	size_t i;

	for (i = 0; i < hwlen && i < HWADDR_LEN; i++) {
		if (i > 0)
			*p ++= ':';
		p += snprintf(p, 3, "%.2x", hwaddr[i]);
	}

	*p ++= '\0';

	return buffer;
}

size_t
hwaddr_aton(unsigned char *buffer, const char *addr)
{
	char c[3];
	const char *p = addr;
	unsigned char *bp = buffer;
	size_t len = 0;

	c[2] = '\0';
	while (*p) {
		c[0] = *p++;
		c[1] = *p++;
		/* Ensure that digits are hex */
		if (isxdigit((unsigned char)c[0]) == 0 ||
		    isxdigit((unsigned char)c[1]) == 0)
		{
			errno = EINVAL;
			return 0;
		}
		/* We should have at least two entries 00:01 */
		if (len == 0 && *p == '\0') {
			errno = EINVAL;
			return 0;
		}
		/* Ensure that next data is EOL or a seperator with data */
		if (!(*p == '\0' || (*p == ':' && *(p + 1) != '\0'))) {
			errno = EINVAL;
			return 0;
		}
		if (*p)
			p++;
		if (bp)
			*bp++ = (unsigned char)strtol(c, NULL, 16);
		len++;
	}
	return len;
}

int
do_interface(const char *ifname,
	     _unused unsigned char *hwaddr, _unused size_t *hwlen,
	     struct in_addr *addr, struct in_addr *net, int get)
{
	int s;
	struct ifconf ifc;
	int retval = 0, found = 0;
	int len = 10 * sizeof(struct ifreq);
	int lastlen = 0;
	char *p;
	union {
		char *buffer;
		struct ifreq *ifr;
	} ifreqs;
	struct sockaddr_in address;
	struct ifreq *ifr;
	struct sockaddr_in netmask;
#ifdef AF_LINK
	struct sockaddr_dl *sdl;
#endif

	if ((s = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
		return -1;

	/* Not all implementations return the needed buffer size for
	 * SIOGIFCONF so we loop like so for all until it works */
	memset(&ifc, 0, sizeof(ifc));
	for (;;) {
		ifc.ifc_len = len;
		ifc.ifc_buf = xmalloc((size_t)len);
		if (ioctl(s, SIOCGIFCONF, &ifc) == -1) {
			if (errno != EINVAL || lastlen != 0) {
				close(s);
				free(ifc.ifc_buf);	
				return -1;
			}
		} else {
			if (ifc.ifc_len == lastlen)
				break;
			lastlen = ifc.ifc_len;
		}

		free(ifc.ifc_buf);
		ifc.ifc_buf = NULL;
		len *= 2;
	}

	for (p = (char *)ifc.ifc_buf; p < (char *)ifc.ifc_buf + ifc.ifc_len;) {
		/* Cast the ifc buffer to an ifreq cleanly */
		ifreqs.buffer = p;
		ifr = ifreqs.ifr;

#ifndef __linux__
		if (ifr->ifr_addr.sa_len > sizeof(ifr->ifr_ifru))
			p += offsetof(struct ifreq, ifr_ifru) +
				ifr->ifr_addr.sa_len;
		else
#endif
			p += sizeof(*ifr);

		if (strcmp(ifname, ifr->ifr_name) != 0)
			continue;

		found = 1;

#ifdef AF_LINK
		if (hwaddr && hwlen && ifr->ifr_addr.sa_family == AF_LINK) {
			sdl = xmalloc(ifr->ifr_addr.sa_len);
			memcpy(sdl, &ifr->ifr_addr, ifr->ifr_addr.sa_len);
			*hwlen = sdl->sdl_alen;
			memcpy(hwaddr, LLADDR(sdl), *hwlen);
			free(sdl);
			retval = 1;
			break;
		}
#endif

		if (ifr->ifr_addr.sa_family == AF_INET)	{
			memcpy(&address, &ifr->ifr_addr, sizeof(address));
			if (ioctl(s, SIOCGIFNETMASK, ifr) == -1)
				continue;
			memcpy(&netmask, &ifr->ifr_addr, sizeof(netmask));
			if (get) {
				addr->s_addr = address.sin_addr.s_addr;
				net->s_addr = netmask.sin_addr.s_addr;
				retval = 1;
				break;
			} else {
				if (address.sin_addr.s_addr == addr->s_addr &&
				    (!net ||
				     netmask.sin_addr.s_addr == net->s_addr))
				{
					retval = 1;
					break;
				}
			}
		}

	}

	if (!found)
		errno = ENXIO;
	close(s);
	free(ifc.ifc_buf);
	return retval;
}

int
up_interface(const char *ifname)
{
	int s;
	struct ifreq ifr;
	int retval = -1;
#ifdef __linux__
	char *p;
#endif

	if ((s = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
		return -1;
	memset(&ifr, 0, sizeof(ifr));
	strlcpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name));
#ifdef __linux__
	/* We can only bring the real interface up */
	if ((p = strchr(ifr.ifr_name, ':')))
		*p = '\0';
#endif
	if (ioctl(s, SIOCGIFFLAGS, &ifr) == 0) {
		if ((ifr.ifr_flags & IFF_UP))
			retval = 0;
		else {
			ifr.ifr_flags |= IFF_UP;
			if (ioctl(s, SIOCSIFFLAGS, &ifr) == 0)
				retval = 0;
		}
	}
	close(s);
	return retval;
}

int
carrier_status(const char *ifname)
{
	int s;
	struct ifreq ifr;
	int retval = -1;
#ifdef SIOCGIFMEDIA
	struct ifmediareq ifmr;
#endif
#ifdef __linux__
	char *p;
#endif

	if ((s = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
		return -1;
	memset(&ifr, 0, sizeof(ifr));
	strlcpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name));
#ifdef __linux__
	/* We can only test the real interface up */
	if ((p = strchr(ifr.ifr_name, ':')))
		*p = '\0';
#endif
	if ((retval = ioctl(s, SIOCGIFFLAGS, &ifr)) == 0) {
		if (ifr.ifr_flags & IFF_UP && ifr.ifr_flags & IFF_RUNNING)
			retval = 1;
		else
			retval = 0;
	}

#ifdef SIOCGIFMEDIA
	if (retval == 1) {
		memset(&ifmr, 0, sizeof(ifmr));
		strncpy(ifmr.ifm_name, ifr.ifr_name, sizeof(ifmr.ifm_name));
		if (ioctl(s, SIOCGIFMEDIA, &ifmr) != -1 &&
		    ifmr.ifm_status & IFM_AVALID)
		{
			if (!(ifmr.ifm_status & IFM_ACTIVE))
				retval = 0;
		}
	}
#endif
	close(s);
	return retval;
}

struct interface *
read_interface(const char *ifname, _unused int metric)
{
	int s;
	struct ifreq ifr;
	struct interface *iface = NULL;
	unsigned char *hwaddr = NULL;
	size_t hwlen = 0;
	sa_family_t family = 0;

	memset(&ifr, 0, sizeof(ifr));
	strlcpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name));

	if ((s = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
		return NULL;

#ifdef __linux__
	strlcpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name));
	if (ioctl(s, SIOCGIFHWADDR, &ifr) == -1)
		goto eexit;

	switch (ifr.ifr_hwaddr.sa_family) {
	case ARPHRD_ETHER:
	case ARPHRD_IEEE802:
		hwlen = ETHER_ADDR_LEN;
		break;
	case ARPHRD_IEEE1394:
		hwlen = EUI64_ADDR_LEN;
	case ARPHRD_INFINIBAND:
		hwlen = INFINIBAND_ADDR_LEN;
		break;
	}

	hwaddr = xmalloc(sizeof(unsigned char) * HWADDR_LEN);
	memcpy(hwaddr, ifr.ifr_hwaddr.sa_data, hwlen);
	family = ifr.ifr_hwaddr.sa_family;
#else
	ifr.ifr_metric = metric;
	strlcpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name));
	if (ioctl(s, SIOCSIFMETRIC, &ifr) == -1)
		goto eexit;

	hwaddr = xmalloc(sizeof(unsigned char) * HWADDR_LEN);
	if (do_interface(ifname, hwaddr, &hwlen, NULL, NULL, 0) != 1)
		goto eexit;

	family = ARPHRD_ETHER;
#endif

	strlcpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name));
	if (ioctl(s, SIOCGIFMTU, &ifr) == -1)
		goto eexit;

	/* Ensure that the MTU is big enough for DHCP */
	if (ifr.ifr_mtu < MTU_MIN) {
		ifr.ifr_mtu = MTU_MIN;
		strlcpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name));
		if (ioctl(s, SIOCSIFMTU, &ifr) == -1)
			goto eexit;
	}

	if (up_interface(ifname) != 0)
		goto eexit;

	iface = xzalloc(sizeof(*iface));
	strlcpy(iface->name, ifname, IF_NAMESIZE);
	snprintf(iface->leasefile, PATH_MAX, LEASEFILE, ifname);
	memcpy(&iface->hwaddr, hwaddr, hwlen);
	iface->hwlen = hwlen;

	iface->family = family;
	iface->arpable = !(ifr.ifr_flags & (IFF_NOARP | IFF_LOOPBACK));

	/* 0 is a valid fd, so init to -1 */
	iface->raw_fd = -1;
	iface->udp_fd = -1;
	iface->arp_fd = -1;
	iface->link_fd = -1;

eexit:
	close(s);
	free(hwaddr);
	return iface;
}

int
do_mtu(const char *ifname, short int mtu)
{
	struct ifreq ifr;
	int r;
	int s;

	if ((s = socket(AF_INET, SOCK_DGRAM, 0)) == -1)
		return -1;

	memset(&ifr, 0, sizeof(ifr));
	strlcpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name));
	ifr.ifr_mtu = mtu;
	r = ioctl(s, mtu ? SIOCSIFMTU : SIOCGIFMTU, &ifr);
	close(s);
	if (r == -1)
		return -1;
	return ifr.ifr_mtu;
}

void
free_routes(struct rt *routes)
{
	struct rt *r;

	while (routes) {
		r = routes->next;
		free(routes);
		routes = r;
	}
}

int
open_udp_socket(struct interface *iface)
{
	int s;
	union sockunion {
		struct sockaddr sa;
		struct sockaddr_in sin;
	} su;
	int n;
#ifdef SO_BINDTODEVICE
	struct ifreq ifr;
#endif

	if ((s = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1)
		return -1;

	n = 1;
	if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR, &n, sizeof(n)) == -1)
		goto eexit;
#ifdef SO_BINDTODEVICE
	memset(&ifr, 0, sizeof(ifr));
	strlcpy(ifr.ifr_name, iface->name, sizeof(ifr.ifr_name));
	if (setsockopt(s, SOL_SOCKET, SO_BINDTODEVICE, &ifr, sizeof(ifr)) == -1)
		goto eexit;
#endif
	/* As we don't use this socket for receiving, set the
	 * receive buffer to 1 */
	n = 1;
	if (setsockopt(s, SOL_SOCKET, SO_RCVBUF, &n, sizeof(n)) == -1)
		goto eexit;
	memset(&su, 0, sizeof(su));
	su.sin.sin_family = AF_INET;
	su.sin.sin_port = htons(DHCP_CLIENT_PORT);
	su.sin.sin_addr.s_addr = iface->addr.s_addr;
	if (bind(s, &su.sa, sizeof(su)) == -1)
		goto eexit;

	iface->udp_fd = s;
	set_cloexec(s);
	return 0;

eexit:
	close(s);
	return -1;
}

ssize_t
send_packet(const struct interface *iface, struct in_addr to,
	    const uint8_t *data, ssize_t len)
{
	union sockunion {
		struct sockaddr sa;
		struct sockaddr_in sin;
	} su;

	memset(&su, 0, sizeof(su));
	su.sin.sin_family = AF_INET;
	su.sin.sin_addr.s_addr = to.s_addr;
	su.sin.sin_port = htons(DHCP_SERVER_PORT);

	return sendto(iface->udp_fd, data, len, 0, &su.sa, sizeof(su));
}

struct udp_dhcp_packet
{
	struct ip ip;
	struct udphdr udp;
	struct dhcp_message dhcp;
};
const size_t udp_dhcp_len = sizeof(struct udp_dhcp_packet);

static uint16_t
checksum(const void *data, uint16_t len)
{
	const uint8_t *addr = data;
	uint32_t sum = 0;

	while (len > 1) {
		sum += addr[0] * 256 + addr[1];
		addr += 2;
		len -= 2;
	}

	if (len == 1)
		sum += *addr * 256;

	sum = (sum >> 16) + (sum & 0xffff);
	sum += (sum >> 16);

	sum = htons(sum);

	return ~sum;
}

ssize_t
make_udp_packet(uint8_t **packet, const uint8_t *data, size_t length,
		struct in_addr source, struct in_addr dest)
{
	struct udp_dhcp_packet *udpp;
	struct ip *ip;
	struct udphdr *udp;

	udpp = xzalloc(sizeof(*udpp));
	ip = &udpp->ip;
	udp = &udpp->udp;

	/* OK, this is important :)
	 * We copy the data to our packet and then create a small part of the
	 * ip structure and an invalid ip_len (basically udp length).
	 * We then fill the udp structure and put the checksum
	 * of the whole packet into the udp checksum.
	 * Finally we complete the ip structure and ip checksum.
	 * If we don't do the ordering like so then the udp checksum will be
	 * broken, so find another way of doing it! */

	memcpy(&udpp->dhcp, data, length);

	ip->ip_p = IPPROTO_UDP;
	ip->ip_src.s_addr = source.s_addr;
	if (dest.s_addr == 0)
		ip->ip_dst.s_addr = INADDR_BROADCAST;
	else
		ip->ip_dst.s_addr = dest.s_addr;

	udp->uh_sport = htons(DHCP_CLIENT_PORT);
	udp->uh_dport = htons(DHCP_SERVER_PORT);
	udp->uh_ulen = htons(sizeof(*udp) + length);
	ip->ip_len = udp->uh_ulen;
	udp->uh_sum = checksum(udpp, sizeof(*udpp));

	ip->ip_v = IPVERSION;
	ip->ip_hl = 5;
	ip->ip_id = 0;
	ip->ip_tos = IPTOS_LOWDELAY;
	ip->ip_len = htons (sizeof(*ip) + sizeof(*udp) + length);
	ip->ip_id = 0;
	ip->ip_off = htons(IP_DF); /* Don't fragment */
	ip->ip_ttl = IPDEFTTL;

	ip->ip_sum = checksum(ip, sizeof(*ip));

	*packet = (uint8_t *)udpp;
	return sizeof(*ip) + sizeof(*udp) + length;
}

ssize_t
get_udp_data(const uint8_t **data, const uint8_t *udp)
{
	struct udp_dhcp_packet packet;

	memcpy(&packet, udp, sizeof(packet));
	*data = udp + offsetof(struct udp_dhcp_packet, dhcp);
	return ntohs(packet.ip.ip_len) - sizeof(packet.ip) - sizeof(packet.udp);
}

int
valid_udp_packet(const uint8_t *data, size_t data_len)
{
	struct udp_dhcp_packet packet;
	uint16_t bytes, udpsum;

	if (data_len > sizeof(packet)) {
		errno = EINVAL;
		return -1;
	}
	memcpy(&packet, data, data_len);
	if (checksum(&packet.ip, sizeof(packet.ip)) != 0) {
		errno = EINVAL;
		return -1;
	}

	bytes = ntohs(packet.ip.ip_len);
	if (data_len < bytes) {
		errno = EINVAL;
		return -1;
	}
	udpsum = packet.udp.uh_sum;
	packet.udp.uh_sum = 0;
	packet.ip.ip_hl = 0;
	packet.ip.ip_v = 0;
	packet.ip.ip_tos = 0;
	packet.ip.ip_len = packet.udp.uh_ulen;
	packet.ip.ip_id = 0;
	packet.ip.ip_off = 0;
	packet.ip.ip_ttl = 0;
	packet.ip.ip_sum = 0;
	if (udpsum && checksum(&packet, bytes) != udpsum) {
		errno = EINVAL;
		return -1;
	}

	return 0;
}

int
send_arp(const struct interface *iface, int op, in_addr_t sip, in_addr_t tip)
{
	struct arphdr *arp;
	size_t arpsize;
	uint8_t *p;
	int retval;

	arpsize = sizeof(*arp) + 2 * iface->hwlen + 2 * sizeof(sip);
	arp = xmalloc(arpsize);
	arp->ar_hrd = htons(iface->family);
	arp->ar_pro = htons(ETHERTYPE_IP);
	arp->ar_hln = iface->hwlen;
	arp->ar_pln = sizeof(sip);
	arp->ar_op = htons(op);
	p = (uint8_t *)arp;
	p += sizeof(*arp);
	memcpy(p, iface->hwaddr, iface->hwlen);
	p += iface->hwlen;
	memcpy(p, &sip, sizeof(sip));
	p += sizeof(sip);
	/* ARP requests should ignore this */
	retval = iface->hwlen;
	while (retval--)
		*p++ = '\0';
	memcpy(p, &tip, sizeof(tip));
	p += sizeof(tip);
	retval = send_raw_packet(iface, ETHERTYPE_ARP, arp, arpsize);
	free(arp);
	return retval;
}