mirror of
https://github.com/sheumann/hush.git
synced 2024-12-27 16:31:24 +00:00
109 lines
3.6 KiB
C
109 lines
3.6 KiB
C
/* vi: set sw=4 ts=4: */
|
|
/*
|
|
* clientsocket.c -- DHCP client socket creation
|
|
*
|
|
* udhcp client
|
|
*
|
|
* Russ Dill <Russ.Dill@asu.edu> July 2001
|
|
*
|
|
* 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., 675 Mass Ave, Cambridge, MA 02139, USA.
|
|
*/
|
|
|
|
#include <features.h>
|
|
#if (defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1) || defined(_NEWLIB_VERSION)
|
|
#include <netpacket/packet.h>
|
|
#include <net/ethernet.h>
|
|
#else
|
|
#include <asm/types.h>
|
|
#include <linux/if_packet.h>
|
|
#include <linux/if_ether.h>
|
|
#endif
|
|
#include <linux/filter.h>
|
|
|
|
#include "common.h"
|
|
#include "dhcpd.h"
|
|
#include "dhcpc.h"
|
|
|
|
int raw_socket(int ifindex)
|
|
{
|
|
int fd;
|
|
struct sockaddr_ll sock;
|
|
|
|
/*
|
|
* Comment:
|
|
*
|
|
* I've selected not to see LL header, so BPF doesn't see it, too.
|
|
* The filter may also pass non-IP and non-ARP packets, but we do
|
|
* a more complete check when receiving the message in userspace.
|
|
*
|
|
* and filter shamelessly stolen from:
|
|
*
|
|
* http://www.flamewarmaster.de/software/dhcpclient/
|
|
*
|
|
* There are a few other interesting ideas on that page (look under
|
|
* "Motivation"). Use of netlink events is most interesting. Think
|
|
* of various network servers listening for events and reconfiguring.
|
|
* That would obsolete sending HUP signals and/or make use of restarts.
|
|
*
|
|
* Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
|
|
* License: GPL v2.
|
|
*
|
|
* TODO: make conditional?
|
|
*/
|
|
#define SERVER_AND_CLIENT_PORTS ((67 << 16) + 68)
|
|
static const struct sock_filter filter_instr[] = {
|
|
/* check for udp */
|
|
BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
|
|
BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 2, 0), /* L5, L1, is UDP? */
|
|
/* ugly check for arp on ethernet-like and IPv4 */
|
|
BPF_STMT(BPF_LD|BPF_W|BPF_ABS, 2), /* L1: */
|
|
BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 0x08000604, 3, 4), /* L3, L4 */
|
|
/* skip IP header */
|
|
BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0), /* L5: */
|
|
/* check udp source and destination ports */
|
|
BPF_STMT(BPF_LD|BPF_W|BPF_IND, 0),
|
|
BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, SERVER_AND_CLIENT_PORTS, 0, 1), /* L3, L4 */
|
|
/* returns */
|
|
BPF_STMT(BPF_RET|BPF_K, ~0UL), /* L3: pass */
|
|
BPF_STMT(BPF_RET|BPF_K, 0), /* L4: reject */
|
|
};
|
|
static const struct sock_fprog filter_prog = {
|
|
.len = sizeof(filter_instr) / sizeof(filter_instr[0]),
|
|
/* casting const away: */
|
|
.filter = (struct sock_filter *) filter_instr,
|
|
};
|
|
|
|
DEBUG("opening raw socket on ifindex %d", ifindex);
|
|
|
|
fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
|
|
DEBUG("got raw socket fd %d", fd);
|
|
|
|
if (SERVER_PORT == 67 && CLIENT_PORT == 68) {
|
|
/* Use only if standard ports are in use */
|
|
/* Ignoring error (kernel may lack support for this) */
|
|
if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
|
|
sizeof(filter_prog)) >= 0)
|
|
DEBUG("attached filter to raw socket fd %d", fd);
|
|
}
|
|
|
|
sock.sll_family = AF_PACKET;
|
|
sock.sll_protocol = htons(ETH_P_IP);
|
|
sock.sll_ifindex = ifindex;
|
|
xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
|
|
DEBUG("bound to raw socket fd %d", fd);
|
|
|
|
return fd;
|
|
}
|