1 /* vi: set sw=4 ts=4: */
3 * clientsocket.c -- DHCP client socket creation
7 * Russ Dill <Russ.Dill@asu.edu> July 2001
9 * This program is free software; you can redistribute it and/or modify
10 * it under the terms of the GNU General Public License as published by
11 * the Free Software Foundation; either version 2 of the License, or
12 * (at your option) any later version.
14 * This program is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
17 * GNU General Public License for more details.
19 * You should have received a copy of the GNU General Public License
20 * along with this program; if not, write to the Free Software
21 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
28 //#include <features.h>
29 #include <asm/types.h>
30 #if (defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1) || defined(_NEWLIB_VERSION)
31 #include <netpacket/packet.h>
32 #include <net/ethernet.h>
34 #include <linux/if_packet.h>
35 #include <linux/if_ether.h>
37 #include <linux/filter.h>
39 int FAST_FUNC udhcp_raw_socket(int ifindex)
42 struct sockaddr_ll sock;
47 * I've selected not to see LL header, so BPF doesn't see it, too.
48 * The filter may also pass non-IP and non-ARP packets, but we do
49 * a more complete check when receiving the message in userspace.
51 * and filter shamelessly stolen from:
53 * http://www.flamewarmaster.de/software/dhcpclient/
55 * There are a few other interesting ideas on that page (look under
56 * "Motivation"). Use of netlink events is most interesting. Think
57 * of various network servers listening for events and reconfiguring.
58 * That would obsolete sending HUP signals and/or make use of restarts.
60 * Copyright: 2006, 2007 Stefan Rompf <sux@loplof.de>.
63 * TODO: make conditional?
65 #define SERVER_AND_CLIENT_PORTS ((67 << 16) + 68)
66 static const struct sock_filter filter_instr[] = {
68 BPF_STMT(BPF_LD|BPF_B|BPF_ABS, 9),
69 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, IPPROTO_UDP, 2, 0), /* L5, L1, is UDP? */
70 /* ugly check for arp on ethernet-like and IPv4 */
71 BPF_STMT(BPF_LD|BPF_W|BPF_ABS, 2), /* L1: */
72 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, 0x08000604, 3, 4), /* L3, L4 */
74 BPF_STMT(BPF_LDX|BPF_B|BPF_MSH, 0), /* L5: */
75 /* check udp source and destination ports */
76 BPF_STMT(BPF_LD|BPF_W|BPF_IND, 0),
77 BPF_JUMP(BPF_JMP|BPF_JEQ|BPF_K, SERVER_AND_CLIENT_PORTS, 0, 1), /* L3, L4 */
79 BPF_STMT(BPF_RET|BPF_K, 0x0fffffff ), /* L3: pass */
80 BPF_STMT(BPF_RET|BPF_K, 0), /* L4: reject */
82 static const struct sock_fprog filter_prog = {
83 .len = sizeof(filter_instr) / sizeof(filter_instr[0]),
84 /* casting const away: */
85 .filter = (struct sock_filter *) filter_instr,
88 log1("Opening raw socket on ifindex %d", ifindex); //log2?
90 fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
91 log1("Got raw socket fd %d", fd); //log2?
93 if (SERVER_PORT == 67 && CLIENT_PORT == 68) {
94 /* Use only if standard ports are in use */
95 /* Ignoring error (kernel may lack support for this) */
96 if (setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter_prog,
97 sizeof(filter_prog)) >= 0)
98 log1("Attached filter to raw socket fd %d", fd); // log?
101 sock.sll_family = AF_PACKET;
102 sock.sll_protocol = htons(ETH_P_IP);
103 sock.sll_ifindex = ifindex;
104 xbind(fd, (struct sockaddr *) &sock, sizeof(sock));
105 log1("Created raw socket");