diff options
Diffstat (limited to 'networking/udhcp/dhcpc.c')
| -rw-r--r-- | networking/udhcp/dhcpc.c | 102 |
1 files changed, 98 insertions, 4 deletions
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c index 3e2cd1217..a03e25ca4 100644 --- a/networking/udhcp/dhcpc.c +++ b/networking/udhcp/dhcpc.c @@ -1,11 +1,22 @@ /* vi: set sw=4 ts=4: */ -/* dhcpc.c - * +/* * udhcp DHCP client * * Russ Dill <Russ.Dill@asu.edu> July 2001 * - * Licensed under the GPL v2 or later, see the file LICENSE in this tarball. + * 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 <syslog.h> /* Override ENABLE_FEATURE_PIDFILE - ifupdown needs our pidfile to always exist */ @@ -15,6 +26,16 @@ #include "dhcpc.h" #include "options.h" +#include <asm/types.h> +#if (defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1) || defined(_NEWLIB_VERSION) +# include <netpacket/packet.h> +# include <net/ethernet.h> +#else +# include <linux/if_packet.h> +# include <linux/if_ether.h> +#endif +#include <linux/filter.h> + static int sockfd = -1; @@ -42,6 +63,79 @@ static smallint state; /* struct client_config_t client_config is in bb_common_bufsiz1 */ + +static int udhcp_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, 0x0fffffff ), /* 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, + }; + + log1("Opening raw socket on ifindex %d", ifindex); //log2? + + fd = xsocket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP)); + log1("Got raw socket fd %d", fd); //log2? + + 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) + log1("Attached filter to raw socket fd %d", fd); // log? + } + + sock.sll_family = AF_PACKET; + sock.sll_protocol = htons(ETH_P_IP); + sock.sll_ifindex = ifindex; + xbind(fd, (struct sockaddr *) &sock, sizeof(sock)); + log1("Created raw socket"); + + return fd; +} + + /* just a little helper */ static void change_listen_mode(int new_mode) { @@ -60,7 +154,7 @@ static void change_listen_mode(int new_mode) sockfd = udhcp_listen_socket(/*INADDR_ANY,*/ CLIENT_PORT, client_config.interface); else if (new_mode != LISTEN_NONE) sockfd = udhcp_raw_socket(client_config.ifindex); - /* else LISTEN_NONE: sockfd stay closed */ + /* else LISTEN_NONE: sockfd stays closed */ } |