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 */
 }