svn commit: trunk/busybox/networking/udhcp

[vda at busybox.net]

Author: vda
Date: 2007-11-24 19:15:24 -0800 (Sat, 24 Nov 2007)
New Revision: 20528

Log:
dhcpc: cope with buggy DHCP servers which send oversized packets
(Cristian Ionescu-Idbohrn <cristian.ionescu-idbohrn at axis.com>)



Modified:
   trunk/busybox/networking/udhcp/Config.in
   trunk/busybox/networking/udhcp/common.h
   trunk/busybox/networking/udhcp/options.c


Changeset:
Modified: trunk/busybox/networking/udhcp/Config.in
===================================================================
--- trunk/busybox/networking/udhcp/Config.in	2007-11-24 16:09:25 UTC (rev 20527)
+++ trunk/busybox/networking/udhcp/Config.in	2007-11-25 03:15:24 UTC (rev 20528)
@@ -82,3 +82,25 @@
 	help
 	  If selected, both client and server will support passing of domain
 	  search lists via option 119, specified in RFC3397.
+
+config UDHCPC_SLACK_FOR_BUGGY_SERVERS
+	int "DHCP options slack buffer size"
+	default 80
+	range 0 924
+	depends on APP_UDHCPD || APP_UDHCPC
+	help
+	  Some buggy DHCP servers will send DHCP offer packets with option
+	  field larger than we expect (which might also be considered a
+	  buffer overflow attempt). These packets are normally discarded.
+	  If circumstances beyond your control force you to support such
+	  servers, this may help. The upper limit (924) makes dhcpc accept
+	  even 1500 byte packets (maximum-sized ethernet packets).
+
+	  This options does not make dhcp[cd] emit non-standard
+	  sized packets.
+
+	  Known buggy DHCP servers:
+	  3Com OfficeConnect Remote 812 ADSL Router:
+	    seems to confuse maximum allowed UDP packet size with
+	    maximum size of entire IP packet, and sends packets which are
+	    28 bytes too large.

Modified: trunk/busybox/networking/udhcp/common.h
===================================================================
--- trunk/busybox/networking/udhcp/common.h	2007-11-24 16:09:25 UTC (rev 20527)
+++ trunk/busybox/networking/udhcp/common.h	2007-11-25 03:15:24 UTC (rev 20528)
@@ -21,6 +21,8 @@
 #include <netinet/udp.h>
 #include <netinet/ip.h>
 
+#define DHCP_OPTIONS_BUFSIZE 308
+
 struct dhcpMessage {
 	uint8_t op;
 	uint8_t htype;
@@ -37,7 +39,7 @@
 	uint8_t sname[64];
 	uint8_t file[128];
 	uint32_t cookie;
-	uint8_t options[308]; /* 312 - cookie */
+	uint8_t options[DHCP_OPTIONS_BUFSIZE + CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS];
 } ATTRIBUTE_PACKED;
 
 struct udp_dhcp_packet {
@@ -49,7 +51,7 @@
 /* Let's see whether compiler understood us right */
 struct BUG_bad_sizeof_struct_udp_dhcp_packet {
 	char BUG_bad_sizeof_struct_udp_dhcp_packet
-                [sizeof(struct udp_dhcp_packet) != 576 ? -1 : 1];
+		[(sizeof(struct udp_dhcp_packet) != 576 + CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS) ? -1 : 1];
 };
 
 void udhcp_init_header(struct dhcpMessage *packet, char type);

Modified: trunk/busybox/networking/udhcp/options.c
===================================================================
--- trunk/busybox/networking/udhcp/options.c	2007-11-24 16:09:25 UTC (rev 20527)
+++ trunk/busybox/networking/udhcp/options.c	2007-11-25 03:15:24 UTC (rev 20528)
@@ -145,7 +145,7 @@
 	int end = end_option(optionptr);
 
 	/* end position + string length + option code/length + end option */
-	if (end + string[OPT_LEN] + 2 + 1 >= 308) {
+	if (end + string[OPT_LEN] + 2 + 1 >= DHCP_OPTIONS_BUFSIZE) {
 		bb_error_msg("option 0x%02x did not fit into the packet",
 				string[OPT_CODE]);
 		return 0;