From 72e76044cfda377486a5199a0d35d71edf669a42 Mon Sep 17 00:00:00 2001
From: Denis Vlasenko <vda.linux@googlemail.com>
Date: Sun, 25 Nov 2007 03:15:24 +0000
Subject: dhcpc: cope with buggy DHCP servers which send oversized packets
(Cristian Ionescu-Idbohrn <cristian.ionescu-idbohrn@axis.com>)
---
networking/udhcp/Config.in | 22 ++++++++++++++++++++++
networking/udhcp/common.h | 6 ++++--
networking/udhcp/options.c | 2 +-
3 files changed, 27 insertions(+), 3 deletions(-)
diff --git a/networking/udhcp/Config.in b/networking/udhcp/Config.in
index 734db65cc..1aef69ba7 100644
--- a/networking/udhcp/Config.in
+++ b/networking/udhcp/Config.in
@@ -82,3 +82,25 @@ config FEATURE_RFC3397
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.
diff --git a/networking/udhcp/common.h b/networking/udhcp/common.h
index 4f2d31c98..eecb72ca2 100644
--- a/networking/udhcp/common.h
+++ b/networking/udhcp/common.h
@@ -21,6 +21,8 @@ extern const uint8_t MAC_BCAST_ADDR[6]; /* six all-ones */
#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 @@ struct dhcpMessage {
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 @@ struct udp_dhcp_packet {
/* 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);
diff --git a/networking/udhcp/options.c b/networking/udhcp/options.c
index 2b4f1644f..6744e2ad0 100644
--- a/networking/udhcp/options.c
+++ b/networking/udhcp/options.c
@@ -145,7 +145,7 @@ int add_option_string(uint8_t *optionptr, uint8_t *string)
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;
--
cgit v1.2.3-55-g6feb