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List: busybox
Subject: Re: dhcp problem with several routers
From: Denys Vlasenko <vda.linux () googlemail ! com>
Date: 2007-12-20 19:47:41
Message-ID: 200712201947.41382.vda.linux () googlemail ! com
[Download RAW message or body]
On Thursday 20 December 2007 16:13, ftrenc wrote:
> Hi
>
> I've been having problems with the dhcp when connecting to several
> routers. I saw you aplied this solution to the problem:
>
> http://busybox.net/cgi-bin/viewcvs.cgi/trunk/busybox/networking/udhcp/clien
>tpacket.c?rev=20565&r1=20483&r2=20565
>
>
> but I still having the same problems.
>
> The problem it's that router answers us with 1090 bytes frame. Finally
> we saw that making the dhcp discover to not send the amount of padding
> it sends though the router at the end of frame, there was no problem,
> and also the router don't send us that amount of padding to.
>
>
> Our solution to the problem (Packet.c):
You indeed found a problem. We don't calculate DHCP packet lenght,
and always send full-sized packets.
Can you try attached patch?
In case patch doesn't apply to your tree,
I attached entire networking/udhcp/* directory in an archive too.
--
vda
["udhcp.tar.bz2" (application/x-tbz)]
["6.patch" (text/x-diff)]
diff -d -urpN busybox.5/networking/udhcp/clientpacket.c \
busybox.6/networking/udhcp/clientpacket.c
--- busybox.5/networking/udhcp/clientpacket.c 2007-12-11 13:11:57.000000000 +0000
+++ busybox.6/networking/udhcp/clientpacket.c 2007-12-20 19:43:29.000000000 +0000
@@ -86,7 +86,7 @@ int send_decline(uint32_t xid, uint32_t
bb_info_msg("Sending decline...");
- return udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
+ return udhcp_send_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
}
#endif
@@ -106,7 +106,7 @@ int send_discover(uint32_t xid, uint32_t
add_simple_option(packet.options, DHCP_MAX_SIZE, htons(576));
add_requests(&packet);
bb_info_msg("Sending discover...");
- return udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
+ return udhcp_send_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
}
@@ -126,7 +126,7 @@ int send_selecting(uint32_t xid, uint32_
add_requests(&packet);
addr.s_addr = requested;
bb_info_msg("Sending select for %s...", inet_ntoa(addr));
- return udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
+ return udhcp_send_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
}
@@ -143,9 +143,9 @@ int send_renew(uint32_t xid, uint32_t se
add_requests(&packet);
bb_info_msg("Sending renew...");
if (server)
- return udhcp_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
+ return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, \
SERVER_PORT);
- return udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
+ return udhcp_send_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
}
@@ -163,7 +163,7 @@ int send_release(uint32_t server, uint32
add_simple_option(packet.options, DHCP_SERVER_ID, server);
bb_info_msg("Sending release...");
- return udhcp_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
+ return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
}
@@ -172,7 +172,6 @@ int get_raw_packet(struct dhcpMessage *p
{
int bytes;
struct udp_dhcp_packet packet;
- uint32_t source, dest;
uint16_t check;
memset(&packet, 0, sizeof(struct udp_dhcp_packet));
@@ -207,36 +206,31 @@ int get_raw_packet(struct dhcpMessage *p
return -2;
}
- /* check IP checksum */
+ /* verify IP checksum */
check = packet.ip.check;
packet.ip.check = 0;
- if (check != udhcp_checksum(&(packet.ip), sizeof(packet.ip))) {
- DEBUG("bad IP header checksum, ignoring");
+ if (check != udhcp_checksum(&packet.ip, sizeof(packet.ip))) {
+ DEBUG("Bad IP header checksum, ignoring");
return -1;
}
- /* verify the UDP checksum by replacing the header with a pseudo header */
- source = packet.ip.saddr;
- dest = packet.ip.daddr;
+ /* verify UDP checksum. IP header has to be modified for this */
+ memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
+ /* fields which are not memset: protocol, check, saddr, daddr */
+ packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
check = packet.udp.check;
packet.udp.check = 0;
- memset(&packet.ip, 0, sizeof(packet.ip));
-
- packet.ip.protocol = IPPROTO_UDP;
- packet.ip.saddr = source;
- packet.ip.daddr = dest;
- packet.ip.tot_len = packet.udp.len; /* cheat on the psuedo-header */
if (check && check != udhcp_checksum(&packet, bytes)) {
bb_error_msg("packet with bad UDP checksum received, ignoring");
return -2;
}
- memcpy(payload, &(packet.data), bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
+ memcpy(payload, &packet.data, bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
if (payload->cookie != htonl(DHCP_MAGIC)) {
bb_error_msg("received bogus message (bad magic) - ignoring");
return -2;
}
- DEBUG("oooooh!!! got some!");
+ DEBUG("Got valid DHCP packet");
return bytes - (sizeof(packet.ip) + sizeof(packet.udp));
}
diff -d -urpN busybox.5/networking/udhcp/common.h busybox.6/networking/udhcp/common.h
--- busybox.5/networking/udhcp/common.h 2007-12-11 13:11:57.000000000 +0000
+++ busybox.6/networking/udhcp/common.h 2007-12-20 18:15:03.000000000 +0000
@@ -57,11 +57,11 @@ struct BUG_bad_sizeof_struct_udp_dhcp_pa
void udhcp_init_header(struct dhcpMessage *packet, char type);
int udhcp_get_packet(struct dhcpMessage *packet, int fd);
uint16_t udhcp_checksum(void *addr, int count);
-int udhcp_raw_packet(struct dhcpMessage *payload,
+int udhcp_send_raw_packet(struct dhcpMessage *payload,
uint32_t source_ip, int source_port,
uint32_t dest_ip, int dest_port,
const uint8_t *dest_arp, int ifindex);
-int udhcp_kernel_packet(struct dhcpMessage *payload,
+int udhcp_send_kernel_packet(struct dhcpMessage *payload,
uint32_t source_ip, int source_port,
uint32_t dest_ip, int dest_port);
diff -d -urpN busybox.5/networking/udhcp/packet.c busybox.6/networking/udhcp/packet.c
--- busybox.5/networking/udhcp/packet.c 2007-12-11 13:11:57.000000000 +0000
+++ busybox.6/networking/udhcp/packet.c 2007-12-20 19:15:12.000000000 +0000
@@ -111,7 +111,7 @@ uint16_t udhcp_checksum(void *addr, int
/* Make sure that the left-over byte is added correctly both
* with little and big endian hosts */
uint16_t tmp = 0;
- *(uint8_t *) (&tmp) = * (uint8_t *) source;
+ *(uint8_t*)&tmp = *(uint8_t*)source;
sum += tmp;
}
/* Fold 32-bit sum to 16 bits */
@@ -123,7 +123,7 @@ uint16_t udhcp_checksum(void *addr, int
/* Construct a ip/udp header for a packet, and specify the source and dest hardware \
address */
-int udhcp_raw_packet(struct dhcpMessage *payload,
+int udhcp_send_raw_packet(struct dhcpMessage *payload,
uint32_t source_ip, int source_port,
uint32_t dest_ip, int dest_port, const uint8_t *dest_arp, int ifindex)
{
@@ -131,6 +131,7 @@ int udhcp_raw_packet(struct dhcpMessage
int result;
struct sockaddr_ll dest;
struct udp_dhcp_packet packet;
+ unsigned size;
fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
if (fd < 0) {
@@ -140,6 +141,8 @@ int udhcp_raw_packet(struct dhcpMessage
memset(&dest, 0, sizeof(dest));
memset(&packet, 0, sizeof(packet));
+ packet.data = *payload; /* struct copy */
+ size = (char*)&packet.data.options[end_option(packet.data.options) + 1] - \
(char*)&packet;
dest.sll_family = AF_PACKET;
dest.sll_protocol = htons(ETH_P_IP);
@@ -157,19 +160,19 @@ int udhcp_raw_packet(struct dhcpMessage
packet.ip.daddr = dest_ip;
packet.udp.source = htons(source_port);
packet.udp.dest = htons(dest_port);
- packet.udp.len = htons(sizeof(packet.udp) + sizeof(struct dhcpMessage)); /* cheat \
on the psuedo-header */ + /* size, excluding ip header: */
+ packet.udp.len = htons(size - offsetof(struct udp_dhcp_packet, udp));
+ /* for UDP checksumming, ip.len is set to UDP packet len */
packet.ip.tot_len = packet.udp.len;
- memcpy(&(packet.data), payload, sizeof(struct dhcpMessage));
- packet.udp.check = udhcp_checksum(&packet, sizeof(struct udp_dhcp_packet));
-
- packet.ip.tot_len = htons(sizeof(struct udp_dhcp_packet));
+ packet.udp.check = udhcp_checksum(&packet, size);
+ /* but for sending, it is set to IP packet len */
+ packet.ip.tot_len = htons(size);
packet.ip.ihl = sizeof(packet.ip) >> 2;
packet.ip.version = IPVERSION;
packet.ip.ttl = IPDEFTTL;
- packet.ip.check = udhcp_checksum(&(packet.ip), sizeof(packet.ip));
+ packet.ip.check = udhcp_checksum(&packet.ip, sizeof(packet.ip));
- result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0,
- (struct sockaddr *) &dest, sizeof(dest));
+ result = sendto(fd, &packet, size, 0, (struct sockaddr *) &dest, sizeof(dest));
if (result <= 0) {
bb_perror_msg("sendto");
}
@@ -179,12 +182,13 @@ int udhcp_raw_packet(struct dhcpMessage
/* Let the kernel do all the work for packet generation */
-int udhcp_kernel_packet(struct dhcpMessage *payload,
+int udhcp_send_kernel_packet(struct dhcpMessage *payload,
uint32_t source_ip, int source_port,
uint32_t dest_ip, int dest_port)
{
int fd, result;
struct sockaddr_in client;
+ unsigned size;
fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (fd < 0)
@@ -212,7 +216,8 @@ int udhcp_kernel_packet(struct dhcpMessa
return -1;
}
- result = write(fd, payload, sizeof(struct dhcpMessage));
+ size = (char*)&payload->options[end_option(payload->options) + 1] - \
(char*)&payload; + result = write(fd, payload, size);
close(fd);
return result;
}
diff -d -urpN busybox.5/networking/udhcp/serverpacket.c \
busybox.6/networking/udhcp/serverpacket.c
--- busybox.5/networking/udhcp/serverpacket.c 2007-12-11 13:11:57.000000000 +0000
+++ busybox.6/networking/udhcp/serverpacket.c 2007-12-20 18:14:40.000000000 +0000
@@ -30,7 +30,7 @@ static int send_packet_to_relay(struct d
{
DEBUG("Forwarding packet to relay");
- return udhcp_kernel_packet(payload, server_config.server, SERVER_PORT,
+ return udhcp_send_kernel_packet(payload, server_config.server, SERVER_PORT,
payload->giaddr, SERVER_PORT);
}
@@ -58,7 +58,7 @@ static int send_packet_to_client(struct
ciaddr = payload->yiaddr;
chaddr = payload->chaddr;
}
- return udhcp_raw_packet(payload, server_config.server, SERVER_PORT,
+ return udhcp_send_raw_packet(payload, server_config.server, SERVER_PORT,
ciaddr, CLIENT_PORT, chaddr, server_config.ifindex);
}
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